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2025,37(4):1091-1095, DOI: 10.18307/2025.0400
Abstract:
Precise biological monitoring is essential for safeguarding the safety bottom line in building a Beautiful China. Based on state-of-the-art environmental DNA (eDNA) technology and combining eight novel studies in eDNA issue of Journal of Lake Sciencesin 2025, this paper provides a brief review of the latest innovations, key challenges and bottlenecks in eDNA technology, and future development directions, with a view to informing multi-application scenarios in the context of global ecological security.
Precise biological monitoring is essential for safeguarding the safety bottom line in building a Beautiful China. Based on state-of-the-art environmental DNA (eDNA) technology and combining eight novel studies in eDNA issue of Journal of Lake Sciencesin 2025, this paper provides a brief review of the latest innovations, key challenges and bottlenecks in eDNA technology, and future development directions, with a view to informing multi-application scenarios in the context of global ecological security.
2025,37(4):1096-1105, DOI: 10.18307/2025.0403
Abstract:
Lake Yutan is one of the four main water supply initiatives in western Chongqing, with two inflow rivers. It is a typical multi-habitat ecosystem. To date, the fish composition and diversity in Lake Yutan have been scarcely reported. In this study, environmental DNA (eDNA) technology combined with the traditional fish survey was used to investigate the fish community and diversity in Lake Yutan, aiming to explore the potentials of eDNA technology in assessing fish diversity within river-reservoir habitats. The results showed that a total of 36 fish species categorized into 4 orders, 11 families, and 32 genera were identified by eDNA technology. The analysis of relative sequence abundance revealed higher relative abundance for Hypophthalmichthys nobilisand Hypophthalmichthys molitrix . A total of 21 fish species, categorized into 3 orders, 9 families, and 20 genera, were captured by the traditional fish survey. A total of 42 fish species were detected using the eDNA technology and traditional fish survey, with 15 species being jointly investigated, accounting for 71.43% of the total fishes captured through the traditional fish survey. The results of αand βdiversity analysis based on sequence abundance revealed variations in fish composition and diversity across the lake region, estuary, and the buffer zone at the inlet. The fish diversity in the estuary and inlet buffer zone were higher than that observed in the lake region. In summary, our findings demonstrated that the application of eDNA technology had a superior detection rate for fish species compared with the traditional fish survey, and thereby could serve as an invaluable non-invasive supplementary tool for monitoring fishery resources and enhancing the reliability of river-reservoir habitat resource survey.
Lake Yutan is one of the four main water supply initiatives in western Chongqing, with two inflow rivers. It is a typical multi-habitat ecosystem. To date, the fish composition and diversity in Lake Yutan have been scarcely reported. In this study, environmental DNA (eDNA) technology combined with the traditional fish survey was used to investigate the fish community and diversity in Lake Yutan, aiming to explore the potentials of eDNA technology in assessing fish diversity within river-reservoir habitats. The results showed that a total of 36 fish species categorized into 4 orders, 11 families, and 32 genera were identified by eDNA technology. The analysis of relative sequence abundance revealed higher relative abundance for Hypophthalmichthys nobilisand Hypophthalmichthys molitrix . A total of 21 fish species, categorized into 3 orders, 9 families, and 20 genera, were captured by the traditional fish survey. A total of 42 fish species were detected using the eDNA technology and traditional fish survey, with 15 species being jointly investigated, accounting for 71.43% of the total fishes captured through the traditional fish survey. The results of αand βdiversity analysis based on sequence abundance revealed variations in fish composition and diversity across the lake region, estuary, and the buffer zone at the inlet. The fish diversity in the estuary and inlet buffer zone were higher than that observed in the lake region. In summary, our findings demonstrated that the application of eDNA technology had a superior detection rate for fish species compared with the traditional fish survey, and thereby could serve as an invaluable non-invasive supplementary tool for monitoring fishery resources and enhancing the reliability of river-reservoir habitat resource survey.
2025,37(4):1106-1117, DOI: 10.18307/2025.0404
Abstract:
Due to the interference of strong human activities, the ecological problems of urban lakes have become increasingly prominent. As a high-level consumer of the aquatic food chain, fish is an important part of the aquatic ecosystem and an important indicator of the health of aquatic ecosystems. In this study, ten urban lakes in Wuhan and its surrounding cities were selected as study areas. Fish data monitored by environmental DNA (eDNA) were used to analyze the characteristics of fish communities and establish a fish-based index of biotic integrity (F-IBI). The health status of lakes were evaluated and studied through F-IBI evaluation system targeting the ecological health of urban lake water bodies. The research revealed that during the survey periods, there were 50 fish species belonging to 39 genera, 10 families, and 7 orders. Among them, 7 species, including Hemiculter bleekeri, Hypophthalmichthys nobilis, Rhinogobius cliffordpopei, Rhinogobius giurinus, Cyprinus carpio, Megalobrama amblycephalaandCarassius auratus were identified as dominant species. At the order and family levels, Cypriniformes and Cyprinidae fish were the dominant groups. The F-IBI evaluation result showed that among all the 27 sampling sites in ten lakes, 11 sites were evaluated being health, accounting for 40.74%; 4 sites being sub-health, accounting for 14.81%; 10 sites being general, accounting for 37.04%; 2 sites being poor, accounting for 7.41%. Analysis based on the lake water quality data showed that the evaluation results reasonably reflected the health of the different urban lake ecosystem. The study indicated that the eDNA-based F-IBI method performs well in ecosystem health assessment of urban lakes. The research results provided strong basic supports for guiding the precise ecological restoration and ecosystem management.
Due to the interference of strong human activities, the ecological problems of urban lakes have become increasingly prominent. As a high-level consumer of the aquatic food chain, fish is an important part of the aquatic ecosystem and an important indicator of the health of aquatic ecosystems. In this study, ten urban lakes in Wuhan and its surrounding cities were selected as study areas. Fish data monitored by environmental DNA (eDNA) were used to analyze the characteristics of fish communities and establish a fish-based index of biotic integrity (F-IBI). The health status of lakes were evaluated and studied through F-IBI evaluation system targeting the ecological health of urban lake water bodies. The research revealed that during the survey periods, there were 50 fish species belonging to 39 genera, 10 families, and 7 orders. Among them, 7 species, including Hemiculter bleekeri, Hypophthalmichthys nobilis, Rhinogobius cliffordpopei, Rhinogobius giurinus, Cyprinus carpio, Megalobrama amblycephalaandCarassius auratus were identified as dominant species. At the order and family levels, Cypriniformes and Cyprinidae fish were the dominant groups. The F-IBI evaluation result showed that among all the 27 sampling sites in ten lakes, 11 sites were evaluated being health, accounting for 40.74%; 4 sites being sub-health, accounting for 14.81%; 10 sites being general, accounting for 37.04%; 2 sites being poor, accounting for 7.41%. Analysis based on the lake water quality data showed that the evaluation results reasonably reflected the health of the different urban lake ecosystem. The study indicated that the eDNA-based F-IBI method performs well in ecosystem health assessment of urban lakes. The research results provided strong basic supports for guiding the precise ecological restoration and ecosystem management.
Environmental DNA-based biotic monitoring reveals fish community assembly mechanisms in urban rivers
He Wenxiang, Zou Yanting, Hu Danxin, Hao Huibo, Wu Jingze, Zheng Kanghua, Liu Zifang, Li Feilong, Zhang Yuan
2025,37(4):1118-1127, DOI: 10.18307/2025.0408
Abstract:
The deterioration of water quality, loss of habitats, and degradation of ecosystems in urban rivers, caused by intensified urbanization, have significantly impacted aquatic biological communities, including fish. In order to establish effective conservation strategies for fish populations, it is imperative to undertake a comprehensive analysis of the relative contributions of stochastic and deterministic processes in community assembly. In this study, fish monitoring was conducted at 30 sampling sites in Guangzhou's urban rivers using both environmental DNA (eDNA) and traditional survey methods. The subsequent analysis focused on the composition and assembly mechanisms of fish communities. The results demonstrated that: (1) The fish communities inhabiting the urban rivers of Guangzhou demonstrated notable biodiversity. The eDNA monitoring survey identified 15 orders, 39 families, and 139 species, whereas the conventional survey recorded 6 orders, 10 families, and 32 species (genera). The fish assemblage was predominantly composed of Cypriniformes, Gobiiformes, and Siluriformes, with invasive species such as Coptodon zillii demonstrating ecological dominance. (2) The analysis revealed that environmental factors accounted for 49.26% and 61.15% of the observed variance in community structure, as measured by eDNA and traditional survey data, respectively. Key water quality parameters, including pH, dissolved oxygen, and the permanganate index, exerted significant effects on the restructuring of fish communities. This underscores their pivotal role in shaping community diversity and spatial distribution patterns. (3) Analysis of community assembly mechanisms indicated that deterministic processes primarily governed the assembly of fish communities in Guangzhou's rivers, while the impact of stochastic processes, including dispersal limitation, remained significant.
The deterioration of water quality, loss of habitats, and degradation of ecosystems in urban rivers, caused by intensified urbanization, have significantly impacted aquatic biological communities, including fish. In order to establish effective conservation strategies for fish populations, it is imperative to undertake a comprehensive analysis of the relative contributions of stochastic and deterministic processes in community assembly. In this study, fish monitoring was conducted at 30 sampling sites in Guangzhou's urban rivers using both environmental DNA (eDNA) and traditional survey methods. The subsequent analysis focused on the composition and assembly mechanisms of fish communities. The results demonstrated that: (1) The fish communities inhabiting the urban rivers of Guangzhou demonstrated notable biodiversity. The eDNA monitoring survey identified 15 orders, 39 families, and 139 species, whereas the conventional survey recorded 6 orders, 10 families, and 32 species (genera). The fish assemblage was predominantly composed of Cypriniformes, Gobiiformes, and Siluriformes, with invasive species such as Coptodon zillii demonstrating ecological dominance. (2) The analysis revealed that environmental factors accounted for 49.26% and 61.15% of the observed variance in community structure, as measured by eDNA and traditional survey data, respectively. Key water quality parameters, including pH, dissolved oxygen, and the permanganate index, exerted significant effects on the restructuring of fish communities. This underscores their pivotal role in shaping community diversity and spatial distribution patterns. (3) Analysis of community assembly mechanisms indicated that deterministic processes primarily governed the assembly of fish communities in Guangzhou's rivers, while the impact of stochastic processes, including dispersal limitation, remained significant.
Guan Xiaoyu, Yan Hanlu, Yin Zhili, Chen Qiuwen, Huang Tiancheng, Liu Lingyan, Lin Yuqing, He Shufeng
2025,37(4):1128-1139, DOI: 10.18307/2025.0406
Abstract:
This study, conducted in Guizhou Province, China, utilized environmental DNA (eDNA) technology to conduct a fish diversity survey in 30 typical mountainous rivers across seven river systems. The results of the study revealed a total of 89 fish species, with 83 of these species being identified to the species level. The majority of the identified species belonged to the order Cypriniformes, including five exotic species and four rare or endangered species. It is noteworthy that at least 74 species (89.2% of those identified to the species level) have been previously documented in existing studies .With respect to their habitat, benthic and demersal fish were predominant, while omnivorous and carnivorous species were more prevalent based on their feeding habits.Cyprinus carpio, Carassius auratus, Hypophthalmichthys nobilisand Rhinogobius giurinu were found to be widely distributed, appearing in over 90% of the sampling sites. Fish diversity indices (Richness, Shannon-Wiener, Simpson, and Pielou) indicated favorable fish diversity conditions in the surveyed rivers, with no significant altitudinal gradient patterns observed in the diversity indices. Utilizing piecewise structural equation modelling, we conducted a comprehensive analysis of the factors influencing the four fish diversity indices. These factors included altitude, landscape type, physicochemical parameters, pollution indicators, ecological flow satisfaction, and human activities. The results of the analysis revealed that physicochemical parameters and pollution indicators emerged as the primary factors affecting fish diversity in the mountainous rivers of Guizhou Province. In contrast, human activities and ecological flow satisfaction were found to be secondary factors. Furthermore, an aggregated boosted treeanalysis was employed to assess the importance of various water quality parameters on fish diversity indices, revealing that water temperature, conductivity, and ammonia nitrogen were the primary water quality factors affecting fish diversity. Additionally, among the environmental factors examined, pollution indicators, human activities, and ecological flow satisfaction directly influenced fish diversity indices, whereas other factors exerted indirect effects. Notably, different diversity indices exhibited varying responses to the same environmental factors. This study provides methodological insights for fish diversity surveys in mountainous rivers and offers a data-driven foundation and theoretical support for the conservation of fish biodiversity in these ecosystems.
This study, conducted in Guizhou Province, China, utilized environmental DNA (eDNA) technology to conduct a fish diversity survey in 30 typical mountainous rivers across seven river systems. The results of the study revealed a total of 89 fish species, with 83 of these species being identified to the species level. The majority of the identified species belonged to the order Cypriniformes, including five exotic species and four rare or endangered species. It is noteworthy that at least 74 species (89.2% of those identified to the species level) have been previously documented in existing studies .With respect to their habitat, benthic and demersal fish were predominant, while omnivorous and carnivorous species were more prevalent based on their feeding habits.Cyprinus carpio, Carassius auratus, Hypophthalmichthys nobilisand Rhinogobius giurinu were found to be widely distributed, appearing in over 90% of the sampling sites. Fish diversity indices (Richness, Shannon-Wiener, Simpson, and Pielou) indicated favorable fish diversity conditions in the surveyed rivers, with no significant altitudinal gradient patterns observed in the diversity indices. Utilizing piecewise structural equation modelling, we conducted a comprehensive analysis of the factors influencing the four fish diversity indices. These factors included altitude, landscape type, physicochemical parameters, pollution indicators, ecological flow satisfaction, and human activities. The results of the analysis revealed that physicochemical parameters and pollution indicators emerged as the primary factors affecting fish diversity in the mountainous rivers of Guizhou Province. In contrast, human activities and ecological flow satisfaction were found to be secondary factors. Furthermore, an aggregated boosted treeanalysis was employed to assess the importance of various water quality parameters on fish diversity indices, revealing that water temperature, conductivity, and ammonia nitrogen were the primary water quality factors affecting fish diversity. Additionally, among the environmental factors examined, pollution indicators, human activities, and ecological flow satisfaction directly influenced fish diversity indices, whereas other factors exerted indirect effects. Notably, different diversity indices exhibited varying responses to the same environmental factors. This study provides methodological insights for fish diversity surveys in mountainous rivers and offers a data-driven foundation and theoretical support for the conservation of fish biodiversity in these ecosystems.
Ren Yichen, Fan Fangwei, Xi Yilong, Chen Feizhou, Li Yun, Ding Jianing, Gao Jiawei, Gu Yu, Li Huabing
2025,37(4):1140-1150, DOI: 10.18307/2025.0407
Abstract:
Zooplankton is an important component of aquatic ecosystems, and is sensitive to external disturbances and changes in the water environment. Monitoring its species diversity and community composition can not only help us better understand the dynamics of lake ecosystems, but also provide a scientific basis for water quality management, which is of great significance for understanding lake ecosystems. In recent years, environmental DNA (eDNA) metabarcoding technology has been increasingly used in biological surveys. However, whether the results based on eDNA technology are in line with those obtained through traditional morphological identification for detecting zooplankton diversity in the field, remains unclear. In this study, we conducted a 2-year seasonal field survey in 2014 and 2015 in Lake Fuxian, aiming to compare the results obtained by eDNA technology and morphological identification in detecting the species diversity and community composition of zooplankton. The results showed that: (1) the eDNA metabarcoding technology based on high-throughput sequencing of mitochondrial CytochromecOxidase Ⅰ gene ( COI ) and morphological identification obtained the same seasonal trend of alpha diversity (species richness and Shannon-Wiener index) changes of zooplankton in Lake Fuxian during our 2-year period of field monitoring; (2) Compared to morphological identification, eDNA technology based on COI gene high-throughput sequencing could detect more species; though the number of rotifer species identified at the genus level was lower than that identified by morphological methods; (3) Both methods found that the zooplankton community structure in Lake Fuxian exhibited temporal decay trends, but eDNA technology was more effective than morphological identification in distinguishing seasonal differences in zooplankton community composition. Despite the limitations of eDNA technology in detecting rotifer species and zooplankton biomass, it has a clear advantage in detecting seasonal variations in zooplankton diversity and community structure.This study attempted to apply eDNA technology to zooplankton detection in lakes using field anniversary monitoring samples, and confirmed that COI based eDNA technology has higher resolution in the discrimination of zooplankton community composition, but its database needs to be improved before promoting eDNA technology in zooplankton diversity research and water ecology monitoring.
Zooplankton is an important component of aquatic ecosystems, and is sensitive to external disturbances and changes in the water environment. Monitoring its species diversity and community composition can not only help us better understand the dynamics of lake ecosystems, but also provide a scientific basis for water quality management, which is of great significance for understanding lake ecosystems. In recent years, environmental DNA (eDNA) metabarcoding technology has been increasingly used in biological surveys. However, whether the results based on eDNA technology are in line with those obtained through traditional morphological identification for detecting zooplankton diversity in the field, remains unclear. In this study, we conducted a 2-year seasonal field survey in 2014 and 2015 in Lake Fuxian, aiming to compare the results obtained by eDNA technology and morphological identification in detecting the species diversity and community composition of zooplankton. The results showed that: (1) the eDNA metabarcoding technology based on high-throughput sequencing of mitochondrial CytochromecOxidase Ⅰ gene ( COI ) and morphological identification obtained the same seasonal trend of alpha diversity (species richness and Shannon-Wiener index) changes of zooplankton in Lake Fuxian during our 2-year period of field monitoring; (2) Compared to morphological identification, eDNA technology based on COI gene high-throughput sequencing could detect more species; though the number of rotifer species identified at the genus level was lower than that identified by morphological methods; (3) Both methods found that the zooplankton community structure in Lake Fuxian exhibited temporal decay trends, but eDNA technology was more effective than morphological identification in distinguishing seasonal differences in zooplankton community composition. Despite the limitations of eDNA technology in detecting rotifer species and zooplankton biomass, it has a clear advantage in detecting seasonal variations in zooplankton diversity and community structure.This study attempted to apply eDNA technology to zooplankton detection in lakes using field anniversary monitoring samples, and confirmed that COI based eDNA technology has higher resolution in the discrimination of zooplankton community composition, but its database needs to be improved before promoting eDNA technology in zooplankton diversity research and water ecology monitoring.
2025,37(4):1151-1161, DOI: 10.18307/2025.0405
Abstract:
Environmental DNA (eDNA) technology has emerged as a revolutionary tool in the ecology research, yet its application in phytoplankton monitoring remains relatively limited. To investigate the impact of human activity on phytoplankton communities in plateau wetlands, water samples were collected from both the north side (high-disturbed area of anthropogenic activities) and south side (low-disturbed area) of Lake Caohai, Guizhou Province. The composition, biodiversity, and environmental correlation of the phytoplankton community were analyzed by the techniques of metagenomics combined with eDNA. Results showed that the phytoplankton communities in Lake Caohai included 9 phyla, 58 families, 101 genera, and 152 species. In the taxa of phylum, Cyanophyta was dominant with an average percentage of 93.57%±3.06%. At genus level,Microcystis ,Aphanizomenon, Cyanobium , andSnowellawere dominant. While at the species level,Microcystis aeruginosaandAphanizomenon flos-aquaewere dominant. Furthermore, it was observed that areas high disturbed exhibited significantly lower biodiversity in phytoplankton communities compared to low-disturbed areas. Principal component analysis (PCA) indicated distinct differences in phytoplankton community composition between the two regions. LEfSe analysis further revealed that Microcystaceae, Synechococcaceae and Coelosphaeriaceae were the biomarkers in the high-disturbed area, while Aphanizomenonaceae, and Microcoleaceae in the low-disturbance area. Mantel test analysis, co-occurrence network analysis, and redundancy analysis (RDA) showed that total phosphorus was the key environmental factor affecting phytoplankton communities. Human activities influenced the biomass, biodiversity, and community structure of phytoplankton by changing the key water environment such as total phosphorus and total dissolved solids. In this paper, eDNA metagenomics technology was employed to elucidate the phytoplankton communities changes in Lake Caohai Wetland under different human activities, and provided valuable insights for the application of this technology in biological monitoring and phytoplankton assessment in plateau wetlands.
Environmental DNA (eDNA) technology has emerged as a revolutionary tool in the ecology research, yet its application in phytoplankton monitoring remains relatively limited. To investigate the impact of human activity on phytoplankton communities in plateau wetlands, water samples were collected from both the north side (high-disturbed area of anthropogenic activities) and south side (low-disturbed area) of Lake Caohai, Guizhou Province. The composition, biodiversity, and environmental correlation of the phytoplankton community were analyzed by the techniques of metagenomics combined with eDNA. Results showed that the phytoplankton communities in Lake Caohai included 9 phyla, 58 families, 101 genera, and 152 species. In the taxa of phylum, Cyanophyta was dominant with an average percentage of 93.57%±3.06%. At genus level,Microcystis ,Aphanizomenon, Cyanobium , andSnowellawere dominant. While at the species level,Microcystis aeruginosaandAphanizomenon flos-aquaewere dominant. Furthermore, it was observed that areas high disturbed exhibited significantly lower biodiversity in phytoplankton communities compared to low-disturbed areas. Principal component analysis (PCA) indicated distinct differences in phytoplankton community composition between the two regions. LEfSe analysis further revealed that Microcystaceae, Synechococcaceae and Coelosphaeriaceae were the biomarkers in the high-disturbed area, while Aphanizomenonaceae, and Microcoleaceae in the low-disturbance area. Mantel test analysis, co-occurrence network analysis, and redundancy analysis (RDA) showed that total phosphorus was the key environmental factor affecting phytoplankton communities. Human activities influenced the biomass, biodiversity, and community structure of phytoplankton by changing the key water environment such as total phosphorus and total dissolved solids. In this paper, eDNA metagenomics technology was employed to elucidate the phytoplankton communities changes in Lake Caohai Wetland under different human activities, and provided valuable insights for the application of this technology in biological monitoring and phytoplankton assessment in plateau wetlands.
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000-000, DOI: 10.18307/2026.0142
Available online: July 25, 2025
Abstract:
The impact of the "four colliding" typhoons has become the focus of attention in the disaster prevention and reduction system in the Taihu basin. However, the risk impact of wind, storm, tide, and flood brought by it on the safety of flood prevention is still unclear. It is considerable to carry out the analysis of rainstorm, flood and its movement caused by the typical typhoon of "four colliding".It takes the two typical typhoons "Fitow" and "In-Fa" since 1990 as samples, and other typhoons with two or three colliding as references. Based on hydrological and engineering data, the impact of "four colliding" typhoons is compared. The results showed that: (1) The "four colliding" typhoons all caused extreme rainfall, with a large total amount and wide range, resulting in the rainfall that was more than 70% higher than the average of the two and three colliding typhoons. The higher part was basically the same as the rainfall caused by typhoon Morakot in 2009. (2) The water levels of the Taihu Lake has risen by the second and third place respectively since 1949. In particular, "In-Fa" caused numbered floods, and the maximum tilt of the Taihu Lake was more than 1.00 m. The highest water (tide) level of 33 sites in the river network broke the historical records, and the high water levels lasted for a long time, which seriously threatened the safety of regional flood prevention. (3) It was dominated by storage during "Fitow", and then the drainage capacity of backbone projects was significantly enhanced. During "In-Fa", the flood movement pattern changed to both storage and drainage, with the storage and drainage ratio changing from 1:0.6 to 1:1.1, and the proportion of drainage increased. (4) During the rainstorm of the two typhoons, the drainage was obviously restricted by the astronomical spring tide jacking. After the rainfall stopped and the astronomical spring tide passed, the drainage of the backbone projects increased significantly, especially the Yangtze river to the north and the Huangpu river to the east. (5) Although the drainage capacity of the backbone projects has been significantly strengthened, it still needs to be further improved in the face of the "four colliding" typhoon and the transfer of regional flood disaster risks. The research results could provide a reference for the scientific defense of the "four colliding" typhoon in the Taihu basin in the future.
The impact of the "four colliding" typhoons has become the focus of attention in the disaster prevention and reduction system in the Taihu basin. However, the risk impact of wind, storm, tide, and flood brought by it on the safety of flood prevention is still unclear. It is considerable to carry out the analysis of rainstorm, flood and its movement caused by the typical typhoon of "four colliding".It takes the two typical typhoons "Fitow" and "In-Fa" since 1990 as samples, and other typhoons with two or three colliding as references. Based on hydrological and engineering data, the impact of "four colliding" typhoons is compared. The results showed that: (1) The "four colliding" typhoons all caused extreme rainfall, with a large total amount and wide range, resulting in the rainfall that was more than 70% higher than the average of the two and three colliding typhoons. The higher part was basically the same as the rainfall caused by typhoon Morakot in 2009. (2) The water levels of the Taihu Lake has risen by the second and third place respectively since 1949. In particular, "In-Fa" caused numbered floods, and the maximum tilt of the Taihu Lake was more than 1.00 m. The highest water (tide) level of 33 sites in the river network broke the historical records, and the high water levels lasted for a long time, which seriously threatened the safety of regional flood prevention. (3) It was dominated by storage during "Fitow", and then the drainage capacity of backbone projects was significantly enhanced. During "In-Fa", the flood movement pattern changed to both storage and drainage, with the storage and drainage ratio changing from 1:0.6 to 1:1.1, and the proportion of drainage increased. (4) During the rainstorm of the two typhoons, the drainage was obviously restricted by the astronomical spring tide jacking. After the rainfall stopped and the astronomical spring tide passed, the drainage of the backbone projects increased significantly, especially the Yangtze river to the north and the Huangpu river to the east. (5) Although the drainage capacity of the backbone projects has been significantly strengthened, it still needs to be further improved in the face of the "four colliding" typhoon and the transfer of regional flood disaster risks. The research results could provide a reference for the scientific defense of the "four colliding" typhoon in the Taihu basin in the future.
000-000, DOI: 10.18307/2026.0114
Available online: July 25, 2025
Abstract:
In agricultural watersheds across China, small water bodies serve as important phosphorus retention and storage sites, acting as protective barriers for rivers and lakes. However, under conditions of long-term phosphorus accumulation and specific environmental factors, there is a risk of phosphorus release. Currently, there is a lack of research on the phosphorus release risk of small water bodies and on the dynamic changes in phosphorus retention and release, as well as the influencing factors, through long-term experiments. This study focuses on a typical agricultural watershed and conducts sediment sampling from 4 types of ponds, along with a 6-month static incubation experiment. The study analyzes the phosphorus forms in sediments and the phosphorus exchange dynamics at the sediment-water interface, assessing the phosphorus release risk of the ponds and its influencing factors. The results showed that: (1) The total phosphorus (TP) content in pond sediments ranged from 0.55 to 3.02 g/kg, higher than that of other types of wetlands. The highest phosphorus content was found in village ponds, while the lowest was observed in paddy ponds. (2) In agricultural watersheds of the middle and lower reaches of the Yangtze River, and under the condition of long-term existence of ponds, the phosphorus exchange at the sediment-overlying water interface exhibits significant seasonal variations: sediments release phosphorus to the overlying water in summer and autumn, while phosphorus settles from the overlying water to the sediments in autumn and winter. Given similar years of existence, the phosphorus sink capacity of ponds decreases in the following order: forest pond > paddy pond = dryland pond > village pond. This study revealed the large phosphorus accumulation in agricultural ponds in China, highlighting their long-term function as phosphorus sinks that transform into phosphorus sources during the summer and autumn. The findings also clarified the influence of surrounding land use types and provided scientific guidance for improving management strategies for different pond types. These insights are widely applicable to non-point source pollution control and the protection of aquatic environments in rivers and lakes.
In agricultural watersheds across China, small water bodies serve as important phosphorus retention and storage sites, acting as protective barriers for rivers and lakes. However, under conditions of long-term phosphorus accumulation and specific environmental factors, there is a risk of phosphorus release. Currently, there is a lack of research on the phosphorus release risk of small water bodies and on the dynamic changes in phosphorus retention and release, as well as the influencing factors, through long-term experiments. This study focuses on a typical agricultural watershed and conducts sediment sampling from 4 types of ponds, along with a 6-month static incubation experiment. The study analyzes the phosphorus forms in sediments and the phosphorus exchange dynamics at the sediment-water interface, assessing the phosphorus release risk of the ponds and its influencing factors. The results showed that: (1) The total phosphorus (TP) content in pond sediments ranged from 0.55 to 3.02 g/kg, higher than that of other types of wetlands. The highest phosphorus content was found in village ponds, while the lowest was observed in paddy ponds. (2) In agricultural watersheds of the middle and lower reaches of the Yangtze River, and under the condition of long-term existence of ponds, the phosphorus exchange at the sediment-overlying water interface exhibits significant seasonal variations: sediments release phosphorus to the overlying water in summer and autumn, while phosphorus settles from the overlying water to the sediments in autumn and winter. Given similar years of existence, the phosphorus sink capacity of ponds decreases in the following order: forest pond > paddy pond = dryland pond > village pond. This study revealed the large phosphorus accumulation in agricultural ponds in China, highlighting their long-term function as phosphorus sinks that transform into phosphorus sources during the summer and autumn. The findings also clarified the influence of surrounding land use types and provided scientific guidance for improving management strategies for different pond types. These insights are widely applicable to non-point source pollution control and the protection of aquatic environments in rivers and lakes.
000-000, DOI: 10.18307/2026.0135
Available online: July 22, 2025
Abstract:
Poyang Lake, China’s largest freshwater lake, serves as a crucial wintering ground for geese of East Asian. This study employed satellite tracking data from 2019 to 2024 to analyze the migratory phenology and spatial distribution patterns of Greater White-fronted Goose Anser albifrons, Swan Goose Anser cygnoides, and Bean Goose Anser fabalis. By integrating duration and home range data, we quantified the importance of Poyang Lake’s sub-lakes to these species. Our results demonstrate phenological differences in arrival and departure timing among the goose species. Greater White-fronted Geese arrived earliest (October 16th to October 28th), followed by Swan Geese (October 9th to November 30th), with Bean Geese arriving latest (November 1st to November 17th). The average overwintering duration in Poyang Lake was approximately 149±8 days for Greater White-fronted Geese, 123±7 days for Bean Geese, and 128±26 days for Swan Geese. Analysis of migratory timing dynamics revealed relative stability and low interannual variation for Greater White-fronted and Bean Geese, while Swan Geese exhibited greater interannual variability. Spatially, protected areas remained the most important distribution areas for geese. However, increasing duration and home range expansion outside of protected areas were observed, particularly for Bean and Swan Geese. This study quantified the duration and spatial utilization of geese in sub-lakes, highlighting their ecological role in supporting migratory goose populations. It also identified important conservation areas for geese and determined protection gaps. We recommend expanding protected area boundaries to cover existing protection gaps and strengthening habitat management measures both inside and outside protected areas to ensure the long-term sustainability of these important wintering habitats. This research provides scientific support for identifying critical habitats and developing targeted conservation strategies for geese and their habitats.
Poyang Lake, China’s largest freshwater lake, serves as a crucial wintering ground for geese of East Asian. This study employed satellite tracking data from 2019 to 2024 to analyze the migratory phenology and spatial distribution patterns of Greater White-fronted Goose Anser albifrons, Swan Goose Anser cygnoides, and Bean Goose Anser fabalis. By integrating duration and home range data, we quantified the importance of Poyang Lake’s sub-lakes to these species. Our results demonstrate phenological differences in arrival and departure timing among the goose species. Greater White-fronted Geese arrived earliest (October 16th to October 28th), followed by Swan Geese (October 9th to November 30th), with Bean Geese arriving latest (November 1st to November 17th). The average overwintering duration in Poyang Lake was approximately 149±8 days for Greater White-fronted Geese, 123±7 days for Bean Geese, and 128±26 days for Swan Geese. Analysis of migratory timing dynamics revealed relative stability and low interannual variation for Greater White-fronted and Bean Geese, while Swan Geese exhibited greater interannual variability. Spatially, protected areas remained the most important distribution areas for geese. However, increasing duration and home range expansion outside of protected areas were observed, particularly for Bean and Swan Geese. This study quantified the duration and spatial utilization of geese in sub-lakes, highlighting their ecological role in supporting migratory goose populations. It also identified important conservation areas for geese and determined protection gaps. We recommend expanding protected area boundaries to cover existing protection gaps and strengthening habitat management measures both inside and outside protected areas to ensure the long-term sustainability of these important wintering habitats. This research provides scientific support for identifying critical habitats and developing targeted conservation strategies for geese and their habitats.
000-000, DOI: 10.18307/2026.0152
Available online: July 22, 2025
Abstract:
The Songzi River is one of the primary channels through which the Jingjiang River diverts water into Dongting Lake, and changes in its water diversion have significant implications for flood control in the river-lake system, water resource utilization, and water environmental ecology. Based on analysis of measured data and physical model experiments, this study investigates the relationships among water-sediment evolution, riverbed scouring, and diversion changes in the Yangtze main channel and Songzi Mouth reach following the operation of the Three Gorges Project.The results show that compared with the period from 1990 to 2002, the annual average sediment transport at Zhicheng Station decreased by approximately 90.6% during 2003–2022, with a synchronous reduction of about 87.1% in sediment diversion at Songzi Mouth. From 2003 to 2022, the bankfull channel between Zhicheng and Yangjiaonao experienced a total scouring volume of 239 million m3, with an average scouring depth of 2.3 m, leading to significant riverbed coarsening. In contrast, the bankfull channel at the Songzi Mouth reach was scoured by 43.25 million m3, with an average scouring depth of 3.0 m, forming a differential scouring rate compared to the pebble-sand mixed bed in the main channel.Physical model predictions indicate that long-term action of subsaturated flow will cause continuous downcutting of the sandy riverbed downstream of Yangjiaonao in the Yangtze main channel, leading to progressive declines in water levels at Yangjiaonao and corresponding reductions in diversion at Songzi Mouth. For a discharge of 7000 m3/s at Zhicheng Station, water levels at Yangjiaonao are projected to decrease by 1.58 m and 2.57 m in 2035 and 2050, respectively, resulting in diversion reductions of 8.3% and 16.7%. However, asymmetric scouring between the inner and outer parts of the mouth (with higher scouring rates in the sandy mouth reach, expanding the cross-sectional flow area) leads to increased diversion at Songzi Mouth by the end of 2035, even considering the water level decline at Yangjiaonao. During low-flow periods (with a discharge of 7000 m3/s at Zhicheng Station), diversion actually increases by 20.8%, with contribution rates of -33% from the Yangjiaonao water level drop and 133% from asymmetric mouth scouring. As the discharge increases, the absolute values of both contribution rates rise significantly, but their combined effect results in minimal net change in diversion volume, suggesting that these influences are primarily concentrated during medium- to low-flow periods.The differential riverbed composition regulates the scouring process and maintains stable diversion at Songzi Mouth. Increased low-flow diversion is beneficial for water resource allocation in Dongting Lake, but it may moderately lower main channel water levels and affect navigation during medium- to low-flow periods.
The Songzi River is one of the primary channels through which the Jingjiang River diverts water into Dongting Lake, and changes in its water diversion have significant implications for flood control in the river-lake system, water resource utilization, and water environmental ecology. Based on analysis of measured data and physical model experiments, this study investigates the relationships among water-sediment evolution, riverbed scouring, and diversion changes in the Yangtze main channel and Songzi Mouth reach following the operation of the Three Gorges Project.The results show that compared with the period from 1990 to 2002, the annual average sediment transport at Zhicheng Station decreased by approximately 90.6% during 2003–2022, with a synchronous reduction of about 87.1% in sediment diversion at Songzi Mouth. From 2003 to 2022, the bankfull channel between Zhicheng and Yangjiaonao experienced a total scouring volume of 239 million m3, with an average scouring depth of 2.3 m, leading to significant riverbed coarsening. In contrast, the bankfull channel at the Songzi Mouth reach was scoured by 43.25 million m3, with an average scouring depth of 3.0 m, forming a differential scouring rate compared to the pebble-sand mixed bed in the main channel.Physical model predictions indicate that long-term action of subsaturated flow will cause continuous downcutting of the sandy riverbed downstream of Yangjiaonao in the Yangtze main channel, leading to progressive declines in water levels at Yangjiaonao and corresponding reductions in diversion at Songzi Mouth. For a discharge of 7000 m3/s at Zhicheng Station, water levels at Yangjiaonao are projected to decrease by 1.58 m and 2.57 m in 2035 and 2050, respectively, resulting in diversion reductions of 8.3% and 16.7%. However, asymmetric scouring between the inner and outer parts of the mouth (with higher scouring rates in the sandy mouth reach, expanding the cross-sectional flow area) leads to increased diversion at Songzi Mouth by the end of 2035, even considering the water level decline at Yangjiaonao. During low-flow periods (with a discharge of 7000 m3/s at Zhicheng Station), diversion actually increases by 20.8%, with contribution rates of -33% from the Yangjiaonao water level drop and 133% from asymmetric mouth scouring. As the discharge increases, the absolute values of both contribution rates rise significantly, but their combined effect results in minimal net change in diversion volume, suggesting that these influences are primarily concentrated during medium- to low-flow periods.The differential riverbed composition regulates the scouring process and maintains stable diversion at Songzi Mouth. Increased low-flow diversion is beneficial for water resource allocation in Dongting Lake, but it may moderately lower main channel water levels and affect navigation during medium- to low-flow periods.
Available online: July 17, 2025
Abstract:
Surface water-heat-carbon fluxes are critical indicators reflecting the water-carbon cycles in lake ecosystems under changing climates, yet the impact of extreme environmental conditions such as drought on these processes remains to be further clarified. Poyang Lake is the largest freshwater lake in China and an internationally important wetland. It is not only a key node for the regulation of water resources in the Yangtze River Basin, but also plays an important role in the global carbon cycle and water cycle. In 2022, a rare consecutive meteorological drought event occurred in the Poyang Lake Basin during the summer and autumn seasons, and the most severe drought since 1949 hit the lake area. In this study, the multi-year monitoring data from the eddy covariance instrument at the Poyang Lake Wetland Observation and Research Station were adopted. The station is located on the beach of Poyang Lake (29°27" N, 116°03" E), and it has been continuously monitoring the variation processes of the water-heat-carbon fluxes in the lake since 2015. This study analyzed the variation patterns of water-heat-carbon fluxes and their response characteristics to the extreme drought event in Poyang Lake, in 2022. The results showed that: (1) On an annual scale, the latent heat flux was relatively high from July to September, with the peak value occurring in August, and the annual average value was 49.5 W/m2. The sensible heat flux was relatively high from September to November, with the peak value occurring in October, and the annual average value was 10.6 W/m2. The CO? flux exhibited obvious seasonal variations, and the carbon source and carbon sink shifted with hydrometeorological factors such as water level and net radiation. The annual CO? flux average value was 15.0 μmol·m?2·s?1. (2) On a daily scale, the sensible heat and latent heat fluxes were basically synchronous, showing a single peak at noon, while the CO? flux had a single peak at night. (3) The extreme drought event significantly intensified the carbon source effect of the wetland ecosystem by changing the energy allocation pattern. During the drought period, the latent heat flux, sensible heat flux, and CO? flux increased to 1.23 times, 1.78 times, and 5.44 times of the average values in the same historical period, respectively. (4) The correlation analysis showed that air temperature, wind speed, net radiation, precipitation, relative humidity, NDVI, and water level were the main factors affecting the water-heat-carbon fluxes. The stepwise regression analysis further revealed the influence mechanisms of various factors on the fluxes under different periods and underlying surface conditions. During the extreme drought period, when the underlying surface was water body, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: wind speed, air temperature > relative humidity > net radiation, water level. When the underlying surface was the beach, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: air temperature > wind speed, wind speed > NDVI, air temperature > VPD > precipitation. The extreme drought event mainly promoted the energy allocation to the sensible heat flux through the increase of air temperature, wind speed, and net radiation, and significantly stimulated the CO? release. This study revealed the response mechanisms of water-heat-carbon fluxes in lakes to extreme climate events and provided a scientific basis for predicting the responses of lake ecosystems under future climate change scenarios.
Surface water-heat-carbon fluxes are critical indicators reflecting the water-carbon cycles in lake ecosystems under changing climates, yet the impact of extreme environmental conditions such as drought on these processes remains to be further clarified. Poyang Lake is the largest freshwater lake in China and an internationally important wetland. It is not only a key node for the regulation of water resources in the Yangtze River Basin, but also plays an important role in the global carbon cycle and water cycle. In 2022, a rare consecutive meteorological drought event occurred in the Poyang Lake Basin during the summer and autumn seasons, and the most severe drought since 1949 hit the lake area. In this study, the multi-year monitoring data from the eddy covariance instrument at the Poyang Lake Wetland Observation and Research Station were adopted. The station is located on the beach of Poyang Lake (29°27" N, 116°03" E), and it has been continuously monitoring the variation processes of the water-heat-carbon fluxes in the lake since 2015. This study analyzed the variation patterns of water-heat-carbon fluxes and their response characteristics to the extreme drought event in Poyang Lake, in 2022. The results showed that: (1) On an annual scale, the latent heat flux was relatively high from July to September, with the peak value occurring in August, and the annual average value was 49.5 W/m2. The sensible heat flux was relatively high from September to November, with the peak value occurring in October, and the annual average value was 10.6 W/m2. The CO? flux exhibited obvious seasonal variations, and the carbon source and carbon sink shifted with hydrometeorological factors such as water level and net radiation. The annual CO? flux average value was 15.0 μmol·m?2·s?1. (2) On a daily scale, the sensible heat and latent heat fluxes were basically synchronous, showing a single peak at noon, while the CO? flux had a single peak at night. (3) The extreme drought event significantly intensified the carbon source effect of the wetland ecosystem by changing the energy allocation pattern. During the drought period, the latent heat flux, sensible heat flux, and CO? flux increased to 1.23 times, 1.78 times, and 5.44 times of the average values in the same historical period, respectively. (4) The correlation analysis showed that air temperature, wind speed, net radiation, precipitation, relative humidity, NDVI, and water level were the main factors affecting the water-heat-carbon fluxes. The stepwise regression analysis further revealed the influence mechanisms of various factors on the fluxes under different periods and underlying surface conditions. During the extreme drought period, when the underlying surface was water body, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: wind speed, air temperature > relative humidity > net radiation, water level. When the underlying surface was the beach, the importance ranking of the influencing factors for the latent heat flux, sensible heat flux, and CO? flux was: air temperature > wind speed, wind speed > NDVI, air temperature > VPD > precipitation. The extreme drought event mainly promoted the energy allocation to the sensible heat flux through the increase of air temperature, wind speed, and net radiation, and significantly stimulated the CO? release. This study revealed the response mechanisms of water-heat-carbon fluxes in lakes to extreme climate events and provided a scientific basis for predicting the responses of lake ecosystems under future climate change scenarios.
Available online: July 17, 2025
Abstract:
Water quality is a key factor in safeguarding ecosystem functions, protecting human health, and achieving sustainable development. Land use characteristics (including type, intensity, and landscape configuration) serve as important indicators of human activity and have significant impacts on river water quality, which vary across different spatial and temporal scales. This study focuses on the source region of the Chishui River and integrates two spatial scales: riparian buffer and sub-watershed. By applying variation partitioning analysis (VPA) and random forest modeling, we comprehensively quantify the independent and combined contributions of land use type, intensity, and landscape pattern to water quality, while identifying key influencing factors and their corresponding spatial scales. The results show that:① Landscape pattern is the dominant factor affecting water quality (explaining 33–58% of the variation), followed by land use type (11–22%) and intensity (4–16%);② Riparian landscape configuration exerts a more significant influence on water quality, while land use intensity at the sub-watershed scale provides stronger explanatory power;③ The proportion of built-up land, construction intensity (LUI_Con), and agricultural intensity (LUI_Cul) are key predictors of water quality, while forest cover and landscape connectivity play important roles in reducing TN and COD concentrations. These findings suggest that watershed water quality management should consider land use characteristics at multiple scales to identify optimal combinations of riparian and sub-watershed interventions. Specifically, we recommend prioritizing the control of industrial and domestic point-source pollution at the riparian scale, while enhancing agricultural non-point source management at the sub-watershed scale—thus forming an integrated "point-source and non-point source" control system. This study offers new empirical evidence on the multidimensional interactions and scale effects of land use–water quality relationships, providing important theoretical and practical insights for watershed resource protection and spatial planning optimization.
Water quality is a key factor in safeguarding ecosystem functions, protecting human health, and achieving sustainable development. Land use characteristics (including type, intensity, and landscape configuration) serve as important indicators of human activity and have significant impacts on river water quality, which vary across different spatial and temporal scales. This study focuses on the source region of the Chishui River and integrates two spatial scales: riparian buffer and sub-watershed. By applying variation partitioning analysis (VPA) and random forest modeling, we comprehensively quantify the independent and combined contributions of land use type, intensity, and landscape pattern to water quality, while identifying key influencing factors and their corresponding spatial scales. The results show that:① Landscape pattern is the dominant factor affecting water quality (explaining 33–58% of the variation), followed by land use type (11–22%) and intensity (4–16%);② Riparian landscape configuration exerts a more significant influence on water quality, while land use intensity at the sub-watershed scale provides stronger explanatory power;③ The proportion of built-up land, construction intensity (LUI_Con), and agricultural intensity (LUI_Cul) are key predictors of water quality, while forest cover and landscape connectivity play important roles in reducing TN and COD concentrations. These findings suggest that watershed water quality management should consider land use characteristics at multiple scales to identify optimal combinations of riparian and sub-watershed interventions. Specifically, we recommend prioritizing the control of industrial and domestic point-source pollution at the riparian scale, while enhancing agricultural non-point source management at the sub-watershed scale—thus forming an integrated "point-source and non-point source" control system. This study offers new empirical evidence on the multidimensional interactions and scale effects of land use–water quality relationships, providing important theoretical and practical insights for watershed resource protection and spatial planning optimization.
Available online: July 17, 2025
Abstract:
The sediment peak regulation (SPR) in the Three Gorges Reservoir (TGR) during flood season can significantly improve the sediment discharge effect. Studying the control indicators of SPR is of great importance for ensuring the safety of reservoir storage capacity and improving the comprehensive benefits of reservoir. On the basis of data recorded at hydrological stations in the TGR between 2003 and 2023, the characteristics of sediment transport during flood season in the reservoir were identified. After the impoundment of cascade reservoirs in the lower reaches of Jinsha River, the start-up control and process regulation indicators of the SPR in the TGR were discussed. The results indicate that the amount of sediment entering the TGR was greatly reduced since the cascade reservoirs in the lower reaches of Jinsha River were impounded. Sediment transport in the TGR occurred mainly during flood events. The main consideration is to start the SPR for the floods with forecasted peak discharge at Cuntan station not less than 50,000 m3/s or forecasted peak sediment concentration at Cuntan station not less than 1.5 kg/m3, and forecasted 7-day average sediment concentration at Cuntan station not less than 0.5kg/m3. With flood control safety as the premise, and taking into account the multi-objective benefit of the reservoir and the measured flow and sediment conditions during the SPR, dynamic scheduling can be implemented according to the dispatching strategies of the three periods: water discharge peak blocking, sediment transport in the reservoir, and sediment discharge in front of the dam. In addition, real-time monitoring and forecasting of sediment during flood season is the basis of SPR. It is necessary to continuously optimize the sediment monitoring and forecasting technologies, so as to accurately control the start time and regulation process of SPR, and improve the comprehensive benefits of the TGR. This study can provide technical support for the optimization and refinement of SPR in the TGR during flood season.
The sediment peak regulation (SPR) in the Three Gorges Reservoir (TGR) during flood season can significantly improve the sediment discharge effect. Studying the control indicators of SPR is of great importance for ensuring the safety of reservoir storage capacity and improving the comprehensive benefits of reservoir. On the basis of data recorded at hydrological stations in the TGR between 2003 and 2023, the characteristics of sediment transport during flood season in the reservoir were identified. After the impoundment of cascade reservoirs in the lower reaches of Jinsha River, the start-up control and process regulation indicators of the SPR in the TGR were discussed. The results indicate that the amount of sediment entering the TGR was greatly reduced since the cascade reservoirs in the lower reaches of Jinsha River were impounded. Sediment transport in the TGR occurred mainly during flood events. The main consideration is to start the SPR for the floods with forecasted peak discharge at Cuntan station not less than 50,000 m3/s or forecasted peak sediment concentration at Cuntan station not less than 1.5 kg/m3, and forecasted 7-day average sediment concentration at Cuntan station not less than 0.5kg/m3. With flood control safety as the premise, and taking into account the multi-objective benefit of the reservoir and the measured flow and sediment conditions during the SPR, dynamic scheduling can be implemented according to the dispatching strategies of the three periods: water discharge peak blocking, sediment transport in the reservoir, and sediment discharge in front of the dam. In addition, real-time monitoring and forecasting of sediment during flood season is the basis of SPR. It is necessary to continuously optimize the sediment monitoring and forecasting technologies, so as to accurately control the start time and regulation process of SPR, and improve the comprehensive benefits of the TGR. This study can provide technical support for the optimization and refinement of SPR in the TGR during flood season.
Available online: July 15, 2025
Abstract:
There is highly risk of odorous compounds trouble in drinking water source reservoirs in the Changjiang River catchment in later spring. However, the key drivers for the odorous compound occurrence are remain unclear. During May 2024, we investigated nine drinking water source reservoirs across the upper, middle and lower reaches of the Changjiang River, measuring four odorous compounds, included 2-methylisoborneol (2-MIB), geosmin (GSM), β-cyclocitral (CYC) and β-ionone (ION), along with associated environmental factors. Results showed that 2-MIB was the most common odorous compound, with an average concentration of 35.5 ng/L across the 32 samples from 9 reservoirs (59.4 % exceeding the detection threshold of 10.0 ng/L). In contrast, GSM posed a lower risk, with an average concentration of 2.9 ng/L and only 12.5 % exceeding the threshold value of 10 ng/L, while CYC (averaged at 18.2 ng/L) and ION (averaged at 7.2 ng/L) exhibited minimal odorous concerns. Pseudanabaena sp. was identified as a likely major producer of 2-MIB, with its cell density showing a significant positive correlation with the concentration of 2-MIB. However, the presence of 2-MIB in two reservoirs without detectable Pseudanabaena suggests more complex 2-MIB sources in some reservoirs. Furthermore, 2-MIB levels were also positively related to the trophic state index (TSI), indicating that eutrophication could promoted 2-MIB production. Rainfall amount in 7 days ahead the sampling (RF7) was negative relative to 2-MIB concentration, suggested that short-term weather condition also influence the odorous situation in reservoirs. Despite generally mesotrophic conditions, the widespread 2-MIB exceedances highlight a persistent risk in these reservoirs. To ensure drinking water quality, measures such as reducing external nutrient loads and optimizing aquatic food webs are recommended.
There is highly risk of odorous compounds trouble in drinking water source reservoirs in the Changjiang River catchment in later spring. However, the key drivers for the odorous compound occurrence are remain unclear. During May 2024, we investigated nine drinking water source reservoirs across the upper, middle and lower reaches of the Changjiang River, measuring four odorous compounds, included 2-methylisoborneol (2-MIB), geosmin (GSM), β-cyclocitral (CYC) and β-ionone (ION), along with associated environmental factors. Results showed that 2-MIB was the most common odorous compound, with an average concentration of 35.5 ng/L across the 32 samples from 9 reservoirs (59.4 % exceeding the detection threshold of 10.0 ng/L). In contrast, GSM posed a lower risk, with an average concentration of 2.9 ng/L and only 12.5 % exceeding the threshold value of 10 ng/L, while CYC (averaged at 18.2 ng/L) and ION (averaged at 7.2 ng/L) exhibited minimal odorous concerns. Pseudanabaena sp. was identified as a likely major producer of 2-MIB, with its cell density showing a significant positive correlation with the concentration of 2-MIB. However, the presence of 2-MIB in two reservoirs without detectable Pseudanabaena suggests more complex 2-MIB sources in some reservoirs. Furthermore, 2-MIB levels were also positively related to the trophic state index (TSI), indicating that eutrophication could promoted 2-MIB production. Rainfall amount in 7 days ahead the sampling (RF7) was negative relative to 2-MIB concentration, suggested that short-term weather condition also influence the odorous situation in reservoirs. Despite generally mesotrophic conditions, the widespread 2-MIB exceedances highlight a persistent risk in these reservoirs. To ensure drinking water quality, measures such as reducing external nutrient loads and optimizing aquatic food webs are recommended.
kongjie, zhouzhongfa, wangyanbi, lirui, lili, zhangxinyue, dingcaixia, xierukai, sunyaopeng, caoweitang
Available online: July 15, 2025
Abstract:
The influx of a large amount of sulfate (SO42-) into water bodies can deteriorate the water environment quality. During the period from 2019 to 2023, water samples from the Pingzhai Reservoir Basin in the southwestern karst area, precipitation samples, and sewage samples were collected. The physical and chemical indicators of the water bodies, as well as the characteristics of sulfate sulfur and oxygen isotopes (δ34SSO4, δ18OSO4), hydrogen and oxygen isotopes of water (δDH2O, δ18OH2O), and dissolved inorganic carbon isotopes (δ13CDIC) were analyzed during the monitoring period. Qualitative and quantitative studies on the sources of SO42- in the water bodies were carried out. The hydrochemical types of the basin are mainly of the Ca-HCO3 type and Ca-HCO3-SO4 type, and the hydrochemical characteristics are influenced by the dissolution of carbonate rocks. Isotope characteristics reveal that the biogeochemical process of SO42- in the Pingzhai Reservoir Basin is dominated by oxidation (when sulfides are oxidized, on average, 61% of the oxygen comes from the surrounding water bodies). During the monitoring period, the sources of SO42- in the basin are mainly sulfide oxidation, soil organic sulfur, and agricultural sulfur fertilizers. The results of quantitative calculations show that sulfide oxidation has the highest average contribution rate (72.9%), followed by soil organic sulfur (14.1%) and agricultural sulfur fertilizers (12.9%). The results of uncertainty analysis indicate that the contribution rate of agricultural sulfur fertilizers is the most stable, while that of sulfide oxidation shows relatively large uncertainty. The research results can provide data reference and scientific basis for the protection of water environment quality in the Pingzhai Reservoir and similar karst areas.
The influx of a large amount of sulfate (SO42-) into water bodies can deteriorate the water environment quality. During the period from 2019 to 2023, water samples from the Pingzhai Reservoir Basin in the southwestern karst area, precipitation samples, and sewage samples were collected. The physical and chemical indicators of the water bodies, as well as the characteristics of sulfate sulfur and oxygen isotopes (δ34SSO4, δ18OSO4), hydrogen and oxygen isotopes of water (δDH2O, δ18OH2O), and dissolved inorganic carbon isotopes (δ13CDIC) were analyzed during the monitoring period. Qualitative and quantitative studies on the sources of SO42- in the water bodies were carried out. The hydrochemical types of the basin are mainly of the Ca-HCO3 type and Ca-HCO3-SO4 type, and the hydrochemical characteristics are influenced by the dissolution of carbonate rocks. Isotope characteristics reveal that the biogeochemical process of SO42- in the Pingzhai Reservoir Basin is dominated by oxidation (when sulfides are oxidized, on average, 61% of the oxygen comes from the surrounding water bodies). During the monitoring period, the sources of SO42- in the basin are mainly sulfide oxidation, soil organic sulfur, and agricultural sulfur fertilizers. The results of quantitative calculations show that sulfide oxidation has the highest average contribution rate (72.9%), followed by soil organic sulfur (14.1%) and agricultural sulfur fertilizers (12.9%). The results of uncertainty analysis indicate that the contribution rate of agricultural sulfur fertilizers is the most stable, while that of sulfide oxidation shows relatively large uncertainty. The research results can provide data reference and scientific basis for the protection of water environment quality in the Pingzhai Reservoir and similar karst areas.
huanglinsheng, zhaijinlong, sunzhe, xuying, Gao Jian, Xinyihao, qinhaitao, zhaojinling, ruanchao, xuyatian, luojuhua
Available online: July 09, 2025
Abstract:
Enclosure aquaculture (EA) in lakes is one of the primary types of inland freshwater aquaculture, making significant contributions to food security, employment, and economic growth. However, with the rapid booms in EA intensity, the ecological balance of lakes is gradually being disrupted. Thus, it is crucial to profoundly understand the spatiotemporal dynamics of EA for lake ecosystem preservation and restoration. Compared to field surveys, satellite remote sensing offers advantages such as large-scale coverage, traceability, and cost-effectiveness, making it the optimal choice for monitoring lake EA. This study developed an automatic algorithm for monitoring EA based on Sentinel-1 SAR data and the U-Net model. The algorithm was validated on 10 selected typical lakes, and it achieved a classification accuracy of over 80% in all cases. Additionally, the algorithm was used for monitoring EA lakes in the Yangtze-Huaihe River Basin, providing insights into the spatiotemporal evolution of EA from 2016 to 2023. The results show that a total of 48 lakes (larger than 10 km2) in the Yangtze-Huaihe River Basin engaged in aquaculture activities. From 2016 to 2023, the area of EA in these lakes significantly decreased, with the total area shrinking from 2118.72 km2 to 462.94 km2. Among these lakes, 36 (approximately 77%) have completely removed their enclosure nets. Our findings offer crucial support for evaluating the dynamics of lake water environments and the transformation of aquatic ecosystems pre- and post-enclosure EA removal. Additionally, they offer a scientific basis for formulating measures aimed at lake ecosystem restoration, environmental protection, and sustainable development.
Enclosure aquaculture (EA) in lakes is one of the primary types of inland freshwater aquaculture, making significant contributions to food security, employment, and economic growth. However, with the rapid booms in EA intensity, the ecological balance of lakes is gradually being disrupted. Thus, it is crucial to profoundly understand the spatiotemporal dynamics of EA for lake ecosystem preservation and restoration. Compared to field surveys, satellite remote sensing offers advantages such as large-scale coverage, traceability, and cost-effectiveness, making it the optimal choice for monitoring lake EA. This study developed an automatic algorithm for monitoring EA based on Sentinel-1 SAR data and the U-Net model. The algorithm was validated on 10 selected typical lakes, and it achieved a classification accuracy of over 80% in all cases. Additionally, the algorithm was used for monitoring EA lakes in the Yangtze-Huaihe River Basin, providing insights into the spatiotemporal evolution of EA from 2016 to 2023. The results show that a total of 48 lakes (larger than 10 km2) in the Yangtze-Huaihe River Basin engaged in aquaculture activities. From 2016 to 2023, the area of EA in these lakes significantly decreased, with the total area shrinking from 2118.72 km2 to 462.94 km2. Among these lakes, 36 (approximately 77%) have completely removed their enclosure nets. Our findings offer crucial support for evaluating the dynamics of lake water environments and the transformation of aquatic ecosystems pre- and post-enclosure EA removal. Additionally, they offer a scientific basis for formulating measures aimed at lake ecosystem restoration, environmental protection, and sustainable development.
Available online: July 09, 2025
Abstract:
The sediment seed bank"s ability to efficiently connect previous vegetation"s genetic memory with future vegetation"s development trend is crucial for maintaining community species diversity, restoring ecosystems, and promoting the natural regeneration of aquatic vegetation in shallow lakes. The submerged plant survey and seed bank germination experiments were used in this study to analyze the spatial distribution characteristics of the submerged plant seed bank of Caohai Lake in Guizhou. A comprehensive restoration potential evaluation model was built based on the submerged vegetation, sediment seed bank, sediment, and water quality characteristics to evaluate the restoration potential of various lake areas. Results showed that: (1) the seed bank"s density ranged from 976 to 23,537 seeds/m2, which was comparatively well preserved; it contained nine species from five families, seven genus. The dominant families were the Potamogetonaceae, Hydrocharitaceae, and Najadaceae. The dominant species was Charophyte, which had the highest seed bank density (mean 6057 seeds/m2), which was noticeably higher than others. (2) The sediment seed bank in the Caohai Lake demonstrated obvious spatial heterogeneity, with higher density in the southern and northeast inshore areas and lower density in the mid-lake area. The seed bank was primarily distributed in the surface sediment (0–15 cm), indicating an obvious "surface aggregation" phenomenon. The discrete coefficient analysis revealed that Charophyte, Vallisneria natans, and Potamogenton perfoliatus L had aggregated distribution patterns, while the remaining species had uniform distribution patterns. Furthermore, Sorensen"s similarity coefficient analysis suggested that the succession of submerged communities in Caohai Lake may be quite stable. (3) The southwest and northeast of the Caohai near-shore lake area have high recovery potential for submerged and are designated as "priority recovery areas" The recovery strategy entails keeping water levels low throughout the critical period of submerged seed germination and utilizing the seed bank to achieve natural submerged recovery. The near-shore areas in the northwest and north have a low potential for restoration due to the deeper water level and low seed bank density and are considered“transition zones". The restoration strategy is gradually restoring submerged Caohai Lake by manually adding seeds or planting seedlings under low-water operations. The outlet, southeast side, and center of the lake are considered the“key restoration areas” due to their lowest restoration potential. Because of the serious nutrient loading and the high density of the seed bank, the restoration strategy is to control endogenous pollution and improve water quality, create suitable habitats, and use the seed bank to realize the near-natural restoration of submerged plants. This study can provide a theoretical basis and support for recovering aquatic plant ecosystems in shallow lakes undergoing degradation.
The sediment seed bank"s ability to efficiently connect previous vegetation"s genetic memory with future vegetation"s development trend is crucial for maintaining community species diversity, restoring ecosystems, and promoting the natural regeneration of aquatic vegetation in shallow lakes. The submerged plant survey and seed bank germination experiments were used in this study to analyze the spatial distribution characteristics of the submerged plant seed bank of Caohai Lake in Guizhou. A comprehensive restoration potential evaluation model was built based on the submerged vegetation, sediment seed bank, sediment, and water quality characteristics to evaluate the restoration potential of various lake areas. Results showed that: (1) the seed bank"s density ranged from 976 to 23,537 seeds/m2, which was comparatively well preserved; it contained nine species from five families, seven genus. The dominant families were the Potamogetonaceae, Hydrocharitaceae, and Najadaceae. The dominant species was Charophyte, which had the highest seed bank density (mean 6057 seeds/m2), which was noticeably higher than others. (2) The sediment seed bank in the Caohai Lake demonstrated obvious spatial heterogeneity, with higher density in the southern and northeast inshore areas and lower density in the mid-lake area. The seed bank was primarily distributed in the surface sediment (0–15 cm), indicating an obvious "surface aggregation" phenomenon. The discrete coefficient analysis revealed that Charophyte, Vallisneria natans, and Potamogenton perfoliatus L had aggregated distribution patterns, while the remaining species had uniform distribution patterns. Furthermore, Sorensen"s similarity coefficient analysis suggested that the succession of submerged communities in Caohai Lake may be quite stable. (3) The southwest and northeast of the Caohai near-shore lake area have high recovery potential for submerged and are designated as "priority recovery areas" The recovery strategy entails keeping water levels low throughout the critical period of submerged seed germination and utilizing the seed bank to achieve natural submerged recovery. The near-shore areas in the northwest and north have a low potential for restoration due to the deeper water level and low seed bank density and are considered“transition zones". The restoration strategy is gradually restoring submerged Caohai Lake by manually adding seeds or planting seedlings under low-water operations. The outlet, southeast side, and center of the lake are considered the“key restoration areas” due to their lowest restoration potential. Because of the serious nutrient loading and the high density of the seed bank, the restoration strategy is to control endogenous pollution and improve water quality, create suitable habitats, and use the seed bank to realize the near-natural restoration of submerged plants. This study can provide a theoretical basis and support for recovering aquatic plant ecosystems in shallow lakes undergoing degradation.
Available online: July 03, 2025
Abstract:
In order to quantitatively evaluate the impact of human activities on the changes of hydrologic drought characteristics in Poyang Lake Basin, This article analyzes the inter-annual variation trend of precipitation, temperature, evaporation and runoff from 1959 to 2022 according to the data of meteorological and hydrologic stations in the basin. The relationship curve between cumulative annual precipitation and runoff in the five watershed divisions of Poyang Lake is drawn by using the double cumulative curve method, based on which and combined with the mutation point test,the reference period and change period affected by human activities are divided. According to the measured data of precipitation, evaporation and runoff for each period, the parameters of the two - parameter monthly water balance model are calibrated, and the simulation results are tested using Nash efficiency coefficient, correlation coefficient, and water balance error. By simulating the reduction and reconstruction of monthly runoff during the reference and change periods, and the impact of climate change and human activities on runoff is obtained; Using the SRI as the hydrological drought index, drought events during the change period were identified through run length theory. The characteristics of annual average cumulative drought intensity, the maximum severity of a single drought, and drought frequency before and after parameter reduction were compared. The results show that human activities have generally reduced the runoff depth in the basin, with more significant impacts on the dry season. Spatially, the impacts on the Fu River and Rao River basins are the most obvious, with the annual average runoff depth and the runoff depth during the dry season decreasing by 8.5%, 9.2%, 12.0%, and 12.3% respectively. The frequency and severity of hydrological droughts in the Poyang Lake Basin during the change period have generally increased. The average annual number of droughts, the average annual drought severity, and the maximum severity of a single drought have increased by approximately 21.3%, 55.4%, and 24.3% respectively compared with the reference period. The research can provide a reference for the long-term prediction of the drought trend in the Poyang Lake Basin.
In order to quantitatively evaluate the impact of human activities on the changes of hydrologic drought characteristics in Poyang Lake Basin, This article analyzes the inter-annual variation trend of precipitation, temperature, evaporation and runoff from 1959 to 2022 according to the data of meteorological and hydrologic stations in the basin. The relationship curve between cumulative annual precipitation and runoff in the five watershed divisions of Poyang Lake is drawn by using the double cumulative curve method, based on which and combined with the mutation point test,the reference period and change period affected by human activities are divided. According to the measured data of precipitation, evaporation and runoff for each period, the parameters of the two - parameter monthly water balance model are calibrated, and the simulation results are tested using Nash efficiency coefficient, correlation coefficient, and water balance error. By simulating the reduction and reconstruction of monthly runoff during the reference and change periods, and the impact of climate change and human activities on runoff is obtained; Using the SRI as the hydrological drought index, drought events during the change period were identified through run length theory. The characteristics of annual average cumulative drought intensity, the maximum severity of a single drought, and drought frequency before and after parameter reduction were compared. The results show that human activities have generally reduced the runoff depth in the basin, with more significant impacts on the dry season. Spatially, the impacts on the Fu River and Rao River basins are the most obvious, with the annual average runoff depth and the runoff depth during the dry season decreasing by 8.5%, 9.2%, 12.0%, and 12.3% respectively. The frequency and severity of hydrological droughts in the Poyang Lake Basin during the change period have generally increased. The average annual number of droughts, the average annual drought severity, and the maximum severity of a single drought have increased by approximately 21.3%, 55.4%, and 24.3% respectively compared with the reference period. The research can provide a reference for the long-term prediction of the drought trend in the Poyang Lake Basin.
Available online: July 02, 2025
Abstract:
Rivers are links connecting the biogeochemical processes among terrestrial, oceanic, and atmospheric carbon pools, and are important participants in the global water and carbon cycles. Riverine partial pressure of carbon dioxide (pCO2) is a key indicator reflecting the CO2 exchange process at the riverine water-air interface, which exhibits complex spatiotemporal variations due to the co-impacts of various natural and anthropogenic factors. However, the current understanding of the main controlling factors and their effects on riverine pCO2 is still very limited. In this study, the spatiotemporal distribution characteristics of riverine pCO2 were identified, and the relative contributions and controlling effects of the potential controlling factors were quantified and revealed using an interpretable machine learning method (boost regression tree (BRT) and accumulated local effects (ALE)), based on monthly datasets with high spatial resolution in the Han River Basin (HRB). Results indicated that multi-year average riverine pCO2 in the HRB showed an increasing trend from upstream to downstream, and was higher than the atmospheric average. The fluctuation type of multi-year monthly average riverine pCO2 in the HRB could be classified into three types based on the k-Shape clustering algorithm, with stationary (T1), unimodal (T2), and bimodal (T3) structures, respectively. The BRT model effectively simulated the multi-year average and multi-year monthly average values of riverine pCO2 in the HRB, showing high performances (r > 0.86, NSE > 0.75) and acceptable errors (MAE < 212.18 μatm, RMSE < 274.16 μatm) in replicate experiments. Multi-year average riverine pCO2 was mainly controlled by temperature factors, with a total relative contribution rate of about 66.1%. Relative contributions of controlling factors for multi-year monthly average riverine pCO2 varied greatly among each fluctuation type, while temperature factors still played a critical role (approximately 26.6% ~ 46.9%). Vegetation and water quantity factors had high contributions in type T2 and T3, respectively, while the importance of water quality factors was relatively limited (less than about 20.1%). The nonlinear and non-monotonic relationships between riverine pCO2 and its potential controlling factors were revealed based on ALE analysis results, and showed significant differences between multi-year average and multi-year monthly average scales, as well as between different fluctuation types. This study revealed the complex spatiotemporal variations of the main controlling factors and their effects on riverine pCO2 in the HRB, improving the understanding of riverine carbon cycle process.
Rivers are links connecting the biogeochemical processes among terrestrial, oceanic, and atmospheric carbon pools, and are important participants in the global water and carbon cycles. Riverine partial pressure of carbon dioxide (pCO2) is a key indicator reflecting the CO2 exchange process at the riverine water-air interface, which exhibits complex spatiotemporal variations due to the co-impacts of various natural and anthropogenic factors. However, the current understanding of the main controlling factors and their effects on riverine pCO2 is still very limited. In this study, the spatiotemporal distribution characteristics of riverine pCO2 were identified, and the relative contributions and controlling effects of the potential controlling factors were quantified and revealed using an interpretable machine learning method (boost regression tree (BRT) and accumulated local effects (ALE)), based on monthly datasets with high spatial resolution in the Han River Basin (HRB). Results indicated that multi-year average riverine pCO2 in the HRB showed an increasing trend from upstream to downstream, and was higher than the atmospheric average. The fluctuation type of multi-year monthly average riverine pCO2 in the HRB could be classified into three types based on the k-Shape clustering algorithm, with stationary (T1), unimodal (T2), and bimodal (T3) structures, respectively. The BRT model effectively simulated the multi-year average and multi-year monthly average values of riverine pCO2 in the HRB, showing high performances (r > 0.86, NSE > 0.75) and acceptable errors (MAE < 212.18 μatm, RMSE < 274.16 μatm) in replicate experiments. Multi-year average riverine pCO2 was mainly controlled by temperature factors, with a total relative contribution rate of about 66.1%. Relative contributions of controlling factors for multi-year monthly average riverine pCO2 varied greatly among each fluctuation type, while temperature factors still played a critical role (approximately 26.6% ~ 46.9%). Vegetation and water quantity factors had high contributions in type T2 and T3, respectively, while the importance of water quality factors was relatively limited (less than about 20.1%). The nonlinear and non-monotonic relationships between riverine pCO2 and its potential controlling factors were revealed based on ALE analysis results, and showed significant differences between multi-year average and multi-year monthly average scales, as well as between different fluctuation types. This study revealed the complex spatiotemporal variations of the main controlling factors and their effects on riverine pCO2 in the HRB, improving the understanding of riverine carbon cycle process.
Available online: July 01, 2025
Abstract:
As one of the largest developing countries in the world, China is facing an increasingly severe pollution problem with PAEs (phthalates). PAEs, as plasticizers, are widely used in industries, food industry, and pharmaceutical industry. Due to their large usage and lack of standardized treatment, they have accumulated in the environment over the long term, showing significant toxicity. To explore the occurrence characteristics of PAEs in typical Chinese lakes and the effects of human activities, this study systematically analyzed the multi-media occurrence, spatial distribution, ecological risks, and potential sources of PAEs in the water bodies and sediments of 30 typical lakes in China. The results indicate that the concentration range of PAEs in the aqueous and sediment phases is 0.01~27.60 μg/L and 28.8~74935 ng/g, respectively, with di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) being the main PAEs in both phases; the spatial distribution of the lake areas shows significant differences, with the most severe pollution occurring in the middle and lower reaches of the Yangtze River. Among them, di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the main components of PAEs in lake water and sediments, with the highest contribution rates. The spatial distribution of the lake areas shows significant differences, with the lakes in the middle and lower reaches of the Yangtze River being the most severely polluted. Based on the ecological risk assessment using risk quotients (RQ), it was found that about 30% of the lakes pose a high risk to crustaceans, with DEHP and DBP being the main PAEs components posing high risks. Further principal component analysis and multiple linear regression showed that industrial wastewater discharge and agricultural production activities are the main sources of PAEs pollution, especially with a significant positive correlation (p < 0.05) between the use of agricultural films, pesticide usage, and the concentrations of DEHP and DBP. The study results indicate that PAEs have significant multi-media distribution characteristics in the lake water-sediment system and are profoundly influenced by human activities. Therefore, it is recommended to strengthen the management of PAEs additives in agricultural production and improve the removal efficiency of PAEs in industrial wastewater treatment processes to reduce the pollution load of lake water bodies. This study reveals the environmental behavior, risk characteristics, and anthropogenic driving mechanisms of PAEs in typical Chinese lakes, providing a scientific basis for the formulation of water ecological and environmental protection strategies.
As one of the largest developing countries in the world, China is facing an increasingly severe pollution problem with PAEs (phthalates). PAEs, as plasticizers, are widely used in industries, food industry, and pharmaceutical industry. Due to their large usage and lack of standardized treatment, they have accumulated in the environment over the long term, showing significant toxicity. To explore the occurrence characteristics of PAEs in typical Chinese lakes and the effects of human activities, this study systematically analyzed the multi-media occurrence, spatial distribution, ecological risks, and potential sources of PAEs in the water bodies and sediments of 30 typical lakes in China. The results indicate that the concentration range of PAEs in the aqueous and sediment phases is 0.01~27.60 μg/L and 28.8~74935 ng/g, respectively, with di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) being the main PAEs in both phases; the spatial distribution of the lake areas shows significant differences, with the most severe pollution occurring in the middle and lower reaches of the Yangtze River. Among them, di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the main components of PAEs in lake water and sediments, with the highest contribution rates. The spatial distribution of the lake areas shows significant differences, with the lakes in the middle and lower reaches of the Yangtze River being the most severely polluted. Based on the ecological risk assessment using risk quotients (RQ), it was found that about 30% of the lakes pose a high risk to crustaceans, with DEHP and DBP being the main PAEs components posing high risks. Further principal component analysis and multiple linear regression showed that industrial wastewater discharge and agricultural production activities are the main sources of PAEs pollution, especially with a significant positive correlation (p < 0.05) between the use of agricultural films, pesticide usage, and the concentrations of DEHP and DBP. The study results indicate that PAEs have significant multi-media distribution characteristics in the lake water-sediment system and are profoundly influenced by human activities. Therefore, it is recommended to strengthen the management of PAEs additives in agricultural production and improve the removal efficiency of PAEs in industrial wastewater treatment processes to reduce the pollution load of lake water bodies. This study reveals the environmental behavior, risk characteristics, and anthropogenic driving mechanisms of PAEs in typical Chinese lakes, providing a scientific basis for the formulation of water ecological and environmental protection strategies.
Available online: June 27, 2025
Abstract:
Abstract: In recent years, excessive input and inefficient utilization of nitrogen and phosphorus in the cropping system of the Poyang Lake Basin have led to significant losses of these elements, resulting in persistent exceedances of nitrogen and phosphorus standards, as well as other environmental issues. Therefore, quantitatively tracing the spatiotemporal patterns of nitrogen and phosphorus metabolism in the cropping system of Poyang Lake Basin is crucial for ensuring the sustainability of the basin"s ecosystem. This study applied the Material Flow Analysis (MFA) method to investigate the spatiotemporal variations of nitrogen and phosphorus fluxes in cropping systems across the Poyang Lake Basin from 2000 to 2022.Four scenarios were designed based on the current status of nitrogen and phosphorus pollutant emissions: a baseline scenario, a scenario with reduced fertilizer inputs to arable land, a scenario with increased straw recycling rates, and a scenario with comprehensive measures. The emission reduction potentials was quantitatively calculated under various scenarios and finally the optimal strategies for nitrogen and phosphorus pollutant emission reduction and prevention were proposed. The results show that the nitrogen and phosphorus inputs in the basin initially increased, then fluctuated stably, peaking around 2015. Spatially, the total nitrogen and phosphorus inputs are highest in the coastal lake district, reaching 281,000 tons of nitrogen and 64,000 tons of phosphorus, respectively, with chemical and organic fertilizers accounting for over half of the total inputs. In terms of the nutrient use efficiency, the combined use rate of nitrogen and phosphorus were 48.5% and 31.0% respectively. The nitrogen and phosphorus utilization rates for all crops has declined since 2010, and the nutrient input nitrogen and phosphorus ratio has also decreased continuously, with an average N/P of 3.9. Scenario analysis suggests that implementing measures to reduce chemical fertilizer use could decrease nitrogen output by 150,000 tonnes by 2050, nitrogen and phosphorus emissions can be reduced by 159,000 tons, reducing pollutants by 53.4%. compared with the baseline scenario, the ratio of N/P discharged into the environment can rise to 6.5. Reducing fertilizer application accounts for 75.7% of the emission reduction, demonstrating its effectiveness as a mitigation strategy. By quantitatively analyzing the nitrogen and phosphorus structure of cropping system and tracing the nitrogen and phosphorus inputs over the past 20 years in Poyang Lake Basin, identifying and judging the change trend of the nitrogen and phosphorus ratio, This analysis allows us to systematically evaluate the key processes of the agricultural system and provides a scientific basis for developing effective integrated nitrogen and phosphorus management measures in the Poyang Lake Basin by evaluating the potential outcomes of future scenarios.
Abstract: In recent years, excessive input and inefficient utilization of nitrogen and phosphorus in the cropping system of the Poyang Lake Basin have led to significant losses of these elements, resulting in persistent exceedances of nitrogen and phosphorus standards, as well as other environmental issues. Therefore, quantitatively tracing the spatiotemporal patterns of nitrogen and phosphorus metabolism in the cropping system of Poyang Lake Basin is crucial for ensuring the sustainability of the basin"s ecosystem. This study applied the Material Flow Analysis (MFA) method to investigate the spatiotemporal variations of nitrogen and phosphorus fluxes in cropping systems across the Poyang Lake Basin from 2000 to 2022.Four scenarios were designed based on the current status of nitrogen and phosphorus pollutant emissions: a baseline scenario, a scenario with reduced fertilizer inputs to arable land, a scenario with increased straw recycling rates, and a scenario with comprehensive measures. The emission reduction potentials was quantitatively calculated under various scenarios and finally the optimal strategies for nitrogen and phosphorus pollutant emission reduction and prevention were proposed. The results show that the nitrogen and phosphorus inputs in the basin initially increased, then fluctuated stably, peaking around 2015. Spatially, the total nitrogen and phosphorus inputs are highest in the coastal lake district, reaching 281,000 tons of nitrogen and 64,000 tons of phosphorus, respectively, with chemical and organic fertilizers accounting for over half of the total inputs. In terms of the nutrient use efficiency, the combined use rate of nitrogen and phosphorus were 48.5% and 31.0% respectively. The nitrogen and phosphorus utilization rates for all crops has declined since 2010, and the nutrient input nitrogen and phosphorus ratio has also decreased continuously, with an average N/P of 3.9. Scenario analysis suggests that implementing measures to reduce chemical fertilizer use could decrease nitrogen output by 150,000 tonnes by 2050, nitrogen and phosphorus emissions can be reduced by 159,000 tons, reducing pollutants by 53.4%. compared with the baseline scenario, the ratio of N/P discharged into the environment can rise to 6.5. Reducing fertilizer application accounts for 75.7% of the emission reduction, demonstrating its effectiveness as a mitigation strategy. By quantitatively analyzing the nitrogen and phosphorus structure of cropping system and tracing the nitrogen and phosphorus inputs over the past 20 years in Poyang Lake Basin, identifying and judging the change trend of the nitrogen and phosphorus ratio, This analysis allows us to systematically evaluate the key processes of the agricultural system and provides a scientific basis for developing effective integrated nitrogen and phosphorus management measures in the Poyang Lake Basin by evaluating the potential outcomes of future scenarios.
Yue Lintan, Yang Yifan, Zhuang Xinfeng, Chen Weiyu, Kong Xiangzhen, Deng Jianming, Zhao Zhonghua, Lu Yingcheng, Zhu Guangwei, Qin Boqiang
Available online: June 25, 2025
Abstract:
The intensification of global warming has led to a significant increase in the frequency and intensity of heatwave events. Exploring their impact on ecological processes such as lake nutrient salts, chlorophyll-a (Chla), and phytoplankton growth is crucial for understanding the ecological response and feedback mechanisms of lakes under heatwave conditions and providing scientific support for lake management and regulation under climate change. This study, based on the GOTM-WET model, simulated the impact of the 2022 summer heatwave on Chla concentration in North Taihu Lake, with a focus on analyzing the effects of different heatwave intensities on Chla and their possible mechanisms. The results indicated that the 2022 summer heatwave significantly suppressed Chla concentration, and the inhibitory effect intensified with the increase in heatwave intensity. Further analysis revealed that the maximum water temperature during the 2022 heatwave exceeded 37°C, possibly surpassing the optimal growth temperature for most algae, thereby inhibiting their growth. Additionally, the heatwave intensified water column stratification, leading to a reduction in total nitrogen (TN) and total phosphorus (TP) concentrations in the surface layer and their accumulation in the bottom layer. This vertical differentiation of nutrients limited the nutrient supply required for surface algae growth, further suppressing the increase in Chla concentration. This study revealed the potential impact mechanisms of dual factors of water temperature and nutrients on lake algae growth under extreme high-temperature conditions, deepening the understanding of the effects of heatwave events on lake ecosystem processes.
The intensification of global warming has led to a significant increase in the frequency and intensity of heatwave events. Exploring their impact on ecological processes such as lake nutrient salts, chlorophyll-a (Chla), and phytoplankton growth is crucial for understanding the ecological response and feedback mechanisms of lakes under heatwave conditions and providing scientific support for lake management and regulation under climate change. This study, based on the GOTM-WET model, simulated the impact of the 2022 summer heatwave on Chla concentration in North Taihu Lake, with a focus on analyzing the effects of different heatwave intensities on Chla and their possible mechanisms. The results indicated that the 2022 summer heatwave significantly suppressed Chla concentration, and the inhibitory effect intensified with the increase in heatwave intensity. Further analysis revealed that the maximum water temperature during the 2022 heatwave exceeded 37°C, possibly surpassing the optimal growth temperature for most algae, thereby inhibiting their growth. Additionally, the heatwave intensified water column stratification, leading to a reduction in total nitrogen (TN) and total phosphorus (TP) concentrations in the surface layer and their accumulation in the bottom layer. This vertical differentiation of nutrients limited the nutrient supply required for surface algae growth, further suppressing the increase in Chla concentration. This study revealed the potential impact mechanisms of dual factors of water temperature and nutrients on lake algae growth under extreme high-temperature conditions, deepening the understanding of the effects of heatwave events on lake ecosystem processes.
Available online: June 23, 2025
Abstract:
Dongting Lake is an important lake in the middle reach of the Yangtze River, and accurately modelling the runoff corresponding relationships of its various input and output stations is crucial for regional ecological protection and flood control and drought defense. To address the complex runoff response relationships in the Dongting Lake basin, this study proposes a multiple-input and multiple-output runoff response model based on graph neural networks. Firstly, the model utilizes the basin topological spatial structure of the Yangtze River, Dongting Lake and Sishui to transform the original observation sequences at each station into graph-structured data to characterize the spatial characteristics of the basin. Secondly, through the mutual correlation analysis method, the time lag relationship between the observed variables at each station is identified to determine the input feature step of the model. Finally, graph neural networks are employed to aggregate and update the features to capture the complex spatial and temporal dependencies among the control station, and to realize the runoff simulation at multiple stations. The results show that in the flood event, compared with the backpropagation neural network (BP) and the long-short term memory neural network (LSTM) models, the graph neural network (GNN) model can achieve the improvement rates over 5% for Nash-Sutcliffe efficiency coefficient (NSE) and mean absolute error (MAE) indicators, and the correlation coefficients (R^2) is more than 0.97, while in the dry water cutoff events, the True Positive Rate (TPR) and Precision are generally more than 0.96. GNN has significant advantages in the simulation of hydrological events such as floods and droughts, which can provide a scientific support for the ecological protection of Dongting Lake and its flood control and drought resistance.
Dongting Lake is an important lake in the middle reach of the Yangtze River, and accurately modelling the runoff corresponding relationships of its various input and output stations is crucial for regional ecological protection and flood control and drought defense. To address the complex runoff response relationships in the Dongting Lake basin, this study proposes a multiple-input and multiple-output runoff response model based on graph neural networks. Firstly, the model utilizes the basin topological spatial structure of the Yangtze River, Dongting Lake and Sishui to transform the original observation sequences at each station into graph-structured data to characterize the spatial characteristics of the basin. Secondly, through the mutual correlation analysis method, the time lag relationship between the observed variables at each station is identified to determine the input feature step of the model. Finally, graph neural networks are employed to aggregate and update the features to capture the complex spatial and temporal dependencies among the control station, and to realize the runoff simulation at multiple stations. The results show that in the flood event, compared with the backpropagation neural network (BP) and the long-short term memory neural network (LSTM) models, the graph neural network (GNN) model can achieve the improvement rates over 5% for Nash-Sutcliffe efficiency coefficient (NSE) and mean absolute error (MAE) indicators, and the correlation coefficients (R^2) is more than 0.97, while in the dry water cutoff events, the True Positive Rate (TPR) and Precision are generally more than 0.96. GNN has significant advantages in the simulation of hydrological events such as floods and droughts, which can provide a scientific support for the ecological protection of Dongting Lake and its flood control and drought resistance.
Available online: June 23, 2025
Abstract:
Scientific research on hydrological drought in lake-floodplains and its impact on hydrological connectivity is of great significance for local water resources management and wetland ecological protection. Based on the reconstructed high spatiotemporal resolution inundation datasets from 2000 to 2023 by applying the ESTARFM model (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model), hydrological drought and hydrological connectivity in the Poyang Lake were quantitatively characterized by the standardized inundation area index and the geostatistical hydrological connectivity function, and then their evolution characteristics were analyzed. On this basis, the response of hydrological connectivity to hydrological drought was further clarified by using the methods of STL (Seasonal and Trend decomposition using Loess) time series decomposition and multivariate linear fitting function. The results showed that both annual and interannual variations of hydrological drought in Poyang Lake were complicated, with a high frequency of occurrence and an increasing drought tendency. The hydrological connectivity in the north-south direction of the Poyang Lake is stronger than that in the east-west direction. In recent years, the hydrological connectivity of the Poyang Lake has shown a fluctuating downward trend, which is related to the intensity changes of lake hydrological drought. Further quantitative analysis found that with the increase of the degree of hydrological drought, hydrological connectivity in the Poyang Lake showed a decreasing trend. In the east-west direction, the annual average hydrological connectivity of light drought, medium drought, severe drought and extreme drought in the Poyang Lake can decrease by 45.2%, 50.0%, 54.6% and 70.7%, respectively, compared to no drought scenario. Similarly, in the north-south direction, the annual average hydrological connectivity can decrease by 32.1%, 35.6%, 39.0% and 50.7%, respectively. The changes of hydrological connectivity caused by hydrological drought in the Poyang Lake area will further impact affect the growth and distribution of wetland vegetation, and the results of this study provide scientific basis for the management practice of lake ecosystems under extreme water conditions.
Scientific research on hydrological drought in lake-floodplains and its impact on hydrological connectivity is of great significance for local water resources management and wetland ecological protection. Based on the reconstructed high spatiotemporal resolution inundation datasets from 2000 to 2023 by applying the ESTARFM model (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model), hydrological drought and hydrological connectivity in the Poyang Lake were quantitatively characterized by the standardized inundation area index and the geostatistical hydrological connectivity function, and then their evolution characteristics were analyzed. On this basis, the response of hydrological connectivity to hydrological drought was further clarified by using the methods of STL (Seasonal and Trend decomposition using Loess) time series decomposition and multivariate linear fitting function. The results showed that both annual and interannual variations of hydrological drought in Poyang Lake were complicated, with a high frequency of occurrence and an increasing drought tendency. The hydrological connectivity in the north-south direction of the Poyang Lake is stronger than that in the east-west direction. In recent years, the hydrological connectivity of the Poyang Lake has shown a fluctuating downward trend, which is related to the intensity changes of lake hydrological drought. Further quantitative analysis found that with the increase of the degree of hydrological drought, hydrological connectivity in the Poyang Lake showed a decreasing trend. In the east-west direction, the annual average hydrological connectivity of light drought, medium drought, severe drought and extreme drought in the Poyang Lake can decrease by 45.2%, 50.0%, 54.6% and 70.7%, respectively, compared to no drought scenario. Similarly, in the north-south direction, the annual average hydrological connectivity can decrease by 32.1%, 35.6%, 39.0% and 50.7%, respectively. The changes of hydrological connectivity caused by hydrological drought in the Poyang Lake area will further impact affect the growth and distribution of wetland vegetation, and the results of this study provide scientific basis for the management practice of lake ecosystems under extreme water conditions.
Available online: June 19, 2025
Abstract:
Dissolved organic matter (DOM) is a kind of substances with various structural compositions, complex physicochemical properties and wide molecular weight distribution, which mainly contains humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acid, hydroxyl, phenolic, aldehyde and other reactive groups, etc. DOM exists widely in lake ecosystems, and it can participate in a variety of biogeochemical processes, influence the migration transformation and behavior of biotic elements and pollutants, and play an important role in the conversion of carbon sinks in ecosystems. DOM in lake water has various environmental behaviors. For example, DOM can be adsorbed to the surface of water particles, and the distribution of DOM in the dissolved/suspended phase can be regulated; DOM in lakes will undergo photo- and microbial degradation, which will change the content and structural composition of DOM samples; the multifunctional groups in DOM in lakes can be easily complexed with metal ions, and can also undergo electron transfer to produce reactive oxygen species. In addition, lake DOM also has significant ecological and environmental effects. DOM can be loaded on the surface of colloidal particles, affecting the stability of colloidal particles and transparency of the water body; DOM binding with heavy metals will change the bioavailability of heavy metal and the health of lake ecosystems; lake DOM can promote organic pollutant degradation through the mediating role of reactive oxygen species, or inhibit pollutant degradation through the role of light shielding. It should be pointed out that the behavior and ecological effects of lake DOM are closely related to its molecular weight, active group and molecular structure. In this paper, we systematically review the behavior and ecological effects of lake DOM and its correlation with the molecular structure compositions. Results obtained can provide theoretical guidance and technical support for the process and mechanism of lake pollution, lake restoration and regulation, lake management and planning.
Dissolved organic matter (DOM) is a kind of substances with various structural compositions, complex physicochemical properties and wide molecular weight distribution, which mainly contains humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acid, hydroxyl, phenolic, aldehyde and other reactive groups, etc. DOM exists widely in lake ecosystems, and it can participate in a variety of biogeochemical processes, influence the migration transformation and behavior of biotic elements and pollutants, and play an important role in the conversion of carbon sinks in ecosystems. DOM in lake water has various environmental behaviors. For example, DOM can be adsorbed to the surface of water particles, and the distribution of DOM in the dissolved/suspended phase can be regulated; DOM in lakes will undergo photo- and microbial degradation, which will change the content and structural composition of DOM samples; the multifunctional groups in DOM in lakes can be easily complexed with metal ions, and can also undergo electron transfer to produce reactive oxygen species. In addition, lake DOM also has significant ecological and environmental effects. DOM can be loaded on the surface of colloidal particles, affecting the stability of colloidal particles and transparency of the water body; DOM binding with heavy metals will change the bioavailability of heavy metal and the health of lake ecosystems; lake DOM can promote organic pollutant degradation through the mediating role of reactive oxygen species, or inhibit pollutant degradation through the role of light shielding. It should be pointed out that the behavior and ecological effects of lake DOM are closely related to its molecular weight, active group and molecular structure. In this paper, we systematically review the behavior and ecological effects of lake DOM and its correlation with the molecular structure compositions. Results obtained can provide theoretical guidance and technical support for the process and mechanism of lake pollution, lake restoration and regulation, lake management and planning.
Available online: June 19, 2025
Abstract:
Lake-reservoir type water sources are crucial to China’s water supply, playing a vital role in ensuring regional water security. This study focused on the Panjiakou Reservoir, a key water source for the Luanhe-Tianjin Water Diversion Project. A three-dimensional numerical model was performed to unveil the response of bottom hypoxia under varying reservoir operations and nitrate concentrations in the inflow. Based on these findings, we proposed comprehensive strategies for preventing and controlling bottom hypoxia. In this paper, the measured reservoir data from 2017 to 2018 were used to verify the reliability of the model. Results show that increasing the reservoir"s outflow significantly shortened the duration of bottom hypoxia and weakened its severity in the later stage of thermal stratification. Moreover, a substantial reduction in the nitrate concentration in the inflow resulted in a significant increase in the duration, severity, and spatial extent of bottom hypoxia. Based on the actual operation of the reservoir and the requirements for meeting the standards of water supply quality, this article suggests: 1) joint scheduling with the downstream Daheiting Reservoir should be implemented, adjusting the outflow volumes during January-April and September-December to concentrate the discharge in mid-to-late October. This optimization reduced the duration of severe hypoxia and the maximum hypoxic area by 54% and 23%, respectively. 2) Second, we recommended reducing the upstream nitrate concentration to 1.5-2 mg/L as part of the watershed pollution control efforts. This approach ensured that the total nitrogen (TN) concentration in the discharged water satisfied the standards, while maximizing the mitigating effect of nitrate on bottom hypoxia. Our study proposed a comprehensive strategy for reservoir water quality protection from multiple perspectives, including "upstream pollution source concentration control, reservoir hypoxia prevention, and downstream water quality standards compliance", which were of importance for the protection and restoration of aquatic environments in the deep water source reservoirs.
Lake-reservoir type water sources are crucial to China’s water supply, playing a vital role in ensuring regional water security. This study focused on the Panjiakou Reservoir, a key water source for the Luanhe-Tianjin Water Diversion Project. A three-dimensional numerical model was performed to unveil the response of bottom hypoxia under varying reservoir operations and nitrate concentrations in the inflow. Based on these findings, we proposed comprehensive strategies for preventing and controlling bottom hypoxia. In this paper, the measured reservoir data from 2017 to 2018 were used to verify the reliability of the model. Results show that increasing the reservoir"s outflow significantly shortened the duration of bottom hypoxia and weakened its severity in the later stage of thermal stratification. Moreover, a substantial reduction in the nitrate concentration in the inflow resulted in a significant increase in the duration, severity, and spatial extent of bottom hypoxia. Based on the actual operation of the reservoir and the requirements for meeting the standards of water supply quality, this article suggests: 1) joint scheduling with the downstream Daheiting Reservoir should be implemented, adjusting the outflow volumes during January-April and September-December to concentrate the discharge in mid-to-late October. This optimization reduced the duration of severe hypoxia and the maximum hypoxic area by 54% and 23%, respectively. 2) Second, we recommended reducing the upstream nitrate concentration to 1.5-2 mg/L as part of the watershed pollution control efforts. This approach ensured that the total nitrogen (TN) concentration in the discharged water satisfied the standards, while maximizing the mitigating effect of nitrate on bottom hypoxia. Our study proposed a comprehensive strategy for reservoir water quality protection from multiple perspectives, including "upstream pollution source concentration control, reservoir hypoxia prevention, and downstream water quality standards compliance", which were of importance for the protection and restoration of aquatic environments in the deep water source reservoirs.
Available online: June 18, 2025
Abstract:
Abstract: The construction of the Three Gorges Dam has significantly altered water and sediment fluxes in the Yangtze River, yet its impact on microbially mediated multifunctionality (carbon, nitrogen, and phosphorus cycling) in sediments remains unclear. This study employed 16S amplicon sequencing, co-occurrence network analysis, and structural equation modeling to investigate the effects of the dam on bacterial community composition, diversity, and multifunctionality in upstream and downstream sediments. Results revealed that upstream sediments were dominated by Proteobacteria (~25.5%), while downstream sediments were dominated by Desulfobacterota (~24.8%). The dam significantly reduced bacterial α-diversity in downstream sediments, which was closely correlated with reductions in moisture (~35.4%), cation exchange capacity (~49.6%), and dissolved organic carbon (~49.9%). Structural equation modeling indicated that reduced α-diversity directly impaired ecological functions and indirectly decreased multifunctionality by weakening bacterial network interactions. This study highlights the adverse ecological impacts of the Three Gorges Dam on downstream sediment functions and recommends long-term monitoring of dissolved organic carbon and cation exchange capacity, alongside optimized reservoir management, to mitigate biodiversity loss.
Abstract: The construction of the Three Gorges Dam has significantly altered water and sediment fluxes in the Yangtze River, yet its impact on microbially mediated multifunctionality (carbon, nitrogen, and phosphorus cycling) in sediments remains unclear. This study employed 16S amplicon sequencing, co-occurrence network analysis, and structural equation modeling to investigate the effects of the dam on bacterial community composition, diversity, and multifunctionality in upstream and downstream sediments. Results revealed that upstream sediments were dominated by Proteobacteria (~25.5%), while downstream sediments were dominated by Desulfobacterota (~24.8%). The dam significantly reduced bacterial α-diversity in downstream sediments, which was closely correlated with reductions in moisture (~35.4%), cation exchange capacity (~49.6%), and dissolved organic carbon (~49.9%). Structural equation modeling indicated that reduced α-diversity directly impaired ecological functions and indirectly decreased multifunctionality by weakening bacterial network interactions. This study highlights the adverse ecological impacts of the Three Gorges Dam on downstream sediment functions and recommends long-term monitoring of dissolved organic carbon and cation exchange capacity, alongside optimized reservoir management, to mitigate biodiversity loss.
Available online: June 18, 2025
Abstract:
As an emerging solution to address fish passage challenges in high dams, the fish collection and transportation system was first implemented in China in the early 21st century at several high-head hydropower stations. However, limited data have been reported on its effectiveness. The Wudongde Hydropower Station pioneered a tailrace outlet fish collection scheme, constructing a fish collection and transportation system to assist fish migration. Based on fish collection data from the Wudongde fish collection and transportation system from 2021 to 2023, this study analyzed the characteristics of collected fish using Diversity index, Index of relative importance, Fish autecology matrix , and Ward clustering. The results were cross-validated with environmental impact assessment and design requirements to preliminarily evaluate the system’s efficacy. During 2021–2023, the Wudongde fish collection and transportation system collected 95,281 individuals from 52 fish species. Statistical analyses revealed: (1) All 10 main and secondary fish passing objects were collected, with Percocypris pingi exhibiting the largest average size. (2) The collected specimens of Coreius guichenoti, Rhinogobio ventralis, Jinshaia sinensis, Leptobotia elongata, and Schizothoracinae fishes were mainly 4-year-old, 3-year-old, 6-year-old, 4-year-old, and 4-year-old, respectively. (3) Fish diversity indices indicated moderate overall diversity and a relatively simple community structure. (4) Dominant species included Hemiculter leucisculus, Botia superciliaris, and Pseudogyrinocheilus procheilus, collectively accounting for 87.3% of the total catch. (5) At the species level, Sticky and demersal eggs，Settlement were predominant. Lotic type species dominated, but lentic type also comprised a notable proportion. (6) Ward clustering showed distinct seasonal differences, with July and August forming separate clusters due to high collection volumes, while other months grouped into another cluster. Overall, the Wudongde fish collection and transportation system facilitated migration for most fish species in the river section, with no size-selective bias observed. Preliminary assessment suggests that the majority of the main and secondary fish passing objects collected are potential breeding populations that have reached the age of first sexual maturity. Compared with the breeding time proposed in the environmental impact assessment and design stage, the collection month of some fish objects is delayed or advanced, and the change of fish composition is basically in line with the prediction in the design stage. Compared to similar fish passage facilities, the Wudongde fish collection and transportation system demonstrated superior efficacy by utilizing turbine tailwater for fish attraction, effectively mitigating the hydropower station’s barrier effects. Future efforts should optimize system operations, enhance monitoring, and scientifically evaluate its effectiveness to promote connectivity restoration in the lower Jinsha River.
As an emerging solution to address fish passage challenges in high dams, the fish collection and transportation system was first implemented in China in the early 21st century at several high-head hydropower stations. However, limited data have been reported on its effectiveness. The Wudongde Hydropower Station pioneered a tailrace outlet fish collection scheme, constructing a fish collection and transportation system to assist fish migration. Based on fish collection data from the Wudongde fish collection and transportation system from 2021 to 2023, this study analyzed the characteristics of collected fish using Diversity index, Index of relative importance, Fish autecology matrix , and Ward clustering. The results were cross-validated with environmental impact assessment and design requirements to preliminarily evaluate the system’s efficacy. During 2021–2023, the Wudongde fish collection and transportation system collected 95,281 individuals from 52 fish species. Statistical analyses revealed: (1) All 10 main and secondary fish passing objects were collected, with Percocypris pingi exhibiting the largest average size. (2) The collected specimens of Coreius guichenoti, Rhinogobio ventralis, Jinshaia sinensis, Leptobotia elongata, and Schizothoracinae fishes were mainly 4-year-old, 3-year-old, 6-year-old, 4-year-old, and 4-year-old, respectively. (3) Fish diversity indices indicated moderate overall diversity and a relatively simple community structure. (4) Dominant species included Hemiculter leucisculus, Botia superciliaris, and Pseudogyrinocheilus procheilus, collectively accounting for 87.3% of the total catch. (5) At the species level, Sticky and demersal eggs，Settlement were predominant. Lotic type species dominated, but lentic type also comprised a notable proportion. (6) Ward clustering showed distinct seasonal differences, with July and August forming separate clusters due to high collection volumes, while other months grouped into another cluster. Overall, the Wudongde fish collection and transportation system facilitated migration for most fish species in the river section, with no size-selective bias observed. Preliminary assessment suggests that the majority of the main and secondary fish passing objects collected are potential breeding populations that have reached the age of first sexual maturity. Compared with the breeding time proposed in the environmental impact assessment and design stage, the collection month of some fish objects is delayed or advanced, and the change of fish composition is basically in line with the prediction in the design stage. Compared to similar fish passage facilities, the Wudongde fish collection and transportation system demonstrated superior efficacy by utilizing turbine tailwater for fish attraction, effectively mitigating the hydropower station’s barrier effects. Future efforts should optimize system operations, enhance monitoring, and scientifically evaluate its effectiveness to promote connectivity restoration in the lower Jinsha River.
Available online: June 16, 2025
Abstract:
In recent years, summer heatwaves continued to occur in summer and influenced sediment properties in shallow lakes. The sediments located at the sediment-water interface (SWI) directly impact the lakes ecological health, due to its unique structural characteristics. In order to investigate the temperature effect on sediment structural properties, this study conducted sampling in Lake Gehu before and after high temperature, complemented by indoor simulation experiments. Firstly, sampling results indicated that elevated temperatures induce a decline in the density and yield stress of lake sediments, promoting the formation of fluid sediments (density < 1.25 g/cm3). Secondly, the simulation experiment also showed the same trend. As the temperature rose from 25 ℃ to 35 ℃, the density of sediments at the SWI displayed an exponentially decreasing trend from 1.244 g/cm3 to 1.229 g/cm3. Meanwhile, the increase in temperature led an increase of the sediment median size from the initial 17.22 μm to 21.16 μm, resulting in the flocculation and aggregation of sediment particles. Additionally, increasing temperatures resulted in a higher polysaccharide/protein ratio in extracellular polymeric substances (EPSs), which decreased the stability of sediments. Rheological tests and calculation of critical shear stress showed that the yield stress and critical shear stress of sediments exponentially decreased with increasing temperature. Overall, this study demonstrated that high temperatures can lead a loose and porous sediment structures with a threshold at 29 ℃, which can cause sediment particle resuspension and suspension. Overall, this study has deepened the understanding of the impact of rising temperatures on sediment properties, elucidated the response dynamics of fluid mud characteristics to its resuspension potential under elevated temperature conditions. It has provided an in-depth understanding of the characteristics of fluid sediments and their potential for resuspension.
In recent years, summer heatwaves continued to occur in summer and influenced sediment properties in shallow lakes. The sediments located at the sediment-water interface (SWI) directly impact the lakes ecological health, due to its unique structural characteristics. In order to investigate the temperature effect on sediment structural properties, this study conducted sampling in Lake Gehu before and after high temperature, complemented by indoor simulation experiments. Firstly, sampling results indicated that elevated temperatures induce a decline in the density and yield stress of lake sediments, promoting the formation of fluid sediments (density < 1.25 g/cm3). Secondly, the simulation experiment also showed the same trend. As the temperature rose from 25 ℃ to 35 ℃, the density of sediments at the SWI displayed an exponentially decreasing trend from 1.244 g/cm3 to 1.229 g/cm3. Meanwhile, the increase in temperature led an increase of the sediment median size from the initial 17.22 μm to 21.16 μm, resulting in the flocculation and aggregation of sediment particles. Additionally, increasing temperatures resulted in a higher polysaccharide/protein ratio in extracellular polymeric substances (EPSs), which decreased the stability of sediments. Rheological tests and calculation of critical shear stress showed that the yield stress and critical shear stress of sediments exponentially decreased with increasing temperature. Overall, this study demonstrated that high temperatures can lead a loose and porous sediment structures with a threshold at 29 ℃, which can cause sediment particle resuspension and suspension. Overall, this study has deepened the understanding of the impact of rising temperatures on sediment properties, elucidated the response dynamics of fluid mud characteristics to its resuspension potential under elevated temperature conditions. It has provided an in-depth understanding of the characteristics of fluid sediments and their potential for resuspension.
Available online: June 16, 2025
Abstract:
The operation of the Three Gorges Project led to significant channel adjustments in the downstream reaches, and thus changed the diversion patterns of flow and sediment in bifurcated reaches, which had a significant impact on flood control, navigation, water diversion, and ecology. This study investigated the variation characteristics of four distinct bifurcated reaches in the reach between Jianli and Shijitou of the Middle Yangtze River. Using a two-dimensional flow-sediment transport model, this study compared the flow and sediment diversion ratios before and after the reservoir operation under different flow regimes, and consequently identified the drivers behind the variation in diversion patterns. The results demonstrate that during the post-operation period, the straight bifurcated reach underwent erosion and deposition, while both the main and second branches of the curved bifurcated reach underwent erosion, primarily occurring in the low-water channels. River regulation projects prevented the retreat of high floodplain of the mid-channel bar (MCB) and caused the deposition of low floodplain of the MCB. The channels with higher erosion intensity evolved into the main branches, causing the shift in the main and second branches of some bifurcated reaches. The low-discharge diversion ratios in the right branch of the bifurcated reaches of Nanmenzhou and Luxikou increased from 0.42 and 0.40 to 0.95 and 0.81, respectively, with both showing an increase of over 100%. The imbalanced erosion in the bifurcated reaches is the primary cause for the variation in flow and sediment diversion patterns, with the impact decreasing for a higher discharge. For every 1.0 m increase in the relative scour depth between the main and secondary branch, the flow diversion ratio of the main branch would increase by approximately 7.6–15.8%, and the sediment diversion ratio would increase by approximately 8.2–11.8%. Changes in the mid-channel bar planform would further influence the flow diversion patterns. Sediment deposition on the low floodplain was adverse to the inflow entering the left branch of the Nanyangzhou reach, while the retreat of the high floodplain in the left branch further decreased the flow diversion ratio under the medium to high discharge conditions.
The operation of the Three Gorges Project led to significant channel adjustments in the downstream reaches, and thus changed the diversion patterns of flow and sediment in bifurcated reaches, which had a significant impact on flood control, navigation, water diversion, and ecology. This study investigated the variation characteristics of four distinct bifurcated reaches in the reach between Jianli and Shijitou of the Middle Yangtze River. Using a two-dimensional flow-sediment transport model, this study compared the flow and sediment diversion ratios before and after the reservoir operation under different flow regimes, and consequently identified the drivers behind the variation in diversion patterns. The results demonstrate that during the post-operation period, the straight bifurcated reach underwent erosion and deposition, while both the main and second branches of the curved bifurcated reach underwent erosion, primarily occurring in the low-water channels. River regulation projects prevented the retreat of high floodplain of the mid-channel bar (MCB) and caused the deposition of low floodplain of the MCB. The channels with higher erosion intensity evolved into the main branches, causing the shift in the main and second branches of some bifurcated reaches. The low-discharge diversion ratios in the right branch of the bifurcated reaches of Nanmenzhou and Luxikou increased from 0.42 and 0.40 to 0.95 and 0.81, respectively, with both showing an increase of over 100%. The imbalanced erosion in the bifurcated reaches is the primary cause for the variation in flow and sediment diversion patterns, with the impact decreasing for a higher discharge. For every 1.0 m increase in the relative scour depth between the main and secondary branch, the flow diversion ratio of the main branch would increase by approximately 7.6–15.8%, and the sediment diversion ratio would increase by approximately 8.2–11.8%. Changes in the mid-channel bar planform would further influence the flow diversion patterns. Sediment deposition on the low floodplain was adverse to the inflow entering the left branch of the Nanyangzhou reach, while the retreat of the high floodplain in the left branch further decreased the flow diversion ratio under the medium to high discharge conditions.
Available online: June 16, 2025
Abstract:
Frequent outbreaks of Cladophora blooms in the newly formed littoral zone of Qinghai Lake have been observed due to the warming and humidification of the Qinghai-Tibet Plateau climate. Previous studies on the extraction of Cladophora blooms mainly relied on multi-source satellite remote sensing imagery. However, the limitations of image spatial resolution and mixed-pixel effects hindered the accurate identification of the true distribution and detailed features of the blooms. This study utilized low-altitude UAV imagery combined with the Attention DeepLab V3+ deep learning model to automatically extract Cladophora bloom features in Qinghai Lake. A comparative analysis was conducted with results derived from spectral indice and machine learning methods, and the differences between UAV imagery and optical satellite remote sensing imagery in extracting Cladophora blooms were explored. The results revealed the following: (1) Attention DeepLab V3+ could accurately detect Cladophora blooms without prior thresholds, achieving a kappa coefficient, precision, recall, and F1 score of 0.985, 0.969, 0.983, and 0.976, respectively. (2) Compared with existing methods, the model’s kappa coefficient and F1 score improved by 4.47%-29.75% and 6.35%-34.02%, respectively, demonstrating superior adaptability to complex bloom distribution patterns, especially in capturing boundary details and separating voids. (3) Optical satellite remote sensing imagery tended to overestimate Cladophora blooms in Qinghai Lake, with mean relative error values ranging from 5.5% to 323.47%. This study leveraged the high-resolution advantages of UAV imagery to provide technical support for accurately assessing the true distribution of Cladophora blooms in Qinghai Lake and laid a foundation for the monitoring and tracking of algal blooms features in other water bodies.
Frequent outbreaks of Cladophora blooms in the newly formed littoral zone of Qinghai Lake have been observed due to the warming and humidification of the Qinghai-Tibet Plateau climate. Previous studies on the extraction of Cladophora blooms mainly relied on multi-source satellite remote sensing imagery. However, the limitations of image spatial resolution and mixed-pixel effects hindered the accurate identification of the true distribution and detailed features of the blooms. This study utilized low-altitude UAV imagery combined with the Attention DeepLab V3+ deep learning model to automatically extract Cladophora bloom features in Qinghai Lake. A comparative analysis was conducted with results derived from spectral indice and machine learning methods, and the differences between UAV imagery and optical satellite remote sensing imagery in extracting Cladophora blooms were explored. The results revealed the following: (1) Attention DeepLab V3+ could accurately detect Cladophora blooms without prior thresholds, achieving a kappa coefficient, precision, recall, and F1 score of 0.985, 0.969, 0.983, and 0.976, respectively. (2) Compared with existing methods, the model’s kappa coefficient and F1 score improved by 4.47%-29.75% and 6.35%-34.02%, respectively, demonstrating superior adaptability to complex bloom distribution patterns, especially in capturing boundary details and separating voids. (3) Optical satellite remote sensing imagery tended to overestimate Cladophora blooms in Qinghai Lake, with mean relative error values ranging from 5.5% to 323.47%. This study leveraged the high-resolution advantages of UAV imagery to provide technical support for accurately assessing the true distribution of Cladophora blooms in Qinghai Lake and laid a foundation for the monitoring and tracking of algal blooms features in other water bodies.
Available online: June 13, 2025
Abstract:
Lake Taihu is a large eutrophication lake, the endogenous pollution and release characteristics of sediments in different lake areas were significantly different. The study investigated and analyzed the variation of endogenous pollution and nitrogen and phosphorus diffusion fluxes in Xuhu (grass-dominated zone) and Zhushan Bay(algae-dominated zone) with different water depths. The results showed that: The total nitrogen content in the sediments of Xuhu Lake and Zhushan Lake was 2.59~3.33g·kg-1 and 2.95~3.63g·kg-1, and the total phosphorus content was 0.462~0.652g·kg-1 and 0.749~0.916g·kg-1, respectively. The nutrient content in the sediments of the algae lake area was significantly higher than that in the grass lake area, and the content fluctuated irregularly with the change of water depth. Phosphorus speciation analysis of sediments showed that: Ca-P were the main sediments in Xuhu Bay, and the proportion of Ca-P in total phosphorus decreased significantly with the increase of water depth.The phosphorus morphology in the sediments of Zhushan Lake was dominated by Fe-P, and the proportions of Fe-P, Al-P and Ca-P in the total phosphorus gradually increased with the increase of water depth. The SRP content at the sediment-water interface in the shallow water area of Xuhu is significantly higher than that in the deep water area, while the difference in Fe2+ and NH4+ concentrations between different water depths is relatively small. The SRP, Fe2+ and NH4+ contents at the sediment-water interface in the shallow water area of Zhu Mountain Lake are all higher than those in the deep water area.The endogenous release risk of Xuhu and Zhushan Lake was small, and the NH4+ diffusion flux of Xuhu Lake decreased first and then increased with the increase of water depth, and the NH4+ diffusion flux of Zhushan Lake increased significantly with the increase of water depth. The results play an important role in understanding the nitrogen and phosphorus migration of water depth at the sediment-water interface in the grass/algae lake area of Taihu Lake.
Lake Taihu is a large eutrophication lake, the endogenous pollution and release characteristics of sediments in different lake areas were significantly different. The study investigated and analyzed the variation of endogenous pollution and nitrogen and phosphorus diffusion fluxes in Xuhu (grass-dominated zone) and Zhushan Bay(algae-dominated zone) with different water depths. The results showed that: The total nitrogen content in the sediments of Xuhu Lake and Zhushan Lake was 2.59~3.33g·kg-1 and 2.95~3.63g·kg-1, and the total phosphorus content was 0.462~0.652g·kg-1 and 0.749~0.916g·kg-1, respectively. The nutrient content in the sediments of the algae lake area was significantly higher than that in the grass lake area, and the content fluctuated irregularly with the change of water depth. Phosphorus speciation analysis of sediments showed that: Ca-P were the main sediments in Xuhu Bay, and the proportion of Ca-P in total phosphorus decreased significantly with the increase of water depth.The phosphorus morphology in the sediments of Zhushan Lake was dominated by Fe-P, and the proportions of Fe-P, Al-P and Ca-P in the total phosphorus gradually increased with the increase of water depth. The SRP content at the sediment-water interface in the shallow water area of Xuhu is significantly higher than that in the deep water area, while the difference in Fe2+ and NH4+ concentrations between different water depths is relatively small. The SRP, Fe2+ and NH4+ contents at the sediment-water interface in the shallow water area of Zhu Mountain Lake are all higher than those in the deep water area.The endogenous release risk of Xuhu and Zhushan Lake was small, and the NH4+ diffusion flux of Xuhu Lake decreased first and then increased with the increase of water depth, and the NH4+ diffusion flux of Zhushan Lake increased significantly with the increase of water depth. The results play an important role in understanding the nitrogen and phosphorus migration of water depth at the sediment-water interface in the grass/algae lake area of Taihu Lake.
Available online: June 11, 2025
Abstract:
The Chaobai River basin, a biodiversity hotspot in Beijing, plays a crucial role in understanding the river"s ecosystem and improving protection quality through studies on large benthic animal biodiversity and community stability. In this study, 44 sampling sites were set up in the mountainous and plain sections of the Chaobai River basin, and surveys of large benthic animal communities and their diversity were conducted in September 2020 (autumn), December 2020 (winter), April 2021 (spring), and July 2021 (summer). Using data from these surveys, we analyzed the spatiotemporal changes in multidimensional biodiversity and community stability of benthic animals in the Chaobai River basin and explored the relationships between various biodiversity and community stability indices using Pearson correlation coefficients and generalized linear models. Results showed that seasonal changes in biodiversity and community stability of benthic animals in the Chaobai River were not significant, while differences between mountainous and plain areas were pronounced. The Margalef richness index and other species diversity indices were higher in the mountainous area, but the Pielou evenness index was lower. Functional diversity indices indicated richer functional traits and more redundant species in the mountainous section. Secondary productivity, turnover rate, and species competition intensity of benthic animals were lower in the mountainous area of the Chaobai River than in the plain area, while cohesion was higher, suggesting greater community stability in the mountainous area. Pearson correlation analysis revealed significant correlations between different biodiversity indices, while correlations between indices representing community stability were weak and not significant (p>0.05). Analysis of the correlation between diversity and stability found that more uniform species distribution, higher species richness, and greater niche differentiation led to higher secondary productivity, larger turnover rate, less species competition, and greater community cohesion, resulting in higher community stability. The most parsimonious models for community stability in both mountainous and plain areas favored taxonomic and functional diversity to explain changes in benthic animal community stability in the Chaobai River. Functional divergence (FDiv) was selected most frequently, indicating that differences in species trait abundance and interspecific niche complementarity are key factors affecting benthic animal community stability in the Chaobai River. However, only the model for secondary productivity in the plain area had relatively high explanatory power, while other models had low explanatory power, suggesting that long-term environmental factors may have a greater impact on benthic animal community stability in the Chaobai River.
The Chaobai River basin, a biodiversity hotspot in Beijing, plays a crucial role in understanding the river"s ecosystem and improving protection quality through studies on large benthic animal biodiversity and community stability. In this study, 44 sampling sites were set up in the mountainous and plain sections of the Chaobai River basin, and surveys of large benthic animal communities and their diversity were conducted in September 2020 (autumn), December 2020 (winter), April 2021 (spring), and July 2021 (summer). Using data from these surveys, we analyzed the spatiotemporal changes in multidimensional biodiversity and community stability of benthic animals in the Chaobai River basin and explored the relationships between various biodiversity and community stability indices using Pearson correlation coefficients and generalized linear models. Results showed that seasonal changes in biodiversity and community stability of benthic animals in the Chaobai River were not significant, while differences between mountainous and plain areas were pronounced. The Margalef richness index and other species diversity indices were higher in the mountainous area, but the Pielou evenness index was lower. Functional diversity indices indicated richer functional traits and more redundant species in the mountainous section. Secondary productivity, turnover rate, and species competition intensity of benthic animals were lower in the mountainous area of the Chaobai River than in the plain area, while cohesion was higher, suggesting greater community stability in the mountainous area. Pearson correlation analysis revealed significant correlations between different biodiversity indices, while correlations between indices representing community stability were weak and not significant (p>0.05). Analysis of the correlation between diversity and stability found that more uniform species distribution, higher species richness, and greater niche differentiation led to higher secondary productivity, larger turnover rate, less species competition, and greater community cohesion, resulting in higher community stability. The most parsimonious models for community stability in both mountainous and plain areas favored taxonomic and functional diversity to explain changes in benthic animal community stability in the Chaobai River. Functional divergence (FDiv) was selected most frequently, indicating that differences in species trait abundance and interspecific niche complementarity are key factors affecting benthic animal community stability in the Chaobai River. However, only the model for secondary productivity in the plain area had relatively high explanatory power, while other models had low explanatory power, suggesting that long-term environmental factors may have a greater impact on benthic animal community stability in the Chaobai River.
Available online: June 11, 2025
Abstract:
This study quantifies the spatiotemporal dynamics of blue and green water resources in the Min-Tuo River Basin and disentangles their differential sensitivities to climate and land-use changes, thereby proposing context-specific management strategies and adaptive pathways for sustainable water governance.Utilizing the Soil and Water Assessment Tool (SWAT) model and the Future Land-Use Simulation (FLUS) model, combined with climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6),we analyzed historical changes (1981–2021) and projected future dynamics of blue and green water up to 2100. Key findings include:(1)From 1981 to 2021, the Min-Tuo River Basin was dominated by blue water, accounting for 63.2% of the total water resources. Climate change served as the core driving factor for variations in blue and green water, with contribution rates of 79.12% and 63.29%, respectively.(2)Between 1990 and 2020, cultivated land and grassland decreased by 4.0% and 2.1% , respectively, while urban land expanded by 138% , significantly reducing agricultural and grassland areas and exacerbating spatial imbalances in water resources.By 2040, urban land is projected to further expand by 135% , further compressing the spatial extent of grassland and cultivated land. This expansion will concentrate in the Chengdu Plain?in the eastern part of the basin, exacerbating water scarcity risks in densely populated areas.(3)Future climate trends indicate a precipitation increase of 1.43-1.80 mm/a,temperature rise of 0.025-0.042℃/a,Green water will significantly increase by 0.35-1.02 mm/a, while blue water decreases until 2050 before rebounding. Among the four Shared Socioeconomic Pathways (SSPs), the fossil fuel-dominated pathway (SSP5-8.5) exhibits the most pronounced changes in blue and green water, whereas curbing urban expansion and prioritizing sustainable development (SSP1-2.6) could effectively alleviate water resource pressure.(4)blue water concentrates in the southwestern basin, while green water hotspots shift southeastward. The Chengdu Plain faces heightened risks of water scarcity and extreme events due to population density and elevated temperatures.This study provides a scientific basis for adaptive water management strategies in the Min-Tuo River Basin under climate and land-use pressures.
This study quantifies the spatiotemporal dynamics of blue and green water resources in the Min-Tuo River Basin and disentangles their differential sensitivities to climate and land-use changes, thereby proposing context-specific management strategies and adaptive pathways for sustainable water governance.Utilizing the Soil and Water Assessment Tool (SWAT) model and the Future Land-Use Simulation (FLUS) model, combined with climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6),we analyzed historical changes (1981–2021) and projected future dynamics of blue and green water up to 2100. Key findings include:(1)From 1981 to 2021, the Min-Tuo River Basin was dominated by blue water, accounting for 63.2% of the total water resources. Climate change served as the core driving factor for variations in blue and green water, with contribution rates of 79.12% and 63.29%, respectively.(2)Between 1990 and 2020, cultivated land and grassland decreased by 4.0% and 2.1% , respectively, while urban land expanded by 138% , significantly reducing agricultural and grassland areas and exacerbating spatial imbalances in water resources.By 2040, urban land is projected to further expand by 135% , further compressing the spatial extent of grassland and cultivated land. This expansion will concentrate in the Chengdu Plain?in the eastern part of the basin, exacerbating water scarcity risks in densely populated areas.(3)Future climate trends indicate a precipitation increase of 1.43-1.80 mm/a,temperature rise of 0.025-0.042℃/a,Green water will significantly increase by 0.35-1.02 mm/a, while blue water decreases until 2050 before rebounding. Among the four Shared Socioeconomic Pathways (SSPs), the fossil fuel-dominated pathway (SSP5-8.5) exhibits the most pronounced changes in blue and green water, whereas curbing urban expansion and prioritizing sustainable development (SSP1-2.6) could effectively alleviate water resource pressure.(4)blue water concentrates in the southwestern basin, while green water hotspots shift southeastward. The Chengdu Plain faces heightened risks of water scarcity and extreme events due to population density and elevated temperatures.This study provides a scientific basis for adaptive water management strategies in the Min-Tuo River Basin under climate and land-use pressures.
Available online: June 09, 2025
Abstract:
To investigate the impact of fluoride pollution on bacterial communities in the water-soil system, this study collected 66 sets of surface water, sediment, and riparian soil samples from the Qingshui River basin in Ningxia in 2022. The samples were categorized into three groups based on the fluoride concentration in the surface water: low fluoride group (F? < 1.0 mg/L), high fluoride I group (1.0 ≤ F? < 1.5 mg/L), and high fluoride II group (F? ≥ 1.5 mg/L). Bacterial community responses were systematically analyzed through 16S rDNA high-throughput sequencing and polymorphic fluoride species analysis. The results revealed that fluoride pollution decreased bacterial α-diversity (low fluoride group > high fluoride I group > high fluoride II group), although the Chao1 index of sediments increased due to niche release by rare species. The phyla Campilobacterota and Desulfobacterota were identified as fluoride-tolerant bacterial phyla, with species of Desulfobacterota participating in sulfate reduction to alleviate fluoride toxicity at low abundances. Genera such as Sulfurovum were recognized as fluoride-tolerant bacterial genera in the water-soil system. Bacteria facilitated the conversion of residual fixed fluoride (Res-F) in sediments and soils by decomposing and transforming it into other forms, with soil environments proving more favorable for bacterial decomposition of Res-F. This study establishes the first framework linking bacterial communities to polymorphic fluoride in the Qingshui River basin, enhancing the understanding of the impact of fluoride on bacterial communities in river ecosystems. It provides a scientific basis for the development of effective ecological and environmental protection policies, contributing to mitigating or reducing the potential risks of fluoride pollution to the ecological environment.
To investigate the impact of fluoride pollution on bacterial communities in the water-soil system, this study collected 66 sets of surface water, sediment, and riparian soil samples from the Qingshui River basin in Ningxia in 2022. The samples were categorized into three groups based on the fluoride concentration in the surface water: low fluoride group (F? < 1.0 mg/L), high fluoride I group (1.0 ≤ F? < 1.5 mg/L), and high fluoride II group (F? ≥ 1.5 mg/L). Bacterial community responses were systematically analyzed through 16S rDNA high-throughput sequencing and polymorphic fluoride species analysis. The results revealed that fluoride pollution decreased bacterial α-diversity (low fluoride group > high fluoride I group > high fluoride II group), although the Chao1 index of sediments increased due to niche release by rare species. The phyla Campilobacterota and Desulfobacterota were identified as fluoride-tolerant bacterial phyla, with species of Desulfobacterota participating in sulfate reduction to alleviate fluoride toxicity at low abundances. Genera such as Sulfurovum were recognized as fluoride-tolerant bacterial genera in the water-soil system. Bacteria facilitated the conversion of residual fixed fluoride (Res-F) in sediments and soils by decomposing and transforming it into other forms, with soil environments proving more favorable for bacterial decomposition of Res-F. This study establishes the first framework linking bacterial communities to polymorphic fluoride in the Qingshui River basin, enhancing the understanding of the impact of fluoride on bacterial communities in river ecosystems. It provides a scientific basis for the development of effective ecological and environmental protection policies, contributing to mitigating or reducing the potential risks of fluoride pollution to the ecological environment.
Available online: June 04, 2025
Abstract:
To quantitatively evaluate the content of algae-derived phosphorus in Lake Taihu and the influence of the algal community structure on it, and to provide data support for a better understanding of the growth and decay of algae and the internal phosphorus cycle in the lake, this study calculated the concentration of total algae-derived phosphorus in Lake Taihu and its proportion to total phosphorus in the lake based on the monitoring data and investigation data of algae and water quality of Lake Taihu from 2021 to 2023. The results showed that from 2021 to 2023, the total algal density of Lake Taihu decreased from 6.3 × 107 cells/L to 4.4 × 107 cells/L （annual average value）, the proportion of Microcystis decreased from 79.8% to 35.6%. On the other hand, the density and proportion of cyanophyta, green algae and diatoms increased significantly, and the structure of the whole lake"s algal community changed significantly. During the same period, the total phosphorus concentration in the Lake Taihu fluctuated from 0.053 mg/L to 0.062 mg/L, and the average proportion of particulate total phosphorus was 60.4%, of which the proportion of algae-derived phosphorus in particulate total phosphorus and total phosphorus was 49.4% and 29.6%, respectively, indicating that algae-derived phosphorus is an important component of particulate phosphorus. According to the further subdivision of the algal community structure, it is found that the algae-derived phosphorus in Lake Taihu is mainly contributed by three categories including cyanobacteria, diatom and chlorophyta. From 2021 to 2022, the contribution rates of cyanobacteria to algae derived phosphorus were 66.5% and 65.7%, respectively. With the rapid decrease in cyanobacteria density in 2023, their contribution and proportion of algae derived-phosphorus also significantly decreased, while the contribution and proportion of algae-derived phosphorus from diatom increased from 23.9% to 56.1%. The total algae and cyanobacteria density in 2023 had significantly decreased compared to 2021, but due to the increase in the proportion of diatom, chlorophyta and other categories, the increase in algae-derived phosphorus provided by them compensated for the decrease in cyanobacteria algae-derived phosphorus, ultimately leading to an increase in the total algae-derived phosphorus in the entire lake instead of a decrease. Although the increase in algal density of diatom and other categories is not as significant as the decrease in cyanobacteria density, they have larger cell volume and higher monomeric phosphorus content, thus exhibiting a more significant compensatory effect on algal-derived phosphorus.
To quantitatively evaluate the content of algae-derived phosphorus in Lake Taihu and the influence of the algal community structure on it, and to provide data support for a better understanding of the growth and decay of algae and the internal phosphorus cycle in the lake, this study calculated the concentration of total algae-derived phosphorus in Lake Taihu and its proportion to total phosphorus in the lake based on the monitoring data and investigation data of algae and water quality of Lake Taihu from 2021 to 2023. The results showed that from 2021 to 2023, the total algal density of Lake Taihu decreased from 6.3 × 107 cells/L to 4.4 × 107 cells/L （annual average value）, the proportion of Microcystis decreased from 79.8% to 35.6%. On the other hand, the density and proportion of cyanophyta, green algae and diatoms increased significantly, and the structure of the whole lake"s algal community changed significantly. During the same period, the total phosphorus concentration in the Lake Taihu fluctuated from 0.053 mg/L to 0.062 mg/L, and the average proportion of particulate total phosphorus was 60.4%, of which the proportion of algae-derived phosphorus in particulate total phosphorus and total phosphorus was 49.4% and 29.6%, respectively, indicating that algae-derived phosphorus is an important component of particulate phosphorus. According to the further subdivision of the algal community structure, it is found that the algae-derived phosphorus in Lake Taihu is mainly contributed by three categories including cyanobacteria, diatom and chlorophyta. From 2021 to 2022, the contribution rates of cyanobacteria to algae derived phosphorus were 66.5% and 65.7%, respectively. With the rapid decrease in cyanobacteria density in 2023, their contribution and proportion of algae derived-phosphorus also significantly decreased, while the contribution and proportion of algae-derived phosphorus from diatom increased from 23.9% to 56.1%. The total algae and cyanobacteria density in 2023 had significantly decreased compared to 2021, but due to the increase in the proportion of diatom, chlorophyta and other categories, the increase in algae-derived phosphorus provided by them compensated for the decrease in cyanobacteria algae-derived phosphorus, ultimately leading to an increase in the total algae-derived phosphorus in the entire lake instead of a decrease. Although the increase in algal density of diatom and other categories is not as significant as the decrease in cyanobacteria density, they have larger cell volume and higher monomeric phosphorus content, thus exhibiting a more significant compensatory effect on algal-derived phosphorus.
Available online: June 04, 2025
Abstract:
The red swamp crayfish, Procambarus clarkii, and the golden apple snail, Pomacea canaliculata, are globally widespread invasive species that can cause serious damage to aquatic ecosystems in the invaded areas. However, the impact of their co-invasion on native ecosystems has only rarely been studied. To explore the niche competition between co-invasive and native species, we investigated a natural pond that was co-invaded by P. clarkii and P. canaliculata. We used a fatty acid biomarker technique to analyze differences in feeding habits, niche widths, and trophic levels among P. clarkii, P. canaliculata, and the native snail Bellamya aeruginosa. We also conducted indoor predation control experiments to verify that the alien species directly prey on B. aeruginosa. Principal component analysis (PCA) of fatty acids in muscles revealed larger areas of the confidence ellipses in P. clarkii and P. canaliculata compared to B. aeruginosa, indicating that the alien species had broader niche widths and superior trophic resource exploitation. Also, the percentage content of C18:1 n-9 + C22:6 n-3 was significantly higher in P. clarkii than in P. canaliculata and B. aeruginosa, suggesting that the crayfish is more carnivorous. C15 + C17 content was significantly higher in B. aeruginosa than in the alien species, suggesting bacteria as the native snail"s main carbon source. In contrast, C18:2 + C18:3 content was significantly higher in the alien species, demonstrating that their main carbon source is vascular plant material. Finally, the ratio of polyunsaturated to saturated fatty acids (PUFA/SFA) was also higher in the alien species, indicating that they reside at a higher trophic level and exhibit stronger competitive abilities compared to B. aeruginosa. Our indoor predation experiments showed that P. clarkii significantly more often preyed on juvenile B. aeruginosa than on juvenile P. canaliculata. We also observed predation of adult P. canaliculata on juvenile B. aeruginosa, albeit at a lower rate. In summary, by combining the results of fatty acid biomarker techniques and indoor predation control experiments, we demonstrate that both the niche width and the trophic level of P. clarkii are higher than those of P. canaliculata, while P. canaliculata exhibits significantly broader niche widths and higher trophic positions comparing to the native species B. aeruginosa. The co-invasion of these two species thus may have a significant negative impact on native snails.
The red swamp crayfish, Procambarus clarkii, and the golden apple snail, Pomacea canaliculata, are globally widespread invasive species that can cause serious damage to aquatic ecosystems in the invaded areas. However, the impact of their co-invasion on native ecosystems has only rarely been studied. To explore the niche competition between co-invasive and native species, we investigated a natural pond that was co-invaded by P. clarkii and P. canaliculata. We used a fatty acid biomarker technique to analyze differences in feeding habits, niche widths, and trophic levels among P. clarkii, P. canaliculata, and the native snail Bellamya aeruginosa. We also conducted indoor predation control experiments to verify that the alien species directly prey on B. aeruginosa. Principal component analysis (PCA) of fatty acids in muscles revealed larger areas of the confidence ellipses in P. clarkii and P. canaliculata compared to B. aeruginosa, indicating that the alien species had broader niche widths and superior trophic resource exploitation. Also, the percentage content of C18:1 n-9 + C22:6 n-3 was significantly higher in P. clarkii than in P. canaliculata and B. aeruginosa, suggesting that the crayfish is more carnivorous. C15 + C17 content was significantly higher in B. aeruginosa than in the alien species, suggesting bacteria as the native snail"s main carbon source. In contrast, C18:2 + C18:3 content was significantly higher in the alien species, demonstrating that their main carbon source is vascular plant material. Finally, the ratio of polyunsaturated to saturated fatty acids (PUFA/SFA) was also higher in the alien species, indicating that they reside at a higher trophic level and exhibit stronger competitive abilities compared to B. aeruginosa. Our indoor predation experiments showed that P. clarkii significantly more often preyed on juvenile B. aeruginosa than on juvenile P. canaliculata. We also observed predation of adult P. canaliculata on juvenile B. aeruginosa, albeit at a lower rate. In summary, by combining the results of fatty acid biomarker techniques and indoor predation control experiments, we demonstrate that both the niche width and the trophic level of P. clarkii are higher than those of P. canaliculata, while P. canaliculata exhibits significantly broader niche widths and higher trophic positions comparing to the native species B. aeruginosa. The co-invasion of these two species thus may have a significant negative impact on native snails.
Available online: June 04, 2025
Abstract:
Methylphosphonate (MPn), a typical organophosphonate characterized by a C-P bond, profoundly influences phosphorus cycling and methane (CH4) production mechanisms in aquatic ecosystems through its biosynthesis and degradation processes. However, there is limited research on the dynamics of MPn in water bodies and the MPn accumulation capacity of algae. In this study, liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (LC-MS/MS) was employed to quantify MPn in 21 water samples and 15 algal species. Combined with field monitoring, algal laboratory cultivation, and raw water incubation experiments (including MPn/Pi addition, BES treatment, algal filtration, and dark treatment), the relationship between MPn dynamics and CH4 generation was investigated. The results revealed that MPn was detected in 52.4% (11/21) of water samples (1.50±0.24~6.99±0.59 μg/L), and 93.3% (14/15) of algal strains accumulated intracellular MPn (1.87±0.57~22.24±5.81 μg/L). Notably, Microcystis sp. FACHB-3602 exhibited dynamic MPn accumulation during 7 days cultivation (peak value: 8.63±0.85 μg/L), indicating that algae are a significant biological source of MPn in aquatic ecosystems. In both water samples and algae, the contribution of MPn-P to dissolved organic phosphorus (DOP) (0.70%~37.85%、0.21%~0.90%) was significantly higher than that of MPn-C to dissolved organic carbon (DOC) (0.00%~0.05%、0.00%~0.01%), highlighting the dominant role of MPn in phosphorus cycling from an ecological stoichiometric perspective. Raw water incubation experiments demonstrated that MPn addition increased CH4 production by 157.43% compared to the control, while simultaneous addition of inorganic phosphorus (Pi) suppressed CH4 generation. Algal filtration reduced CH4 production by 23.96%, whereas dark treatment promoted CH4 accumulation. These findings suggest that algal-bacterial interactions regulate MPn turnover and aerobic CH4 production, modulated by inorganic phosphorus availability. This study provides critical theoretical insights for further exploration of MPn’s role in aquatic phosphorus cycling and aerobic CH4 production mechanisms.
Methylphosphonate (MPn), a typical organophosphonate characterized by a C-P bond, profoundly influences phosphorus cycling and methane (CH4) production mechanisms in aquatic ecosystems through its biosynthesis and degradation processes. However, there is limited research on the dynamics of MPn in water bodies and the MPn accumulation capacity of algae. In this study, liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (LC-MS/MS) was employed to quantify MPn in 21 water samples and 15 algal species. Combined with field monitoring, algal laboratory cultivation, and raw water incubation experiments (including MPn/Pi addition, BES treatment, algal filtration, and dark treatment), the relationship between MPn dynamics and CH4 generation was investigated. The results revealed that MPn was detected in 52.4% (11/21) of water samples (1.50±0.24~6.99±0.59 μg/L), and 93.3% (14/15) of algal strains accumulated intracellular MPn (1.87±0.57~22.24±5.81 μg/L). Notably, Microcystis sp. FACHB-3602 exhibited dynamic MPn accumulation during 7 days cultivation (peak value: 8.63±0.85 μg/L), indicating that algae are a significant biological source of MPn in aquatic ecosystems. In both water samples and algae, the contribution of MPn-P to dissolved organic phosphorus (DOP) (0.70%~37.85%、0.21%~0.90%) was significantly higher than that of MPn-C to dissolved organic carbon (DOC) (0.00%~0.05%、0.00%~0.01%), highlighting the dominant role of MPn in phosphorus cycling from an ecological stoichiometric perspective. Raw water incubation experiments demonstrated that MPn addition increased CH4 production by 157.43% compared to the control, while simultaneous addition of inorganic phosphorus (Pi) suppressed CH4 generation. Algal filtration reduced CH4 production by 23.96%, whereas dark treatment promoted CH4 accumulation. These findings suggest that algal-bacterial interactions regulate MPn turnover and aerobic CH4 production, modulated by inorganic phosphorus availability. This study provides critical theoretical insights for further exploration of MPn’s role in aquatic phosphorus cycling and aerobic CH4 production mechanisms.
Bao Hangtong, Li yiping, Zhao guoli, Li ronghui, Zhu ya, Yu min, Pan haiping, Wang yaning, Wang can, Wang chuer, Huang xusheng
Available online: June 04, 2025
Abstract:
Dawangtan Reservoir is a typical large drinking water source reservoir in the south subtropical region. The dominance of cyanobacteria and blooms due to eutrophication are major threats to water supply security. Therefore, elucidating the phytoplankton community characteristics and identifying the driving factors of filamentous cyanobacteria dominance hold imperative significance for developing effective bloom mitigation strategies and enhancing reservoir water management protocols. This study conducted quarterly investigations on the water physical and chemical environment and phytoplankton community of the Dawangtan Reservoir from December 2021 to October 2022, aiming to explore the seasonal dynamics of the phytoplankton community and the driving factors behind the dominance of filamentous cyanobacteria. The results indicate that the phytoplankton in Dawangtan Reservoir comprises 7 phylum and 127 species, predominantly belonging to Chlorophyta, Bacillariophyta and Cyanophyta, and can be classified into 26 functional groups. The cell density of phytoplankton ranges between 1.2×106 cells/L and 430×106 cells/L, with the highest density observed in Autumn, Spring, Winter, and Summer. The biomass ranges from 0.14 mg/L to 51 mg/L, with the highest biomass in Autumn, Winter and Spring, and the lowest in Summer. The dominant genera are filamentous cyanobacteria such as Limnothrix and Pseudanabaena, and the S1 functional group is the long-term dominant functional group. The comprehensive trophic level index of the Dawangtan Reservoir ranges from 36.02 to 49.57, demonstrating that the reservoir is characterized by a Mesotrophic status. Mantel tests and Redundancy analysis (RDA) revealed that water temperature, transparency, and nitrogen concentration are significant explanatory variables for the dominance of filamentous cyanobacteria. The absolute dominance of filamentous cyanobacteria was observed during the Summer and Autumn, characterized by lower transparency, reduced nitrogen concentration, and elevated water temperatures. Among them, Autumn may be a high - risk period for algae blooms of Limnothrix and Pseudanabaena. Combined with the functional group, the turbidity environment of large reservoirs is an important reason for the dominance of filamentous cyanobacteria. In Autumn, water temperature and nutrient conditions were in the suitable range for Limnothrix and Pseudanabaena, which were the key driving factors for their large-scale proliferation. Under the threat posed by filamentous cyanobacteria such as Limnothrix and Pseudanabaena, attention should be directed toward investigating the causative factors of elevated turbidity and chromaticity in reservoir water bodies. Enhancing water transparency through targeted interventions is critical to suppress the dominant formation of these filamentous cyanobacterial species.
Dawangtan Reservoir is a typical large drinking water source reservoir in the south subtropical region. The dominance of cyanobacteria and blooms due to eutrophication are major threats to water supply security. Therefore, elucidating the phytoplankton community characteristics and identifying the driving factors of filamentous cyanobacteria dominance hold imperative significance for developing effective bloom mitigation strategies and enhancing reservoir water management protocols. This study conducted quarterly investigations on the water physical and chemical environment and phytoplankton community of the Dawangtan Reservoir from December 2021 to October 2022, aiming to explore the seasonal dynamics of the phytoplankton community and the driving factors behind the dominance of filamentous cyanobacteria. The results indicate that the phytoplankton in Dawangtan Reservoir comprises 7 phylum and 127 species, predominantly belonging to Chlorophyta, Bacillariophyta and Cyanophyta, and can be classified into 26 functional groups. The cell density of phytoplankton ranges between 1.2×106 cells/L and 430×106 cells/L, with the highest density observed in Autumn, Spring, Winter, and Summer. The biomass ranges from 0.14 mg/L to 51 mg/L, with the highest biomass in Autumn, Winter and Spring, and the lowest in Summer. The dominant genera are filamentous cyanobacteria such as Limnothrix and Pseudanabaena, and the S1 functional group is the long-term dominant functional group. The comprehensive trophic level index of the Dawangtan Reservoir ranges from 36.02 to 49.57, demonstrating that the reservoir is characterized by a Mesotrophic status. Mantel tests and Redundancy analysis (RDA) revealed that water temperature, transparency, and nitrogen concentration are significant explanatory variables for the dominance of filamentous cyanobacteria. The absolute dominance of filamentous cyanobacteria was observed during the Summer and Autumn, characterized by lower transparency, reduced nitrogen concentration, and elevated water temperatures. Among them, Autumn may be a high - risk period for algae blooms of Limnothrix and Pseudanabaena. Combined with the functional group, the turbidity environment of large reservoirs is an important reason for the dominance of filamentous cyanobacteria. In Autumn, water temperature and nutrient conditions were in the suitable range for Limnothrix and Pseudanabaena, which were the key driving factors for their large-scale proliferation. Under the threat posed by filamentous cyanobacteria such as Limnothrix and Pseudanabaena, attention should be directed toward investigating the causative factors of elevated turbidity and chromaticity in reservoir water bodies. Enhancing water transparency through targeted interventions is critical to suppress the dominant formation of these filamentous cyanobacterial species.
Available online: June 03, 2025
Abstract:
The treatment of organic micropollutants has become a globally concerned environmental issue. Integrating the characteristics of watershed, establishing an effective screening method to identify high-risk contaminants is key to achieving effective control of organic micropollutants. In this study, we focused on the shallow lake area （Taihu Lake）, and utilizing the concentration and toxicological data of contaminants in water and sediment，we developed a screening method for preferential control of organic micropollutants based on exposure risk and hazard risk indicators. By using the 2/3 cumulative rank method, 123 aqueous phase contaminants were scored and 33 contaminants, including fluvalinate, permethrin and triphenyl phosphate were identified as priority contaminants. Among them, 31 substances were determined through aqueous phase data assessment while Ethynylestradiol and perfluorododecanoic acid were added as supplementary targets following the incorporation of sediment exposure risk assessment data, which shows that exposure data of contaminants in sediments serves as an essential supplement to the scoring system for priority control frameworks Among the selected 33 priority contaminants, 17 substances appear in various control lists of different countries ,but 16 substances have not received sufficient attention. The uncertainty in this paper mainly stems from the lack of toxicity data for some contaminants and the acquisition of related thresholds as well as insufficient timeliness and synchronization of monitoring data, and it is recommended that future work should focus on establishing monitoring standards for organic micropollutants and improving toxicity data, This study can provide support for the effective control of emerging contaminants in river and lake regions nationwide
The treatment of organic micropollutants has become a globally concerned environmental issue. Integrating the characteristics of watershed, establishing an effective screening method to identify high-risk contaminants is key to achieving effective control of organic micropollutants. In this study, we focused on the shallow lake area （Taihu Lake）, and utilizing the concentration and toxicological data of contaminants in water and sediment，we developed a screening method for preferential control of organic micropollutants based on exposure risk and hazard risk indicators. By using the 2/3 cumulative rank method, 123 aqueous phase contaminants were scored and 33 contaminants, including fluvalinate, permethrin and triphenyl phosphate were identified as priority contaminants. Among them, 31 substances were determined through aqueous phase data assessment while Ethynylestradiol and perfluorododecanoic acid were added as supplementary targets following the incorporation of sediment exposure risk assessment data, which shows that exposure data of contaminants in sediments serves as an essential supplement to the scoring system for priority control frameworks Among the selected 33 priority contaminants, 17 substances appear in various control lists of different countries ,but 16 substances have not received sufficient attention. The uncertainty in this paper mainly stems from the lack of toxicity data for some contaminants and the acquisition of related thresholds as well as insufficient timeliness and synchronization of monitoring data, and it is recommended that future work should focus on establishing monitoring standards for organic micropollutants and improving toxicity data, This study can provide support for the effective control of emerging contaminants in river and lake regions nationwide
Available online: May 26, 2025
Abstract:
Chlorophyll-a is an important indicator of primary productivity in lake ecosystems, and its concentration changes reflect the nutrient status and ecological health of the water. This study, based on water quality and environmental data from 2011 to 2024 for Chagannaoer, uses correlation and redundancy analysis to reveal the interannual and intra-annual variation characteristics of chlorophyll-a concentration and its key driving factors. The results show that between 2011 and 2024, the interannual variation of chlorophyll-a concentration in Chagannaoer was stable, with the highest concentrations in summer and the lowest in spring, and a decreasing trend from north to south. Interannually, chlorophyll-a concentration was negatively correlated with the permanganate index and positively correlated with water volume, water depth, precipitation, evaporation, and temperature. Runoff also had a promoting effect on its concentration.
Chlorophyll-a is an important indicator of primary productivity in lake ecosystems, and its concentration changes reflect the nutrient status and ecological health of the water. This study, based on water quality and environmental data from 2011 to 2024 for Chagannaoer, uses correlation and redundancy analysis to reveal the interannual and intra-annual variation characteristics of chlorophyll-a concentration and its key driving factors. The results show that between 2011 and 2024, the interannual variation of chlorophyll-a concentration in Chagannaoer was stable, with the highest concentrations in summer and the lowest in spring, and a decreasing trend from north to south. Interannually, chlorophyll-a concentration was negatively correlated with the permanganate index and positively correlated with water volume, water depth, precipitation, evaporation, and temperature. Runoff also had a promoting effect on its concentration.
Available online: May 26, 2025
Abstract:
Dissolved organic matter (DOM) plays a pivotal role in aquatic ecosystems and biogeochemical cycles. Understanding the composition characteristics, sources, and influencing factors of DOM in typical lakes and reservoirs across northern China is crucial for effective organic matter pollution control and ensuring safe water transfer. This study collected 130 surface water samples from eight representative water bodies: Xiaoxingkai Lake (XXKH), Songhua Lake (SHH), Dahuofang Reservoir (DHF), Guanting Reservoir (GT), Yuqiao Reservoir (YQ), Baiyangdian Lake (BYD), Hengshui Lake (HSH), and Nansi Lake (NSH). The key findings are as follows: (1) Through parallel factor analysis (PARAFAC), three distinct fluorescent components were identified in the DOM of these lakes and reservoirs: humic-like substances (C1), tryptophan-like substances (C2), and tyrosine-like substances (C3). DOM in northeastern lakes and reservoirs exhibited strong humification characteristics with relatively low autochthonous contributions, while those in North China demonstrated pronounced autochthonous features. Notably, BYD displayed unique DOM characteristics with higher DOM content and protein-like components compared to other studied water bodies. (2) Humic-like substances from anthropogenic sources significantly positively correlated with COD and HIX (p < 0.01). Protein-like components (C2, C3) showed significant positive correlations with DOC, FI, and BIX (p < 0.01), but negative correlations with HIX (p < 0.01). DOM components correlated more strongly with nitrogen than phosphorus nutrients. (3) Environmental factors significantly influenced DOM dynamics. Larger drainage areas prolonged DOM retention time, promoting the accumulation of autochthonous DOM components. Greater water depth facilitated DOM preservation. Elevated temperatures enhanced DOM transformation within lakes, strengthening autochthonous characteristics while weakening allochthonous features. In high-precipitation regions, terrestrial humic substances were transported into water bodies through runoff, enhancing exogenous DOM characteristics. Biological factors, including algae, aquatic vegetation, and microorganisms, primarily influenced DOM dynamics through endogenous processes, collectively regulating nutrient cycling and ecological functions. In areas with intensive human activities, increased endogenous DOM production was observed in lake and reservoir waters. Furthermore, regions with higher vegetation coverage contributed more humic-like components to aquatic systems. This comprehensive analysis provides valuable insights into DOM dynamics in northern China"s lakes and reservoirs, offering scientific basis for water quality management and pollution control strategies.
Dissolved organic matter (DOM) plays a pivotal role in aquatic ecosystems and biogeochemical cycles. Understanding the composition characteristics, sources, and influencing factors of DOM in typical lakes and reservoirs across northern China is crucial for effective organic matter pollution control and ensuring safe water transfer. This study collected 130 surface water samples from eight representative water bodies: Xiaoxingkai Lake (XXKH), Songhua Lake (SHH), Dahuofang Reservoir (DHF), Guanting Reservoir (GT), Yuqiao Reservoir (YQ), Baiyangdian Lake (BYD), Hengshui Lake (HSH), and Nansi Lake (NSH). The key findings are as follows: (1) Through parallel factor analysis (PARAFAC), three distinct fluorescent components were identified in the DOM of these lakes and reservoirs: humic-like substances (C1), tryptophan-like substances (C2), and tyrosine-like substances (C3). DOM in northeastern lakes and reservoirs exhibited strong humification characteristics with relatively low autochthonous contributions, while those in North China demonstrated pronounced autochthonous features. Notably, BYD displayed unique DOM characteristics with higher DOM content and protein-like components compared to other studied water bodies. (2) Humic-like substances from anthropogenic sources significantly positively correlated with COD and HIX (p < 0.01). Protein-like components (C2, C3) showed significant positive correlations with DOC, FI, and BIX (p < 0.01), but negative correlations with HIX (p < 0.01). DOM components correlated more strongly with nitrogen than phosphorus nutrients. (3) Environmental factors significantly influenced DOM dynamics. Larger drainage areas prolonged DOM retention time, promoting the accumulation of autochthonous DOM components. Greater water depth facilitated DOM preservation. Elevated temperatures enhanced DOM transformation within lakes, strengthening autochthonous characteristics while weakening allochthonous features. In high-precipitation regions, terrestrial humic substances were transported into water bodies through runoff, enhancing exogenous DOM characteristics. Biological factors, including algae, aquatic vegetation, and microorganisms, primarily influenced DOM dynamics through endogenous processes, collectively regulating nutrient cycling and ecological functions. In areas with intensive human activities, increased endogenous DOM production was observed in lake and reservoir waters. Furthermore, regions with higher vegetation coverage contributed more humic-like components to aquatic systems. This comprehensive analysis provides valuable insights into DOM dynamics in northern China"s lakes and reservoirs, offering scientific basis for water quality management and pollution control strategies.
Available online: May 26, 2025
Abstract:
The middle and lower reaches of the Yangtze River are key waterbird habitats along the East Asian ? Australasian Flyway. However, habitat degradation and fragmentation, driven by climate change and human activities, pose severe threats to waterbird diversity. This study utilized citizen science data and the MaxEnt model to predict potential habitats for 123 waterbird species, identifying biodiversity hotspots as ecological sources. By integrating circuit theory and ecological resistance surfaces, we delineated ecological corridors and “pinch points”. The key waterbird habitats, including ecological sources and pinch points, were overlaid with the existing protected areas to assess conservation gaps. Our results show that: (1) the total potential area for key waterbird habitats in the middle and lower Yangtze River is 30,322 km2, of which 27,669 km2 is ecological source area and 2,653 km2 is composed of pinch points; (2) although 26.85% of key habitats are protected, only 12.24% of ecological pinch points are, indicating a significant gap in the protection of highly connected habitats; (3) the total area of conservation gaps is 9,417.5 km2, with 44 habitats partially protected and 19 completely unprotected. Based on the spatial distribution of these gaps, we propose four key conservation strategies: establishing food resource corridors, optimizing multi-objective management of protected areas, restoring ecological connectivity in critical river sections, and prioritizing the inclusion of high-biodiversity areas in the protected area network. Incorporating flexible conservation approaches, such as Other Effective Area-based Conservation Measures (OECMs), can fill gaps in traditional systems and provide practical solutions for enhancing waterbird diversity conservation.
The middle and lower reaches of the Yangtze River are key waterbird habitats along the East Asian ? Australasian Flyway. However, habitat degradation and fragmentation, driven by climate change and human activities, pose severe threats to waterbird diversity. This study utilized citizen science data and the MaxEnt model to predict potential habitats for 123 waterbird species, identifying biodiversity hotspots as ecological sources. By integrating circuit theory and ecological resistance surfaces, we delineated ecological corridors and “pinch points”. The key waterbird habitats, including ecological sources and pinch points, were overlaid with the existing protected areas to assess conservation gaps. Our results show that: (1) the total potential area for key waterbird habitats in the middle and lower Yangtze River is 30,322 km2, of which 27,669 km2 is ecological source area and 2,653 km2 is composed of pinch points; (2) although 26.85% of key habitats are protected, only 12.24% of ecological pinch points are, indicating a significant gap in the protection of highly connected habitats; (3) the total area of conservation gaps is 9,417.5 km2, with 44 habitats partially protected and 19 completely unprotected. Based on the spatial distribution of these gaps, we propose four key conservation strategies: establishing food resource corridors, optimizing multi-objective management of protected areas, restoring ecological connectivity in critical river sections, and prioritizing the inclusion of high-biodiversity areas in the protected area network. Incorporating flexible conservation approaches, such as Other Effective Area-based Conservation Measures (OECMs), can fill gaps in traditional systems and provide practical solutions for enhancing waterbird diversity conservation.
Available online: May 26, 2025
Abstract:
As the economy rapidly develops, freshwater ecosystems suffer from eutrophication, leading to a series of aquatic ecological issues, including water quality deterioration and a decline in biodiversity. The most critical step in the ecological restoration of eutrophic shallow lakes is to achieve the transition of primary producers from phytoplankton to submerged macrophytes. Current ecological restoration projects of lakes often emphasize water quality improvement but lack research on the impact on greenhouse gas fluxes. This study investigated the restored and unrestored areas of Lake Xuanwu to compare the physicochemical parameters of the water and the carbon dioxide (CO2) and methane (CH4) fluxes at the water-atmosphere interface between the two areas. The results show that the concentration of chlorophyll a (Chl a) in the unrestored area was significantly higher than that in the restored area in all four seasons, reaching up to five times as much in the summer. The concentrations of total nitrogen (TN) and phosphorus (TP) in the unrestored area were also significantly higher than those in the restored area. The CO2 diffusion flux in the restored area was much lower than that in the unrestored area in all seasons. The CH4 diffusion flux at the water-atmosphere interface in the unrestored area was higher than that in the restored area in all seasons. Within the unrestored area, the phytoplankton biomass has a strong positive correlation with TP, pH, and Chl a, and a strong negative correlation with NO3--N, DIC, etc. In the restored area, the submerged plant biomass has a strong but non-significantly positive correlation with salinity and conductivity, and a negative correlation with NH4+-N, PO43--P, CO2 and CH4 fluxes. Overall, ecological restoration can effectively inhibit the rapid growth and reproduction of phytoplankton by restoring submerged macrophytes, improve the water quality of eutrophic shallow lakes, and reduce the flux of carbon-containing greenhouse gases by increasing the concentration of dissolved oxygen in water and sediment. This study will provide scientific references for improving the carbon sequestration and sink function of lake.
As the economy rapidly develops, freshwater ecosystems suffer from eutrophication, leading to a series of aquatic ecological issues, including water quality deterioration and a decline in biodiversity. The most critical step in the ecological restoration of eutrophic shallow lakes is to achieve the transition of primary producers from phytoplankton to submerged macrophytes. Current ecological restoration projects of lakes often emphasize water quality improvement but lack research on the impact on greenhouse gas fluxes. This study investigated the restored and unrestored areas of Lake Xuanwu to compare the physicochemical parameters of the water and the carbon dioxide (CO2) and methane (CH4) fluxes at the water-atmosphere interface between the two areas. The results show that the concentration of chlorophyll a (Chl a) in the unrestored area was significantly higher than that in the restored area in all four seasons, reaching up to five times as much in the summer. The concentrations of total nitrogen (TN) and phosphorus (TP) in the unrestored area were also significantly higher than those in the restored area. The CO2 diffusion flux in the restored area was much lower than that in the unrestored area in all seasons. The CH4 diffusion flux at the water-atmosphere interface in the unrestored area was higher than that in the restored area in all seasons. Within the unrestored area, the phytoplankton biomass has a strong positive correlation with TP, pH, and Chl a, and a strong negative correlation with NO3--N, DIC, etc. In the restored area, the submerged plant biomass has a strong but non-significantly positive correlation with salinity and conductivity, and a negative correlation with NH4+-N, PO43--P, CO2 and CH4 fluxes. Overall, ecological restoration can effectively inhibit the rapid growth and reproduction of phytoplankton by restoring submerged macrophytes, improve the water quality of eutrophic shallow lakes, and reduce the flux of carbon-containing greenhouse gases by increasing the concentration of dissolved oxygen in water and sediment. This study will provide scientific references for improving the carbon sequestration and sink function of lake.
zhang hao, shi xiaohong, lu junping, zhao shengnan, sun biao, Cui Zhimou, quan dong, Lu Zongfu, sun jiale
Available online: May 22, 2025
Abstract:
Phytoplankton play a key role in maintaining the stability and function of ecosystems. However, there is still limited research on the structure of phytoplankton communities in lake ice during the ice-covered period and their relationship with environmental factors. To reveal the characteristics of phytoplankton communities in lake ice and their influencing factors, a sampling survey was conducted in February 2023 on the phytoplankton and physicochemical indicators in the ice of Dong Juye Lake, Wuliangsuhai, Hasuhai, and Chagannaoer. The results showed that: (1) A total of 132 species of phytoplankton were identified in the ice layers of Wuliangsuhai, Dong Juye Lake, Chagannaoer, and Hasuhai. In Dong Juye Lake, 26 species of phytoplankton were identified, with Chlorella sp. as the dominant species; in Wuliangsuhai, 80 species were identified, with Zygnema sp. as the dominant species; in Hasuhai, 54 species were identified, with Microcystis sp. as the dominant species; and in Chagannaoer, 34 species were identified, with Anabaena as the dominant species. (2) The ecosystem in Dong Juye Lake ice was relatively simple with low biodiversity; the ecosystem in Wuliangsuhai ice was rich with high biodiversity; the biodiversity in Hasuhai and Chagannaoer ice was at an intermediate level. The similarity of algae species between different lakes showed significant differences. The highest similarity was found between Wuliangsuhai and Hasuhai, while the greatest difference was observed between Dong Juye Lake and Wuliangsuhai, with Chagannaoer showing some uniqueness. The density of phytoplankton in lake ice showed a significant positive correlation with total nitrogen, ice temperature, and salinity, and a significant negative correlation with pH and chlorophyll a concentration.
Phytoplankton play a key role in maintaining the stability and function of ecosystems. However, there is still limited research on the structure of phytoplankton communities in lake ice during the ice-covered period and their relationship with environmental factors. To reveal the characteristics of phytoplankton communities in lake ice and their influencing factors, a sampling survey was conducted in February 2023 on the phytoplankton and physicochemical indicators in the ice of Dong Juye Lake, Wuliangsuhai, Hasuhai, and Chagannaoer. The results showed that: (1) A total of 132 species of phytoplankton were identified in the ice layers of Wuliangsuhai, Dong Juye Lake, Chagannaoer, and Hasuhai. In Dong Juye Lake, 26 species of phytoplankton were identified, with Chlorella sp. as the dominant species; in Wuliangsuhai, 80 species were identified, with Zygnema sp. as the dominant species; in Hasuhai, 54 species were identified, with Microcystis sp. as the dominant species; and in Chagannaoer, 34 species were identified, with Anabaena as the dominant species. (2) The ecosystem in Dong Juye Lake ice was relatively simple with low biodiversity; the ecosystem in Wuliangsuhai ice was rich with high biodiversity; the biodiversity in Hasuhai and Chagannaoer ice was at an intermediate level. The similarity of algae species between different lakes showed significant differences. The highest similarity was found between Wuliangsuhai and Hasuhai, while the greatest difference was observed between Dong Juye Lake and Wuliangsuhai, with Chagannaoer showing some uniqueness. The density of phytoplankton in lake ice showed a significant positive correlation with total nitrogen, ice temperature, and salinity, and a significant negative correlation with pH and chlorophyll a concentration.
Available online: May 22, 2025
Abstract:
Based on the monitoring data of water quality at 5 stations in Baiyangdian lake in recent 30 years, this study comprehensively applied multi-source statistical analysis methods and literature research to systematically reveal the trend of water quality evolution, influencing factors, and control measures in Baiyangdian lake. Results showed that: ①The year of 2005 and 2015 were the periods of poor water quality in Baiyangdian lake over the past 30 years. From 2022 to 2023, the water quality of the lake area remained stable at Class III, and by 2023, the water quality was at its best level over 30 years. The main pollution indicators were COD and TP in recent years. Large scale ecological water replenishment was the main reason for the significant improvement of water quality in Baiyangdian lake. ② From 2009 to 2023, the COD, TN, and TP concentrations in the Dianqu area were in significant downward trends, with annual decrease rate of 0.611mg.(L.a)-1 (α=0.01), 0.21 mg.(L.a)-1 (α=0.01), and 0.013 mg.(L.a)-1 (α=0.05), respectively. ③The water quality indicators across various monitoring stations in Baiyangdian Lake can be spatially categorized into three groups, with the Nanliuzhuang station in the western region showing the poorest water quality. Eutrophication indicators are further classified into two categories, with northern sites exhibiting a higher nitrogen-to-phosphorus ratio compared to the southern sites. Over recent years, Baiyangdian Lake has become predominantly phosphorus-limited, despite being a nitrogen-polluted system overall. ④The inflow and water level are the key factors affecting the water quality of Baiyangdian Lake in recent years. From a regional perspective, targeted management strategies are necessary for different areas of the lake. In the western region, particularly at the Nanliuzhuang site, efforts should focus on controlling external nutrient inputs. In the northern sites, priority should be given to reducing total nitrogen concentrations, while in the southern sites, the main focus should be on controlling chemical oxygen demand and total phosphorus levels. Looking ahead, local authorities should intensify efforts to manage endogenous pollution, particularly from sediments and organic matter (humus) within the lake. Furthermore, a coordinated approach to pollution control across the entire watershed is essential to address both external and internal sources of contamination..
Based on the monitoring data of water quality at 5 stations in Baiyangdian lake in recent 30 years, this study comprehensively applied multi-source statistical analysis methods and literature research to systematically reveal the trend of water quality evolution, influencing factors, and control measures in Baiyangdian lake. Results showed that: ①The year of 2005 and 2015 were the periods of poor water quality in Baiyangdian lake over the past 30 years. From 2022 to 2023, the water quality of the lake area remained stable at Class III, and by 2023, the water quality was at its best level over 30 years. The main pollution indicators were COD and TP in recent years. Large scale ecological water replenishment was the main reason for the significant improvement of water quality in Baiyangdian lake. ② From 2009 to 2023, the COD, TN, and TP concentrations in the Dianqu area were in significant downward trends, with annual decrease rate of 0.611mg.(L.a)-1 (α=0.01), 0.21 mg.(L.a)-1 (α=0.01), and 0.013 mg.(L.a)-1 (α=0.05), respectively. ③The water quality indicators across various monitoring stations in Baiyangdian Lake can be spatially categorized into three groups, with the Nanliuzhuang station in the western region showing the poorest water quality. Eutrophication indicators are further classified into two categories, with northern sites exhibiting a higher nitrogen-to-phosphorus ratio compared to the southern sites. Over recent years, Baiyangdian Lake has become predominantly phosphorus-limited, despite being a nitrogen-polluted system overall. ④The inflow and water level are the key factors affecting the water quality of Baiyangdian Lake in recent years. From a regional perspective, targeted management strategies are necessary for different areas of the lake. In the western region, particularly at the Nanliuzhuang site, efforts should focus on controlling external nutrient inputs. In the northern sites, priority should be given to reducing total nitrogen concentrations, while in the southern sites, the main focus should be on controlling chemical oxygen demand and total phosphorus levels. Looking ahead, local authorities should intensify efforts to manage endogenous pollution, particularly from sediments and organic matter (humus) within the lake. Furthermore, a coordinated approach to pollution control across the entire watershed is essential to address both external and internal sources of contamination..
Available online: May 22, 2025
Abstract:
Dissolved organic matter (DOM) in the water columns constitutes a vital component of the carbon cycle within lake ecosystems. To investigate the impact of urbanization on DOM characteristics of urban lakes, we took Dishui Lake, the largest urban artificial lake in China, as a case study. We examined the temporal and spatial variation characteristics of chromophoric dissolved organic matter (CDOM) in Dishui Lake and its surrounding water system from winter to summer (January, March, and July) using ultraviolet-visible absorption spectroscopy and three-dimensional fluorescence spectroscopy. The influence of the urban construction, Lingang New City, Shanghai, on the composition and source of CDOM in water was preliminarily explored. The results are as follows: ①Tyrosine-like C1, tryptophan-like C2 and terrestrial humic-like C3 were identified through parallel factor analysis (PARAFAC). The contribution of protein-like (C1 and C2) components to fluorescence intensity decreased, while the contribution of C3 increased. ②Most values of the autogenetic index (BIX) is >1.0 or close to 1, and the fluorescence index (FI) ranged from 1.4 to 1.9, indicating that the characteristics of CDOM during the temperature rising (from winter to summer) is influenced by both endogenous and exogenous inputs, and biological activity (microbial source) is the main source and has strong autogenetic characteristics. Influenced by exogenous input from rainfall or surface runoff, the relative concentration of CDOM was diluted and decreased in the spring and summer seasons. In January, a (254) was significantly higher than that in March and July (P<0.01), and the molecular weight of CDOM was low. ③The land use types of river channels around the lake are primarily residential areas and newly built parks, and building site under construction with 0.8 1, high biological metabolic activity in the water body and significant impact of CDOM on human activities. The C3 fluorescence intensity gradually decreased from the river channels to the lake district, indicating that terrestrial humic-like substances mainly entered Dishui Lake through river channel. ④The fluorescence parameters BIX and FI were significantly correlated with protein-like components and nitrogen concentrations (P<0.05), can serve as potential indicators for future water quality monitoring of Dishui Lake. Our study suggests that rainfall, runoff input, land use type, and rapid urbanization collectively affect the CDOM characteristics of the lake, and the relevant results can provide a basis for further understanding the composition characteristics and water environment management of dissolved organic matter in urban water bodies under the background of urban development.
Dissolved organic matter (DOM) in the water columns constitutes a vital component of the carbon cycle within lake ecosystems. To investigate the impact of urbanization on DOM characteristics of urban lakes, we took Dishui Lake, the largest urban artificial lake in China, as a case study. We examined the temporal and spatial variation characteristics of chromophoric dissolved organic matter (CDOM) in Dishui Lake and its surrounding water system from winter to summer (January, March, and July) using ultraviolet-visible absorption spectroscopy and three-dimensional fluorescence spectroscopy. The influence of the urban construction, Lingang New City, Shanghai, on the composition and source of CDOM in water was preliminarily explored. The results are as follows: ①Tyrosine-like C1, tryptophan-like C2 and terrestrial humic-like C3 were identified through parallel factor analysis (PARAFAC). The contribution of protein-like (C1 and C2) components to fluorescence intensity decreased, while the contribution of C3 increased. ②Most values of the autogenetic index (BIX) is >1.0 or close to 1, and the fluorescence index (FI) ranged from 1.4 to 1.9, indicating that the characteristics of CDOM during the temperature rising (from winter to summer) is influenced by both endogenous and exogenous inputs, and biological activity (microbial source) is the main source and has strong autogenetic characteristics. Influenced by exogenous input from rainfall or surface runoff, the relative concentration of CDOM was diluted and decreased in the spring and summer seasons. In January, a (254) was significantly higher than that in March and July (P<0.01), and the molecular weight of CDOM was low. ③The land use types of river channels around the lake are primarily residential areas and newly built parks, and building site under construction with 0.8
Mo Luqing, Tai Yiping, Dai Yunv, Tao Ran, Zhang Xiaomeng, Yu Bailun, Zhang Jie, Ou Tingzhe, Li Ming, Xuan Qianhong, Zhou Xinmin, Huang Jiajun, Yang Yang
Available online: May 20, 2025
Abstract:
The study of attached algae communities assembly mechanisms is essential for understanding the restoration of river ecosystem structure and function. This study analyzed attached algae communities in three representative rivers flowing through Guangzhou—Chebei River (natural habitat), Liede River (highly canalized), and Shahe River (mixed habitat)—that are subject to a low water level operation strategy. The analysis covered four consecutive flood seasons from 2020 to 2023, focusing on the recovery and environmental drivers of these communities under near-natural restoration measures. The results show that a total of 193 algal species across 6 phyla, 53 families, and 90 genera were recorded, with Bacillariophyta being dominant (51.26%). No significant spatial differences (P>0.05) in algal standing stock were found, while significant annual differences (P<0.001) occurred, indicating higher temporal than spatial heterogeneity. Chebei river had the highest total number of species (184), while Liede river showed the highest abundance (2.47×109 cells/m2) (3.16×103 mg/m2), Shannon Diversity Index (3.14), and Evenness Index (0.66). Annually, Liede river had the largest increases in number of species and Shannon Diversity Index (41.43%, and 15.58%, respectively), and Shahe river had the highest abundance and biomass increase (92.62%, and 96.53% respectively), with Evenness Index remaining stable at around 0.6.These findings highlight the effectiveness of near-natural restoration for attached algae recovery. Niche analysis revealed a collaborative community structure with efficient resource use and low competition. The standardized random rate analysis revealed that deterministic and stochastic processes both play dominant roles during restoration. Environmental heterogeneity impacts the relative dominance of these two processes. Redundancy analysis indicated that TN, TP, DO, water depth, and flow velocity are key factors affecting the recovery of rivers attached algae communities. The research results provide empirical support and a scientific basis for the effectiveness of near-natural restoration in urban river channels.
The study of attached algae communities assembly mechanisms is essential for understanding the restoration of river ecosystem structure and function. This study analyzed attached algae communities in three representative rivers flowing through Guangzhou—Chebei River (natural habitat), Liede River (highly canalized), and Shahe River (mixed habitat)—that are subject to a low water level operation strategy. The analysis covered four consecutive flood seasons from 2020 to 2023, focusing on the recovery and environmental drivers of these communities under near-natural restoration measures. The results show that a total of 193 algal species across 6 phyla, 53 families, and 90 genera were recorded, with Bacillariophyta being dominant (51.26%). No significant spatial differences (P>0.05) in algal standing stock were found, while significant annual differences (P<0.001) occurred, indicating higher temporal than spatial heterogeneity. Chebei river had the highest total number of species (184), while Liede river showed the highest abundance (2.47×109 cells/m2) (3.16×103 mg/m2), Shannon Diversity Index (3.14), and Evenness Index (0.66). Annually, Liede river had the largest increases in number of species and Shannon Diversity Index (41.43%, and 15.58%, respectively), and Shahe river had the highest abundance and biomass increase (92.62%, and 96.53% respectively), with Evenness Index remaining stable at around 0.6.These findings highlight the effectiveness of near-natural restoration for attached algae recovery. Niche analysis revealed a collaborative community structure with efficient resource use and low competition. The standardized random rate analysis revealed that deterministic and stochastic processes both play dominant roles during restoration. Environmental heterogeneity impacts the relative dominance of these two processes. Redundancy analysis indicated that TN, TP, DO, water depth, and flow velocity are key factors affecting the recovery of rivers attached algae communities. The research results provide empirical support and a scientific basis for the effectiveness of near-natural restoration in urban river channels.
Available online: May 14, 2025
Abstract:
In recent years, inland water bodies such as lakes and reservoirs have been recognized as hotspots for carbon emissions, with the diffusion and release of greenhouse gases like carbon dioxide (CO2) and methane (CH4) at the water-air interface being the most significant pathways for carbon emissions from these water bodies. Diffusion release refers to the mass transfer process of gases between gas and liquid phases, where the gas-liquid mass transfer coefficient is a key parameter for calculating the flux of greenhouse gas diffusion. Wind speed is generally considered the primary factor affecting the gas-liquid mass transfer coefficient in the surface waters of lakes and reservoirs. However, most current research on the impact of wind speed on the gas-liquid mass transfer coefficient of greenhouse gases is based on field observations of tracer gases, lacking mechanistic experimental studies that consider the characteristics of gas-liquid mass transfer. This results in uncertainties when quantitatively assessin
In recent years, inland water bodies such as lakes and reservoirs have been recognized as hotspots for carbon emissions, with the diffusion and release of greenhouse gases like carbon dioxide (CO2) and methane (CH4) at the water-air interface being the most significant pathways for carbon emissions from these water bodies. Diffusion release refers to the mass transfer process of gases between gas and liquid phases, where the gas-liquid mass transfer coefficient is a key parameter for calculating the flux of greenhouse gas diffusion. Wind speed is generally considered the primary factor affecting the gas-liquid mass transfer coefficient in the surface waters of lakes and reservoirs. However, most current research on the impact of wind speed on the gas-liquid mass transfer coefficient of greenhouse gases is based on field observations of tracer gases, lacking mechanistic experimental studies that consider the characteristics of gas-liquid mass transfer. This results in uncertainties when quantitatively assessin
Available online: May 14, 2025
Abstract:
Against the backdrop of intensifying climate change and urbanization, the increasing frequency of extreme compound hydrological events has disrupted urban production and daily life, posing threats to public safety and property. Understanding the joint frequency characteristics and underlying mechanisms of these extreme events is critical for ensuring water security. This study employs copula-based joint distribution theory to analyze the joint frequency characteristics of extreme rainfall-flood, flood-tide, and rainfall-tide compound events in the Taihu basin, revealing the changing patterns of their co-occurrence probabilities across different urbanization stages. Compared to the early period, extreme water levels, tidal levels, and rainfall during the rapid urbanization phase have shown a significant increase, with the annual maximum 1-day rainfall rising by more than 15% and the annual maximum 1-day water level increasing by over 6%. Moreover, the mean values of hydrological elements in the Wuchengxiyu sub-region are consistently higher than those in the Yangchengdianmao sub-region. The Wuchengxiyu sub-region faces a higher risk of extreme rainfall-flood compound events, while the Yangchengdianmao sub-region is more prone to extreme rainfall-tide and flood-tide compound events. The study highlights that extreme compound hydrological events in the Taihu basin are significantly influenced by urbanization intensity, with the probability of encountering such events during the rapid urbanization period approximately doubling. Notably, the rate of change in return periods is greater in the Wuchengxiyu sub-region than in the Yangchengdianmao sub-region. These findings provide valuable scientific insights for engineering hydrological design and flood risk mitigation in the Taihu basin and other rapidly urbanizing regions.
Against the backdrop of intensifying climate change and urbanization, the increasing frequency of extreme compound hydrological events has disrupted urban production and daily life, posing threats to public safety and property. Understanding the joint frequency characteristics and underlying mechanisms of these extreme events is critical for ensuring water security. This study employs copula-based joint distribution theory to analyze the joint frequency characteristics of extreme rainfall-flood, flood-tide, and rainfall-tide compound events in the Taihu basin, revealing the changing patterns of their co-occurrence probabilities across different urbanization stages. Compared to the early period, extreme water levels, tidal levels, and rainfall during the rapid urbanization phase have shown a significant increase, with the annual maximum 1-day rainfall rising by more than 15% and the annual maximum 1-day water level increasing by over 6%. Moreover, the mean values of hydrological elements in the Wuchengxiyu sub-region are consistently higher than those in the Yangchengdianmao sub-region. The Wuchengxiyu sub-region faces a higher risk of extreme rainfall-flood compound events, while the Yangchengdianmao sub-region is more prone to extreme rainfall-tide and flood-tide compound events. The study highlights that extreme compound hydrological events in the Taihu basin are significantly influenced by urbanization intensity, with the probability of encountering such events during the rapid urbanization period approximately doubling. Notably, the rate of change in return periods is greater in the Wuchengxiyu sub-region than in the Yangchengdianmao sub-region. These findings provide valuable scientific insights for engineering hydrological design and flood risk mitigation in the Taihu basin and other rapidly urbanizing regions.
Available online: May 14, 2025
Abstract:
As a representative subtropical plateau wetland ecosystem in China, Caohai Lake is characterized by abundant aquatic flora and fauna resources and high ecological value. However, recent intensification of eutrophication has triggered massive decline of submerged macrophytes, driving the gradual regime shift from a macrophyte-dominated clear-water state to an algae-dominated turbid-water state, profoundly impacting ecosystem functions and biodiversity. Based on field investigations conducted during 2022-2023, this study systematically examined the current status and characteristics of macroinvertebrate communities in Caohai Lake, comparing differences with historical data from macrophyte-dominated periods (1983 and 2014), thereby revealing the response mechanisms of macroinvertebrate communities during the regime shift. Results showed that current macroinvertebrate communities exhibited a mean density of 146.49 ± 16.62 ind./m2 and biomass of 15.93 ± 14.02 g/m2, with Shannon-Weiner diversity index (0.73 ± 0.06), Margalef richness index (0.37 ± 0.03), and Pielou evenness index (0.66 ± 0.04). Functional feeding groups comprised 94.69% collectors, 2.81% predators, 1.58% scrapers, and 0.92% filter-feeders. Spatial distribution patterns of macroinvertebrate communities corresponded with submerged macrophyte distribution. Biomass showed significant seasonal variation (p < 0.05), being higher in autumn and winter than spring and summer, while other community characteristics exhibited no significant seasonal differences. Redundancy analysis identified dissolved oxygen (DO), water depth (WD), pH, permanganate index (CODMn), transparency (SD), and conductivity (Cond) as key environmental drivers. Over two decades, CODMn showed persistent increase while Chl.a concentration rose and SD declined annually post-regime shift. Comparative analysis revealed dominance of scrapers (Gastropoda) during the clear-water state versus gather-collectors (Tubificidae and Chironomidae) in the turbid-water state, with higher species richness, density, biomass, and diversity indices observed during the macrophyte-dominated phase. This study provides critical scientific basis for comprehensive assessment of Caohai Lake"s aquatic ecosystem status, understanding macroinvertebrate responses during plateau lake regime shifts, and implementing targeted ecological restoration measures.
As a representative subtropical plateau wetland ecosystem in China, Caohai Lake is characterized by abundant aquatic flora and fauna resources and high ecological value. However, recent intensification of eutrophication has triggered massive decline of submerged macrophytes, driving the gradual regime shift from a macrophyte-dominated clear-water state to an algae-dominated turbid-water state, profoundly impacting ecosystem functions and biodiversity. Based on field investigations conducted during 2022-2023, this study systematically examined the current status and characteristics of macroinvertebrate communities in Caohai Lake, comparing differences with historical data from macrophyte-dominated periods (1983 and 2014), thereby revealing the response mechanisms of macroinvertebrate communities during the regime shift. Results showed that current macroinvertebrate communities exhibited a mean density of 146.49 ± 16.62 ind./m2 and biomass of 15.93 ± 14.02 g/m2, with Shannon-Weiner diversity index (0.73 ± 0.06), Margalef richness index (0.37 ± 0.03), and Pielou evenness index (0.66 ± 0.04). Functional feeding groups comprised 94.69% collectors, 2.81% predators, 1.58% scrapers, and 0.92% filter-feeders. Spatial distribution patterns of macroinvertebrate communities corresponded with submerged macrophyte distribution. Biomass showed significant seasonal variation (p < 0.05), being higher in autumn and winter than spring and summer, while other community characteristics exhibited no significant seasonal differences. Redundancy analysis identified dissolved oxygen (DO), water depth (WD), pH, permanganate index (CODMn), transparency (SD), and conductivity (Cond) as key environmental drivers. Over two decades, CODMn showed persistent increase while Chl.a concentration rose and SD declined annually post-regime shift. Comparative analysis revealed dominance of scrapers (Gastropoda) during the clear-water state versus gather-collectors (Tubificidae and Chironomidae) in the turbid-water state, with higher species richness, density, biomass, and diversity indices observed during the macrophyte-dominated phase. This study provides critical scientific basis for comprehensive assessment of Caohai Lake"s aquatic ecosystem status, understanding macroinvertebrate responses during plateau lake regime shifts, and implementing targeted ecological restoration measures.
Available online: May 14, 2025
Abstract:
Algae in aquatic ecosystems can enter the atmosphere through bubble bursting at the water-air interface and subsequently spread via aerosol transmission. This process not only represents a significant dispersal mechanism influencing algal population structures in adjacent water bodies but also elevates health risks through increased airborne harmful algae and exacerbates atmospheric nutrient enrichment. Current understanding of airborne algae remains limited, with existing research predominantly documented in international literature. This review systematically examines the distribution characteristics of airborne algae, encompassing dominant taxa, seasonal fluctuations, and diurnal variation patterns. It further elucidates key environmental determinants such as temperature, humidity, and wind speed that govern algal survival and atmospheric transport. Special attention is given to health implications arising from aerosolized harmful algae and cyanotoxins. To address existing knowledge gaps, future research should prioritize three critical domains: 1) Colonization dynamics investigating airborne algae viability and reproductive potential in atmospheric environments; 2) Source-sink identification to trace emission hotspots and deposition patterns; 3) Comprehensive risk assessment frameworks to evaluate long-term health impacts of algal aerosols and establish early warning systems. These proposed directions aim to advance fundamental understanding and inform evidence-based environmental management strategies
Algae in aquatic ecosystems can enter the atmosphere through bubble bursting at the water-air interface and subsequently spread via aerosol transmission. This process not only represents a significant dispersal mechanism influencing algal population structures in adjacent water bodies but also elevates health risks through increased airborne harmful algae and exacerbates atmospheric nutrient enrichment. Current understanding of airborne algae remains limited, with existing research predominantly documented in international literature. This review systematically examines the distribution characteristics of airborne algae, encompassing dominant taxa, seasonal fluctuations, and diurnal variation patterns. It further elucidates key environmental determinants such as temperature, humidity, and wind speed that govern algal survival and atmospheric transport. Special attention is given to health implications arising from aerosolized harmful algae and cyanotoxins. To address existing knowledge gaps, future research should prioritize three critical domains: 1) Colonization dynamics investigating airborne algae viability and reproductive potential in atmospheric environments; 2) Source-sink identification to trace emission hotspots and deposition patterns; 3) Comprehensive risk assessment frameworks to evaluate long-term health impacts of algal aerosols and establish early warning systems. These proposed directions aim to advance fundamental understanding and inform evidence-based environmental management strategies
Available online: May 14, 2025
Abstract:
Emergent plants can not only absorb nutrients from water and sediment as a "sink" during the growth period, but also release nutrients such as nitrogen and phosphorus into the water environment as a "source" during the decline period. If the biomass is large, it may cause "secondary pollution" of water. In order to explore the nutrient release rule of typical emergent plants in Hengshui Lake and the microbial mechanism affecting plant decomposition, the dominant species Phragmites australis and Typha angustifolia were selected as the research objects, and the decomposition bag method was used to carry out in-situ decomposition tests in Hengshui Lake at the end of February 2023. The "vertical decomposition" of plants was simulated in the experimental group which was not in contact with water surface, and the decomposition of emergent plants was simulated in the experimental group which was flooded under water surface. The results showed that: (1) The decomposition rates of P. australis and T. angustifolia were significantly different under flooded and non-flooded conditions (p< 0.01). The decomposition of P. australis and T. angustifolia was more conducive to the decomposition of P. australis and T. angustifolia, but the long-term flooding might lead to the accumulation of elements. (2) The decomposition rate of T. angustifolia was faster than that of P. australis, because the decomposition rate was positively correlated with the initial N and P contents and the relative abundance of nitrogen and phosphorus cycling genes., and negatively correlated with the initial cellulose, lignin and soluble sugar contents. (3) The abundance of nitrogen fixing genes increased gradually with the increase of decomposition degree, and the increase of N content in P. australis and T. angustifolia litter was positively correlated with the nitrogen fixing genes of nitrogen fixing microorganisms.
Emergent plants can not only absorb nutrients from water and sediment as a "sink" during the growth period, but also release nutrients such as nitrogen and phosphorus into the water environment as a "source" during the decline period. If the biomass is large, it may cause "secondary pollution" of water. In order to explore the nutrient release rule of typical emergent plants in Hengshui Lake and the microbial mechanism affecting plant decomposition, the dominant species Phragmites australis and Typha angustifolia were selected as the research objects, and the decomposition bag method was used to carry out in-situ decomposition tests in Hengshui Lake at the end of February 2023. The "vertical decomposition" of plants was simulated in the experimental group which was not in contact with water surface, and the decomposition of emergent plants was simulated in the experimental group which was flooded under water surface. The results showed that: (1) The decomposition rates of P. australis and T. angustifolia were significantly different under flooded and non-flooded conditions (p< 0.01). The decomposition of P. australis and T. angustifolia was more conducive to the decomposition of P. australis and T. angustifolia, but the long-term flooding might lead to the accumulation of elements. (2) The decomposition rate of T. angustifolia was faster than that of P. australis, because the decomposition rate was positively correlated with the initial N and P contents and the relative abundance of nitrogen and phosphorus cycling genes., and negatively correlated with the initial cellulose, lignin and soluble sugar contents. (3) The abundance of nitrogen fixing genes increased gradually with the increase of decomposition degree, and the increase of N content in P. australis and T. angustifolia litter was positively correlated with the nitrogen fixing genes of nitrogen fixing microorganisms.
Available online: May 13, 2025
Abstract:
To explore the impact of the changes of agricultural cropping-breeding mode(ACBM) on the water quantity and quality of rivers, Four Lakes Main Channel(FLMC) in the Jianghan Plain was taken as the research object. Based on observation data from 2010 to 2023, the trend of annual water quantity and quality changes was analyzed. Remote sensing images and statistical yearbook data were used to identify the interannual area change characteristics of different land utilization types, and the trends of nitrogen and phosphorus point source load were ascertained nearly 10 years, and redundancy analysis (RDA) and Correlation heat map were applied to explore the response of the main channel’s nitrogen and phosphorus concentration to the changes.The results indicate that: ①From 2010 to 2023, the concentration of total nitrogen and total phosphorus in FLMC , which the inter-annual was "increase and then decrease and then tend to be stable", the annual performance was "low in winter and spring, high in summer and autumn", and the spatial performance was "low and high in the middle of the inlet and outlet". The annual displacement of the total trunk canal is mainly concentrated in April to September, accounting for 65.7% of the whole year. ②In recent 10 years, the ACBM in the Sihu Basin has changed significantly, mainly showing that the dry land cultivation area has decreased by about 15%, the paddy field cultivation area has increased by about 19%, and the freshwater aquaculture area has increased by about 2% from 2010 to 2016, and decreased by more than 4% from 2016 to 2022. ③The variation characteristics of the total water quantity in the FLMC are not only affected by rainfall, but also related to the variation of rainfall runoff of different land use types in the basin, among which paddy field and dry land are the main influencing factors, and their contributions account for 366% and -236% of the total water quantity change, respectively. ④In recent 10 years, the changes of N and P concentration in the FLMC were positively correlated with the changes of N and P pollution load in the basin (79.7% interpretation, *p < 0.01), and the main factors that caused the changes of N and P pollution load in the basin were freshwater breeding and livestock breeding. In addition, the contribution of rice field cultivation to N and P loads increased from 6% to 26% in nearly 10 years, and the proportion of N and P loads gradually became prominent, and the risk of water environment pollution in the future cannot be ignored.
To explore the impact of the changes of agricultural cropping-breeding mode(ACBM) on the water quantity and quality of rivers, Four Lakes Main Channel(FLMC) in the Jianghan Plain was taken as the research object. Based on observation data from 2010 to 2023, the trend of annual water quantity and quality changes was analyzed. Remote sensing images and statistical yearbook data were used to identify the interannual area change characteristics of different land utilization types, and the trends of nitrogen and phosphorus point source load were ascertained nearly 10 years, and redundancy analysis (RDA) and Correlation heat map were applied to explore the response of the main channel’s nitrogen and phosphorus concentration to the changes.The results indicate that: ①From 2010 to 2023, the concentration of total nitrogen and total phosphorus in FLMC , which the inter-annual was "increase and then decrease and then tend to be stable", the annual performance was "low in winter and spring, high in summer and autumn", and the spatial performance was "low and high in the middle of the inlet and outlet". The annual displacement of the total trunk canal is mainly concentrated in April to September, accounting for 65.7% of the whole year. ②In recent 10 years, the ACBM in the Sihu Basin has changed significantly, mainly showing that the dry land cultivation area has decreased by about 15%, the paddy field cultivation area has increased by about 19%, and the freshwater aquaculture area has increased by about 2% from 2010 to 2016, and decreased by more than 4% from 2016 to 2022. ③The variation characteristics of the total water quantity in the FLMC are not only affected by rainfall, but also related to the variation of rainfall runoff of different land use types in the basin, among which paddy field and dry land are the main influencing factors, and their contributions account for 366% and -236% of the total water quantity change, respectively. ④In recent 10 years, the changes of N and P concentration in the FLMC were positively correlated with the changes of N and P pollution load in the basin (79.7% interpretation, *p < 0.01), and the main factors that caused the changes of N and P pollution load in the basin were freshwater breeding and livestock breeding. In addition, the contribution of rice field cultivation to N and P loads increased from 6% to 26% in nearly 10 years, and the proportion of N and P loads gradually became prominent, and the risk of water environment pollution in the future cannot be ignored.
Available online: May 13, 2025
Abstract:
This study aims to systematically analyze the spatial distribution characteristics of humic acid (HA) in sediments from different regions of Lake Taihu and its influence on methane production. Surface sediment samples were collected from Dongtaihu Lake, Meiliang Bay, the central lake area, and Dapukou for quantitative analysis. Fourier-transform infrared spectroscopy (FTIR), spectrophotometry, elemental analysis, electrochemical measurements, and quinone group quantification were employed to characterize the HA content, structural properties, and redox characteristics, including electron accepting capacity (EAC) and electron donating capacity (EDC).
This study aims to systematically analyze the spatial distribution characteristics of humic acid (HA) in sediments from different regions of Lake Taihu and its influence on methane production. Surface sediment samples were collected from Dongtaihu Lake, Meiliang Bay, the central lake area, and Dapukou for quantitative analysis. Fourier-transform infrared spectroscopy (FTIR), spectrophotometry, elemental analysis, electrochemical measurements, and quinone group quantification were employed to characterize the HA content, structural properties, and redox characteristics, including electron accepting capacity (EAC) and electron donating capacity (EDC).
Song Zenghui, Yao Xuexing, Muhammad Waqas Yonas, Yang Guanglang, Kong Yemei, Bai Guoxin, Zhang Xiaonan, Zhang Lei
Available online: May 13, 2025
Abstract:
After the impoundment of the Three Gorges Dam for more than 20 years, over 50% of 1st order tributaries have experienced harmful algal blooms (HABs), primarily dominated by Dinoflagellates, Cyanobacteria and Green Algae. Investigating the relationship between HABs and endogenous nutrient accumulation will help in the early warning of HABs and in predicting the ecological environment in the Three Gorges Reservoir (TGR). The sediment cores are undoubtedly valuable materials for studying the effects of internal nutrient accumulation and algal bloom impacts. This study selected two 1st order tributaries both mainly located in Yunyang County of the TGR, namely Pengxi River which have been heavily algal bloomed, and Modao River barely reported with bloom. Sediment cores were collected from both mid-reaches to investigate the effects of blooms on sediment deposition under similar climatic and geographic conditions. Through the 210Pb dating methods, the sedimentation deposition depths after TGR impoundment in Pengxi and Modao River were 45cm and 30cm, with average sedimentation rates of 2.3 and 1.5cm.a-1, respectively, showing Modao River was only 65% of Pengxi River in this rate. The sediment cores show that prior to impoundment of TGR, the average contents of organic matter (OM), TN, TP, Available Phosphorus (AP), and Alkali-hydrolyzable Nitrogen (AN) in Pengxi River sediments were 9154.9, 454.1, 432.1, 13.3, and 60.4 mg.kg?1, respectively; in Modao River, the respective values were 12342.4, 756.5, 530.2, 17.0, and 63.2 mg.kg?1, which were 35%, 67%, 23%, 28%, and 5% higher than those in Pengxi River. As of the 2023 layer in the core, OM content in Pengxi and Modao River sediments was 19182.2 and 13878.6 mg.kg?1, respectively, with the latter being only 72% of the former. TN, TP, AP, and AN in Pengxi River sediments increased by 96%, 37%, 77%, and 51%, respectively, compared to its pre-impoundment levels, while Modao River showed increases of 16%, 13%, 8%, with AN decreasing by 2% based on the similar relative comparison. The results of 16S and 18S DNA high-throughput sequencing of 5 cm sections from the top 20 cm of the sediment cores revealed no significant differences in the microbial community composition between the two rivers. However, combining core dating, surface DNA sequencing and phytoplankton community data during bloom periods indicated that between 2010 and 2023, the relative abundances of Dinoflagellates and Green Algae in the 0~5 cm layer of Pengxi River cores increased by 2.1 and 0.1 times, respectively, compared to the 15~20 cm layer. Conversely, in Modao River during the same period, Dinoflagellates and Green Algae relative abundances decreased by 50% and 70%, respectively. A significant positive correlation was found between the relative abundance of Dinoflagellates and organic matter in both rivers" sediment cores (P<0.05), suggesting that Dinoflagellate blooms are the primary cause of the differences in endogenous organic matter deposition post-impoundment. As endogenous organic matter accumulates, the risk of future algal blooms, especially Dinoflagellate blooms, in the 1st order tributaries of TGR will increase. Organic matter content and the dynamics of endogenous nutrient accumulation in sediments could serve as key indicators for predicting the future scale of Dinoflagellate blooms in the tributaries of the reservoir.
After the impoundment of the Three Gorges Dam for more than 20 years, over 50% of 1st order tributaries have experienced harmful algal blooms (HABs), primarily dominated by Dinoflagellates, Cyanobacteria and Green Algae. Investigating the relationship between HABs and endogenous nutrient accumulation will help in the early warning of HABs and in predicting the ecological environment in the Three Gorges Reservoir (TGR). The sediment cores are undoubtedly valuable materials for studying the effects of internal nutrient accumulation and algal bloom impacts. This study selected two 1st order tributaries both mainly located in Yunyang County of the TGR, namely Pengxi River which have been heavily algal bloomed, and Modao River barely reported with bloom. Sediment cores were collected from both mid-reaches to investigate the effects of blooms on sediment deposition under similar climatic and geographic conditions. Through the 210Pb dating methods, the sedimentation deposition depths after TGR impoundment in Pengxi and Modao River were 45cm and 30cm, with average sedimentation rates of 2.3 and 1.5cm.a-1, respectively, showing Modao River was only 65% of Pengxi River in this rate. The sediment cores show that prior to impoundment of TGR, the average contents of organic matter (OM), TN, TP, Available Phosphorus (AP), and Alkali-hydrolyzable Nitrogen (AN) in Pengxi River sediments were 9154.9, 454.1, 432.1, 13.3, and 60.4 mg.kg?1, respectively; in Modao River, the respective values were 12342.4, 756.5, 530.2, 17.0, and 63.2 mg.kg?1, which were 35%, 67%, 23%, 28%, and 5% higher than those in Pengxi River. As of the 2023 layer in the core, OM content in Pengxi and Modao River sediments was 19182.2 and 13878.6 mg.kg?1, respectively, with the latter being only 72% of the former. TN, TP, AP, and AN in Pengxi River sediments increased by 96%, 37%, 77%, and 51%, respectively, compared to its pre-impoundment levels, while Modao River showed increases of 16%, 13%, 8%, with AN decreasing by 2% based on the similar relative comparison. The results of 16S and 18S DNA high-throughput sequencing of 5 cm sections from the top 20 cm of the sediment cores revealed no significant differences in the microbial community composition between the two rivers. However, combining core dating, surface DNA sequencing and phytoplankton community data during bloom periods indicated that between 2010 and 2023, the relative abundances of Dinoflagellates and Green Algae in the 0~5 cm layer of Pengxi River cores increased by 2.1 and 0.1 times, respectively, compared to the 15~20 cm layer. Conversely, in Modao River during the same period, Dinoflagellates and Green Algae relative abundances decreased by 50% and 70%, respectively. A significant positive correlation was found between the relative abundance of Dinoflagellates and organic matter in both rivers" sediment cores (P<0.05), suggesting that Dinoflagellate blooms are the primary cause of the differences in endogenous organic matter deposition post-impoundment. As endogenous organic matter accumulates, the risk of future algal blooms, especially Dinoflagellate blooms, in the 1st order tributaries of TGR will increase. Organic matter content and the dynamics of endogenous nutrient accumulation in sediments could serve as key indicators for predicting the future scale of Dinoflagellate blooms in the tributaries of the reservoir.
Available online: May 13, 2025
Abstract:
Global warming has led to significant changes in the thermodynamic characteristics of lakes on the Tibetan Plateau, resulting in vital impact on lake ecosystem and water quality changes. In this study, continuous observations of lake water temperature and meteorological conditions were carried out in the largest lake—Selin Co, Tibet, the characteristics of intra-annual thermodynamic dynamic of Selin Co and its responding to meteorological conditions are revealed. The results show that Selin Co is a dimictic lake based on continuous observations of water temperature profiles from June 2021 to December 2022. The thermodynamic state can be divided into four phases: winter freezing, spring mixing, summer stratification and fall mixing. Selin Co starts to stratify during the freezing period (mid-March). The melting of the lake ice, the enhanced radiation penetrating the ice and the high salinity resulted in a rapid and stable stratification of the water column under the ice. However, Selin Co did not undergo complete mixing of the water column in the spring, probably due to the salinity gradient, and the mixing phenomenon was confined to the surface 0-30 m, with the bottom waters remaining slowly warmed.The Schmidt Stability ranged from 0 to 520J/m2 in Selin Co. From the characteristics of the thermocline, the daily variation patterns of the thermocline in 2021 and 2022 are very similar, with the maximum depth of the thermocline around 17 m during the summer stratification period. Wind speed and radiation have different driving mechanisms for thermal stratification during different periods. Wind and radiation contribute concurrently to thermal stratification during the formation period, and weakening radiation being the main cause of the disappearance of thermodynamic stratification. Comparative analysis showed that air temperature changes were more variable than surface water temperature, which lagged air temperature by about 21 days. This study conducted the observation and research on the thermodynamic characteristics of Selin Co and its influencing factors for the first time, providing a scientific basis for an in-depth understanding of the changes in water temperature of inland lakes on the Tibetan Plateau and their response to regional climate change, as well as lake modeling research.
Global warming has led to significant changes in the thermodynamic characteristics of lakes on the Tibetan Plateau, resulting in vital impact on lake ecosystem and water quality changes. In this study, continuous observations of lake water temperature and meteorological conditions were carried out in the largest lake—Selin Co, Tibet, the characteristics of intra-annual thermodynamic dynamic of Selin Co and its responding to meteorological conditions are revealed. The results show that Selin Co is a dimictic lake based on continuous observations of water temperature profiles from June 2021 to December 2022. The thermodynamic state can be divided into four phases: winter freezing, spring mixing, summer stratification and fall mixing. Selin Co starts to stratify during the freezing period (mid-March). The melting of the lake ice, the enhanced radiation penetrating the ice and the high salinity resulted in a rapid and stable stratification of the water column under the ice. However, Selin Co did not undergo complete mixing of the water column in the spring, probably due to the salinity gradient, and the mixing phenomenon was confined to the surface 0-30 m, with the bottom waters remaining slowly warmed.The Schmidt Stability ranged from 0 to 520J/m2 in Selin Co. From the characteristics of the thermocline, the daily variation patterns of the thermocline in 2021 and 2022 are very similar, with the maximum depth of the thermocline around 17 m during the summer stratification period. Wind speed and radiation have different driving mechanisms for thermal stratification during different periods. Wind and radiation contribute concurrently to thermal stratification during the formation period, and weakening radiation being the main cause of the disappearance of thermodynamic stratification. Comparative analysis showed that air temperature changes were more variable than surface water temperature, which lagged air temperature by about 21 days. This study conducted the observation and research on the thermodynamic characteristics of Selin Co and its influencing factors for the first time, providing a scientific basis for an in-depth understanding of the changes in water temperature of inland lakes on the Tibetan Plateau and their response to regional climate change, as well as lake modeling research.
Available online: May 13, 2025
Abstract:
Climate change and the operation of hydraulic projects have significantly altered the water cycle in the Three Gorges Reservoir area. The Three Gorges Reservoir area has experienced recurrent seasonal droughts in recent years. Analyzing the evolution characteristics and driving mechanisms of seasonal agricultural drought in this? region, as well as coupled with the quantitative determination of yield reduction thresholds under current drought defense conditions, is significantly important for developing a systematic response to agricultural droughts. Firstly, the spatiotemporal evolution of seasonal agricultural drought in the reservoir area from 1982 to 2022 was investigated, based on the Standardized Soil Moisture Index (SSMI). Furthermore, additional analyses were conducted using Path Analysis to explore key driving factors. Additionally, drought return periods and representative drought years were determined using Copula theory, and historical typical drought scenarios are extracted. On this basis, effective rainfall was introduced to improve the parameters of the Jensen model, considering losses due to evaporation, interception, and runoff. A new method for calculating the drought-induced crop yield reduction thresholds under historical typical drought scenarios and current defense conditions was proposed based on the improved Jensen model. recurrence of historically typical drought. The results showed that agricultural droughts in the Three Gorges Reservoir area intensified between 1982 and 2022, with significant spatiotemporal variability. Specifically, the tail section of the reservoir was identified as the high-frequency agricultural drought-prone area, while the middle reaches were characterized by long-duration, high-intensity, and severe droughts. Similarly, the upper reaches were prone to extreme, long-duration droughts. Further analysis revealed that future agricultural droughts in the reservoir area were expected to decrease overall. The key driving factor for summer-fall droughts was precipitation, while potential evapotranspiration was the directly influenced factor for winter-spring consecutive droughts. Finally, under the current water conservancy defense conditions, drought-induced crop yield reduction thresholds for return periods of 2, 5, 10, 20, and 50 years were calculated as 1.23%, 5.12%, 8.13%, 15.44%, and 22.32%, respectively. Overall, these findings provided technical support for drought-resilient water resource planning, drought replenishment scheduling, and scenario-based water management in the Three Gorges Reservoir area.
Climate change and the operation of hydraulic projects have significantly altered the water cycle in the Three Gorges Reservoir area. The Three Gorges Reservoir area has experienced recurrent seasonal droughts in recent years. Analyzing the evolution characteristics and driving mechanisms of seasonal agricultural drought in this? region, as well as coupled with the quantitative determination of yield reduction thresholds under current drought defense conditions, is significantly important for developing a systematic response to agricultural droughts. Firstly, the spatiotemporal evolution of seasonal agricultural drought in the reservoir area from 1982 to 2022 was investigated, based on the Standardized Soil Moisture Index (SSMI). Furthermore, additional analyses were conducted using Path Analysis to explore key driving factors. Additionally, drought return periods and representative drought years were determined using Copula theory, and historical typical drought scenarios are extracted. On this basis, effective rainfall was introduced to improve the parameters of the Jensen model, considering losses due to evaporation, interception, and runoff. A new method for calculating the drought-induced crop yield reduction thresholds under historical typical drought scenarios and current defense conditions was proposed based on the improved Jensen model. recurrence of historically typical drought. The results showed that agricultural droughts in the Three Gorges Reservoir area intensified between 1982 and 2022, with significant spatiotemporal variability. Specifically, the tail section of the reservoir was identified as the high-frequency agricultural drought-prone area, while the middle reaches were characterized by long-duration, high-intensity, and severe droughts. Similarly, the upper reaches were prone to extreme, long-duration droughts. Further analysis revealed that future agricultural droughts in the reservoir area were expected to decrease overall. The key driving factor for summer-fall droughts was precipitation, while potential evapotranspiration was the directly influenced factor for winter-spring consecutive droughts. Finally, under the current water conservancy defense conditions, drought-induced crop yield reduction thresholds for return periods of 2, 5, 10, 20, and 50 years were calculated as 1.23%, 5.12%, 8.13%, 15.44%, and 22.32%, respectively. Overall, these findings provided technical support for drought-resilient water resource planning, drought replenishment scheduling, and scenario-based water management in the Three Gorges Reservoir area.
Available online: May 13, 2025
Abstract:
After the operation of the Three Gorges Reservoir, the intensity of bank collapse has significantly increased in the middle and lower Yangtze River, in which bank collapses show concealment and suddenness, making the quantification and assessment of bank collapse challenging. Three typical reaches, Xiangjiazou, Qigongling, and Chengdezhou along the middle and lower reaches of the Yangtze River were selected. Based on multi-source remote sensing images and topographic data, the indicators for quantifying bank collapse were analyzed, including bank slope ratio, elevation difference of the beach-trough, toe erosion degree, distance of main flow to bank, and bankline change. Thresholds for these five indicators were quantified, and furthermore the fuzzy analytic hierarchy process was used to determine the weights of the indicators. The results indicate that the distance of main flow to bank and bankline change are the primary factors influencing bank collapse, with weights of approximately 0.4 and 0.25, respectively. The bank slope ratio, elevation difference of the beach-trough, and toe erosion degree are the secondary factors, with weights ranging from 0.1 to 0.15. The threshold values for the indicators of bank collapse differ among the various reaches: the bank slope ratio and toe erosion degree for Xiangjiazou are 0.04 and 0.1, respectively;0.5 and 0.16 for Qigongling; and both are 0.2 for Chengdezhou. In all three reachers, the elevation difference of the beach-trough is over 15 m, the threshold for bankline change between 0 and 0.5 m, and the ratio of main flow-bank distance to channel width between 0.3 and 0.4.
After the operation of the Three Gorges Reservoir, the intensity of bank collapse has significantly increased in the middle and lower Yangtze River, in which bank collapses show concealment and suddenness, making the quantification and assessment of bank collapse challenging. Three typical reaches, Xiangjiazou, Qigongling, and Chengdezhou along the middle and lower reaches of the Yangtze River were selected. Based on multi-source remote sensing images and topographic data, the indicators for quantifying bank collapse were analyzed, including bank slope ratio, elevation difference of the beach-trough, toe erosion degree, distance of main flow to bank, and bankline change. Thresholds for these five indicators were quantified, and furthermore the fuzzy analytic hierarchy process was used to determine the weights of the indicators. The results indicate that the distance of main flow to bank and bankline change are the primary factors influencing bank collapse, with weights of approximately 0.4 and 0.25, respectively. The bank slope ratio, elevation difference of the beach-trough, and toe erosion degree are the secondary factors, with weights ranging from 0.1 to 0.15. The threshold values for the indicators of bank collapse differ among the various reaches: the bank slope ratio and toe erosion degree for Xiangjiazou are 0.04 and 0.1, respectively;0.5 and 0.16 for Qigongling; and both are 0.2 for Chengdezhou. In all three reachers, the elevation difference of the beach-trough is over 15 m, the threshold for bankline change between 0 and 0.5 m, and the ratio of main flow-bank distance to channel width between 0.3 and 0.4.
Available online: May 13, 2025
Abstract:
The characteristics of thermal density flow in tributary reservoirs are an important basis for studying the mechanism of algal blooms. The density difference caused by water temperature difference between the mainstream reservoir and the tributary bay leads the mainstream of the Yangtze River flows into the tributary bay through the middle layer, surface layer and bottom layer in spring-summer, autumn and winter, respectively. The normal operation of the Three Gorges Reservoir goes through four stages every year: pre-flood drawdown season, flood season, post-flood storage season and dry season, with a maximum daily water level fluctuation of 3.0 m/d. Based on the calibrated and verified three-dimensional hydrodynamic and water temperature mathematical model of the Xiangxi Bay, different water level fluctuation conditions were simulated to analyze the characteristics of thermal density flow. The results show that with the water level rises, the backflow velocity and backflow thickness of the mainstream of the Yangtze River increase, while the inflow velocity of the upstream decreases. With the water level drops, the backflow velocity and backflow thickness of the mainstream of the Yangtze River decrease, while the inflow velocity of the upstream increases. The greater the daily increase of water level, the greater the backflow distance of the density flow from the mainstream of the Yangtze River. The greater the daily decrease of water level, the much smaller the backflow distance of the density flow from the mainstream of the Yangtze River. The maximum decline of the backflow distance from the mainstream of the Yangtze River is 40 percent with the daily water level decrease of 2.0 m/d. Cyclical water level fluctuation can cause cyclical water flow in tributary reservoirs. A high frequency of water level fluctuations (1.0 m every 6 hours) forces the mainstream reservoir and the tributary bay to be completely mixed in the middle and lower reaches of the tributary bay, which would reduce hydraulic residence time and limit the growth and aggregation of algae. Short-term (≤4 d) and small-amplitude (≤2.0 m/d) water level fluctuations are difficult to change the stable water temperature stratification state of the Xiangxi Bay, and the average depth of the thermocline does not exceed 5.0 m.
The characteristics of thermal density flow in tributary reservoirs are an important basis for studying the mechanism of algal blooms. The density difference caused by water temperature difference between the mainstream reservoir and the tributary bay leads the mainstream of the Yangtze River flows into the tributary bay through the middle layer, surface layer and bottom layer in spring-summer, autumn and winter, respectively. The normal operation of the Three Gorges Reservoir goes through four stages every year: pre-flood drawdown season, flood season, post-flood storage season and dry season, with a maximum daily water level fluctuation of 3.0 m/d. Based on the calibrated and verified three-dimensional hydrodynamic and water temperature mathematical model of the Xiangxi Bay, different water level fluctuation conditions were simulated to analyze the characteristics of thermal density flow. The results show that with the water level rises, the backflow velocity and backflow thickness of the mainstream of the Yangtze River increase, while the inflow velocity of the upstream decreases. With the water level drops, the backflow velocity and backflow thickness of the mainstream of the Yangtze River decrease, while the inflow velocity of the upstream increases. The greater the daily increase of water level, the greater the backflow distance of the density flow from the mainstream of the Yangtze River. The greater the daily decrease of water level, the much smaller the backflow distance of the density flow from the mainstream of the Yangtze River. The maximum decline of the backflow distance from the mainstream of the Yangtze River is 40 percent with the daily water level decrease of 2.0 m/d. Cyclical water level fluctuation can cause cyclical water flow in tributary reservoirs. A high frequency of water level fluctuations (1.0 m every 6 hours) forces the mainstream reservoir and the tributary bay to be completely mixed in the middle and lower reaches of the tributary bay, which would reduce hydraulic residence time and limit the growth and aggregation of algae. Short-term (≤4 d) and small-amplitude (≤2.0 m/d) water level fluctuations are difficult to change the stable water temperature stratification state of the Xiangxi Bay, and the average depth of the thermocline does not exceed 5.0 m.
Available online: May 13, 2025
Abstract:
Floating/emergent aquatic vegetation is an important aquatic vegetation group in lakes, and its area/coverage is an important parameter for lake ecological health assessment and carbon sequestration potential accounting. Accurately obtaining the area/coverage of floating/emergent aquatic vegetation over large lake areas and understanding their changes is crucial for lake ecological restoration and carbon sink accounting. Satellite remote sensing is the most effective means to obtain the area/cover of floating/emergent aquatic vegetation in lakes. However, traditional satellite monitoring methods can only obtain the presence or absence of aquatic vegetation within satellite pixels, and cannot quantitatively estimate the coverage of aquatic vegetation in the pixels Consequently, it is impossible to quantitatively and accurately obtain the area/coverage of floating/emergent aquatic vegetation in lakes. To address this issue, we utilized UAV, Sentinel-2 MSI, and Landsat 8 OLI remote sensing data. Using the XGBoost modeling method, we developed quantitative estimation models for floating and emergent aquatic vegetation coverage at the Sentinel-2 MSI and Landsat 8 OLI pixel scales through a stepwise upscaling approach, and successfully applied it to China’s four largest freshwater lakes. The results showed that the test sets of the two estimation models based on Sentinel and Landsat images had R2 of 0.95 and 0.97, RMSE of 7.85% and 4.80%, and MAE of 5.35% and 3.35%, respectively. From 1990 to 2022, Lake Dongting and Lake Poyang showed highly significant increasing trends (p ＜ 0.01), Lake Taihu showed an increasing and then decreasing trend (p ＜ 0.01), and Lake Hongze had a non-significant increasing trend (p = 0.59). The long-term application of the model in the four largest freshwater lakes proved the robustness and application potential of the model, which is expected to provide methodological and data support for the accounting of carbon sinks in lake ecosystems and the assessment of carbon sequestration potential.
Floating/emergent aquatic vegetation is an important aquatic vegetation group in lakes, and its area/coverage is an important parameter for lake ecological health assessment and carbon sequestration potential accounting. Accurately obtaining the area/coverage of floating/emergent aquatic vegetation over large lake areas and understanding their changes is crucial for lake ecological restoration and carbon sink accounting. Satellite remote sensing is the most effective means to obtain the area/cover of floating/emergent aquatic vegetation in lakes. However, traditional satellite monitoring methods can only obtain the presence or absence of aquatic vegetation within satellite pixels, and cannot quantitatively estimate the coverage of aquatic vegetation in the pixels Consequently, it is impossible to quantitatively and accurately obtain the area/coverage of floating/emergent aquatic vegetation in lakes. To address this issue, we utilized UAV, Sentinel-2 MSI, and Landsat 8 OLI remote sensing data. Using the XGBoost modeling method, we developed quantitative estimation models for floating and emergent aquatic vegetation coverage at the Sentinel-2 MSI and Landsat 8 OLI pixel scales through a stepwise upscaling approach, and successfully applied it to China’s four largest freshwater lakes. The results showed that the test sets of the two estimation models based on Sentinel and Landsat images had R2 of 0.95 and 0.97, RMSE of 7.85% and 4.80%, and MAE of 5.35% and 3.35%, respectively. From 1990 to 2022, Lake Dongting and Lake Poyang showed highly significant increasing trends (p ＜ 0.01), Lake Taihu showed an increasing and then decreasing trend (p ＜ 0.01), and Lake Hongze had a non-significant increasing trend (p = 0.59). The long-term application of the model in the four largest freshwater lakes proved the robustness and application potential of the model, which is expected to provide methodological and data support for the accounting of carbon sinks in lake ecosystems and the assessment of carbon sequestration potential.
Available online: May 13, 2025
Abstract:
In order to investigate the occurrence characteristics and transmission laws of organochlorine pesticides (OCPs) in Luhu Lake, a typical suburban lake in the middle reaches of the Yangtze River, water and sediment samples were collected from 40 sites in Luhu Lake, located in Jiangxia District, Wuhan, China. 24 kinds of OCPs were determined by gas chromatography (GC-ECD) to analyze the pollution characteristics, sources and multi-medium transmission laws. The results showed that, all 24 kinds of OCPs were detected in the study area, and the total amounts of OCPs ranged 0.64 to 6.97 ng·L-1 in dissolved phase, 0.06 to 5.61 ng·L-1 in suspended particulate matter, 0.47 to 14.16 ng·g-1 in surface sediments, respectively. Compared with other lakes, the OCPs concentrations were at a low level. HCHs accounted for the largest proportion in dissolved phase, while HCHs, DDTs and Aldrin were the main pollutants in suspended particulate matter and sediment. The results of characteristic ratio traceability analysis showed that HCHs and DDTs were mainly historical residues in the study area. The main sources of HCHs in water and sediment were agrolindane application and mixed sources respectively, and DDTs were mainly degraded in an anaerobic environment. The multi-medium transmission of OCPs was analyzed by the cosine theta similarity metric, partition coefficient and fugacity approach. The distribution coefficient (Kd) between dissolved phase and suspended particulate matter showed that OCPs in water were more easily to be adsorbed by suspended particulate matter with an increase in the octanol-water partition coefficient (KOW). The fugacity fraction between water and sediment (ffSW) decreased with an increase in KOW, indicating that the sediments in the study area were sinks of OCPs with high KOW such as HCB and Aldrin.
In order to investigate the occurrence characteristics and transmission laws of organochlorine pesticides (OCPs) in Luhu Lake, a typical suburban lake in the middle reaches of the Yangtze River, water and sediment samples were collected from 40 sites in Luhu Lake, located in Jiangxia District, Wuhan, China. 24 kinds of OCPs were determined by gas chromatography (GC-ECD) to analyze the pollution characteristics, sources and multi-medium transmission laws. The results showed that, all 24 kinds of OCPs were detected in the study area, and the total amounts of OCPs ranged 0.64 to 6.97 ng·L-1 in dissolved phase, 0.06 to 5.61 ng·L-1 in suspended particulate matter, 0.47 to 14.16 ng·g-1 in surface sediments, respectively. Compared with other lakes, the OCPs concentrations were at a low level. HCHs accounted for the largest proportion in dissolved phase, while HCHs, DDTs and Aldrin were the main pollutants in suspended particulate matter and sediment. The results of characteristic ratio traceability analysis showed that HCHs and DDTs were mainly historical residues in the study area. The main sources of HCHs in water and sediment were agrolindane application and mixed sources respectively, and DDTs were mainly degraded in an anaerobic environment. The multi-medium transmission of OCPs was analyzed by the cosine theta similarity metric, partition coefficient and fugacity approach. The distribution coefficient (Kd) between dissolved phase and suspended particulate matter showed that OCPs in water were more easily to be adsorbed by suspended particulate matter with an increase in the octanol-water partition coefficient (KOW). The fugacity fraction between water and sediment (ffSW) decreased with an increase in KOW, indicating that the sediments in the study area were sinks of OCPs with high KOW such as HCB and Aldrin.
Available online: May 08, 2025
Abstract:
The form of phosphorus in lake sediments is a key internal factor affecting its migration and transformation in aquatic ecosystems. This study collected surface and core sediment samples from 36 sites in Hulun Lake and systematically analyzed the distribution characteristics of phosphorus forms in the sediments and their correlations with particle size, pH, organic carbon, and simultaneously extracted iron, aluminum, calcium, and manganese. Significant positive correlations between P(Phosphorus.) contents and Al (Aluminum), Ca (Calcium), Fe (Iron) and Mn (Manganese) highlighted the potential effects of metallic oxides on surface adsorption and co-precipitation. Simultaneously, contributed by the larger specific surface area property, P and both mean grain size and pH exhibited in significant negative correlations. Additionally, our results also highlighted the stability of Fe-P (Iron-bound Phosphorus), Al-P (Aluminum-bound Phosphorus) and Ca-P (Calcium-bound Phosphorus) were strongly associated with pH. TOC (Total Organic Carbon) contributed most significantly in P distributions, followed by grain size. This study provides fundamental data on the migration and transformation of phosphorus in northern lake sediments in China, offering new perspectives on understanding the geochemical characteristics of phosphorus in different lake areas and their responses to natural and anthropogenic processes at a national scale.
The form of phosphorus in lake sediments is a key internal factor affecting its migration and transformation in aquatic ecosystems. This study collected surface and core sediment samples from 36 sites in Hulun Lake and systematically analyzed the distribution characteristics of phosphorus forms in the sediments and their correlations with particle size, pH, organic carbon, and simultaneously extracted iron, aluminum, calcium, and manganese. Significant positive correlations between P(Phosphorus.) contents and Al (Aluminum), Ca (Calcium), Fe (Iron) and Mn (Manganese) highlighted the potential effects of metallic oxides on surface adsorption and co-precipitation. Simultaneously, contributed by the larger specific surface area property, P and both mean grain size and pH exhibited in significant negative correlations. Additionally, our results also highlighted the stability of Fe-P (Iron-bound Phosphorus), Al-P (Aluminum-bound Phosphorus) and Ca-P (Calcium-bound Phosphorus) were strongly associated with pH. TOC (Total Organic Carbon) contributed most significantly in P distributions, followed by grain size. This study provides fundamental data on the migration and transformation of phosphorus in northern lake sediments in China, offering new perspectives on understanding the geochemical characteristics of phosphorus in different lake areas and their responses to natural and anthropogenic processes at a national scale.
Available online: May 08, 2025
Abstract:
Based on the 8 indicators of 8 monitoring sections of 8 main rivers entering Taihu Lake from 2020 to 2022, the temporal and spatial differentiation characteristics of pollution in the main rivers entering the lake were analyzed and discussed, and the positive definite matrix factor analysis model was used to analyze the pollution sources. The results showed that: 1. The concentration of pollution indicators in the rivers entering the lake decreased year by year; The concentrations of NH3-N and TN were higher in winter (January-February and December), the concentrations of CODMn and TP were higher in summer (June-September), and the concentrations of COD and BOD5 peaked twice a year (January-May and June-September). 2. The concentration of pollution indicators in the southern part of Taihu Lake, Wangyu River and Xiaoxigang, and Dagang River in the southwest mountainous area are at a relatively low level. The concentrations of pollution indicators in Wujin Port, Taizhu Canal, Taiyun South Canal, Dapu Port and Wuxi Port are relatively high, which contribute greatly to the N and P of Taihu Lake. 3. There are four main types of pollution sources in Taihu Lake, namely livestock and poultry breeding and planting, production and living, industry and aquaculture, with contribution rates of 42.1%, 12.9%, 25.2% and 19.8% respectively. Agricultural non-point sources have a great impact on water pollutants, and the amount of pollutants entering rivers should be reduced according to the water withdrawal paths of livestock, poultry, aquaculture and farmland. In this study, the sources of pollutants entering the river were quantified, and the results of the study could provide a scientific reference for the treatment of Taihu Lake water body.
Based on the 8 indicators of 8 monitoring sections of 8 main rivers entering Taihu Lake from 2020 to 2022, the temporal and spatial differentiation characteristics of pollution in the main rivers entering the lake were analyzed and discussed, and the positive definite matrix factor analysis model was used to analyze the pollution sources. The results showed that: 1. The concentration of pollution indicators in the rivers entering the lake decreased year by year; The concentrations of NH3-N and TN were higher in winter (January-February and December), the concentrations of CODMn and TP were higher in summer (June-September), and the concentrations of COD and BOD5 peaked twice a year (January-May and June-September). 2. The concentration of pollution indicators in the southern part of Taihu Lake, Wangyu River and Xiaoxigang, and Dagang River in the southwest mountainous area are at a relatively low level. The concentrations of pollution indicators in Wujin Port, Taizhu Canal, Taiyun South Canal, Dapu Port and Wuxi Port are relatively high, which contribute greatly to the N and P of Taihu Lake. 3. There are four main types of pollution sources in Taihu Lake, namely livestock and poultry breeding and planting, production and living, industry and aquaculture, with contribution rates of 42.1%, 12.9%, 25.2% and 19.8% respectively. Agricultural non-point sources have a great impact on water pollutants, and the amount of pollutants entering rivers should be reduced according to the water withdrawal paths of livestock, poultry, aquaculture and farmland. In this study, the sources of pollutants entering the river were quantified, and the results of the study could provide a scientific reference for the treatment of Taihu Lake water body.
Available online: April 30, 2025
Abstract:
Ebullition is a major pathway for methane emissions in freshwater ecosystems such as lakes and reservoirs, characterized by high spatiotemporal heterogeneity that makes it difficult to capture ebullition hotspots. exhibiting high spatiotemporal heterogeneity. In shallow zones near the reservoir tail, sediments tend to produce methane that is released in bubble form. However, capturing CH4 ebullition hotspots in open waters is challenging. During ice cover formation, methane-rich bubbles produced by sediments can become trapped and frozen in the ice, forming visible "ice-trapped bubbles" on the ice surface. This phenomenon allows for the identification of CH4 ebullition hotspots based on the characteristics of ice-trapped bubbles. This study investigates the large Dongfeng Reservoir in northeastern China. Using UAV imagery of the winter reservoir ice surface and field surveys of ice-trapped bubble characteristics, an object-oriented classification method was developed to extract and segment images of ice-trapped bubbles. Spatial autocorrelation analysis was employed to explore the spatial distribution patterns of ice-trapped bubbles and identify hotspot areas of bubble aggregation. The results indicate: (1) The diameter of ice-trapped bubbles in the Dongfeng Reservoir tail ranges from 1 to 10 cm. The spatial resolution of UAV imagery at a flight height of 15 m is 0.4 cm, sufficient for identifying ice-trapped bubbles. The morphological top-hat transformation method effectively improves image illumination uniformity and significantly enhances the quality of orthophoto mosaics.(2) Classification and extraction of ice-trapped bubbles based on differences in aspect ratio, brightness, and density between bubbles and ice cracks show high precision, with overall classification accuracies above 0.8 in the three surveyed bubble zones.(3) The proportion of ice-trapped bubble area among the three zones follows the order R2 > R1 > R3, with the total bubble area accounting for 0.24% of the reservoir tail. However, the bubble area proportions within the ten surveyed transects in the three zones vary between 2.6% and 7.8%. The spatial distribution of ice-trapped bubbles exhibits significant clustering (Moran"s I > 0.8, Z > 80), with "high-high" clusters identified as ebullition hotspots covering 21.5% of the reservoir tail area. Using UAV imagery to identify CH4 ebullition hotspots in ice-covered reservoirs can further guide studies on CH4 emission scales in open waters.
Ebullition is a major pathway for methane emissions in freshwater ecosystems such as lakes and reservoirs, characterized by high spatiotemporal heterogeneity that makes it difficult to capture ebullition hotspots. exhibiting high spatiotemporal heterogeneity. In shallow zones near the reservoir tail, sediments tend to produce methane that is released in bubble form. However, capturing CH4 ebullition hotspots in open waters is challenging. During ice cover formation, methane-rich bubbles produced by sediments can become trapped and frozen in the ice, forming visible "ice-trapped bubbles" on the ice surface. This phenomenon allows for the identification of CH4 ebullition hotspots based on the characteristics of ice-trapped bubbles. This study investigates the large Dongfeng Reservoir in northeastern China. Using UAV imagery of the winter reservoir ice surface and field surveys of ice-trapped bubble characteristics, an object-oriented classification method was developed to extract and segment images of ice-trapped bubbles. Spatial autocorrelation analysis was employed to explore the spatial distribution patterns of ice-trapped bubbles and identify hotspot areas of bubble aggregation. The results indicate: (1) The diameter of ice-trapped bubbles in the Dongfeng Reservoir tail ranges from 1 to 10 cm. The spatial resolution of UAV imagery at a flight height of 15 m is 0.4 cm, sufficient for identifying ice-trapped bubbles. The morphological top-hat transformation method effectively improves image illumination uniformity and significantly enhances the quality of orthophoto mosaics.(2) Classification and extraction of ice-trapped bubbles based on differences in aspect ratio, brightness, and density between bubbles and ice cracks show high precision, with overall classification accuracies above 0.8 in the three surveyed bubble zones.(3) The proportion of ice-trapped bubble area among the three zones follows the order R2 > R1 > R3, with the total bubble area accounting for 0.24% of the reservoir tail. However, the bubble area proportions within the ten surveyed transects in the three zones vary between 2.6% and 7.8%. The spatial distribution of ice-trapped bubbles exhibits significant clustering (Moran"s I > 0.8, Z > 80), with "high-high" clusters identified as ebullition hotspots covering 21.5% of the reservoir tail area. Using UAV imagery to identify CH4 ebullition hotspots in ice-covered reservoirs can further guide studies on CH4 emission scales in open waters.
Available online: April 18, 2025
Abstract:
Inland waters are an important natural source of methane to the atmosphere, a potent greenhouse gas. The potential of sediment methane production (PMP) under anaerobic conditions is a key indicator for the level of atmospheric emissions of methane. However, there is a lack of cross-system studies on the sediment PMP in inland waters. The underlying driving mechanisms are still unclear. In this study, we collected data on PMP in inland waters in China including reservoirs, lakes, rivers and wetlands. Combined with some unpublished data (a total of 210 data points), the temporal and spatial distribution of sediment PMP in several different systems was explored, and the drivers of the sediment PMP were identified. We found that PMP is seasonally variable, showing a trend of being significantly greater in the rainy season than in the dry season (~3.5 times, p<0.01)); damming causes a significant increase in PMP by more than ten times, and sediment PMP in reservoirs and lakes is significantly (p<0.01) greater than that of rivers or wetlands. Correlation analysis shows that eutrophication caused by human activities has a significant (p<0.05) driving effect on sediment PMP. Water temperature, water depth and sediment organic matter content have a significant (p<0.01) positive stimulating effect on sediment PMP, while salinity has a significant (p<0.01) inhibitory effect. In the context of global climate change, in order to make good future projections of carbon emissions from inland waters, human disturbances such as damming and eutrophication must be well incorporated, in addition to the natural process of global warming.
Inland waters are an important natural source of methane to the atmosphere, a potent greenhouse gas. The potential of sediment methane production (PMP) under anaerobic conditions is a key indicator for the level of atmospheric emissions of methane. However, there is a lack of cross-system studies on the sediment PMP in inland waters. The underlying driving mechanisms are still unclear. In this study, we collected data on PMP in inland waters in China including reservoirs, lakes, rivers and wetlands. Combined with some unpublished data (a total of 210 data points), the temporal and spatial distribution of sediment PMP in several different systems was explored, and the drivers of the sediment PMP were identified. We found that PMP is seasonally variable, showing a trend of being significantly greater in the rainy season than in the dry season (~3.5 times, p<0.01)); damming causes a significant increase in PMP by more than ten times, and sediment PMP in reservoirs and lakes is significantly (p<0.01) greater than that of rivers or wetlands. Correlation analysis shows that eutrophication caused by human activities has a significant (p<0.05) driving effect on sediment PMP. Water temperature, water depth and sediment organic matter content have a significant (p<0.01) positive stimulating effect on sediment PMP, while salinity has a significant (p<0.01) inhibitory effect. In the context of global climate change, in order to make good future projections of carbon emissions from inland waters, human disturbances such as damming and eutrophication must be well incorporated, in addition to the natural process of global warming.
Available online: April 17, 2025
Abstract:
This paper analyzes the causes of siltation in the Old Course of the Fuhe River based on the sandbar evolution, water and sediment inflow conditions, and the impacts of siltation by the sandbar vegetation. It was found that from 1985 to 2022, the area of sandbars in upstream of the Old Course of the Fuhe River continued to grow and the main channel silted up. The sandbar vegetation in the upstream grows luxuriantly. Under the influence of water blockage by floodplain vegetation, the flow velocity decreases, and the sediment concentration decays along the reaches, which promotes sediment deposition in the upper reaches. After the incoming water and sediment of the upper reaches enter the middle and downstream reaches, the average flow velocity decreases along the reaches due to the widening of the section width, resulting in sediment deposition. Moreover, The diversion water volume of the old course of the Fuhe River shows a decreasing trend year by year. The water and sediment conditions in the Old Course of the Fuhe River are suboptimal. During periods of low flow, siltation occurs frequently, and during high-flow events, the river lacks sufficient power to flush away the sediment deposited during low-flow periods. This dynamic results in a continuous accumulation of sediment within the channel. Based on a two-dimensional mathematical model, we designed multiple water-sediment control scenarios, incorporating various sandbar structures and vegetation distributions. Through detailed calculations and analyses, we proposed the following countermeasures: When the sediment concentration at the inlet of the Fuhe River exceeds 0.01 kg/m3, introducing controlled high-flow events with flow rates maintained between 85 and 125 m3/s can effectively transform the upstream section from a state of siltation to scouring. In the middle and downstream reaches, applying sandbars-cutting techniques and adjusting vegetation distribution can enhance the sediment transport capacity, thereby slowing down the rate of siltation in these areas. These countermeasures aim to provide a valuable reference for similar small and medium-sized rivers, improving their siltation conditions and restoring and maintaining the health and stability of river ecosystems.
This paper analyzes the causes of siltation in the Old Course of the Fuhe River based on the sandbar evolution, water and sediment inflow conditions, and the impacts of siltation by the sandbar vegetation. It was found that from 1985 to 2022, the area of sandbars in upstream of the Old Course of the Fuhe River continued to grow and the main channel silted up. The sandbar vegetation in the upstream grows luxuriantly. Under the influence of water blockage by floodplain vegetation, the flow velocity decreases, and the sediment concentration decays along the reaches, which promotes sediment deposition in the upper reaches. After the incoming water and sediment of the upper reaches enter the middle and downstream reaches, the average flow velocity decreases along the reaches due to the widening of the section width, resulting in sediment deposition. Moreover, The diversion water volume of the old course of the Fuhe River shows a decreasing trend year by year. The water and sediment conditions in the Old Course of the Fuhe River are suboptimal. During periods of low flow, siltation occurs frequently, and during high-flow events, the river lacks sufficient power to flush away the sediment deposited during low-flow periods. This dynamic results in a continuous accumulation of sediment within the channel. Based on a two-dimensional mathematical model, we designed multiple water-sediment control scenarios, incorporating various sandbar structures and vegetation distributions. Through detailed calculations and analyses, we proposed the following countermeasures: When the sediment concentration at the inlet of the Fuhe River exceeds 0.01 kg/m3, introducing controlled high-flow events with flow rates maintained between 85 and 125 m3/s can effectively transform the upstream section from a state of siltation to scouring. In the middle and downstream reaches, applying sandbars-cutting techniques and adjusting vegetation distribution can enhance the sediment transport capacity, thereby slowing down the rate of siltation in these areas. These countermeasures aim to provide a valuable reference for similar small and medium-sized rivers, improving their siltation conditions and restoring and maintaining the health and stability of river ecosystems.
Yangzixuan, CHEN Xiang, Liyiping, Wangyv, Zhuxiaoling, Baohangtong, Panhongzhe, Zhangshuangshuang, Yanchunmin
Available online: April 17, 2025
Abstract:
In order to reveal the characteristics of nutrient pollution and its pollution sources in lake sediments in the city, and to provide a new perspective for the assessment of the environmental effect of comprehensive water environment management, the contents of TN, TP and OM in sediment columnar samples at 25 points in Yiai Lake in Huanggang City were collected and measured, the water quality of overflow sewage from 9 points and outlets of the lake was monitored, the spatial distribution characteristics of lake water quality and sediment nutrients were analyzed, and the sediment pollution risk was assessed by comprehensive pollution index method, and cluster analysis, carbon-nitrogen ratio (C/N) and carbon-phosphorus ratio (C/P) were used A combination of methods to analyze the sources of nutrients in lake sediments. The results showed that: 1) There were spatial differences in the distribution of TN, TP and OM in sediments. The horizontal distribution of TN, TP and OM contents ranged from 940~3677, 323~1667 mg·kg-1 and 1.03%~7.44%, and the overall vertical expression was surface >The contents of TN, TP and OM in the middle and bottom layers and surface sediments ranged from 920~4450 mg·kg-1, 208~1970 mg·kg-1 and 2.05~7.48%, respectively. 2) The TP content of surface sediments was higher than that of the lakes in the middle and lower reaches of the Yangtze River, and the results of the comprehensive pollution index method showed that the TP pollution of surface sediments was serious, and the total phosphorus in 52% of the lake area was in a moderate and severe pollution state, and the degree of TN pollution and comprehensive pollution was low. 3) The nutrient distribution of surface sediments was affected by overflow discharge, non-point source pollution and endogenous release, and the C/N value of surface sediment was 10.67, and the C/P value was between 20.16~190.97. TP mainly comes from non-point source pollution, followed by overflow sewage. The source of TN is similar to that of OM, which is derived from about 45% of endogenous release and 55% of non-point source and overflow pollution.
In order to reveal the characteristics of nutrient pollution and its pollution sources in lake sediments in the city, and to provide a new perspective for the assessment of the environmental effect of comprehensive water environment management, the contents of TN, TP and OM in sediment columnar samples at 25 points in Yiai Lake in Huanggang City were collected and measured, the water quality of overflow sewage from 9 points and outlets of the lake was monitored, the spatial distribution characteristics of lake water quality and sediment nutrients were analyzed, and the sediment pollution risk was assessed by comprehensive pollution index method, and cluster analysis, carbon-nitrogen ratio (C/N) and carbon-phosphorus ratio (C/P) were used A combination of methods to analyze the sources of nutrients in lake sediments. The results showed that: 1) There were spatial differences in the distribution of TN, TP and OM in sediments. The horizontal distribution of TN, TP and OM contents ranged from 940~3677, 323~1667 mg·kg-1 and 1.03%~7.44%, and the overall vertical expression was surface >The contents of TN, TP and OM in the middle and bottom layers and surface sediments ranged from 920~4450 mg·kg-1, 208~1970 mg·kg-1 and 2.05~7.48%, respectively. 2) The TP content of surface sediments was higher than that of the lakes in the middle and lower reaches of the Yangtze River, and the results of the comprehensive pollution index method showed that the TP pollution of surface sediments was serious, and the total phosphorus in 52% of the lake area was in a moderate and severe pollution state, and the degree of TN pollution and comprehensive pollution was low. 3) The nutrient distribution of surface sediments was affected by overflow discharge, non-point source pollution and endogenous release, and the C/N value of surface sediment was 10.67, and the C/P value was between 20.16~190.97. TP mainly comes from non-point source pollution, followed by overflow sewage. The source of TN is similar to that of OM, which is derived from about 45% of endogenous release and 55% of non-point source and overflow pollution.
Available online: April 17, 2025
Abstract:
Suburban lakes, under the dual influence of agricultural expansion and accelerated urbanization, are facing increasingly severe heavy metal pollution, posing threats to aquatic ecosystems and surrounding human health. This study focuses on Shitang Lake, a typical suburban lake in the middle and lower reaches of the Yangtze River. Through sediment core sampling and chronological reconstruction, combined with grain size and elemental concentration analysis, the enrichment factor method and potential ecological risk index were employed to assess and reconstruct the pollution history of Cd, As, Pb, Co, Cu, Ni, Cr, and Zn over the past two centuries. Additionally, correlation analysis, cluster analysis, and positive matrix factorization were used to determine the sources of heavy metals and their relative contributions. The results show that most heavy metals (e.g., As, Pb, Co, Cu, Ni, Cr, and Zn) exhibited low pollution levels and slight ecological risks. However, Cd had significantly higher pollution levels and potential ecological risks, increasing from no pollution to moderate pollution starting in 1981, with strong ecological risk levels reached in 2004. Furthermore, since the mid-1970s, the comprehensive potential ecological risk index of the sed-iment has risen significantly, although the overall risk remains at a slight level. Source analysis revealed that before 1930, heavy metals in Shitang Lake sediments primarily originated from natural weathering (average contribution rate of 63.63%), while industrial and agricultural sources contributed 25.22% and 11.15%, respectively. From 1930 to 1974, the contribution of agricultural sources increased to 23.44%, while natural and industrial sources accounted for 51.72% and 24.84%, respectively. After 1975, the contributions of agricultural and industrial sources rose to 46.74% and 41.19%, becoming the main sources of pollution. This study provides a scientific basis for the prevention and control of heavy metal pollution in the Shitang Lake basin, offers a long-term perspective for the ecological protection of lakes in the middle and lower reaches of the Yangtze River, and serves as a theoretical reference and technical support for managing suburban lake pollution in other developing countries and regions under rapid urbanization.
Suburban lakes, under the dual influence of agricultural expansion and accelerated urbanization, are facing increasingly severe heavy metal pollution, posing threats to aquatic ecosystems and surrounding human health. This study focuses on Shitang Lake, a typical suburban lake in the middle and lower reaches of the Yangtze River. Through sediment core sampling and chronological reconstruction, combined with grain size and elemental concentration analysis, the enrichment factor method and potential ecological risk index were employed to assess and reconstruct the pollution history of Cd, As, Pb, Co, Cu, Ni, Cr, and Zn over the past two centuries. Additionally, correlation analysis, cluster analysis, and positive matrix factorization were used to determine the sources of heavy metals and their relative contributions. The results show that most heavy metals (e.g., As, Pb, Co, Cu, Ni, Cr, and Zn) exhibited low pollution levels and slight ecological risks. However, Cd had significantly higher pollution levels and potential ecological risks, increasing from no pollution to moderate pollution starting in 1981, with strong ecological risk levels reached in 2004. Furthermore, since the mid-1970s, the comprehensive potential ecological risk index of the sed-iment has risen significantly, although the overall risk remains at a slight level. Source analysis revealed that before 1930, heavy metals in Shitang Lake sediments primarily originated from natural weathering (average contribution rate of 63.63%), while industrial and agricultural sources contributed 25.22% and 11.15%, respectively. From 1930 to 1974, the contribution of agricultural sources increased to 23.44%, while natural and industrial sources accounted for 51.72% and 24.84%, respectively. After 1975, the contributions of agricultural and industrial sources rose to 46.74% and 41.19%, becoming the main sources of pollution. This study provides a scientific basis for the prevention and control of heavy metal pollution in the Shitang Lake basin, offers a long-term perspective for the ecological protection of lakes in the middle and lower reaches of the Yangtze River, and serves as a theoretical reference and technical support for managing suburban lake pollution in other developing countries and regions under rapid urbanization.
Available online: April 17, 2025
Abstract:
Nitrous oxide (N2O), a potent greenhouse gas, is a major contributor to climate warming. Urban rivers, characterized by substantial pollutant inputs, are recognized as hotspots for N2O emissions. However, N2O emissions in rivers with weak hydrodynamics in plain areas remain unclear. This study investigated N2O emission patterns in rivers flowing in to Lake Gehu, a plain urban area in China, and analyzed functional microbial abundance using quantitative PCR (q-PCR) to explore the underlying mechanisms during both the dry and wet seasons. The results showed no significant seasonal variation in N2O emissions but highlighted pronounced spatial differences. N2O emissions decreased significantly along the flow direction and were positively correlated with the distance to the lake. For every 1 km decrease in distance from the lake, N2O emission flux decreased by 0.05 mg/(m2·d). Furthermore, N2O emission flux increased with the ratio of nitrifying to denitrifying bacteria, highlighting the critical roles of nitrification and its substrate, ammonium, in regulating N2O production. The average EF?r value in the study area was approximately 5.5 times higher than the default value in the IPCC-2019 guidelines. These findings enhance the understanding of N2O emissions from urban rivers in plain areas and provide a scientific basis for improving regional emission estimates.
Nitrous oxide (N2O), a potent greenhouse gas, is a major contributor to climate warming. Urban rivers, characterized by substantial pollutant inputs, are recognized as hotspots for N2O emissions. However, N2O emissions in rivers with weak hydrodynamics in plain areas remain unclear. This study investigated N2O emission patterns in rivers flowing in to Lake Gehu, a plain urban area in China, and analyzed functional microbial abundance using quantitative PCR (q-PCR) to explore the underlying mechanisms during both the dry and wet seasons. The results showed no significant seasonal variation in N2O emissions but highlighted pronounced spatial differences. N2O emissions decreased significantly along the flow direction and were positively correlated with the distance to the lake. For every 1 km decrease in distance from the lake, N2O emission flux decreased by 0.05 mg/(m2·d). Furthermore, N2O emission flux increased with the ratio of nitrifying to denitrifying bacteria, highlighting the critical roles of nitrification and its substrate, ammonium, in regulating N2O production. The average EF?r value in the study area was approximately 5.5 times higher than the default value in the IPCC-2019 guidelines. These findings enhance the understanding of N2O emissions from urban rivers in plain areas and provide a scientific basis for improving regional emission estimates.
Available online: April 17, 2025
Abstract:
【Objective】The concentration and speciation of arsenic in groundwater are significantly influenced and regulated by microbial activities. The Kuitun River Basin is a typical high-arsenic area, yet research on the metabolic characteristics of arsenic-metabolizing microorganisms in groundwater from this region remains scarce.【Methods】In this study, 11 groundwater samples were collected from the Kuitun River Basin for metagenomic sequencing. The chemical characteristics of high- and low-arsenic groundwater were analyzed, along with the associations between the community structure and functional genes of arsenic-metabolizing microorganisms and environmental factors.【Result】The results indicated that the dominant bacterial phyla in the groundwater of the study area were Proteobacteria, Actinobacteria, and Planctomycetota. At the genus level, the microbial communities in low-arsenic samples exhibited significant species richness and diversity advantages. The abundances of Nitrosomonas, Thiobacillus, and Sulfuritalea were significantly positively correlated with total arsenic. Microorganisms involved in the nitrogen cycle can indirectly affect the arsenic metabolism process. A total of 12 functional genes related to arsenic methylation, arsenite (As(III)) oxidation, arsenate (As(V)) reduction, and arsenic transport were annotated in this study. Total arsenic (As) was significantly negatively correlated with arsC1 (arsenate reductase gene) and arsH (organic arsenical oxidase gene), and significantly positively correlated with AS3MT (arsenic methyltransferase gene).【Conclusion】Arsenic concentrations can inhibit the abundance and diversity of arsenic-metabolizing microbial communities and functional genes, exerting selective pressure on the microbial community structure and enriching arsenic-resistant microorganisms in high-arsenic environments. Multiple arsenic metabolism pathways exist among groundwater microorganisms in the study area, including the As(V) efflux system composed of ArsJ (organic arsenical efflux permease) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase). Arsenic methylation is the primary pathway of microbial arsenic metabolism in high-arsenic groundwater in this basin. The relationship between arsenic-metabolizing microbial communities and functional genes and total arsenic is regulated and influenced by multiple environmental factors, rather than by a single factor. By screening microbial populations with arsenic metabolism capabilities and their key functional genes, this study not only deepened our understanding of arsenic metabolism mechanisms but also provided new strategies for bioremediation technologies for arsenic contamination.
【Objective】The concentration and speciation of arsenic in groundwater are significantly influenced and regulated by microbial activities. The Kuitun River Basin is a typical high-arsenic area, yet research on the metabolic characteristics of arsenic-metabolizing microorganisms in groundwater from this region remains scarce.【Methods】In this study, 11 groundwater samples were collected from the Kuitun River Basin for metagenomic sequencing. The chemical characteristics of high- and low-arsenic groundwater were analyzed, along with the associations between the community structure and functional genes of arsenic-metabolizing microorganisms and environmental factors.【Result】The results indicated that the dominant bacterial phyla in the groundwater of the study area were Proteobacteria, Actinobacteria, and Planctomycetota. At the genus level, the microbial communities in low-arsenic samples exhibited significant species richness and diversity advantages. The abundances of Nitrosomonas, Thiobacillus, and Sulfuritalea were significantly positively correlated with total arsenic. Microorganisms involved in the nitrogen cycle can indirectly affect the arsenic metabolism process. A total of 12 functional genes related to arsenic methylation, arsenite (As(III)) oxidation, arsenate (As(V)) reduction, and arsenic transport were annotated in this study. Total arsenic (As) was significantly negatively correlated with arsC1 (arsenate reductase gene) and arsH (organic arsenical oxidase gene), and significantly positively correlated with AS3MT (arsenic methyltransferase gene).【Conclusion】Arsenic concentrations can inhibit the abundance and diversity of arsenic-metabolizing microbial communities and functional genes, exerting selective pressure on the microbial community structure and enriching arsenic-resistant microorganisms in high-arsenic environments. Multiple arsenic metabolism pathways exist among groundwater microorganisms in the study area, including the As(V) efflux system composed of ArsJ (organic arsenical efflux permease) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase). Arsenic methylation is the primary pathway of microbial arsenic metabolism in high-arsenic groundwater in this basin. The relationship between arsenic-metabolizing microbial communities and functional genes and total arsenic is regulated and influenced by multiple environmental factors, rather than by a single factor. By screening microbial populations with arsenic metabolism capabilities and their key functional genes, this study not only deepened our understanding of arsenic metabolism mechanisms but also provided new strategies for bioremediation technologies for arsenic contamination.
fengning, qinxiwei, mayuliang, pantong, chenjianzhou, dingchengwang, jiangziwen, zhangdong, liuchenglin, liqingkuan, renerfeng, zhangfan
Available online: April 17, 2025
Abstract:
There are abundant brine resources in the Balun Mahai Basin of Qaidam, but the genetic mechanism and potential of brine resources still need to be determined. This study focuses on the intercrystalline brine in the Balema Lake Basin, conducting geochemical research on elements and hydrogen-oxygen isotopes to systematically analyze its water source, solute origins, evolution process, and genesis model. The study also explores the mining potential of potassium, boron, and lithium elements. The results show that the intercrystalline brine in the northern part of the Balema Lake Basin is of the magnesium sulfate subtype, while the southern part predominantly features chloride water. The solutes in the brine mainly originate from the dissolution of halite, potassium salts, and gypsum. The water chemistry is controlled by evaporation, water-rock reactions, and cation exchange. The chloride-type water in the south may be influenced by deep Ca-Cl water flowing along faults. The water chemistry characteristics indicate that the intercrystalline brine is formed by halite dissolution, with low metamorphic degree and poor sealing in the salt-bearing layers. Hydrogen-oxygen isotopes show that the main water source of the intercrystalline brine is atmospheric precipitation or snowmelt from the Qilian Mountains, with the primary recharge sources being the Yuka River and shallow groundwater flowing through the alluvial fan. Strong evaporation and water-rock interactions have significantly impacted the formation of the brine deposits. The differences in water chemistry types and spatial distribution between the northern and southern regions are fundamentally related to the recharge and mixing of these two sources. The brine genesis can be summarized as a "dissolution recharge + deep recharge" dual mining model. The brine in the study area has considerable potential for potassium, boron, and lithium resources. Based on the comprehensive water chemistry characteristics, salt layer thickness, regional salt formation evolution process, drilling sites ZK7618, ZK8014, ZK8024, and ZK8431 are likely favorable targets for mineral exploration.
There are abundant brine resources in the Balun Mahai Basin of Qaidam, but the genetic mechanism and potential of brine resources still need to be determined. This study focuses on the intercrystalline brine in the Balema Lake Basin, conducting geochemical research on elements and hydrogen-oxygen isotopes to systematically analyze its water source, solute origins, evolution process, and genesis model. The study also explores the mining potential of potassium, boron, and lithium elements. The results show that the intercrystalline brine in the northern part of the Balema Lake Basin is of the magnesium sulfate subtype, while the southern part predominantly features chloride water. The solutes in the brine mainly originate from the dissolution of halite, potassium salts, and gypsum. The water chemistry is controlled by evaporation, water-rock reactions, and cation exchange. The chloride-type water in the south may be influenced by deep Ca-Cl water flowing along faults. The water chemistry characteristics indicate that the intercrystalline brine is formed by halite dissolution, with low metamorphic degree and poor sealing in the salt-bearing layers. Hydrogen-oxygen isotopes show that the main water source of the intercrystalline brine is atmospheric precipitation or snowmelt from the Qilian Mountains, with the primary recharge sources being the Yuka River and shallow groundwater flowing through the alluvial fan. Strong evaporation and water-rock interactions have significantly impacted the formation of the brine deposits. The differences in water chemistry types and spatial distribution between the northern and southern regions are fundamentally related to the recharge and mixing of these two sources. The brine genesis can be summarized as a "dissolution recharge + deep recharge" dual mining model. The brine in the study area has considerable potential for potassium, boron, and lithium resources. Based on the comprehensive water chemistry characteristics, salt layer thickness, regional salt formation evolution process, drilling sites ZK7618, ZK8014, ZK8024, and ZK8431 are likely favorable targets for mineral exploration.
Available online: April 17, 2025
Abstract:
The Qaidam basin serves as the primary reservoir of potash salt resources and the key production base for potash fertilizer in China. Recent geological explorations have identified a novel type of potassium-bearing sand and sandstone pore brine deposit in the western foreland alluvial fan of the basin. This newly discovered deposit is believed to contain significant potassium chloride resources, with the brine displaying prominent attributes of high sodium and chlorine levels, and a mineralization model resembling that of "inherited halite rock". Located as a secondary basin and distinct from the Kunteyi basin on the northern margin of Qaidam, the Mahai basin is a small lake basin characterized by various types of brines (intercrystalline brines, confined brines, sand-gravel brines, anticlinal structure brines, etc.). In this study, by conducting a comparative analysis of the major and trace ion content, salinity, and hydrogen and oxygen isotope composition of river water and various brines in the Mahai basin, the following main conclusions have been drawn:① The average K+ content and TDS value of the sand-gravel brines in the Mahai basin are 2.16 g/L and 254.2 g/L, respectively, indicating a notably high ratio of Na++ Cl-/TDS (0.94). These brines belong to the Na-Cl type hydrochemical classification; ② While the potassium K+ content and TDS value of the sand-gravel brines in the Mahai basin are lower than those in the surface brines, intercrystalline brines, and confined brines of Mahai Salt Lake, they are close to the minimum threshold required for industrial potassium salt exploitation, suggesting a certain potential for resource development. The spatial distribution of K+ in sand-gravel brines, intercrystalline brines, and confined brines closely aligns with potassium-containing evaporites. Considering the salinity gradient and gravitational effects influenced by differences in brine TDS and burial depth, it is suggested that the salt solute and potassium in sand-gravel brines originate from the recharge of intercrystalline brines and confined brines; ③ Through the utilization of the K-B-Li equivalent map and analysis of varying B content in different water sources, it is demonstrated that the sand-gravel brines consist of a mixture of Yuqia River water, intercrystalline brines, and confined brines; ④ The δD-δ18O values of the sand-gravel brines in the Mahai basin range from -56.9‰ to -17.6‰ and -5.70‰ to +6.00‰ for hydrogen and oxygen isotopes, respectively. These values exhibit similar characteristics to the confined brines and intercrystalline brines, evenly distributed on both sides of the local evaporation line. Additionally, as the 2H-18O increases, the concentrations of B and Li also increase. These findings indicate that the sand-gravel brines have undergone evaporation and concentration. Consequently, the sand-gravel brines have been inheriting solutes from intercrystalline brines and confined brines over a long period, including ions such as K+, Na+, and Cl-, leading to their similar H-O isotopic signatures.
The Qaidam basin serves as the primary reservoir of potash salt resources and the key production base for potash fertilizer in China. Recent geological explorations have identified a novel type of potassium-bearing sand and sandstone pore brine deposit in the western foreland alluvial fan of the basin. This newly discovered deposit is believed to contain significant potassium chloride resources, with the brine displaying prominent attributes of high sodium and chlorine levels, and a mineralization model resembling that of "inherited halite rock". Located as a secondary basin and distinct from the Kunteyi basin on the northern margin of Qaidam, the Mahai basin is a small lake basin characterized by various types of brines (intercrystalline brines, confined brines, sand-gravel brines, anticlinal structure brines, etc.). In this study, by conducting a comparative analysis of the major and trace ion content, salinity, and hydrogen and oxygen isotope composition of river water and various brines in the Mahai basin, the following main conclusions have been drawn:① The average K+ content and TDS value of the sand-gravel brines in the Mahai basin are 2.16 g/L and 254.2 g/L, respectively, indicating a notably high ratio of Na++ Cl-/TDS (0.94). These brines belong to the Na-Cl type hydrochemical classification; ② While the potassium K+ content and TDS value of the sand-gravel brines in the Mahai basin are lower than those in the surface brines, intercrystalline brines, and confined brines of Mahai Salt Lake, they are close to the minimum threshold required for industrial potassium salt exploitation, suggesting a certain potential for resource development. The spatial distribution of K+ in sand-gravel brines, intercrystalline brines, and confined brines closely aligns with potassium-containing evaporites. Considering the salinity gradient and gravitational effects influenced by differences in brine TDS and burial depth, it is suggested that the salt solute and potassium in sand-gravel brines originate from the recharge of intercrystalline brines and confined brines; ③ Through the utilization of the K-B-Li equivalent map and analysis of varying B content in different water sources, it is demonstrated that the sand-gravel brines consist of a mixture of Yuqia River water, intercrystalline brines, and confined brines; ④ The δD-δ18O values of the sand-gravel brines in the Mahai basin range from -56.9‰ to -17.6‰ and -5.70‰ to +6.00‰ for hydrogen and oxygen isotopes, respectively. These values exhibit similar characteristics to the confined brines and intercrystalline brines, evenly distributed on both sides of the local evaporation line. Additionally, as the 2H-18O increases, the concentrations of B and Li also increase. These findings indicate that the sand-gravel brines have undergone evaporation and concentration. Consequently, the sand-gravel brines have been inheriting solutes from intercrystalline brines and confined brines over a long period, including ions such as K+, Na+, and Cl-, leading to their similar H-O isotopic signatures.
Available online: April 14, 2025
Abstract:
The land use and "source-sink" landscape pattern of watershed have complex effects on water quality by influencing the production, transport and absorption of pollutants. Understanding the response relationship of river water quality to watershed land use and source-sink pattern is the prerequisite and key to optimize watershed landscape allocation. Taking Shangwuxi Basin of Qiandao Lake as the research object, this paper analyzes the spatio-temporal variation characteristics of river total nitrogen, total phosphorus, nitrate nitrogen and phosphate, and analyzes the subcatchment scale land use and "source-sink" landscape pattern and its impact on river water quality. The results show that the water quality index of the main rivers in Shangwuxi Basin presents the spatial characteristics of gradually increasing pollutant concentration from the upper reaches to the lower reaches and from the outer tributaries to the main river. Nitrogen concentration in non-flood season was significantly higher than that in floo
The land use and "source-sink" landscape pattern of watershed have complex effects on water quality by influencing the production, transport and absorption of pollutants. Understanding the response relationship of river water quality to watershed land use and source-sink pattern is the prerequisite and key to optimize watershed landscape allocation. Taking Shangwuxi Basin of Qiandao Lake as the research object, this paper analyzes the spatio-temporal variation characteristics of river total nitrogen, total phosphorus, nitrate nitrogen and phosphate, and analyzes the subcatchment scale land use and "source-sink" landscape pattern and its impact on river water quality. The results show that the water quality index of the main rivers in Shangwuxi Basin presents the spatial characteristics of gradually increasing pollutant concentration from the upper reaches to the lower reaches and from the outer tributaries to the main river. Nitrogen concentration in non-flood season was significantly higher than that in floo
Available online: April 14, 2025
Abstract:
Songnen Plain is controlled by geological structure, climate and other factors, and the fluorine content of groundwater in the region is generally high. In recent years, a huge number of researches have been put in practice based on high-fluorine groundwater, however, comprehensive understanding of the geochemical background in there is scarce, evolution trend and ecological health risks of fluorine in large reservoirs in the high-fluorine area of Songnen Plain likewise. Mechanisms of action and transport of fluorine ion (F-) in surface water of Xianghai Reservoir was analyzed using various methodologies, including mathematical statistics, the Piper three-line diagram, the Gibbs diagram, end-member analysis, PHREEQC hydrogeochemical simulations, as well as risk assessment models for ecological and health. Showing the results is that the concentration range of F- in the surface water of Xianghai Reservoir is 0.69 ~ 3.68 mg/L, and the average concentration is 1.87 mg/L, comparing with the concentration limit of 1.50 mg/L stipulated in China"s Surface Water quality Standard (GB 3838—2002) is higher, set by Class V. The surface water in this region is characterized by high fluorine content, with fluoride (F-) concentrations in the southwest significantly exceeding those found in the northeast. The hydrochemical characteristics of the regional surface water are primarily classified as HCO3-Na, HCO3-Na·Ca, and HCO3-Na·Mg. The main factors contributing to the enrichment of fluorine in Xianghai Reservoir include evaporation and concentration processes, mineral dissolution and precipitation, as well as cation exchange. Xianghai Reservoir belongs to the risk area of fluorine ecology and causes both children and adults facing health risks, with children being significantly more vulnerable to the harmful effects than adults.
Songnen Plain is controlled by geological structure, climate and other factors, and the fluorine content of groundwater in the region is generally high. In recent years, a huge number of researches have been put in practice based on high-fluorine groundwater, however, comprehensive understanding of the geochemical background in there is scarce, evolution trend and ecological health risks of fluorine in large reservoirs in the high-fluorine area of Songnen Plain likewise. Mechanisms of action and transport of fluorine ion (F-) in surface water of Xianghai Reservoir was analyzed using various methodologies, including mathematical statistics, the Piper three-line diagram, the Gibbs diagram, end-member analysis, PHREEQC hydrogeochemical simulations, as well as risk assessment models for ecological and health. Showing the results is that the concentration range of F- in the surface water of Xianghai Reservoir is 0.69 ~ 3.68 mg/L, and the average concentration is 1.87 mg/L, comparing with the concentration limit of 1.50 mg/L stipulated in China"s Surface Water quality Standard (GB 3838—2002) is higher, set by Class V. The surface water in this region is characterized by high fluorine content, with fluoride (F-) concentrations in the southwest significantly exceeding those found in the northeast. The hydrochemical characteristics of the regional surface water are primarily classified as HCO3-Na, HCO3-Na·Ca, and HCO3-Na·Mg. The main factors contributing to the enrichment of fluorine in Xianghai Reservoir include evaporation and concentration processes, mineral dissolution and precipitation, as well as cation exchange. Xianghai Reservoir belongs to the risk area of fluorine ecology and causes both children and adults facing health risks, with children being significantly more vulnerable to the harmful effects than adults.
Available online: April 07, 2025
Abstract:
The Chinese sturgeon (Acipenser sinensis), a flagship species of the Yangtze River, has suffered a dramatic population decline after the construction of the Gezhouba Dam. Currently, its natural reproduction has been disrupted for several years, with the migratory breeding group less than 20 individuals, placing the survival of the natural population in jeopardy. The release of artificially bred individuals has become a crucial measure to sustain the Chinese sturgeon population and facilitate its sustainable population recovery in the wild. However, the current approach to selecting release candidates and locations remains somewhat arbitrary. A fundamental question remains unresolved: Can Chinese sturgeons that have not undergone the downstream migration process from spawning grounds to the ocean during their larval and juvenile stages successfully initiate reproductive migration and navigate back to the spawning grounds on reaching sexual maturity. To investigate this, the current study analyzed release experiments involving Chinese sturgeons in the Yangtze River Estuary. In these experiments, we employed satellite tagging (Pop-up Archival Tags, PAT) to track the artificially bred adult and sub-adult Chinese sturgeons’ migration patterns. The findings indicate that, from 2004 to 2021, a total of 13204 Chinese sturgeons (including natural individuals and artificially bred individuals) were released into the Yangtze River Estuary, in which there were 665 artificially bred adult and sub-adult Chinese sturgeons (aged over three years). Of these, 71 were equipped with PAT tags, and data from 42 of these tags were successfully retrieved. Crucially, among the 21 individuals older than 10 years with valid PAT monitoring data, three exhibited upstream migration behavior along the Yangtze River. These findings suggest that the downstream migration experience during early life stages may not be a prerequisite for upstream migration in sexually mature Chinese sturgeons. To further validate this conclusion and gain a deeper understanding of the breeding migration process following release, more rigorous and detailed experimental research is urgently needed.
The Chinese sturgeon (Acipenser sinensis), a flagship species of the Yangtze River, has suffered a dramatic population decline after the construction of the Gezhouba Dam. Currently, its natural reproduction has been disrupted for several years, with the migratory breeding group less than 20 individuals, placing the survival of the natural population in jeopardy. The release of artificially bred individuals has become a crucial measure to sustain the Chinese sturgeon population and facilitate its sustainable population recovery in the wild. However, the current approach to selecting release candidates and locations remains somewhat arbitrary. A fundamental question remains unresolved: Can Chinese sturgeons that have not undergone the downstream migration process from spawning grounds to the ocean during their larval and juvenile stages successfully initiate reproductive migration and navigate back to the spawning grounds on reaching sexual maturity. To investigate this, the current study analyzed release experiments involving Chinese sturgeons in the Yangtze River Estuary. In these experiments, we employed satellite tagging (Pop-up Archival Tags, PAT) to track the artificially bred adult and sub-adult Chinese sturgeons’ migration patterns. The findings indicate that, from 2004 to 2021, a total of 13204 Chinese sturgeons (including natural individuals and artificially bred individuals) were released into the Yangtze River Estuary, in which there were 665 artificially bred adult and sub-adult Chinese sturgeons (aged over three years). Of these, 71 were equipped with PAT tags, and data from 42 of these tags were successfully retrieved. Crucially, among the 21 individuals older than 10 years with valid PAT monitoring data, three exhibited upstream migration behavior along the Yangtze River. These findings suggest that the downstream migration experience during early life stages may not be a prerequisite for upstream migration in sexually mature Chinese sturgeons. To further validate this conclusion and gain a deeper understanding of the breeding migration process following release, more rigorous and detailed experimental research is urgently needed.
Available online: April 03, 2025
Abstract:
Baiyangdian Lake is the largest freshwater wetland in North China. Fu River is one of the main rivers that flow into Baiyangdian Lake. In recent years, increasing frequency and intensity of extreme rainfall events have introduced new challenges, driving complex spatiotemporal variations in nitrogen and phosphorus concentrations and fluxes. This study systematically investigated the Fu River-Baiyangdian Lake system through field monitoring, water sampling, laboratory measurements and statistical analysis to reveal the dynamics of total nitrogen (TN) and total phosphorus (TP) concentrations and their response to extreme rainfall. Results revealed distinct seasonal trends: TN concentration was highest in spring and winter and lowest in summer, whereas the TP concentration peaked in summer and declined in spring and winter. Spatially, TN and TP concentrations decreased from upstream to downstream along the Fu River. After the "7.29" extreme rainfall event, TN concentration showed a complex increase-decrease-increase trajectory influenced by agricultural runoff, sedimentary nutrient release, and biogeochemical processes such as dilution and denitrification. TP concentration showed a simpler increase-decrease pattern driven by sediment resuspension and subsequent attenuation. Before the extreme rainfall event, nitrogen and phosphorus loads along the river gradually decreased. After the extreme rainfall event, nitrogen and phosphorus loads along the river significantly increased due to the input of non-point source pollutants. Nutrient loads surged significantly after the extreme rainfall event, increasing by factors of 10.5 to 47.4 due to the input of non-point source pollutants. These findings underscore the vulnerability of Baiyangdian Lake to extreme hydrological events and highlight the urgent need for targeted interventions to reduce pollutant loads during such events. This research provides critical insights into nutrient cycling dynamics under changing climatic and hydrological conditions, offering a scientific basis for sustainable water quality management in lake-watershed systems.
Baiyangdian Lake is the largest freshwater wetland in North China. Fu River is one of the main rivers that flow into Baiyangdian Lake. In recent years, increasing frequency and intensity of extreme rainfall events have introduced new challenges, driving complex spatiotemporal variations in nitrogen and phosphorus concentrations and fluxes. This study systematically investigated the Fu River-Baiyangdian Lake system through field monitoring, water sampling, laboratory measurements and statistical analysis to reveal the dynamics of total nitrogen (TN) and total phosphorus (TP) concentrations and their response to extreme rainfall. Results revealed distinct seasonal trends: TN concentration was highest in spring and winter and lowest in summer, whereas the TP concentration peaked in summer and declined in spring and winter. Spatially, TN and TP concentrations decreased from upstream to downstream along the Fu River. After the "7.29" extreme rainfall event, TN concentration showed a complex increase-decrease-increase trajectory influenced by agricultural runoff, sedimentary nutrient release, and biogeochemical processes such as dilution and denitrification. TP concentration showed a simpler increase-decrease pattern driven by sediment resuspension and subsequent attenuation. Before the extreme rainfall event, nitrogen and phosphorus loads along the river gradually decreased. After the extreme rainfall event, nitrogen and phosphorus loads along the river significantly increased due to the input of non-point source pollutants. Nutrient loads surged significantly after the extreme rainfall event, increasing by factors of 10.5 to 47.4 due to the input of non-point source pollutants. These findings underscore the vulnerability of Baiyangdian Lake to extreme hydrological events and highlight the urgent need for targeted interventions to reduce pollutant loads during such events. This research provides critical insights into nutrient cycling dynamics under changing climatic and hydrological conditions, offering a scientific basis for sustainable water quality management in lake-watershed systems.
Available online: April 03, 2025
Abstract:
Phytoplankton, as primary producers in aquatic ecosystems, reflect the ecological structure and functional status of water bodies. The water circulation structure of arid lakes is highly variable, making phytoplankton communities particularly sensitive to environmental changes. This study investigated the structure and succession characteristics of phytoplankton communities in Lake Ulungur, Xinjiang, in May (spring), July (summer), and October (autumn) of 2019. A total of 161 phytoplankton species from 73 genera and 7 phyla were identified across 28 sampling sites, with 85, 49, and 149 species detected in spring, summer, and autumn, respectively. Tetra?dron minimum was the dominant species common to all three seasons. The absolute dominant species in spring were Oocystis lacustis and Synedra acus, while Aphanizomenon flos-aquae and Oocystis marssonii dominated in summer, and Planktolyngbya circumcreta and Aphanizomenon flos-aquae dominated in autumn. The interspecies association characteristics showed significant positive associations among dominant species in spring and autumn, while significant negative associations were observed in summer. Phytoplankton diversity was highest in spring, followed by autumn and summer. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) indicated significant differences in phytoplankton community composition across the three seasons (P < 0.001). Multiple regression on distance matrices (MRM) analysis revealed that water temperature (WT), transparency (SD), and nitrate nitrogen (NO- 3-N) positively influenced community heterogeneity, while the permanganate index (CODMn) had a negative effect. Additionally, the community structure was closely related to the abundance of Oocystis marssonii, Tetra?dron minimum, Microcystis sp., and Staurastrum sp. Overall, the phytoplankton community in Lake Ulungur exhibited stable succession patterns under the influence of seasonal environmental changes and interspecies interactions. This study provides essential ecological insights into the response of phytoplankton in arid lakes to environmental factors and interspecies relationships.
Phytoplankton, as primary producers in aquatic ecosystems, reflect the ecological structure and functional status of water bodies. The water circulation structure of arid lakes is highly variable, making phytoplankton communities particularly sensitive to environmental changes. This study investigated the structure and succession characteristics of phytoplankton communities in Lake Ulungur, Xinjiang, in May (spring), July (summer), and October (autumn) of 2019. A total of 161 phytoplankton species from 73 genera and 7 phyla were identified across 28 sampling sites, with 85, 49, and 149 species detected in spring, summer, and autumn, respectively. Tetra?dron minimum was the dominant species common to all three seasons. The absolute dominant species in spring were Oocystis lacustis and Synedra acus, while Aphanizomenon flos-aquae and Oocystis marssonii dominated in summer, and Planktolyngbya circumcreta and Aphanizomenon flos-aquae dominated in autumn. The interspecies association characteristics showed significant positive associations among dominant species in spring and autumn, while significant negative associations were observed in summer. Phytoplankton diversity was highest in spring, followed by autumn and summer. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) indicated significant differences in phytoplankton community composition across the three seasons (P < 0.001). Multiple regression on distance matrices (MRM) analysis revealed that water temperature (WT), transparency (SD), and nitrate nitrogen (NO- 3-N) positively influenced community heterogeneity, while the permanganate index (CODMn) had a negative effect. Additionally, the community structure was closely related to the abundance of Oocystis marssonii, Tetra?dron minimum, Microcystis sp., and Staurastrum sp. Overall, the phytoplankton community in Lake Ulungur exhibited stable succession patterns under the influence of seasonal environmental changes and interspecies interactions. This study provides essential ecological insights into the response of phytoplankton in arid lakes to environmental factors and interspecies relationships.
Available online: April 03, 2025
Abstract:
We analyzed the characteristics of wind speed and direction, and the general patterns of lake-land breezes as well as the process of typical events, based on wind profiling radar data near the Poyang Lake from June 2021 to May 2023. Main conclusions are as follows: (1) The surface-layer wind speed was generally higher in daytime than in nighttime. The prevailing wind direction was northeast in summer, and was southwest in other seasons. The vertical wind profile conformed to the power law, with the wind profile index in a decreasing order as summer (0.41) > spring (0.29) > winter (0.26) > autumn (0.23). (2) A total of 104 lake-land breezes (14.3%) occurred in the study period, most (38 times) in summer, second in autumn (24 times), third in spring (22 times), and least (20 times) in winter. The lake breezes were longer-lasting and started earlier in spring and summer than in autumn and winter, while the opposite is true for the land breezes. When no land-lake breezes occurred, the southwest winds persisted throughout the day and night, and the wind profile index was 0.31. The surface-layer wind speed was generally lower when lake-land breezes occurred. The wind profile index was 0.57 with the northeast winds prevailing between 6:00–18:00. (3) Lake breezes in general peaked at 14:00 with a maximum height of 440 m, whereas land breezes in general peaked at midnight with a maximum height of 760 m. The seasonally varying patterns in lake-land breezes were related to changing water surfaces and contrasting land-water temperatures of the Poyang Lake. This paper provides preliminary conclusions for understanding the potential role of seasonally flooding lakes in local atmospheric circulation and boundary layer structure.
We analyzed the characteristics of wind speed and direction, and the general patterns of lake-land breezes as well as the process of typical events, based on wind profiling radar data near the Poyang Lake from June 2021 to May 2023. Main conclusions are as follows: (1) The surface-layer wind speed was generally higher in daytime than in nighttime. The prevailing wind direction was northeast in summer, and was southwest in other seasons. The vertical wind profile conformed to the power law, with the wind profile index in a decreasing order as summer (0.41) > spring (0.29) > winter (0.26) > autumn (0.23). (2) A total of 104 lake-land breezes (14.3%) occurred in the study period, most (38 times) in summer, second in autumn (24 times), third in spring (22 times), and least (20 times) in winter. The lake breezes were longer-lasting and started earlier in spring and summer than in autumn and winter, while the opposite is true for the land breezes. When no land-lake breezes occurred, the southwest winds persisted throughout the day and night, and the wind profile index was 0.31. The surface-layer wind speed was generally lower when lake-land breezes occurred. The wind profile index was 0.57 with the northeast winds prevailing between 6:00–18:00. (3) Lake breezes in general peaked at 14:00 with a maximum height of 440 m, whereas land breezes in general peaked at midnight with a maximum height of 760 m. The seasonally varying patterns in lake-land breezes were related to changing water surfaces and contrasting land-water temperatures of the Poyang Lake. This paper provides preliminary conclusions for understanding the potential role of seasonally flooding lakes in local atmospheric circulation and boundary layer structure.
Available online: April 03, 2025
Abstract:
Urban wetlands play an increasingly crucial role, and the health assessment of their ecosystems is an important process that helps us understand the current condition of wetlands and take appropriate protective measures. To explore the ecological health status of the Lhalu Wetland and its relationship with water environmental factors, phytoplankton samples were collected and water environmental factors were measured in the main water systems of Lhalu Wetland in July (summer), October (autumn) 2021, and May (spring) 2022. Phytoplankton species were identified and their cell abundance and biomass were calculated. The ecological health status of the wetland was evaluated using the morphologically -based functional group (MBFG), Water Quality Index (WQI), and Phytoplankton Index of Biotic Integrity (P-IBI). The spatiotemporal distribution characteristics of water quality and morphologically -based functional group, and the correlation between P-IBI values and water environmental factors were analyzed. The research results show: (1) Based on the Water Quality Index (WQI) values, the overall water quality of Lhalu Wetland is evaluated as "good to moderate," with spatial and temporal variations in water quality: spring is superior to autumn, which in turn is superior to summer, and the eastern part is superior to the western part. (2) Based on the Phytoplanktonic Index of Biotic Integrity (P-IBI) values, the overall water ecological health status of Lhalu Wetland across three seasons is evaluated as "health to sub-health," with the spring water ecological health status being superior to autumn, which is superior to summer, and the central-eastern sampling points are generally superior to the south-western and north-eastern parts. (3) The Phytoplanktonic Index of Biotic Integrity (P-IBI) values show a significant positive correlation with the Water Quality Index (WQI) values (P < 0.05), and the evaluation of the water ecological health status of Lhalu Wetland based on P-IBI is closely consistent with the results of WQI evaluation. Dissolved oxygen (DO) is the main water environmental factor affecting the water ecological health status of Lhalu Wetland (P < 0.05), and temperature, water volume, human activities, and land use types are important factors affecting the water quality and water ecological health status of Lhalu Wetland. (4) In spring, the abundance of functional groups "Ⅰ" and "Ⅲ" increases as the water ecological health status of Lhalu Wetland declines. In summer, the ecological health status of the water body has little relationship with the changes in the abundance of functional groups. In autumn, the increase in the abundance of functional groups "Ⅲ" and "Ⅶ" is significantly associated with the decline in the ecological health status of the water body.
Urban wetlands play an increasingly crucial role, and the health assessment of their ecosystems is an important process that helps us understand the current condition of wetlands and take appropriate protective measures. To explore the ecological health status of the Lhalu Wetland and its relationship with water environmental factors, phytoplankton samples were collected and water environmental factors were measured in the main water systems of Lhalu Wetland in July (summer), October (autumn) 2021, and May (spring) 2022. Phytoplankton species were identified and their cell abundance and biomass were calculated. The ecological health status of the wetland was evaluated using the morphologically -based functional group (MBFG), Water Quality Index (WQI), and Phytoplankton Index of Biotic Integrity (P-IBI). The spatiotemporal distribution characteristics of water quality and morphologically -based functional group, and the correlation between P-IBI values and water environmental factors were analyzed. The research results show: (1) Based on the Water Quality Index (WQI) values, the overall water quality of Lhalu Wetland is evaluated as "good to moderate," with spatial and temporal variations in water quality: spring is superior to autumn, which in turn is superior to summer, and the eastern part is superior to the western part. (2) Based on the Phytoplanktonic Index of Biotic Integrity (P-IBI) values, the overall water ecological health status of Lhalu Wetland across three seasons is evaluated as "health to sub-health," with the spring water ecological health status being superior to autumn, which is superior to summer, and the central-eastern sampling points are generally superior to the south-western and north-eastern parts. (3) The Phytoplanktonic Index of Biotic Integrity (P-IBI) values show a significant positive correlation with the Water Quality Index (WQI) values (P < 0.05), and the evaluation of the water ecological health status of Lhalu Wetland based on P-IBI is closely consistent with the results of WQI evaluation. Dissolved oxygen (DO) is the main water environmental factor affecting the water ecological health status of Lhalu Wetland (P < 0.05), and temperature, water volume, human activities, and land use types are important factors affecting the water quality and water ecological health status of Lhalu Wetland. (4) In spring, the abundance of functional groups "Ⅰ" and "Ⅲ" increases as the water ecological health status of Lhalu Wetland declines. In summer, the ecological health status of the water body has little relationship with the changes in the abundance of functional groups. In autumn, the increase in the abundance of functional groups "Ⅲ" and "Ⅶ" is significantly associated with the decline in the ecological health status of the water body.
Available online: April 03, 2025
Abstract:
To make coordinated efforts to protect and restore the Taihu Basin environment is the important content of the integrated high-quality development of the Yangtze River Delta region. It is of great significance in enlightening the policy-making of the regional environmental cooperation and enriching the theory of collaborative environmental governance to systematically study how to coordinate the interests of local main bodies to carry out cross-boundary synergistic paths of environmental governance actions. The paper adopts the qualitative research method of case study and through the long-term tracking and investigation of the Su-Jia transboundary water governance practices, we construct a comprehensive pathway framework for transboundary environmental collaborative governance from the aspects of synergistic content demand and realization guarantee, based on the theory of collaborative governance. The study has found that: Institution, technology and action are the key synergistic contents of the transboundary environmental collaborative governance path, and the synergistic implementation of the three is an important guarantee to promote the success of transboundary environmental collaborative governance. The joint river-chief system pioneered by the Su-Jia grassroots government is more of a governance model through institutional synergy, deepening and expanding the content of action-oriented synergy in the order of institutional cost and implementation cost from low to high, which effectively improves the transboundary river environmental quality, but the content of technical synergy is less substantial, which limits the improvement of transboundary environmental collaborative governance capacity. Coordination of local stakeholders’ interests around transboundary environmental cooperation is the key driving force for the development of its cooperative governance path. The results reveal the focus of synergistic contents, the characteristics of time-sequence combination and synergistic effect of local subjects in the process of transboundary collaborative environmental governance, which are of good practical guiding value.
To make coordinated efforts to protect and restore the Taihu Basin environment is the important content of the integrated high-quality development of the Yangtze River Delta region. It is of great significance in enlightening the policy-making of the regional environmental cooperation and enriching the theory of collaborative environmental governance to systematically study how to coordinate the interests of local main bodies to carry out cross-boundary synergistic paths of environmental governance actions. The paper adopts the qualitative research method of case study and through the long-term tracking and investigation of the Su-Jia transboundary water governance practices, we construct a comprehensive pathway framework for transboundary environmental collaborative governance from the aspects of synergistic content demand and realization guarantee, based on the theory of collaborative governance. The study has found that: Institution, technology and action are the key synergistic contents of the transboundary environmental collaborative governance path, and the synergistic implementation of the three is an important guarantee to promote the success of transboundary environmental collaborative governance. The joint river-chief system pioneered by the Su-Jia grassroots government is more of a governance model through institutional synergy, deepening and expanding the content of action-oriented synergy in the order of institutional cost and implementation cost from low to high, which effectively improves the transboundary river environmental quality, but the content of technical synergy is less substantial, which limits the improvement of transboundary environmental collaborative governance capacity. Coordination of local stakeholders’ interests around transboundary environmental cooperation is the key driving force for the development of its cooperative governance path. The results reveal the focus of synergistic contents, the characteristics of time-sequence combination and synergistic effect of local subjects in the process of transboundary collaborative environmental governance, which are of good practical guiding value.
Available online: March 27, 2025
Abstract:
Polyphosphate (poly-P), a phosphorus component that is widely present in organisms and exhibits high biological activity, plays a critical role in the biogeochemical cycling of phosphorus in eutrophic water bodies. To elucidate the degradation and transformation processes of poly-P at the sediment-water interface and within the water column, as well as its response to key environmental factors in lake sediments, in situ samples were collected from the Zhushan Bay area of Lake Taihu. These samples were used to simulate near-natural conditions for studying the degradation and transformation of poly-P. The results indicated that under near-natural conditions, the short-term hydrolysis rate of dissolved poly-P showed no obvious upper limit and increased with rising concentrations. After two days, the SRP (soluble reactive phosphorus) concentration generated by the hydrolysis of high-concentration poly-P could reach 0.1 ± 0.01 mg·L?1/d. The hydrolysis of poly-P was primarily driven by biological degradation, with key factors influencing the degradation rate including dissolved oxygen, carbon sources, temperature, and sediment resuspension caused by disturbances. Low dissolved oxygen concentrations accelerated the hydrolysis of poly-P and brought the SRP concentration to its peak 12 hours earlier. The addition of carbon sources slightly increased the hydrolysis rate and promoted sustained SRP release throughout the incubation period, with a net increase reaching twice that of the control group. Low temperatures significantly reduced the hydrolysis rate, although the overall SRP concentration continued to rise. Disturbances that led to sediment resuspension increased both the hydrolysis rate of poly-P and the peak SRP concentration. In the sediment, poly-P mainly existed in a strongly bound form within the Al-P fraction, undergoing continuous release and further hydrolysis, while only trace amounts were present as free poly-P in the sediment and pore water. Dissolved poly-P could rapidly settle and hydrolyze within 48 hours under near-natural conditions, contributing to the sustained supply of SRP to the water column. This study on the occurrence and rapid hydrolytic turnover of poly-P in the water column provides insights into tracing and clarifying the sources of active phosphorus that fuel algal cell proliferation during the summer and autumn seasons. It also sheds light on the biogeochemical processes involving polyphosphate in the phosphorus cycle of water bodies.
Polyphosphate (poly-P), a phosphorus component that is widely present in organisms and exhibits high biological activity, plays a critical role in the biogeochemical cycling of phosphorus in eutrophic water bodies. To elucidate the degradation and transformation processes of poly-P at the sediment-water interface and within the water column, as well as its response to key environmental factors in lake sediments, in situ samples were collected from the Zhushan Bay area of Lake Taihu. These samples were used to simulate near-natural conditions for studying the degradation and transformation of poly-P. The results indicated that under near-natural conditions, the short-term hydrolysis rate of dissolved poly-P showed no obvious upper limit and increased with rising concentrations. After two days, the SRP (soluble reactive phosphorus) concentration generated by the hydrolysis of high-concentration poly-P could reach 0.1 ± 0.01 mg·L?1/d. The hydrolysis of poly-P was primarily driven by biological degradation, with key factors influencing the degradation rate including dissolved oxygen, carbon sources, temperature, and sediment resuspension caused by disturbances. Low dissolved oxygen concentrations accelerated the hydrolysis of poly-P and brought the SRP concentration to its peak 12 hours earlier. The addition of carbon sources slightly increased the hydrolysis rate and promoted sustained SRP release throughout the incubation period, with a net increase reaching twice that of the control group. Low temperatures significantly reduced the hydrolysis rate, although the overall SRP concentration continued to rise. Disturbances that led to sediment resuspension increased both the hydrolysis rate of poly-P and the peak SRP concentration. In the sediment, poly-P mainly existed in a strongly bound form within the Al-P fraction, undergoing continuous release and further hydrolysis, while only trace amounts were present as free poly-P in the sediment and pore water. Dissolved poly-P could rapidly settle and hydrolyze within 48 hours under near-natural conditions, contributing to the sustained supply of SRP to the water column. This study on the occurrence and rapid hydrolytic turnover of poly-P in the water column provides insights into tracing and clarifying the sources of active phosphorus that fuel algal cell proliferation during the summer and autumn seasons. It also sheds light on the biogeochemical processes involving polyphosphate in the phosphorus cycle of water bodies.
Available online: March 27, 2025
Abstract:
In situ coverage is a commonly used method for the remediation of eutrophic sediments. Carbon-based materials offer several advantages, including widespread availability, environmental friendliness, and the absence of secondary pollution, particularly when compared to other remediation options. In this study, we pre-treated and structurally characterized activated coke and assessed its potential for sediment remediation for the first time. We examined the effects of activated coke (363.9 g/m2) and the submerged aquatic plant (Hydrilla verticillata, 32.4 g/m2) both individually and in combination on nutrient release from eutrophic sediments, as well as the impact of activated coke on the growth of submerged plants. The results demonstrated that activated coke possesses a high specific surface area and a rich mesoporous structure. Compared to the control group, the concentrations of CODMn, Chl.a, TN, TP, NH3-N, and SRP in the overlying water, as well as the total release fluxes of TN, TP, NH3-N, and SRP from the sediments, were significantly reduced. The combination treatment of activated coke and submerged plants yielded better results for the overlying water and sediment indicators than either treatment alone. Furthermore, the activated coke treatment increased the growth rate of submerged plants by 40.32% and significantly reduced the amount of reactive phosphorus within the plants, thereby decreasing the risk of phosphorus release after their decay. These findings indicate that activated coke has strong potential for application in the ecological restoration of eutrophic water bodies and exhibits a synergistic effect when combined with submerged plants.
In situ coverage is a commonly used method for the remediation of eutrophic sediments. Carbon-based materials offer several advantages, including widespread availability, environmental friendliness, and the absence of secondary pollution, particularly when compared to other remediation options. In this study, we pre-treated and structurally characterized activated coke and assessed its potential for sediment remediation for the first time. We examined the effects of activated coke (363.9 g/m2) and the submerged aquatic plant (Hydrilla verticillata, 32.4 g/m2) both individually and in combination on nutrient release from eutrophic sediments, as well as the impact of activated coke on the growth of submerged plants. The results demonstrated that activated coke possesses a high specific surface area and a rich mesoporous structure. Compared to the control group, the concentrations of CODMn, Chl.a, TN, TP, NH3-N, and SRP in the overlying water, as well as the total release fluxes of TN, TP, NH3-N, and SRP from the sediments, were significantly reduced. The combination treatment of activated coke and submerged plants yielded better results for the overlying water and sediment indicators than either treatment alone. Furthermore, the activated coke treatment increased the growth rate of submerged plants by 40.32% and significantly reduced the amount of reactive phosphorus within the plants, thereby decreasing the risk of phosphorus release after their decay. These findings indicate that activated coke has strong potential for application in the ecological restoration of eutrophic water bodies and exhibits a synergistic effect when combined with submerged plants.
Available online: March 27, 2025
Abstract:
Studies about changes of zooplankton (e.g., Cladoceran) community and biomass, as well as the carbon sources of food web in alpine lake will helpful for the deeply understanding of the response of lake ecosystem to regional climatic and environmental changes. In this study, multi-index analysis of sediment core was carried out in Taiji Lake, an alpine lake in Northwest Yunnan, including the subfossil assemblage of cladoceran, the stable carbon isotope (δ13C) of Daphnia ephippia and chironomid headshield, and geochemical indicators (TN, TP, δ15N and C/N etc.), in order to understand the response pattern of cladoceran to regional environmental change and the characteristic of carbon sources change in the food web in the alpine lake duirng the past 200 years.Changes of TN suggest that the lake nutrient level was continue increasing in the past 200 years. Analysis suggest that exogenous inputs from the catchment and atmospheric nitrogen deposition are the main factors which driving the nutrient enrichement, regional warming and nutrient enrichment also promoted the enhancing of lake primary productivity (Chlorophyll-a). Cladoceran community was dominated by littoral species Alona affinis and the facultative planktonic species Chydorus sphaericus. Before 1970s, there was no significant change of cladoceran community, after then, the relative abundance of C. sphaericus was decreased, associated with increase abundance of A. affinis. RDA analysis shown that the annual average temperature and primary productivity (Chlorophyll-a) were the main driving factors for the succession of cladoceran community in the past 200 years. For the stable carbon isotope values (δ13C), the δ13C of Daphnia ephippia was negative form 1860 to 1940s, probably attributed by the inputs of exogenous material, which supported by the lower lake primary productivity and higher C/N in this period. From 1940 to 2020s, the δ13C of Daphnia ephippia was significantly enriched, which may be affected by the enhanced primary productivity as well as the increase abundance of benthic algae.The δ13C value of chironomid headshell shown minimal change in the past 200 years, only have a negative trend from 1990 to 2010s, probably related to the increase inputs of terrestrial debris which driving by the increase precipitation in this period. Discrepancy in the variation of δ13C values between the Daphnia ephippia and chironomid headshield, indicate that there are different orgainic carbon composition in the planktonic and littoral zone, and affected by the changes of lake primary productivity and terrestrial inputs. Those founds reveal that regional climate change and catchment inputs changed the productivity and carbon source composition of aquatic food web in alpine lake, and ultimately affected the cladoceran community composition and stable carbon isotope values of aquatic organisms.
Studies about changes of zooplankton (e.g., Cladoceran) community and biomass, as well as the carbon sources of food web in alpine lake will helpful for the deeply understanding of the response of lake ecosystem to regional climatic and environmental changes. In this study, multi-index analysis of sediment core was carried out in Taiji Lake, an alpine lake in Northwest Yunnan, including the subfossil assemblage of cladoceran, the stable carbon isotope (δ13C) of Daphnia ephippia and chironomid headshield, and geochemical indicators (TN, TP, δ15N and C/N etc.), in order to understand the response pattern of cladoceran to regional environmental change and the characteristic of carbon sources change in the food web in the alpine lake duirng the past 200 years.Changes of TN suggest that the lake nutrient level was continue increasing in the past 200 years. Analysis suggest that exogenous inputs from the catchment and atmospheric nitrogen deposition are the main factors which driving the nutrient enrichement, regional warming and nutrient enrichment also promoted the enhancing of lake primary productivity (Chlorophyll-a). Cladoceran community was dominated by littoral species Alona affinis and the facultative planktonic species Chydorus sphaericus. Before 1970s, there was no significant change of cladoceran community, after then, the relative abundance of C. sphaericus was decreased, associated with increase abundance of A. affinis. RDA analysis shown that the annual average temperature and primary productivity (Chlorophyll-a) were the main driving factors for the succession of cladoceran community in the past 200 years. For the stable carbon isotope values (δ13C), the δ13C of Daphnia ephippia was negative form 1860 to 1940s, probably attributed by the inputs of exogenous material, which supported by the lower lake primary productivity and higher C/N in this period. From 1940 to 2020s, the δ13C of Daphnia ephippia was significantly enriched, which may be affected by the enhanced primary productivity as well as the increase abundance of benthic algae.The δ13C value of chironomid headshell shown minimal change in the past 200 years, only have a negative trend from 1990 to 2010s, probably related to the increase inputs of terrestrial debris which driving by the increase precipitation in this period. Discrepancy in the variation of δ13C values between the Daphnia ephippia and chironomid headshield, indicate that there are different orgainic carbon composition in the planktonic and littoral zone, and affected by the changes of lake primary productivity and terrestrial inputs. Those founds reveal that regional climate change and catchment inputs changed the productivity and carbon source composition of aquatic food web in alpine lake, and ultimately affected the cladoceran community composition and stable carbon isotope values of aquatic organisms.
Available online: March 25, 2025
Abstract:
Abstract：Baiyangdian, a prominent shallow lake in the North China Plain, has historically been surrounded by numerous pharmaceutical factories and aquaculture facilities, leading to widespread antibiotic contamination. Although the implementation of pollution control measures in recent years has resulted in notable improvements in water quality, limited research has been conducted on the spatial distribution of long-term accumulated antibiotics and their potential ecological risks. To better understand the historical impacts, ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was utilized to investigate the occurrence characteristic of antibiotics in the aquatic environment, G1 evaluation method was employed to establish an antibiotic pollution assessment system and calculate the antibiotic pollution index, ecological risk entropy method was applied to evaluate the potential environmental risks of the typical antibiotics. This study focuses on the distribution patterns of 13 antibiotics, representing three classes—quinolones, sulfonamides, and macrolides—across four typical functional zones of Baiyangdian, following the prohibition of aquaculture activities. The results revealed that the total antibiotic concentration in the overlying water of Baiyangdian ranged from 15.52 to 256.72 ng/L, while the antibiotic concentration in the sediment ranged from 0.63 to 58.56 ng/g. Macrolides and quinolones were identified as the dominant types of antibiotic pollutants. Spatially, the total antibiotic concentration in overlying water was significantly higher in the Fuhe River inflow region compared to other regions, the dominant antibiotics in the surface water were ciprofloxacin, enrofloxacin, roxithromycin, and sulfamethazine, while the dominant antibiotics in the sediment were ofloxacin. The antibiotic pollution assessment system was found to be accurate. An in-depth study was conducted on the distribution of antibiotics across different functional zones. The results showed that antibiotic contamination in Baiyangdian significantly improved after the cessation of aquaculture. The risk assessment indicated that ciprofloxacin, enrofloxacin, and ofloxacin represent a relatively high ecological risk to the Baiyangdian ecosystem. This study provides scientific evidence for restoring and managing the ecosystem functions in the Baiyangdian.
Abstract：Baiyangdian, a prominent shallow lake in the North China Plain, has historically been surrounded by numerous pharmaceutical factories and aquaculture facilities, leading to widespread antibiotic contamination. Although the implementation of pollution control measures in recent years has resulted in notable improvements in water quality, limited research has been conducted on the spatial distribution of long-term accumulated antibiotics and their potential ecological risks. To better understand the historical impacts, ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was utilized to investigate the occurrence characteristic of antibiotics in the aquatic environment, G1 evaluation method was employed to establish an antibiotic pollution assessment system and calculate the antibiotic pollution index, ecological risk entropy method was applied to evaluate the potential environmental risks of the typical antibiotics. This study focuses on the distribution patterns of 13 antibiotics, representing three classes—quinolones, sulfonamides, and macrolides—across four typical functional zones of Baiyangdian, following the prohibition of aquaculture activities. The results revealed that the total antibiotic concentration in the overlying water of Baiyangdian ranged from 15.52 to 256.72 ng/L, while the antibiotic concentration in the sediment ranged from 0.63 to 58.56 ng/g. Macrolides and quinolones were identified as the dominant types of antibiotic pollutants. Spatially, the total antibiotic concentration in overlying water was significantly higher in the Fuhe River inflow region compared to other regions, the dominant antibiotics in the surface water were ciprofloxacin, enrofloxacin, roxithromycin, and sulfamethazine, while the dominant antibiotics in the sediment were ofloxacin. The antibiotic pollution assessment system was found to be accurate. An in-depth study was conducted on the distribution of antibiotics across different functional zones. The results showed that antibiotic contamination in Baiyangdian significantly improved after the cessation of aquaculture. The risk assessment indicated that ciprofloxacin, enrofloxacin, and ofloxacin represent a relatively high ecological risk to the Baiyangdian ecosystem. This study provides scientific evidence for restoring and managing the ecosystem functions in the Baiyangdian.
Available online: March 19, 2025
Abstract:
This study focuses on Xibeikou Reservoir in the Huangbaihe River Basin of western Hubei, where carbonate rocks are exposed. In-situ sampling and laboratory analysis were conducted to monitor and analyze the basic physicochemical parameters and major ions in the surface water and vertical profiles for different seasons and different characteristic cross sections. The spatial and temporal variations, driving factors, and carbon sink capacity of the biological carbon pump(BCP) effect were analyzed from the perspective of hydrochemistry changes. The results indicated that water in Xibeikou Reservoir was weakly alkaline with a water chemistry type of HCO3-Ca.Mg. The spatiotemporal variations of basic physicochemical factors were significant. Water temperature, chlorophyll-a, and pH were generally higher in summer and lower in winter, with higher values observed in the reservoir area compared to the riverine area, while electrical conductivity, TDS, and pCO2 showed the opposite trends. The ion concentrations in the inflow river were generally higher than those in the reservoir. Within the reservoir, concentrations of HCO3-, Ca2+, Mg2+, and K+ were lower in summer while higher in winter. The BCP effect was strongest in summer, followed by spring and autumn, and weakest in winter. Spatially, it was more pronounced in the reservoir area compared to the riverine area, and stronger in the tail area of the reservoir compared to the head. The stable thermal stratification of the reservoir enhanced the BCP effect and suppressed carbon emissions. The correlations between water chlorophyll-a and pCO2 and HCO3- concentrations suggested significant carbon control in the Xibeikou Reservoir. It was preliminarily estimated that the BCP carbon sink flux of Xibeikou Reservoir ranged from 0.04 to 0.07 t/(km2.d), which was comparable to other karst reservoirs. Overall, the estimated BCP carbon sink flux in karst reservoirs in China accounted for approximately 4% to 26% of national reservoir carbon emission flux, highlighting their importance in carbon source-sink accounting and carbon sequestration enhancement.
This study focuses on Xibeikou Reservoir in the Huangbaihe River Basin of western Hubei, where carbonate rocks are exposed. In-situ sampling and laboratory analysis were conducted to monitor and analyze the basic physicochemical parameters and major ions in the surface water and vertical profiles for different seasons and different characteristic cross sections. The spatial and temporal variations, driving factors, and carbon sink capacity of the biological carbon pump(BCP) effect were analyzed from the perspective of hydrochemistry changes. The results indicated that water in Xibeikou Reservoir was weakly alkaline with a water chemistry type of HCO3-Ca.Mg. The spatiotemporal variations of basic physicochemical factors were significant. Water temperature, chlorophyll-a, and pH were generally higher in summer and lower in winter, with higher values observed in the reservoir area compared to the riverine area, while electrical conductivity, TDS, and pCO2 showed the opposite trends. The ion concentrations in the inflow river were generally higher than those in the reservoir. Within the reservoir, concentrations of HCO3-, Ca2+, Mg2+, and K+ were lower in summer while higher in winter. The BCP effect was strongest in summer, followed by spring and autumn, and weakest in winter. Spatially, it was more pronounced in the reservoir area compared to the riverine area, and stronger in the tail area of the reservoir compared to the head. The stable thermal stratification of the reservoir enhanced the BCP effect and suppressed carbon emissions. The correlations between water chlorophyll-a and pCO2 and HCO3- concentrations suggested significant carbon control in the Xibeikou Reservoir. It was preliminarily estimated that the BCP carbon sink flux of Xibeikou Reservoir ranged from 0.04 to 0.07 t/(km2.d), which was comparable to other karst reservoirs. Overall, the estimated BCP carbon sink flux in karst reservoirs in China accounted for approximately 4% to 26% of national reservoir carbon emission flux, highlighting their importance in carbon source-sink accounting and carbon sequestration enhancement.
Available online: March 19, 2025
Abstract:
Since the operation of the Three Gorges Project in 2003, the hydrological regime of the Dongting Lake wetlands has undergone significant changes, subsequently affecting the distribution pattern of wetland vegetation. However, the relationship between the hydrological regime and vegetation distribution is complex, and the underlying mechanisms remain unclear. This study analyzed the spatial and temporal evolution of the Dongting Lake wetland vegetation pattern from 1995 to 2022 through remote sensing interpretation and field investigations, combined with hydrological data to explore the changes in inundation duration of sandbar vegetation before and after the Three Gorges Project and the driving mechanisms behind these changes. The results showed that: 1) The interannual variation trends of water levels in East, West, and South Dongting Lake were generally consistent. The operation of the Three Gorges Project led to a continuous decline in the annual average water level of Dongting Lake, with an average decrease of over 0.3 m and a maximum annual water level decrease exceeding 0.6 m. The duration of high water levels in West and South Dongting Lake shortened, shifting gradually toward lower water levels; 2) From 1995 to 2022, the overall trend of vegetation succession in the Dongting Lake wetlands has been positive, with a continuous expansion in wetland vegetation area, specifically characterized by the encroachment of Phragmites australis communities on Carex brevicuspis, and C. brevicuspis communities on bare mudflats. 3) Changes in inundation duration before and after the operation of the Three Gorges Dam were significant in areas undergoing positive succession(p < 0.01), from bare mudflats to C. brevicuspis and from C. brevicuspis to P. australis, whereas the changes were not significant in areas experiencing regressive succession(p > 0.05), from C. brevicuspis to bare mudflats and from P. australis to C. brevicuspis. This suggests that reductions in inundation duration are a key driving factor promoting the positive succession of wetland vegetation in Dongting Lake.
Since the operation of the Three Gorges Project in 2003, the hydrological regime of the Dongting Lake wetlands has undergone significant changes, subsequently affecting the distribution pattern of wetland vegetation. However, the relationship between the hydrological regime and vegetation distribution is complex, and the underlying mechanisms remain unclear. This study analyzed the spatial and temporal evolution of the Dongting Lake wetland vegetation pattern from 1995 to 2022 through remote sensing interpretation and field investigations, combined with hydrological data to explore the changes in inundation duration of sandbar vegetation before and after the Three Gorges Project and the driving mechanisms behind these changes. The results showed that: 1) The interannual variation trends of water levels in East, West, and South Dongting Lake were generally consistent. The operation of the Three Gorges Project led to a continuous decline in the annual average water level of Dongting Lake, with an average decrease of over 0.3 m and a maximum annual water level decrease exceeding 0.6 m. The duration of high water levels in West and South Dongting Lake shortened, shifting gradually toward lower water levels; 2) From 1995 to 2022, the overall trend of vegetation succession in the Dongting Lake wetlands has been positive, with a continuous expansion in wetland vegetation area, specifically characterized by the encroachment of Phragmites australis communities on Carex brevicuspis, and C. brevicuspis communities on bare mudflats. 3) Changes in inundation duration before and after the operation of the Three Gorges Dam were significant in areas undergoing positive succession(p < 0.01), from bare mudflats to C. brevicuspis and from C. brevicuspis to P. australis, whereas the changes were not significant in areas experiencing regressive succession(p > 0.05), from C. brevicuspis to bare mudflats and from P. australis to C. brevicuspis. This suggests that reductions in inundation duration are a key driving factor promoting the positive succession of wetland vegetation in Dongting Lake.
Available online: March 19, 2025
Abstract:
To solve the problem that the simulated river network extracted directly from the original DEM is not accurate, deviates from the actual water system, and affects the sub-basin division. This paper based on the actual imagery of the region, firstly, lowers the elevation of the original DEM through the actual river positions in the regional actual imagery; secondly, determines the optimal watershed area threshold of the river source by the river network density avoiding subjective threshold selection; thirdly, sets different sub-basin watershed area thresholds, and determines the appropriate sub-basin watershed area threshold and the number of sub-basins through the relationship between the threshold and the number of sub-basins; finally, by comparing the hydrological process simulation results of the three different sub-basin division schemes, the scientificity of the sub-basin division is verified. Taoxi watershed is located in Shucheng County, Lu "an City, Anhui Province.The application study in Taoxi River Basin shows that: in GIS, the elevation of the DEM grid passing through the actual water system is lowered by 40 m firstly, and then the optimal watershed area threshold determined by the river network density avoiding subjective threshold selection is 0.81 km2, the extracted river network is closer to the actual; the number of sub-basins in Taoxi River Basin is divided into 7 by setting the threshold interval of 108~144 km2, the average area is 213.19 km2, the sub-basin area division is consistent with the standard of the first-class small watershed range in China (50~300 km2). Comparing the distributional simulation of Taoxi River basin under three schemes A, B, and C, which were divided into 7 sub-basins and 11 sub-basins after the DEM grid elevation was lowered by 40 m along the main river channel and the original DEM, respectively, and the model parameters were calibrated using a genetic algorithm, the results show that: in daily discharge simulation, with 1982—2012 as the training sample and 2013—2022 as the validation sample, the deterministic coefficient of the training sample discharge simulation was 0.87, 0.87, and 0.86, and the validation sample was 0.9, 0.91, and 0.9, and the simulation accuracy of the three schemes was basically consistent; selecting 20 maximum flood processes within the period of 1982—2021 for simulation, peak discharge, discharge volume, and peak occurrence time were used as accuracy evaluation indicators, and the qualified occasions of schemes A, B, and C were 19, 19, and 16, respectively, with qualified rates of 95%, 95%, and 80%; the average deterministic coefficient of the 20 flood process simulations for schemes A, B, and C were 0.93, 0.94, and 0.93, respectively, and the accuracy evaluation indicators of the first and second grades for schemes A were 16 and 4, respectively; the first and second grades for schemes B were 18 and 2, respectively; and the first and second grades for schemes C were 18 and 2, respectively. In summary, according to the actual river system, dividing the river basin into 7 sub-basins after lowering the elevation of the DEM grid along the main river channel can improve the qualified rate and the accuracy of the simulation, and dividing the Taoxi River basin into 7 sub-basins according to the area range of the first-order sub-basin is similar in terms of the deterministic coefficient and other accuracy indicators compared with dividing it into 11 sub-basins. The research method can provide reference for the construction of distributed hydrological models and the division of sub-basins in similar conditions.
To solve the problem that the simulated river network extracted directly from the original DEM is not accurate, deviates from the actual water system, and affects the sub-basin division. This paper based on the actual imagery of the region, firstly, lowers the elevation of the original DEM through the actual river positions in the regional actual imagery; secondly, determines the optimal watershed area threshold of the river source by the river network density avoiding subjective threshold selection; thirdly, sets different sub-basin watershed area thresholds, and determines the appropriate sub-basin watershed area threshold and the number of sub-basins through the relationship between the threshold and the number of sub-basins; finally, by comparing the hydrological process simulation results of the three different sub-basin division schemes, the scientificity of the sub-basin division is verified. Taoxi watershed is located in Shucheng County, Lu "an City, Anhui Province.The application study in Taoxi River Basin shows that: in GIS, the elevation of the DEM grid passing through the actual water system is lowered by 40 m firstly, and then the optimal watershed area threshold determined by the river network density avoiding subjective threshold selection is 0.81 km2, the extracted river network is closer to the actual; the number of sub-basins in Taoxi River Basin is divided into 7 by setting the threshold interval of 108~144 km2, the average area is 213.19 km2, the sub-basin area division is consistent with the standard of the first-class small watershed range in China (50~300 km2). Comparing the distributional simulation of Taoxi River basin under three schemes A, B, and C, which were divided into 7 sub-basins and 11 sub-basins after the DEM grid elevation was lowered by 40 m along the main river channel and the original DEM, respectively, and the model parameters were calibrated using a genetic algorithm, the results show that: in daily discharge simulation, with 1982—2012 as the training sample and 2013—2022 as the validation sample, the deterministic coefficient of the training sample discharge simulation was 0.87, 0.87, and 0.86, and the validation sample was 0.9, 0.91, and 0.9, and the simulation accuracy of the three schemes was basically consistent; selecting 20 maximum flood processes within the period of 1982—2021 for simulation, peak discharge, discharge volume, and peak occurrence time were used as accuracy evaluation indicators, and the qualified occasions of schemes A, B, and C were 19, 19, and 16, respectively, with qualified rates of 95%, 95%, and 80%; the average deterministic coefficient of the 20 flood process simulations for schemes A, B, and C were 0.93, 0.94, and 0.93, respectively, and the accuracy evaluation indicators of the first and second grades for schemes A were 16 and 4, respectively; the first and second grades for schemes B were 18 and 2, respectively; and the first and second grades for schemes C were 18 and 2, respectively. In summary, according to the actual river system, dividing the river basin into 7 sub-basins after lowering the elevation of the DEM grid along the main river channel can improve the qualified rate and the accuracy of the simulation, and dividing the Taoxi River basin into 7 sub-basins according to the area range of the first-order sub-basin is similar in terms of the deterministic coefficient and other accuracy indicators compared with dividing it into 11 sub-basins. The research method can provide reference for the construction of distributed hydrological models and the division of sub-basins in similar conditions.
Available online: March 19, 2025
Abstract:
Saucer-shaped lakes within the Poyang Lake wetlands are regions with the largest vegetation biomass and the richest species diversity, supporting over 80% of the overwintering migratory birds of the entire wetland. These sub-lakes play a crucial role in maintaining the integrity of the wetland ecosystem and preserving species diversity. A comprehensive understanding of the distribution characteristics of the saucer-shaped lakes in the Poyang Lake floodplain is of great significance for the optimal allocation of regional water resources and the health of the wetland ecosystem. Supported by Google Earth Engine cloud platform, this study constructs a refined spatial catalog database of saucer-shaped lakes in Poyang Lake floodplain by integrating high-resolution, multi-temporal Sentinel-2A/B satellite imagery and multi-source auxiliary data to employ geospatial big data techniques. Based on this database, the study first systematically elucidates the true number, size, and spatial distribution patterns of these sub-lakes, and then explores the causes of the spatial distribution patterns and the major challenges faced by the saucer-shaped lakes in Poyang Lake wetlands. The results show that the Poyang Lake floodplain contains 319 saucer-shaped lakes larger than 0.01 km2, with a total area of 557.68 km2, accounting for approximately 28.88% of the annual average area of Poyang Lake area. Among them, lakes ranging from 0.01 to 1 km2 are the most widely distributed, constituting about 70.85% of the total saucer-shaped lakes. As the area of graded patches increases, the number of saucer-shaped lakes gradually decreases following a power function pattern. Regionally, the Gan-Fu estuarine delta contributes the most to the total area of saucer-shaped lakes, with 242.82 km2 (43.54%), followed by the Xiushui and Raohe River deltas, with 149.67 km2 (26.84%) and 138.62 km2 (24.86%) respectively. The southern lake-type water body zone (Zone II) has the smallest share of saucer-shaped lakes, accounting for only 4.76%, due to its location within the main navigation channel. Overall, the saucer-shaped lakes in the floodplain exhibit a "one main core, two secondary cores, and multi-centers" clustered spatial aggregation pattern, with spatial density evolving from high-density cores spreading outward in concentric zones. The spatial heterogeneity characteristics is marked by a "densely packed southwest, sparsely packed northeast" distribution. As the elevation of the lake-bottom increases, the number and area of saucer-shaped lakes show a trend of initial growth followed by a sharp decline, with a significant distribution dominance in the 12～14 meter elevation range. Under the influence of seasonal flood pulses, the scale and distribution of saucer-shaped lakes in the Poyang Lake floodplain are the result of the combined effects of regional topography, hydrological processes, and human activities. This study provides high-quality data support for research on hydrological process changes and their ecological impacts in Poyang Lake wetlands, and is expected to enhance the scientific basis for water resource management and drought early warning during the dry season in Poyang Lake.
Saucer-shaped lakes within the Poyang Lake wetlands are regions with the largest vegetation biomass and the richest species diversity, supporting over 80% of the overwintering migratory birds of the entire wetland. These sub-lakes play a crucial role in maintaining the integrity of the wetland ecosystem and preserving species diversity. A comprehensive understanding of the distribution characteristics of the saucer-shaped lakes in the Poyang Lake floodplain is of great significance for the optimal allocation of regional water resources and the health of the wetland ecosystem. Supported by Google Earth Engine cloud platform, this study constructs a refined spatial catalog database of saucer-shaped lakes in Poyang Lake floodplain by integrating high-resolution, multi-temporal Sentinel-2A/B satellite imagery and multi-source auxiliary data to employ geospatial big data techniques. Based on this database, the study first systematically elucidates the true number, size, and spatial distribution patterns of these sub-lakes, and then explores the causes of the spatial distribution patterns and the major challenges faced by the saucer-shaped lakes in Poyang Lake wetlands. The results show that the Poyang Lake floodplain contains 319 saucer-shaped lakes larger than 0.01 km2, with a total area of 557.68 km2, accounting for approximately 28.88% of the annual average area of Poyang Lake area. Among them, lakes ranging from 0.01 to 1 km2 are the most widely distributed, constituting about 70.85% of the total saucer-shaped lakes. As the area of graded patches increases, the number of saucer-shaped lakes gradually decreases following a power function pattern. Regionally, the Gan-Fu estuarine delta contributes the most to the total area of saucer-shaped lakes, with 242.82 km2 (43.54%), followed by the Xiushui and Raohe River deltas, with 149.67 km2 (26.84%) and 138.62 km2 (24.86%) respectively. The southern lake-type water body zone (Zone II) has the smallest share of saucer-shaped lakes, accounting for only 4.76%, due to its location within the main navigation channel. Overall, the saucer-shaped lakes in the floodplain exhibit a "one main core, two secondary cores, and multi-centers" clustered spatial aggregation pattern, with spatial density evolving from high-density cores spreading outward in concentric zones. The spatial heterogeneity characteristics is marked by a "densely packed southwest, sparsely packed northeast" distribution. As the elevation of the lake-bottom increases, the number and area of saucer-shaped lakes show a trend of initial growth followed by a sharp decline, with a significant distribution dominance in the 12～14 meter elevation range. Under the influence of seasonal flood pulses, the scale and distribution of saucer-shaped lakes in the Poyang Lake floodplain are the result of the combined effects of regional topography, hydrological processes, and human activities. This study provides high-quality data support for research on hydrological process changes and their ecological impacts in Poyang Lake wetlands, and is expected to enhance the scientific basis for water resource management and drought early warning during the dry season in Poyang Lake.
Li Minne, Wang Yan, Bao Chunpeng, Guo Zhijie, Xu Xu, Chen Xiaolong, Ke Senfan, Lin Chenyu, Tan Junjun, Shi Xiaotao
Available online: March 18, 2025
Abstract:
With the intensification of anthropogenic disturbances, such as water resource development, water pollution, and overfishing, fish diversity and population abundance have significantly declined, posing a severe threat to aquatic ecosystems. Systematic monitoring of fish movement behavior and physiological responses to environmental changes, along with the scientific analysis of the relationship between behavioral responses and environmental factors, is critical for designing habitat conditions centered on the ecological needs of fish species. This is essential for advancing fish conservation research. The development of acoustic and electronic tagging systems has provided a robust scientific tool for fish conservation studies. These tags, with diverse functionalities, can be implanted in fish bodies or attached externally to enable systematic monitoring of fish movement behavior and habitat information. This paper provides a comprehensive review of the acoustic and electronic tags commonly used in fish conservation research, classifying them into four categories based on their functions: short-range coded identification and counting tags, spatial tracking and positioning tags, physiological state monitoring tags, and environmental data logging tags. First, the fundamental features and technical principles of these tags are introduced. Then, the applications and research progress of each tag type are discussed in detail, focusing on areas such as fish passage efficiency monitoring, fish movement tracking, physiological state assessment, and habitat information evaluation. Finally, the existing challenges and future development directions of acoustic and electronic tagging technologies in fish conservation are highlighted based on the current state of applications. This study aims to systematically summarize the application status and developmental trends of acoustic and electronic tagging technologies in fish conservation research, providing scientific and technical guidance for aquatic ecosystem protection.
With the intensification of anthropogenic disturbances, such as water resource development, water pollution, and overfishing, fish diversity and population abundance have significantly declined, posing a severe threat to aquatic ecosystems. Systematic monitoring of fish movement behavior and physiological responses to environmental changes, along with the scientific analysis of the relationship between behavioral responses and environmental factors, is critical for designing habitat conditions centered on the ecological needs of fish species. This is essential for advancing fish conservation research. The development of acoustic and electronic tagging systems has provided a robust scientific tool for fish conservation studies. These tags, with diverse functionalities, can be implanted in fish bodies or attached externally to enable systematic monitoring of fish movement behavior and habitat information. This paper provides a comprehensive review of the acoustic and electronic tags commonly used in fish conservation research, classifying them into four categories based on their functions: short-range coded identification and counting tags, spatial tracking and positioning tags, physiological state monitoring tags, and environmental data logging tags. First, the fundamental features and technical principles of these tags are introduced. Then, the applications and research progress of each tag type are discussed in detail, focusing on areas such as fish passage efficiency monitoring, fish movement tracking, physiological state assessment, and habitat information evaluation. Finally, the existing challenges and future development directions of acoustic and electronic tagging technologies in fish conservation are highlighted based on the current state of applications. This study aims to systematically summarize the application status and developmental trends of acoustic and electronic tagging technologies in fish conservation research, providing scientific and technical guidance for aquatic ecosystem protection.
Available online: March 18, 2025
Abstract:
The two-dimensional hydrodynamic and eutrophication model of a Pumped-Storage Reservoir was developed based on MIKE21 ECOLab, to investigate the methods of improving calibration efficiency, and to analyze the spatiotemporal pattern of residence time, nitrogen, phosphorus, and chlorophyll-a in the pumped-storage reservoir. The results indicate that the calibration sequence for 9 state variables in the ECOLab module is: BOD>PO43-=NH4+>NO2->NO3->Chl-a=FC=TC>DO，and 11 of the 41 parameters are primary calibration parameters. The model satisfactorily represented the hydrodynamic and water quality processes of the reservoir, by validating with actual measurement data from 2022. Using this model, the simulated average residence time of water in the reservoir is 9 days, given an annual water diversion volume of 490 million cubic meters. The residence time along the mainstream direction is relatively shorter, but it increases towards both sides, inversely proportional to the distance from the shore, indicating a high spatial variability. In reservoir bays, the residence time notably increases, reaching a peak of over 200 days. Based on observed water quality data of pumping water over the past five years, the simulation results indicate that the annual average concentrations of inorganic nitrogen, inorganic phosphorus, and chlorophyll-a are 0.75 mg/L, 1.93 μg/L, and 20.93 μg/L, respectively. Influenced by seasonal variations in non-point source pollution inputs from the Dongjiang River basin, the concentrations of nitrogen, phosphorus, and chlorophyll-a are higher during the wet season compared to the dry season. In regions with shorter residence times, nitrogen and phosphorus concentrations tend to increase, while chlorophyll-a concentrations tend to decrease. The outcomes of this study provide important information for model construction and eutrophication control in pumped-storage reservoirs.
The two-dimensional hydrodynamic and eutrophication model of a Pumped-Storage Reservoir was developed based on MIKE21 ECOLab, to investigate the methods of improving calibration efficiency, and to analyze the spatiotemporal pattern of residence time, nitrogen, phosphorus, and chlorophyll-a in the pumped-storage reservoir. The results indicate that the calibration sequence for 9 state variables in the ECOLab module is: BOD>PO43-=NH4+>NO2->NO3->Chl-a=FC=TC>DO，and 11 of the 41 parameters are primary calibration parameters. The model satisfactorily represented the hydrodynamic and water quality processes of the reservoir, by validating with actual measurement data from 2022. Using this model, the simulated average residence time of water in the reservoir is 9 days, given an annual water diversion volume of 490 million cubic meters. The residence time along the mainstream direction is relatively shorter, but it increases towards both sides, inversely proportional to the distance from the shore, indicating a high spatial variability. In reservoir bays, the residence time notably increases, reaching a peak of over 200 days. Based on observed water quality data of pumping water over the past five years, the simulation results indicate that the annual average concentrations of inorganic nitrogen, inorganic phosphorus, and chlorophyll-a are 0.75 mg/L, 1.93 μg/L, and 20.93 μg/L, respectively. Influenced by seasonal variations in non-point source pollution inputs from the Dongjiang River basin, the concentrations of nitrogen, phosphorus, and chlorophyll-a are higher during the wet season compared to the dry season. In regions with shorter residence times, nitrogen and phosphorus concentrations tend to increase, while chlorophyll-a concentrations tend to decrease. The outcomes of this study provide important information for model construction and eutrophication control in pumped-storage reservoirs.
Available online: March 14, 2025
Abstract:
The actual lakes generally experience repeated wind and wave disturbances, and the mud-water interface process has an important influence on the material circulation of lakes during the cyclic process of suspension and calm settlement. In view of the changes of particulate matter and phosphorus at the mud-water interface in the process of disturbance suspension and calm settlement, repeated experiments of disturbance and settlement were carried out. With the oscillating grating as the disturbance device and 12 h as the period, the intermittent disturbance experiment was carried out for a total of 10 periods, and the change law of turbidity, TP, DTP and particles was paid attention to. The experimental results show that the rise of turbidity, TP and DTP caused by re-suspension will gradually decrease in the process of repeated suspension and settlement, and the greater the disturbance intensity, the more obvious the decline of turbidity, TP and DTP peaks after the disturbance. After repeated disturbance, the particle size of the sediment surface becomes larger, and large floc of about 200~400μm appears. In the process of multiple disturbances, "perturbation-aggregation" occurs between suspended particles and particles, the distance between particles is close to each other, the increase of van der Waals gravity causes flocculation between particles, and the existence of organic matter causes a "bridging effect" between particles, which promotes the formation of larger flocs.
The actual lakes generally experience repeated wind and wave disturbances, and the mud-water interface process has an important influence on the material circulation of lakes during the cyclic process of suspension and calm settlement. In view of the changes of particulate matter and phosphorus at the mud-water interface in the process of disturbance suspension and calm settlement, repeated experiments of disturbance and settlement were carried out. With the oscillating grating as the disturbance device and 12 h as the period, the intermittent disturbance experiment was carried out for a total of 10 periods, and the change law of turbidity, TP, DTP and particles was paid attention to. The experimental results show that the rise of turbidity, TP and DTP caused by re-suspension will gradually decrease in the process of repeated suspension and settlement, and the greater the disturbance intensity, the more obvious the decline of turbidity, TP and DTP peaks after the disturbance. After repeated disturbance, the particle size of the sediment surface becomes larger, and large floc of about 200~400μm appears. In the process of multiple disturbances, "perturbation-aggregation" occurs between suspended particles and particles, the distance between particles is close to each other, the increase of van der Waals gravity causes flocculation between particles, and the existence of organic matter causes a "bridging effect" between particles, which promotes the formation of larger flocs.
Available online: March 14, 2025
Abstract:
Hydrological processes are crucial factors affecting the suitability and area changes of waterbird habitats in floodplain wetlands. Currently, extreme hydrological events triggered by global warming have become more frequent. Poyang Lake experienced extreme flooding in 2020 and extreme drought in 2022, and a winter flood in 2015. However, impacts of extreme hydrological events on wintering habitat area of waterbirds in Poyang Lake remain unclear. This study extracted data on the wintering waterbird habitats in Poyang Lake from satellite imagery between 2013 and 2023 for the period from September to February of the following year. By comparing the spatial and temporal changes in waterbird wintering habitats between extreme hydrological event years with normal hydrological years, the study explores the impact of extreme hydrological events on wintering waterbird habitats area at Poyang Lake. The findings are: 1) The area loss of wintering habitats for waterbirds in Poyang Lake caused by extreme flooding in summer (EFS), extreme drought in late summer and autumn (EDSA), and winter flooding (WF) reached as high as 67.62%, 29.83%, and 18.18%, respectively; 2) EFS and EDSA led to a significant reduction in the area of waterbird wintering habitats from September to November, but they did not reduce the habitat area during the critical wintering period (winter) for the waterbirds. Although the intensity of WF was not as severe as that of EFS and EDSA, WF resulted in an average habitat area loss of 14.31% during the critical wintering period for waterbirds; 3) There are significant spatiotemporal differences in the impact of extreme hydrological events on the waterbirds" wintering habitats in Poyang Lake, which are related to the process of the extreme hydrological events and the lake"s elevation. The study"s results are valuable for the management of Poyang Lake and similar floodplain wetlands, as well as for waterbird conservation.
Hydrological processes are crucial factors affecting the suitability and area changes of waterbird habitats in floodplain wetlands. Currently, extreme hydrological events triggered by global warming have become more frequent. Poyang Lake experienced extreme flooding in 2020 and extreme drought in 2022, and a winter flood in 2015. However, impacts of extreme hydrological events on wintering habitat area of waterbirds in Poyang Lake remain unclear. This study extracted data on the wintering waterbird habitats in Poyang Lake from satellite imagery between 2013 and 2023 for the period from September to February of the following year. By comparing the spatial and temporal changes in waterbird wintering habitats between extreme hydrological event years with normal hydrological years, the study explores the impact of extreme hydrological events on wintering waterbird habitats area at Poyang Lake. The findings are: 1) The area loss of wintering habitats for waterbirds in Poyang Lake caused by extreme flooding in summer (EFS), extreme drought in late summer and autumn (EDSA), and winter flooding (WF) reached as high as 67.62%, 29.83%, and 18.18%, respectively; 2) EFS and EDSA led to a significant reduction in the area of waterbird wintering habitats from September to November, but they did not reduce the habitat area during the critical wintering period (winter) for the waterbirds. Although the intensity of WF was not as severe as that of EFS and EDSA, WF resulted in an average habitat area loss of 14.31% during the critical wintering period for waterbirds; 3) There are significant spatiotemporal differences in the impact of extreme hydrological events on the waterbirds" wintering habitats in Poyang Lake, which are related to the process of the extreme hydrological events and the lake"s elevation. The study"s results are valuable for the management of Poyang Lake and similar floodplain wetlands, as well as for waterbird conservation.
Available online: March 14, 2025
Abstract:
Based on the in-situ observation of air-ice-water in Qinghai Lake during the ice-covered period on February 5, 2022, the differences of lake ice variation process in Qinghai Lake under snow, dust, and bare ice conditions were analyzed. The results show that the lake ice development was stable in February, the maximum ice thickness was 36.5cm, the maximum snow depth was 10.4cm, the increase of snow depth will significantly reduce the ice thickness growth rate. The daily variation of lake ice albedo was shown ‘U’ shaped, which was higher in the morning and evening and lower at noon. The albedo of the snow-covered was the largest, with the average value of 0.61, and the albedo under dust and bare ice conditions respectively decreased to 0.27 and 0.16. The net solar radiation also changed with the change of albedo. With the increase of depth, the sensitivity of ice temperature to air temperature gradually decreased, the daily variation decreased, and the lag time increases. The correlation coefficient between air temperature and ice temperature in bare ice was 0.93. The existence of snow reduced the correlation between air temperature and ice temperature, and the thicker of snow, the lower of correlation. Dust had the high absorption characteristic of solar radiation, accelerated the metamorphism and melting of snow and promoted the control of air temperature on ice temperature. The strong wind led to redistribution of snow and dust on ice surface, which indirectly affected the change of ice temperature. The variation of vertical conduction heat flux in the lake ice was similar to that of ice temperature. The heat flux decreased and the daily variation decreased with depth increased. In the bare ice stage, both the value and the daily variation amplitude of the conducted heat flux were greater than that in the snow-covered stage. The diurnal alternations of solar radiation affected the upper ice temperature, and the direction of conduction heat flux reversed accordingly. As the largest lake on the Tibet Plateau, Qinghai Lake has a profound impact on the plateau climate and water resource balance. This study has enriched the measured data of lake ice changes during the freezing period of Qinghai Lake, and provided the foundation for the refinement and parameterization improvement of lake models.
Based on the in-situ observation of air-ice-water in Qinghai Lake during the ice-covered period on February 5, 2022, the differences of lake ice variation process in Qinghai Lake under snow, dust, and bare ice conditions were analyzed. The results show that the lake ice development was stable in February, the maximum ice thickness was 36.5cm, the maximum snow depth was 10.4cm, the increase of snow depth will significantly reduce the ice thickness growth rate. The daily variation of lake ice albedo was shown ‘U’ shaped, which was higher in the morning and evening and lower at noon. The albedo of the snow-covered was the largest, with the average value of 0.61, and the albedo under dust and bare ice conditions respectively decreased to 0.27 and 0.16. The net solar radiation also changed with the change of albedo. With the increase of depth, the sensitivity of ice temperature to air temperature gradually decreased, the daily variation decreased, and the lag time increases. The correlation coefficient between air temperature and ice temperature in bare ice was 0.93. The existence of snow reduced the correlation between air temperature and ice temperature, and the thicker of snow, the lower of correlation. Dust had the high absorption characteristic of solar radiation, accelerated the metamorphism and melting of snow and promoted the control of air temperature on ice temperature. The strong wind led to redistribution of snow and dust on ice surface, which indirectly affected the change of ice temperature. The variation of vertical conduction heat flux in the lake ice was similar to that of ice temperature. The heat flux decreased and the daily variation decreased with depth increased. In the bare ice stage, both the value and the daily variation amplitude of the conducted heat flux were greater than that in the snow-covered stage. The diurnal alternations of solar radiation affected the upper ice temperature, and the direction of conduction heat flux reversed accordingly. As the largest lake on the Tibet Plateau, Qinghai Lake has a profound impact on the plateau climate and water resource balance. This study has enriched the measured data of lake ice changes during the freezing period of Qinghai Lake, and provided the foundation for the refinement and parameterization improvement of lake models.
Available online: March 14, 2025
Abstract:
The unit hydrograph is a simplified way to understand how a watershed responds to rainfall and offers a practical approach for flood forecasting. By approximating real-world watershed processes as a time-invariant linear hydrologic system, Guo turns the unit hydrograph to General Unit Hydrograph (GUH). The traditional runoff hydrological models for flood forecasting require a large number of parameters and datasets. In order to reduce the complexity of flood forecasting and model parameters, a simple GUH model considering rainfall loss and pre-flow is constructed in this study, combining with the Multiple Objective Particle Swarm Optimization (MOPSO) algorithm for parameters optimization. Taking Yuecheng Basin and Jiuzhou Basin as the study basins, different combinations of flood forecasting are constructed according to the improved GUH model、SCS-CN model and Nash unit hydrograph for comparison. The applicability of the model in flood forecasting in small and medium-sized basins is evaluated, and the forecasting accuracy of the improved GUH model at different lead times is discussed. The results showed that: （1）The improved GUH model"s forecasting accuracy was superior to two other runoff hydrological models.（2）The improved GUH model reached a Category II forecast level at both the Yuecheng Basin and Jiuzhou Basin，with mean coefficients of determination for Yuecheng and Jiuzhou Basin were 0.79 and 0.84, and pass rates of 90.91% and 83.33%, respectively;（3）The forecasting accuracy of the improved GUH model gradually decreased with an increase in lead times, but it still maintained a certain level of predictive performance when the lead times was less than four-hour. The improved GUH model, considering rainfall losses and pre-flow, had fewer parameters and a simple structure. It showed potential for flood forecasting and provided new insights for flood forecasting in small and medium-sized watersheds.
The unit hydrograph is a simplified way to understand how a watershed responds to rainfall and offers a practical approach for flood forecasting. By approximating real-world watershed processes as a time-invariant linear hydrologic system, Guo turns the unit hydrograph to General Unit Hydrograph (GUH). The traditional runoff hydrological models for flood forecasting require a large number of parameters and datasets. In order to reduce the complexity of flood forecasting and model parameters, a simple GUH model considering rainfall loss and pre-flow is constructed in this study, combining with the Multiple Objective Particle Swarm Optimization (MOPSO) algorithm for parameters optimization. Taking Yuecheng Basin and Jiuzhou Basin as the study basins, different combinations of flood forecasting are constructed according to the improved GUH model、SCS-CN model and Nash unit hydrograph for comparison. The applicability of the model in flood forecasting in small and medium-sized basins is evaluated, and the forecasting accuracy of the improved GUH model at different lead times is discussed. The results showed that: （1）The improved GUH model"s forecasting accuracy was superior to two other runoff hydrological models.（2）The improved GUH model reached a Category II forecast level at both the Yuecheng Basin and Jiuzhou Basin，with mean coefficients of determination for Yuecheng and Jiuzhou Basin were 0.79 and 0.84, and pass rates of 90.91% and 83.33%, respectively;（3）The forecasting accuracy of the improved GUH model gradually decreased with an increase in lead times, but it still maintained a certain level of predictive performance when the lead times was less than four-hour. The improved GUH model, considering rainfall losses and pre-flow, had fewer parameters and a simple structure. It showed potential for flood forecasting and provided new insights for flood forecasting in small and medium-sized watersheds.
Available online: March 13, 2025
Abstract:
In order to understand the status of early fish resources in the river and lake channel of Poyang Lake during the early period of fishing ban, the survey of juvenile fish was carried out day by day from 5th April to 21st August 2023 in the river and lake channel of the lake mouth of Poyang Lake. The results showed that a total of 142,054 juveniles were collected during the survey period, and 38 species of juveniles were identified, belonging to 7 orders and 9 families; among them, there were 6 dominant species, with Coilia nasus as the first dominant species, which recovered remarkably after the ban on fishing, and the rest of the dominant species in order of predominance were Hemiculter bleekeri, and the other species. Rhinogobius giurinus, Hemiculter leucisculus, Pseudolaubuca sinensis, and Xenocypris argentea. During the survey period, smolts were mainly concentrated in July, and smolt abundance peaked on 21 July at 11,476 ind/100m3. The results of spatial difference analysis showed that the abundance of larvae was significantly greater (P<0.05) on the south bank than on the north bank and at the central sampling site. Redundancy analysis showed that turbidity, flow velocity and water level were the main environmental factors affecting the abundance of juvenile fishes, among which turbidity was significantly and positively correlated with the abundance of juvenile fishes (P<0.05). According to the migratory habits of the parents, the fish were mainly freshwater sedentary fish, with 76.32% and 68.29% of the species and number, respectively; according to the spawning mode of the parents, the fish were mainly drift-spawning fish, with 47.37% and 48.94% of the species and number, respectively. The study showed that the fish species in Hukou were relatively abundant, but mainly consisted of small fishes, and the average abundance of juvenile fish was greater on the south bank (1744 ind/100m3) than on the north bank (431 ind/100m3) and in the centre of the sampling site (259 ind/100m3). The results of this survey supplemented the basic data of early fish resources in the lake mouth of Poyang Lake after the ban on fishing in the Yangtze River, and provided a scientific basis for the protection of fish diversity.
In order to understand the status of early fish resources in the river and lake channel of Poyang Lake during the early period of fishing ban, the survey of juvenile fish was carried out day by day from 5th April to 21st August 2023 in the river and lake channel of the lake mouth of Poyang Lake. The results showed that a total of 142,054 juveniles were collected during the survey period, and 38 species of juveniles were identified, belonging to 7 orders and 9 families; among them, there were 6 dominant species, with Coilia nasus as the first dominant species, which recovered remarkably after the ban on fishing, and the rest of the dominant species in order of predominance were Hemiculter bleekeri, and the other species. Rhinogobius giurinus, Hemiculter leucisculus, Pseudolaubuca sinensis, and Xenocypris argentea. During the survey period, smolts were mainly concentrated in July, and smolt abundance peaked on 21 July at 11,476 ind/100m3. The results of spatial difference analysis showed that the abundance of larvae was significantly greater (P<0.05) on the south bank than on the north bank and at the central sampling site. Redundancy analysis showed that turbidity, flow velocity and water level were the main environmental factors affecting the abundance of juvenile fishes, among which turbidity was significantly and positively correlated with the abundance of juvenile fishes (P<0.05). According to the migratory habits of the parents, the fish were mainly freshwater sedentary fish, with 76.32% and 68.29% of the species and number, respectively; according to the spawning mode of the parents, the fish were mainly drift-spawning fish, with 47.37% and 48.94% of the species and number, respectively. The study showed that the fish species in Hukou were relatively abundant, but mainly consisted of small fishes, and the average abundance of juvenile fish was greater on the south bank (1744 ind/100m3) than on the north bank (431 ind/100m3) and in the centre of the sampling site (259 ind/100m3). The results of this survey supplemented the basic data of early fish resources in the lake mouth of Poyang Lake after the ban on fishing in the Yangtze River, and provided a scientific basis for the protection of fish diversity.
Shi Xiaotao, Gao Shenghui, Ke Senfan, Jiao Yilin, Li Dongqing, Xu Jiawei, Yang Ji, Li Xinyu, Lu Jianyu, Zhu Shilong, Tu Zhiying, Cheng Bixin
Available online: March 13, 2025
Abstract:
Challenges such as the "invisibility" of fishway entrances, the "inaccessibility" of chutes, and "post-passage swimming behavior" have long persisted in the restoration of fish migration routes and the comprehension of fish life history. Specifically, urgent issues such as how fish swim after passing through a dam, whether they get entrapped in reservoir "ecological traps", and if they can traverse the reservoir to reach their habitats require immediate attention. In this study, three typical fish species in the Heishui River of the Jinsha River, namely Schizothorax prenanti, Paracobitis variegatus, and Paracobitis potanini, were chosen as research subjects. The status of these target fish resources was evaluated by means of net-capture methods, and post-passage upstream movement data were gathered using telemetry technology. Subsequently, a quantitative evaluation model of post-passage upstream movement effectiveness was developed, integrating the hydrological and hydrodynamic factors of the reservoir. The key factors influencing this effectiveness were determined, and the response relationships between upstream effectiveness and these factors were established. The results are as follows: 1) Schizothorax prenanti, Paracobitis variegatus, and Paracobitis potanini are dominant species in the area from the upper part of the dam to the fishway and then to the lower part of the dam, accounting for more than 40% of the total catch in aggregate. 2) The fishway passage rate of the three target species was 11.14%, and their success rate of upstream migration from the fishway exit to the reservoir tail was 30.87%. 3) After passing through the fishway, the target fish exhibited different habitat preferences. 70% remained in the near-dam reservoir area, which was the highest proportion; 28% continued to swim upstream to the pebble riverbed area; no target fish were observed to migrate upstream from the gravel braided riverbed area to the meandering gravel-sand riverbed area. 4) The sensitive factors affecting post-passage upstream effectiveness include fish species, flow rate, rate of change in hydrological conditions, and diurnal rhythm. 5) The success rate of upstream migration after passing the dam decreases as the river flow increases; target fish tend to migrate during short periods of rising water; over 60% of target fish chose to migrate at night; the success rate of post-passage upstream migration for Schizothorax prenanti was significantly higher than that for Paracobitis variegatus and Paracobitis potanini. This study, taking the fish from the Jinsha River as an example, analyzed the upstream movement behavior patterns of fish after passing through the dam and identified the key factors driving the habitat selection of target fish.
Challenges such as the "invisibility" of fishway entrances, the "inaccessibility" of chutes, and "post-passage swimming behavior" have long persisted in the restoration of fish migration routes and the comprehension of fish life history. Specifically, urgent issues such as how fish swim after passing through a dam, whether they get entrapped in reservoir "ecological traps", and if they can traverse the reservoir to reach their habitats require immediate attention. In this study, three typical fish species in the Heishui River of the Jinsha River, namely Schizothorax prenanti, Paracobitis variegatus, and Paracobitis potanini, were chosen as research subjects. The status of these target fish resources was evaluated by means of net-capture methods, and post-passage upstream movement data were gathered using telemetry technology. Subsequently, a quantitative evaluation model of post-passage upstream movement effectiveness was developed, integrating the hydrological and hydrodynamic factors of the reservoir. The key factors influencing this effectiveness were determined, and the response relationships between upstream effectiveness and these factors were established. The results are as follows: 1) Schizothorax prenanti, Paracobitis variegatus, and Paracobitis potanini are dominant species in the area from the upper part of the dam to the fishway and then to the lower part of the dam, accounting for more than 40% of the total catch in aggregate. 2) The fishway passage rate of the three target species was 11.14%, and their success rate of upstream migration from the fishway exit to the reservoir tail was 30.87%. 3) After passing through the fishway, the target fish exhibited different habitat preferences. 70% remained in the near-dam reservoir area, which was the highest proportion; 28% continued to swim upstream to the pebble riverbed area; no target fish were observed to migrate upstream from the gravel braided riverbed area to the meandering gravel-sand riverbed area. 4) The sensitive factors affecting post-passage upstream effectiveness include fish species, flow rate, rate of change in hydrological conditions, and diurnal rhythm. 5) The success rate of upstream migration after passing the dam decreases as the river flow increases; target fish tend to migrate during short periods of rising water; over 60% of target fish chose to migrate at night; the success rate of post-passage upstream migration for Schizothorax prenanti was significantly higher than that for Paracobitis variegatus and Paracobitis potanini. This study, taking the fish from the Jinsha River as an example, analyzed the upstream movement behavior patterns of fish after passing through the dam and identified the key factors driving the habitat selection of target fish.
Available online: February 27, 2025
Abstract:
The Three Gorges Reservoir Area (TGRA), being one of the country"s typical ecologically vulnerable areas and areas prone to frequent landslide disasters, the occurrence of landslide disasters severely endangers the health and stability of the reservoir area"s ecosystem. Therefore, the ecological risk assessment of landslide disasters in the Three Gorges Reservoir Area is crucial for the environmental management and ecological risk prevention in the reservoir area. Based on the three-dimensional model of “susceptibility-vulnerability-potential loss”, considering the impact of long - time series, the random forest model was adopted to evaluate the susceptibility of landslide disasters. Landscape pattern indices were used to represent ecological vulnerability, and the potential ecological losses caused by landslide disasters were quantitatively calculated through ecosystem services. The ecological risk assessment of landslide disasters in the Three Gorges Reservoir Area from 2000 to 2020 was carried out. Risk prevention zones were divided, and corresponding risk management measures were proposed. The results indicate that: ①Areas with relatively high and high ecological risks of landslide disasters are scattered in distribution, yet on the whole, they show a zonal distribution along both banks of the Yangtze River. Areas with moderate and relatively low risks spread from both banks of the Yangtze River and its tributaries to the periphery. Low - risk areas account for about 60% of the total area of the study region, mainly concentrated on the periphery of the Three Gorges Reservoir Area. ②The landslide susceptibility and ecological vulnerability in the study area showed an increasing trend from 2000 to 2010, while the potential ecological loss was significantly reduced, resulting in a decreasing trend of landslide ecological risk; the opposite is true from 2010 to 2020, when the landslide ecological risk in the study area showed an increasing trend, and the ecological risk areas of the final high and higher-grade landslide hazard showed an expanding trend. ③The study area was divided into 16 risk prevention zones according to the dominant factors of the risk structure, the trend of risk change, and the potential ecological losses. By reasonably adjusting the intensity and focus of risk management, a multi - scale risk - segmented management strategy for the overall study area, different sections, and key districts and counties is formulated. This aims to achieve comprehensive disaster prevention, precise management measures, and efficient resource allocation.
The Three Gorges Reservoir Area (TGRA), being one of the country"s typical ecologically vulnerable areas and areas prone to frequent landslide disasters, the occurrence of landslide disasters severely endangers the health and stability of the reservoir area"s ecosystem. Therefore, the ecological risk assessment of landslide disasters in the Three Gorges Reservoir Area is crucial for the environmental management and ecological risk prevention in the reservoir area. Based on the three-dimensional model of “susceptibility-vulnerability-potential loss”, considering the impact of long - time series, the random forest model was adopted to evaluate the susceptibility of landslide disasters. Landscape pattern indices were used to represent ecological vulnerability, and the potential ecological losses caused by landslide disasters were quantitatively calculated through ecosystem services. The ecological risk assessment of landslide disasters in the Three Gorges Reservoir Area from 2000 to 2020 was carried out. Risk prevention zones were divided, and corresponding risk management measures were proposed. The results indicate that: ①Areas with relatively high and high ecological risks of landslide disasters are scattered in distribution, yet on the whole, they show a zonal distribution along both banks of the Yangtze River. Areas with moderate and relatively low risks spread from both banks of the Yangtze River and its tributaries to the periphery. Low - risk areas account for about 60% of the total area of the study region, mainly concentrated on the periphery of the Three Gorges Reservoir Area. ②The landslide susceptibility and ecological vulnerability in the study area showed an increasing trend from 2000 to 2010, while the potential ecological loss was significantly reduced, resulting in a decreasing trend of landslide ecological risk; the opposite is true from 2010 to 2020, when the landslide ecological risk in the study area showed an increasing trend, and the ecological risk areas of the final high and higher-grade landslide hazard showed an expanding trend. ③The study area was divided into 16 risk prevention zones according to the dominant factors of the risk structure, the trend of risk change, and the potential ecological losses. By reasonably adjusting the intensity and focus of risk management, a multi - scale risk - segmented management strategy for the overall study area, different sections, and key districts and counties is formulated. This aims to achieve comprehensive disaster prevention, precise management measures, and efficient resource allocation.
Available online: February 20, 2025
Abstract:
Since the operation of the Three Gorges Reservoir, the tributaries have burst out different degrees of bloom, especially the phosphorus eutrophication in Xiangxi River Bay, which has a great impact on the overall water environment and water ecological security of the Three Gorges Reservoir area. Sediment is an important internal source of phosphorus eutrophication in lake and reservoir water, and microbial community plays an important role in the element cycle of sediments, and microbial activity in sediments can significantly affect the morphological changes of phosphorus in sediments. In order to explore the diversity characteristics of microbial community structure in the sediments of Xiangxi River, a tributary of Three Gorges Reservoir, and its response to environmental factors, samples were collected at five representative sites in Xiangxi River during the four seasons from autumn 2021 to summer 2022, based on 16SrRNA high-throughput sequencing analysis and water quality analysis. The bacterial diversity and community structure differences were studied. The results showed that the abundance of microbial diversity was high in the sediments of Xiangxi River. The α diversity index showed a seasonal variation pattern of autumn > winter > spring > summer. The β diversity showed that the microbial communities in the bay had the greatest difference in spring and the least difference in winter. The dominant bacteria are Proteobacteria, Bacteroidota, Acidobacteriota, Nitrospirota, Desulfobacterota, Firmicutes, Chloroflexi, Verrucomicrobiota, Actinobacteriota and so on; Spearman correlation analysis and RDA redundancy analysis showed that overlying water pH value, dissolved oxygen (DO), electrical conductivity (Spcond), overlying water orthophosphate（PO43-）, water temperature (T) and total phosphorus (STP) in overlying water were the main environmental factors affecting the structure and distribution of bacterial community, and STP was the most critical factor. This study is helpful to further understand the effects of microbial seasonal changes on the phosphorus form and content in the sediments of the reservoir bay of Xiangxi River, and provide reference for the improvement and management of water environment in the Three Gorges Reservoir area.
Since the operation of the Three Gorges Reservoir, the tributaries have burst out different degrees of bloom, especially the phosphorus eutrophication in Xiangxi River Bay, which has a great impact on the overall water environment and water ecological security of the Three Gorges Reservoir area. Sediment is an important internal source of phosphorus eutrophication in lake and reservoir water, and microbial community plays an important role in the element cycle of sediments, and microbial activity in sediments can significantly affect the morphological changes of phosphorus in sediments. In order to explore the diversity characteristics of microbial community structure in the sediments of Xiangxi River, a tributary of Three Gorges Reservoir, and its response to environmental factors, samples were collected at five representative sites in Xiangxi River during the four seasons from autumn 2021 to summer 2022, based on 16SrRNA high-throughput sequencing analysis and water quality analysis. The bacterial diversity and community structure differences were studied. The results showed that the abundance of microbial diversity was high in the sediments of Xiangxi River. The α diversity index showed a seasonal variation pattern of autumn > winter > spring > summer. The β diversity showed that the microbial communities in the bay had the greatest difference in spring and the least difference in winter. The dominant bacteria are Proteobacteria, Bacteroidota, Acidobacteriota, Nitrospirota, Desulfobacterota, Firmicutes, Chloroflexi, Verrucomicrobiota, Actinobacteriota and so on; Spearman correlation analysis and RDA redundancy analysis showed that overlying water pH value, dissolved oxygen (DO), electrical conductivity (Spcond), overlying water orthophosphate（PO43-）, water temperature (T) and total phosphorus (STP) in overlying water were the main environmental factors affecting the structure and distribution of bacterial community, and STP was the most critical factor. This study is helpful to further understand the effects of microbial seasonal changes on the phosphorus form and content in the sediments of the reservoir bay of Xiangxi River, and provide reference for the improvement and management of water environment in the Three Gorges Reservoir area.
Liu Huibo, Fan Yifei, Ruan Qizhen, Dai Zetao, Wang Feifei, Yang Sheng Chang, Xu Wenfeng, Liu Lihua, Cao Wenzhi
Available online: February 20, 2025
Abstract:
Bacterioplankton play a crucial role in mass cycling within reservoir ecosystems and drive biogeochemical cycles. Based on the vertical characteristics of water temperature and dissolved oxygen in Wan’an Reservoir, a deep-water reservoir in Southeastern China, this study utilized 16S rRNA gene amplicon sequencing technology to reveal variations in the composition, structure and assembly mechanism of bacterioplankton communities during different thermal stratification periods in the reservoir. The results indicated that the α-diversity of bacterioplankton was highest in the thermocline and lowest in the hypolimnion during the period of thermal stratification formation. During the stabilization period, α-diversity was higher in the hypolimnion and lower in both the thermocline and the mixed layer. In the recession period, α-diversity was elevated in both the thermocline and the hypolimnion, while it remained lower in the mixed layer. Molecular ecological network analysis indicated that during the recession periods of thermal stratification, bacterioplankton exhibited stronger positive correlations, lower modularity, and higher network complexity. During the period of thermal stratification formation, the proportion of key species was highest (30.00%), followed by the recession period (24.38%) and the stabilization period (21.60%). The neutral model explained 79.7%, 78.8%, and 64.1% of the community variations during the formation, stabilization, and recession periods, respectively. The bacterioplankton community assembly was primarily driven by stochastic processes; however, environmental factors also significantly influenced bacterioplankton community structure. Throughout the three periods of thermal stratification, the bacterioplankton community was mainly affected by dissolved oxygen, chlorophyll-a, total nitrogen and total phosphorus. This study aids in the management of water environment and ecological status in reservoirs and the assessment of the health of aquatic ecosystems.
Bacterioplankton play a crucial role in mass cycling within reservoir ecosystems and drive biogeochemical cycles. Based on the vertical characteristics of water temperature and dissolved oxygen in Wan’an Reservoir, a deep-water reservoir in Southeastern China, this study utilized 16S rRNA gene amplicon sequencing technology to reveal variations in the composition, structure and assembly mechanism of bacterioplankton communities during different thermal stratification periods in the reservoir. The results indicated that the α-diversity of bacterioplankton was highest in the thermocline and lowest in the hypolimnion during the period of thermal stratification formation. During the stabilization period, α-diversity was higher in the hypolimnion and lower in both the thermocline and the mixed layer. In the recession period, α-diversity was elevated in both the thermocline and the hypolimnion, while it remained lower in the mixed layer. Molecular ecological network analysis indicated that during the recession periods of thermal stratification, bacterioplankton exhibited stronger positive correlations, lower modularity, and higher network complexity. During the period of thermal stratification formation, the proportion of key species was highest (30.00%), followed by the recession period (24.38%) and the stabilization period (21.60%). The neutral model explained 79.7%, 78.8%, and 64.1% of the community variations during the formation, stabilization, and recession periods, respectively. The bacterioplankton community assembly was primarily driven by stochastic processes; however, environmental factors also significantly influenced bacterioplankton community structure. Throughout the three periods of thermal stratification, the bacterioplankton community was mainly affected by dissolved oxygen, chlorophyll-a, total nitrogen and total phosphorus. This study aids in the management of water environment and ecological status in reservoirs and the assessment of the health of aquatic ecosystems.
