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2026,38(4):1307-1318, DOI: 10.18307/2026.0401
Abstract:
The advancement of limnology and lake science has compellingly demonstrated the critical importance of long-term field observations and experimental research. Globally, scientific institutions have established long-term field observation stations—such as those at Lake Flathead, Lake Trout, USA, and Lake Zurich, Switzerland—to systematically conduct research spanning decades to over a century on the evolution, impact mechanisms, and sustainable management of lake ecosystems. Supported by the Chinese Ecosystem Research Network and the National Science and Technology Infrastructure Platform Center, Chinese scientists have successively constructed field observation and experimental stations at sites including East Lake (Wuhan), Lake Taihu, Lake Poyang, Lake Dongting, and Lake Liangzi, undertaking long-term experimental monitoring and networked comprehensive studies of lake ecosystems. This study systematically reviews the progress of long-term, site-specific observation and experimental research in lake science, both globally and within China. Through cross-national, cross-regional, and cross-lake-type case comparisons, it highlights the irreplaceable role of such sustained, location-based observations in uncovering the dynamics of lake ecosystems. The study emphasizes that only through cross-regional networked observations, enhanced informatization and intelligence in monitoring, and the integration of observational data with simulation models can we deeply analyze the response processes and resilience mechanisms of lake ecosystems to climate change and human disturbances. This synthesis provides crucial scientific support for global lake conservation, ecological restoration, and sustainable utilization, thereby propelling lake science forward from "phenomenon description" to "mechanism analysis" and "predictive early-warning". Ultimately, this work serves the objectives of the United Nations Sustainable Development Agenda and the Beautiful China Initiative.
The advancement of limnology and lake science has compellingly demonstrated the critical importance of long-term field observations and experimental research. Globally, scientific institutions have established long-term field observation stations—such as those at Lake Flathead, Lake Trout, USA, and Lake Zurich, Switzerland—to systematically conduct research spanning decades to over a century on the evolution, impact mechanisms, and sustainable management of lake ecosystems. Supported by the Chinese Ecosystem Research Network and the National Science and Technology Infrastructure Platform Center, Chinese scientists have successively constructed field observation and experimental stations at sites including East Lake (Wuhan), Lake Taihu, Lake Poyang, Lake Dongting, and Lake Liangzi, undertaking long-term experimental monitoring and networked comprehensive studies of lake ecosystems. This study systematically reviews the progress of long-term, site-specific observation and experimental research in lake science, both globally and within China. Through cross-national, cross-regional, and cross-lake-type case comparisons, it highlights the irreplaceable role of such sustained, location-based observations in uncovering the dynamics of lake ecosystems. The study emphasizes that only through cross-regional networked observations, enhanced informatization and intelligence in monitoring, and the integration of observational data with simulation models can we deeply analyze the response processes and resilience mechanisms of lake ecosystems to climate change and human disturbances. This synthesis provides crucial scientific support for global lake conservation, ecological restoration, and sustainable utilization, thereby propelling lake science forward from "phenomenon description" to "mechanism analysis" and "predictive early-warning". Ultimately, this work serves the objectives of the United Nations Sustainable Development Agenda and the Beautiful China Initiative.
2026,38(4):1319-1330, DOI: 10.18307/2026.0402
Abstract:
The Yangtze River, celebrated as the Mother River of the Chinese nation, constitutes a vital cradle of its civilization and a critical lifeline underpinning the nation's economic and social development. The high-quality development of the Yangtze River Economic Belt is fundamentally reliant on the superior ecological environment of its basin. Long-term, fixed-site observation of the basin's aquatic ecosystem provides the essential foundation for coordinating the protection and restoration of its water resources, water environment, and aquatic ecology. It is also of major scientific importance for advancing watershed aquatic ecosystem science and supporting the implementation of the national Yangtze River Conservation Strategy. This paper systematically reviews progress and experiences in the long-term fixed-site observation and experimental research on aquatic ecosystems within major river basins globally and in China. It outlines the developmental history and key achievements of long-term observational and experimental studies on the Yangtze River Basin's aquatic ecosystem. Furthermore, the paper summarizes the progress and outcomes realized since the initiation of the Joint Observation Research Initiative for Aquatic Ecosystem Security in the Yangtze River Basin (2023-2025). Supported by national field stations, this initiative has advanced the compilation of foundational datasets on the water ecological environment and the development of specialized technical standards for aquatic ecological observation. In response to the challenges confronting future long-term observation research in the Yangtze River Basin, this paper proposes forthcoming development trends and highlights priority areas requiring strengthening in subsequent fixed-site observation and experimental studies. This work provides a fundamental scientific basis for research and management decisions pertaining to the protection and restoration of the basin's aquatic ecosystem, while also offering a referential case for long-term in situ hydrological and ecological observation studies in large river basins worldwide.
The Yangtze River, celebrated as the Mother River of the Chinese nation, constitutes a vital cradle of its civilization and a critical lifeline underpinning the nation's economic and social development. The high-quality development of the Yangtze River Economic Belt is fundamentally reliant on the superior ecological environment of its basin. Long-term, fixed-site observation of the basin's aquatic ecosystem provides the essential foundation for coordinating the protection and restoration of its water resources, water environment, and aquatic ecology. It is also of major scientific importance for advancing watershed aquatic ecosystem science and supporting the implementation of the national Yangtze River Conservation Strategy. This paper systematically reviews progress and experiences in the long-term fixed-site observation and experimental research on aquatic ecosystems within major river basins globally and in China. It outlines the developmental history and key achievements of long-term observational and experimental studies on the Yangtze River Basin's aquatic ecosystem. Furthermore, the paper summarizes the progress and outcomes realized since the initiation of the Joint Observation Research Initiative for Aquatic Ecosystem Security in the Yangtze River Basin (2023-2025). Supported by national field stations, this initiative has advanced the compilation of foundational datasets on the water ecological environment and the development of specialized technical standards for aquatic ecological observation. In response to the challenges confronting future long-term observation research in the Yangtze River Basin, this paper proposes forthcoming development trends and highlights priority areas requiring strengthening in subsequent fixed-site observation and experimental studies. This work provides a fundamental scientific basis for research and management decisions pertaining to the protection and restoration of the basin's aquatic ecosystem, while also offering a referential case for long-term in situ hydrological and ecological observation studies in large river basins worldwide.
Zhu Guangwei, Kang Lijuan, Guo Chaoxuan, Shen Ruijie, Cai Yongjiu, Huang Wei, Luo Juhua, Zhang Yunlin, Qin Boqiang
2026,38(4):1331-1350, DOI: 10.18307/2026.0403
Abstract:
Over the past two decades, Lake Taihu has undergone intensive remediation and restoration, compounded by climate change impacts such as warming and heatwaves, driving significant shifts in the composition and structure of its aquatic ecosystem, encompassing phytoplankton, zooplankton, benthic macroinvertebrates, and macrophytes. Leveraging long-term monitoring data from the Taihu Laboratory for Lake Ecosystem Research (TLLER), a National Scientific Observation and Research Station, including water quality, phytoplankton, and macrophyte data spanning 2005 to 2025, macroinvertebrate data from 2007 to 2025, zooplankton data from 2012 to 2025, alongside concurrent hydrological and meteorological observations, this study elucidates the characteristics and underlying mechanisms governing the structural changes in the Lake Taihu ecosystem over the past two decades under the combined influences of declining nitrogen concentrations, rising water temperatures, drought and flood events, fishing bans, and other anthropogenic and climatic drivers. The results demonstrate that: (1) In the past five years, water quality in Lake Taihu has improved markedly. The annual mean total nitrogen concentration decreased from 3.71 mg/L in 2006 to 1.56 mg/L in 2025. The annual mean total phosphorus concentration from 2021 to 2025 (0. 089 mg/L) was 26% lower than the mean from 2005 to 2020 (0.120 mg/L). Pronounced spatial disparities in water quality improvement were observed: heavily polluted northwestern areas exhibited substantial amelioration, whereas southern and eastern areas, historically characterized by better water quality and extensive submerged vegetation, displayed negligible improvement or even degradation. (2) Major biotic assemblages exhibited substantial spatiotemporal dynamics. Since 2023, cyanobacterial biomass has declined significantly, accompanied by a marked reduction in both biomass and dominance of Microcystis spp. —the primary bloom-forming cyanobacterium—while the dominance of filamentous cyanobacteria such as Dolichospermum spp. and Pseudanabaena spp. , as well as diatoms including Aulacoseira spp. , Cyclotella spp. , and Nitzschia spp. , has increased. Within the zooplankton community, the dominance of Bosmina spp. (Cladocera) has diminished considerably, whereas that of Limnoithona sinensis(Copepoda) has risen significantly. Macroinvertebrate density has declined sharply, primarily attributable to a substantial reduction in the dominant pollution-tolerant species Limnodrilus hoffmeisteri, while the dominance and density of the relatively clean-water species Corbicula fluminea have increased notably. Conversely, submerged vegetation remains severely degraded compared to 20 years ago, showing no significant recovery despite recent water quality improvements. Relative to 2014, the distribution area of submerged vegetation in 2025 contracted sharply. The population of Potamogeton wrightii within the traditional submerged vegetation zone along the transect from Guishan to Manshan Island, Xishan, and South Lake Taihu has undergone drastic shrinkage. In East Lake Taihu, submerged plant communities have been largely supplanted by Trapa incisa, forming a continuous monoculture frequently exceeding 95% coverage. The Nymphoides peltata community in South Lake Taihu has experienced severe decline, and vegetation coverage in Xukou Bay also decreased significantly in 2025. (3) From the perspective of ecological diversity, with the exception of phytoplankton, the diversity of most biotic groups has not increased significantly, spatial heterogeneity has diminished, and submerged vegetation remains critically degraded. Consequently, the ecosystem structure of Lake Taihu remains highly vulnerable, with a persistent risk of large-scale cyanobacterial blooms. This study suggests that the management of Lake Taihu may have entered a new phase characterized by “improved water quality—ecosystem restructuring—insufficient system resilience”. While reduced nutrient loading into the lake exerts significant top-down regulation on ecosystem structure, climate warming, declining external nutrient loading, fishing bans, and extreme climatic events such as floods and droughts have emerged as pivotal drivers of biotic shifts. Future management strategies for Lake Taihu should transition from “achieving water quality standards” to “restoring ecosystem health”. It is imperative to strengthen the monitoring and assessment of ecological effects stemming from fish community alterations. While maintaining stringent control over external nitrogen and phosphorus inputs, coordinated measures should be implemented to optimize fish community structure and restore submerged vegetation, thereby enhancing the overall health and resilience of the Lake Taihu ecosystem.
Over the past two decades, Lake Taihu has undergone intensive remediation and restoration, compounded by climate change impacts such as warming and heatwaves, driving significant shifts in the composition and structure of its aquatic ecosystem, encompassing phytoplankton, zooplankton, benthic macroinvertebrates, and macrophytes. Leveraging long-term monitoring data from the Taihu Laboratory for Lake Ecosystem Research (TLLER), a National Scientific Observation and Research Station, including water quality, phytoplankton, and macrophyte data spanning 2005 to 2025, macroinvertebrate data from 2007 to 2025, zooplankton data from 2012 to 2025, alongside concurrent hydrological and meteorological observations, this study elucidates the characteristics and underlying mechanisms governing the structural changes in the Lake Taihu ecosystem over the past two decades under the combined influences of declining nitrogen concentrations, rising water temperatures, drought and flood events, fishing bans, and other anthropogenic and climatic drivers. The results demonstrate that: (1) In the past five years, water quality in Lake Taihu has improved markedly. The annual mean total nitrogen concentration decreased from 3.71 mg/L in 2006 to 1.56 mg/L in 2025. The annual mean total phosphorus concentration from 2021 to 2025 (0. 089 mg/L) was 26% lower than the mean from 2005 to 2020 (0.120 mg/L). Pronounced spatial disparities in water quality improvement were observed: heavily polluted northwestern areas exhibited substantial amelioration, whereas southern and eastern areas, historically characterized by better water quality and extensive submerged vegetation, displayed negligible improvement or even degradation. (2) Major biotic assemblages exhibited substantial spatiotemporal dynamics. Since 2023, cyanobacterial biomass has declined significantly, accompanied by a marked reduction in both biomass and dominance of Microcystis spp. —the primary bloom-forming cyanobacterium—while the dominance of filamentous cyanobacteria such as Dolichospermum spp. and Pseudanabaena spp. , as well as diatoms including Aulacoseira spp. , Cyclotella spp. , and Nitzschia spp. , has increased. Within the zooplankton community, the dominance of Bosmina spp. (Cladocera) has diminished considerably, whereas that of Limnoithona sinensis(Copepoda) has risen significantly. Macroinvertebrate density has declined sharply, primarily attributable to a substantial reduction in the dominant pollution-tolerant species Limnodrilus hoffmeisteri, while the dominance and density of the relatively clean-water species Corbicula fluminea have increased notably. Conversely, submerged vegetation remains severely degraded compared to 20 years ago, showing no significant recovery despite recent water quality improvements. Relative to 2014, the distribution area of submerged vegetation in 2025 contracted sharply. The population of Potamogeton wrightii within the traditional submerged vegetation zone along the transect from Guishan to Manshan Island, Xishan, and South Lake Taihu has undergone drastic shrinkage. In East Lake Taihu, submerged plant communities have been largely supplanted by Trapa incisa, forming a continuous monoculture frequently exceeding 95% coverage. The Nymphoides peltata community in South Lake Taihu has experienced severe decline, and vegetation coverage in Xukou Bay also decreased significantly in 2025. (3) From the perspective of ecological diversity, with the exception of phytoplankton, the diversity of most biotic groups has not increased significantly, spatial heterogeneity has diminished, and submerged vegetation remains critically degraded. Consequently, the ecosystem structure of Lake Taihu remains highly vulnerable, with a persistent risk of large-scale cyanobacterial blooms. This study suggests that the management of Lake Taihu may have entered a new phase characterized by “improved water quality—ecosystem restructuring—insufficient system resilience”. While reduced nutrient loading into the lake exerts significant top-down regulation on ecosystem structure, climate warming, declining external nutrient loading, fishing bans, and extreme climatic events such as floods and droughts have emerged as pivotal drivers of biotic shifts. Future management strategies for Lake Taihu should transition from “achieving water quality standards” to “restoring ecosystem health”. It is imperative to strengthen the monitoring and assessment of ecological effects stemming from fish community alterations. While maintaining stringent control over external nitrogen and phosphorus inputs, coordinated measures should be implemented to optimize fish community structure and restore submerged vegetation, thereby enhancing the overall health and resilience of the Lake Taihu ecosystem.
Wang Jingfu, Yang Haiquan, Zeng Yan, Yin Chao, Chen Quan, Ma Yiming, Fang Jinlong, Zhang Yuting, Li Qiuhua, Li Yulin, Chen Jing'an
2026,38(4):1351-1363, DOI: 10.18307/2026.0404
Abstract:
Over the past 15 years, the Lake Hongfeng Reservoir Ecosystem Field Scientific Observation and Research Station in Guizhou Province has developed into an integrated field platform for monitoring, research, demonstration, and service focused on plateau deep-water reservoirs. Addressing key scientific and technological challenges related to water resource utilization, water security, and aquatic ecological restoration in southwestern China, and building upon long-term, multi-parameter, fixed-site observations of typical reservoirs, this study synthesizes the station's main research achievements: (1) It clarified that reservoir ecosystems possess distinct eco-environmental features—such as great depth, multiple interfaces, inverse seasonal water-level fluctuations, and degradation of the drawdown zone—that significantly differentiate them from natural lakes. (2) It revealed the spatiotemporal dynamics of water quality and eutrophication in Guiyang's Lake Hongfeng and Lake Baihua from 2009 to 2025. (3) From 2003 to 2020, it quantified the relative contributions and mechanisms of climate change and nitrogen/phosphorus nutrients in driving algal blooms in lakes/reservoirs, underscoring the urgency of eutrophication control under a changing climate. (4) It discovered and demonstrated a dissolved inorganic carbon fertilization effect in karst reservoirs, which promotes phytoplankton succession from diatoms and chlorophytes to cyanobacteria, thereby elevating the risk of cyanobacterial blooms. (5) A multi-isotope tracing system was established, including dual-carbon isotopes (δ13C-Δ14C), nitrate nitrogen and oxygen isotopes (δ15N-δ18O), and phosphate oxygen isotopes (δ18Op), providing crucial technical support for precise pollution source identification in watersheds. (6) Using independently developed in situ high-resolution observation technology for the sediment-water interface, the study quantified the phosphorus release flux at this interface in typical reservoirs and identified seasonally hypoxiadriven reductive dissolution of iron-bound phosphorus as a key mechanism of internal phosphorus loading. (7) A suite of ecological restoration technologies and materials—such as in situ sediment passivation, aerated bubble-plume oxygenation, and oxygen nanobubble-enhanced interface re-aeration—were developed and applied in typical reservoirs. Based on these findings, future research priorities for the Lake Hongfeng Station are proposed. Collectively, these outcomes provide important scientific and technological support for safeguarding water resources and water environment security in southwestern China.
Over the past 15 years, the Lake Hongfeng Reservoir Ecosystem Field Scientific Observation and Research Station in Guizhou Province has developed into an integrated field platform for monitoring, research, demonstration, and service focused on plateau deep-water reservoirs. Addressing key scientific and technological challenges related to water resource utilization, water security, and aquatic ecological restoration in southwestern China, and building upon long-term, multi-parameter, fixed-site observations of typical reservoirs, this study synthesizes the station's main research achievements: (1) It clarified that reservoir ecosystems possess distinct eco-environmental features—such as great depth, multiple interfaces, inverse seasonal water-level fluctuations, and degradation of the drawdown zone—that significantly differentiate them from natural lakes. (2) It revealed the spatiotemporal dynamics of water quality and eutrophication in Guiyang's Lake Hongfeng and Lake Baihua from 2009 to 2025. (3) From 2003 to 2020, it quantified the relative contributions and mechanisms of climate change and nitrogen/phosphorus nutrients in driving algal blooms in lakes/reservoirs, underscoring the urgency of eutrophication control under a changing climate. (4) It discovered and demonstrated a dissolved inorganic carbon fertilization effect in karst reservoirs, which promotes phytoplankton succession from diatoms and chlorophytes to cyanobacteria, thereby elevating the risk of cyanobacterial blooms. (5) A multi-isotope tracing system was established, including dual-carbon isotopes (δ13C-Δ14C), nitrate nitrogen and oxygen isotopes (δ15N-δ18O), and phosphate oxygen isotopes (δ18Op), providing crucial technical support for precise pollution source identification in watersheds. (6) Using independently developed in situ high-resolution observation technology for the sediment-water interface, the study quantified the phosphorus release flux at this interface in typical reservoirs and identified seasonally hypoxiadriven reductive dissolution of iron-bound phosphorus as a key mechanism of internal phosphorus loading. (7) A suite of ecological restoration technologies and materials—such as in situ sediment passivation, aerated bubble-plume oxygenation, and oxygen nanobubble-enhanced interface re-aeration—were developed and applied in typical reservoirs. Based on these findings, future research priorities for the Lake Hongfeng Station are proposed. Collectively, these outcomes provide important scientific and technological support for safeguarding water resources and water environment security in southwestern China.
Yu Haihao, Wang Ligong, Lv Tian, Fan Shufeng, Zuo Zhenjun, Wang Zhong, Yu Dan, Xu Xinwei, Liu Chunhua
2026,38(4):1364-1370, DOI: 10.18307/2026.0405
Abstract:
As a critical component of freshwater ecosystems, aquatic plants play an essential role in sustaining the structure, function, and stability of ecosystems. However, under global change scenarios, aquatic plants are confronted with multiple stressors, including eutrophication, climate warming, emerging pollutants, and biological invasions, which have led to a significant decline in aquatic vegetation, particularly submerged macrophytes. Based on systematic research findings accumulated over the years from the Liangzi Lake National Field Station for Scientific Observation and Research, Wuhan University, this paper comprehensively reviews the major advances in the ecology of aquatic plants and their ecosystem functions across the individual, population, community, and ecosystem scales. At the individual and population levels, we revealed the environmental regulatory mechanisms of ecological stoichiometry in aquatic plants and elucidated the adaptive strategies of clonal integration and functional traits in response to heterogeneous habitats. At the community level, we analyzed the key regulatory factors governing the relationship between biodiversity and productivity, as well as the mechanisms underlying interspecific interactions. In the field of invasion ecology, we systematically clarified the driving mechanisms of exotic aquatic plant invasions under the combined effects of environmental change and biotic interactions, and evaluated the ecological impacts of exotic plants on material cycling, epiphytic communities, and pollutant responses. In terms of genetic evolution, we comprehensively employed multi-omics approaches to uncover the phylogeographic patterns, local adaptation mechanisms, and invasion potential of aquatic plants. In the context of ecological restoration, long-term in situ monitoring and restoration practices have verified the effectiveness of submerged vegetation reconstruction in controlling internal nitrogen and phosphorus loading, and new insights into combined remediation technologies and biological regulation strategies were proposed. These studies not only deepen the theoretical understanding of the relationship between the ecological adaptation of aquatic plants and ecosystem functions but also provide an important theoretical basis and practical guidance for the conservation, restoration, and sustainable management of freshwater ecosystems.
As a critical component of freshwater ecosystems, aquatic plants play an essential role in sustaining the structure, function, and stability of ecosystems. However, under global change scenarios, aquatic plants are confronted with multiple stressors, including eutrophication, climate warming, emerging pollutants, and biological invasions, which have led to a significant decline in aquatic vegetation, particularly submerged macrophytes. Based on systematic research findings accumulated over the years from the Liangzi Lake National Field Station for Scientific Observation and Research, Wuhan University, this paper comprehensively reviews the major advances in the ecology of aquatic plants and their ecosystem functions across the individual, population, community, and ecosystem scales. At the individual and population levels, we revealed the environmental regulatory mechanisms of ecological stoichiometry in aquatic plants and elucidated the adaptive strategies of clonal integration and functional traits in response to heterogeneous habitats. At the community level, we analyzed the key regulatory factors governing the relationship between biodiversity and productivity, as well as the mechanisms underlying interspecific interactions. In the field of invasion ecology, we systematically clarified the driving mechanisms of exotic aquatic plant invasions under the combined effects of environmental change and biotic interactions, and evaluated the ecological impacts of exotic plants on material cycling, epiphytic communities, and pollutant responses. In terms of genetic evolution, we comprehensively employed multi-omics approaches to uncover the phylogeographic patterns, local adaptation mechanisms, and invasion potential of aquatic plants. In the context of ecological restoration, long-term in situ monitoring and restoration practices have verified the effectiveness of submerged vegetation reconstruction in controlling internal nitrogen and phosphorus loading, and new insights into combined remediation technologies and biological regulation strategies were proposed. These studies not only deepen the theoretical understanding of the relationship between the ecological adaptation of aquatic plants and ecosystem functions but also provide an important theoretical basis and practical guidance for the conservation, restoration, and sustainable management of freshwater ecosystems.
Xu Hai, Lian Gang, Wu Zhixu, Zhu Mengyuan, Li Huiyun, Shi Kun, Zhang Yunlin, Qin Boqiang, Zhu Guangwei
2026,38(4):1371-1389, DOI: 10.18307/2026.0406
Abstract:
As artificial lakes, reservoirs in China have reached a scale comparable to natural lakes in both number and impounded water volume, constituting a crucial component of the country's manageable surface water resources. The hydrological processes, topography, and management of reservoirs differ significantly from those of natural lakes. Ecologically, reservoirs exhibit hybrid characteristics of riverine and lacustrine ecosystems, resulting in unique limnological mechanisms. Therefore, establishing scientific observation stations to conduct long-term ecological monitoring, in-situ experiments, and restoration technology development is essential for ensuring the ecological security and sustainable utilization of reservoir resources. Taking the 20-year achievements of the Lake Qiandao Ecosystem Research Station (QERS) of the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, as an example, this paper analyzes the progress and research hotspots in large deep-water reservoir ecology. Monitoring of water quality and ecological indicators over the past five years shows that water quality of Lake Qiandao is generally stable at an oligotrophic to mesotrophic state, but key monitoring sections still face risks such as water quality fluctuations and localized abnormal algal proliferation. Stratification of environmental indicators, particularly thermal stratification, is distinct, showing significant seasonal variation and interannual fluctuation. Meteorological and hydrological events (warming, heavy precipitation, high-temperature droughts) as well as human activities (reservoir fishery management, watershed land use changes) have profound impacts on the water quality and ecology of Lake Qiandao. Based on these observations and studies, this paper systematically summarizes the theoretical understanding of QERS regarding thermal stratification dynamics, ecological effects of extreme climate, multi-interface cycling of carbon, nitrogen and phosphorus, phytoplankton community succession, and fish ecological effects. The monitoring, early warning, and ecological restoration technologies developed by QERS have demonstrated significant value for protecting similar source-water reservoirs in China. Looking forward, research priorities for the aquatic ecosystem of Lake Qiandao include: water quality assurance technologies for source-water reservoirs; ecological effects of physical environmental changes in reservoirs; food web structure and ecological regulation in large reservoirs; carbon cycling and greenhouse gas emissions in deep-water reservoirs; and digital twin and AI-driven management systems for reservoir water environments.
As artificial lakes, reservoirs in China have reached a scale comparable to natural lakes in both number and impounded water volume, constituting a crucial component of the country's manageable surface water resources. The hydrological processes, topography, and management of reservoirs differ significantly from those of natural lakes. Ecologically, reservoirs exhibit hybrid characteristics of riverine and lacustrine ecosystems, resulting in unique limnological mechanisms. Therefore, establishing scientific observation stations to conduct long-term ecological monitoring, in-situ experiments, and restoration technology development is essential for ensuring the ecological security and sustainable utilization of reservoir resources. Taking the 20-year achievements of the Lake Qiandao Ecosystem Research Station (QERS) of the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, as an example, this paper analyzes the progress and research hotspots in large deep-water reservoir ecology. Monitoring of water quality and ecological indicators over the past five years shows that water quality of Lake Qiandao is generally stable at an oligotrophic to mesotrophic state, but key monitoring sections still face risks such as water quality fluctuations and localized abnormal algal proliferation. Stratification of environmental indicators, particularly thermal stratification, is distinct, showing significant seasonal variation and interannual fluctuation. Meteorological and hydrological events (warming, heavy precipitation, high-temperature droughts) as well as human activities (reservoir fishery management, watershed land use changes) have profound impacts on the water quality and ecology of Lake Qiandao. Based on these observations and studies, this paper systematically summarizes the theoretical understanding of QERS regarding thermal stratification dynamics, ecological effects of extreme climate, multi-interface cycling of carbon, nitrogen and phosphorus, phytoplankton community succession, and fish ecological effects. The monitoring, early warning, and ecological restoration technologies developed by QERS have demonstrated significant value for protecting similar source-water reservoirs in China. Looking forward, research priorities for the aquatic ecosystem of Lake Qiandao include: water quality assurance technologies for source-water reservoirs; ecological effects of physical environmental changes in reservoirs; food web structure and ecological regulation in large reservoirs; carbon cycling and greenhouse gas emissions in deep-water reservoirs; and digital twin and AI-driven management systems for reservoir water environments.
2026,38(4):1390-1403, DOI: 10.18307/2026.0407
Abstract:
Fatty acids are key biomarkers that act as essential energy substrates and structural components for aquatic organisms while displaying conserved, taxon-specific profiles across primary producer groups, making them effective tracers of nutritional sources and energy flow in aquatic ecosystems. Zooplankton, as critical links between primary producers and higher trophic levels, exhibit fatty acid compositions that reflect dietary quality and utilization efficiency, thereby governing the ecological efficiency of energy transfer to upper food webs. Lake Erhai, the second-largest plateau freshwater lake in Yunnan Province, China, has experienced increasing eutrophication and frequent cyanobacterial blooms in recent years, yet studies on zooplankton fatty acids in this lake remain limited. To examine seasonal variation in zooplankton fatty acid composition and its environmental drivers, four dominant species—Mesocyclops leuckarti, Daphnia galeata, Phyllodiaptomus tunguidus, and Bosmina longirostris—were collected monthly from July to October 2025 at five sampling sites in Lake Erhai. Fatty acids were analyzed by gas chromatography-mass spectrometry (GC-MS), and permutational multivariate analysis of variance (PERMANOVA), similarity percentage analysis (SIMPER), and redundancy analysis were used to evaluate the effects of month, species, site, and environmental variables. Results indicated that: (1) month was the primary factor shaping fatty acid composition, accounting for 40.93% of variance (PERMANOVA, F=25.827, P<0.0001), with no significant main effects of species (R2=0.035, P=0.195) or site (R2=0.059, P=0.082); (2) phytoplankton community composition strongly influenced particulate organic matter (POM) fatty acid quality, with diatoms (especially Cyclotella) and Cryptomonas positively correlated with polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA); (3) variance partitioning showed that POM fatty acids and environmental variables together explained 54.25% of zooplankton fatty acid variance, with pure effects of 28.43% (P=0.001) and 14.28% (P=0.006), respectively, and water temperature as the most influential single factor (R2=0.141, P=0.001); (4) SIMPER analysis revealed that declining water temperature significantly increased zooplankton polyunsaturated fatty acid (PUFA) abundance, with EPA rising from 3.78% in July to 7.86% in October and ARA from 3.41% in September to 9.51% in October, while saturated fatty acids (stearic acid, 18:0; palmitic acid, 16:0) decreased; (5) a temporal lag existed between peak fatty acid quality in POM and zooplankton: POM PUFA peaked at 60.22% in September and fell to 34.68% in October, whereas zooplankton EPA and ARA peaked in October, indicating delayed trophic transfer. These findings clarify seasonal dynamics and drivers of zooplankton fatty acids in a eutrophic plateau lake, providing a scientific basis for understanding nutrient transfer mechanisms in lake food webs.
Fatty acids are key biomarkers that act as essential energy substrates and structural components for aquatic organisms while displaying conserved, taxon-specific profiles across primary producer groups, making them effective tracers of nutritional sources and energy flow in aquatic ecosystems. Zooplankton, as critical links between primary producers and higher trophic levels, exhibit fatty acid compositions that reflect dietary quality and utilization efficiency, thereby governing the ecological efficiency of energy transfer to upper food webs. Lake Erhai, the second-largest plateau freshwater lake in Yunnan Province, China, has experienced increasing eutrophication and frequent cyanobacterial blooms in recent years, yet studies on zooplankton fatty acids in this lake remain limited. To examine seasonal variation in zooplankton fatty acid composition and its environmental drivers, four dominant species—Mesocyclops leuckarti, Daphnia galeata, Phyllodiaptomus tunguidus, and Bosmina longirostris—were collected monthly from July to October 2025 at five sampling sites in Lake Erhai. Fatty acids were analyzed by gas chromatography-mass spectrometry (GC-MS), and permutational multivariate analysis of variance (PERMANOVA), similarity percentage analysis (SIMPER), and redundancy analysis were used to evaluate the effects of month, species, site, and environmental variables. Results indicated that: (1) month was the primary factor shaping fatty acid composition, accounting for 40.93% of variance (PERMANOVA, F=25.827, P<0.0001), with no significant main effects of species (R2=0.035, P=0.195) or site (R2=0.059, P=0.082); (2) phytoplankton community composition strongly influenced particulate organic matter (POM) fatty acid quality, with diatoms (especially Cyclotella) and Cryptomonas positively correlated with polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA); (3) variance partitioning showed that POM fatty acids and environmental variables together explained 54.25% of zooplankton fatty acid variance, with pure effects of 28.43% (P=0.001) and 14.28% (P=0.006), respectively, and water temperature as the most influential single factor (R2=0.141, P=0.001); (4) SIMPER analysis revealed that declining water temperature significantly increased zooplankton polyunsaturated fatty acid (PUFA) abundance, with EPA rising from 3.78% in July to 7.86% in October and ARA from 3.41% in September to 9.51% in October, while saturated fatty acids (stearic acid, 18:0; palmitic acid, 16:0) decreased; (5) a temporal lag existed between peak fatty acid quality in POM and zooplankton: POM PUFA peaked at 60.22% in September and fell to 34.68% in October, whereas zooplankton EPA and ARA peaked in October, indicating delayed trophic transfer. These findings clarify seasonal dynamics and drivers of zooplankton fatty acids in a eutrophic plateau lake, providing a scientific basis for understanding nutrient transfer mechanisms in lake food webs.
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Available online: July 15, 2026
Abstract:
Cylindrospermopsis raciborskii is a bloom-forming cyanobacterium that has attracted global attention following Microcystis and is currently expanding rapidly in southern China. To investigate the distribution patterns and driving factors of C. raciborskii in this area, a field survey was conducted during the dry season in 100 reservoirs across seven river basins of Guangdong Province. The abundance of C. raciborskii was quantified using Real-time quantitative PCR targeting the rpoC1 gene. The results showed that C. raciborskii was detected in all collected samples, with abundances ranging from 4.98×10? to 4.23×10? cells/L. The abundance varied by up to four orders of magnitude among reservoirs, indicating substantial spatial variability in population size. Principal component analysis revealed that spatial variation in environmental factors among reservoirs across river basins in Guangdong Province was primarily driven by nitrogen, phosphorus, and water temperature. At the basin scale, the mean abundance of C. raciborskii in the Pearl River Delta and the western Guangdong coastal river basins was significantly higher than that in the Xijiang, Hanjiang, and Beijiang basins. These two basins were also the most severely affected by C. raciborskii blooms, with heavy blooms occurring in 10 reservoirs. According to the Australian risk classification system for cyanobacterial blooms based on C. raciborskii abundance, 53% of the surveyed reservoirs were categorized as low risk, whereas 23% were classified as Alert Level 2. The binary classification machine learning models of Extreme Gradient Boosting (XGBoost) and Random Forest (RF) together with multiple linear stepwise regression analysis indicated a significant positive relationship between the C. raciborskii abundance and trophic state index (TSI). These results suggest that eutrophication level is the primary driver of the spatial variation in C. raciborskii abundance among reservoirs in Guangdong Province.
Cylindrospermopsis raciborskii is a bloom-forming cyanobacterium that has attracted global attention following Microcystis and is currently expanding rapidly in southern China. To investigate the distribution patterns and driving factors of C. raciborskii in this area, a field survey was conducted during the dry season in 100 reservoirs across seven river basins of Guangdong Province. The abundance of C. raciborskii was quantified using Real-time quantitative PCR targeting the rpoC1 gene. The results showed that C. raciborskii was detected in all collected samples, with abundances ranging from 4.98×10? to 4.23×10? cells/L. The abundance varied by up to four orders of magnitude among reservoirs, indicating substantial spatial variability in population size. Principal component analysis revealed that spatial variation in environmental factors among reservoirs across river basins in Guangdong Province was primarily driven by nitrogen, phosphorus, and water temperature. At the basin scale, the mean abundance of C. raciborskii in the Pearl River Delta and the western Guangdong coastal river basins was significantly higher than that in the Xijiang, Hanjiang, and Beijiang basins. These two basins were also the most severely affected by C. raciborskii blooms, with heavy blooms occurring in 10 reservoirs. According to the Australian risk classification system for cyanobacterial blooms based on C. raciborskii abundance, 53% of the surveyed reservoirs were categorized as low risk, whereas 23% were classified as Alert Level 2. The binary classification machine learning models of Extreme Gradient Boosting (XGBoost) and Random Forest (RF) together with multiple linear stepwise regression analysis indicated a significant positive relationship between the C. raciborskii abundance and trophic state index (TSI). These results suggest that eutrophication level is the primary driver of the spatial variation in C. raciborskii abundance among reservoirs in Guangdong Province.
Available online: July 14, 2026
Abstract:
Current is the core driver of energy and material transport in lake systems and exerts a decisive influence on the distribution of pollutants, algae, and fish. Clarifying the spatiotemporal variability of lake currents is essential for understanding the mechanisms underlying lake ecological and environmental problems and for supporting precise management strategies. Based on high-frequency synchronous observations of wind and current fields from 20 automatic monitoring stations in Lake Chaohu in 2024, this study systematically analyzed the spatiotemporal characteristics of the wind and current fields and explored their response relationships and driving mechanisms. Vector decomposition, Pearson correlation analysis, and circular statistical methods were employed to construct indices including the coefficient of variation of current velocity, directional dispersion coefficient, and composite current velocity ratio, thereby quantitatively evaluating current stability and dynamic characteristics across multiple temporal scales.The results indicate that the wind field over Lake Chaohu is controlled by the East Asian monsoon circulation and exhibits pronounced seasonal transition characteristics. In 2024, the basin-wide mean wind speed was approximately 3.4 m/s, with easterly winds prevailing in spring, southerly winds in summer, northeasterly winds in autumn, and northerly winds in winter. The current field in Lake Chaohu generally exhibited a weak “west-in–east-out” transport pattern, with mean current velocities at individual stations ranging from 3.75 to 9.27 cm/s and a basin-wide mean of 5.18 cm/s. High-velocity zones were mainly distributed in river inflow and outflow estuaries and flow passages on both sides of Laoshan Island, whereas the northwestern lake region, central lake area, and some nearshore zones remained under low-velocity conditions.Vertical current velocities in Lake Chaohu were only on the order of mm/s, indicating limited vertical exchange capacity. The current field exhibited significant fluctuations across seasonal, monthly, and daily scales. Basin-wide vector-averaged current velocities in spring and summer were 0.92 cm/s and 0.89 cm/s, respectively, both substantially higher than the 0.53 cm/s observed in autumn and winter. During the “Yangtze River-to-Lake Chaohu Water Diversion Project” period, daily mean current velocities in the Zhao River inflow region remained between 9.69 and 14.82 cm/s. At eight national monitoring stations, the mean coefficient of variation of current velocity reached 94.06%, the directional dispersion coefficient ranged from 73.5% to 95.8%, and the mean composite current velocity ratio was only 0.28, indicating that the Lake Chaohu current field is characterized by “low velocity, high variability, and strong directional dispersion.”Wind speed and current velocity showed a significant positive correlation overall (p < 0.01), indicating that wind forcing is the primary driver controlling current variability in Lake Chaohu. However, substantial differences were observed in the response intensity of currents to wind forcing among different sites, suggesting that the current field structure is jointly influenced by multiple factors, including lake basin morphology and inflow–outflow discharge conditions. These findings provide a scientific basis for hydrodynamic regulation, identification of weak-flow retention zones, and the prevention and control of eutrophication and algal blooms in shallow lakes.
Current is the core driver of energy and material transport in lake systems and exerts a decisive influence on the distribution of pollutants, algae, and fish. Clarifying the spatiotemporal variability of lake currents is essential for understanding the mechanisms underlying lake ecological and environmental problems and for supporting precise management strategies. Based on high-frequency synchronous observations of wind and current fields from 20 automatic monitoring stations in Lake Chaohu in 2024, this study systematically analyzed the spatiotemporal characteristics of the wind and current fields and explored their response relationships and driving mechanisms. Vector decomposition, Pearson correlation analysis, and circular statistical methods were employed to construct indices including the coefficient of variation of current velocity, directional dispersion coefficient, and composite current velocity ratio, thereby quantitatively evaluating current stability and dynamic characteristics across multiple temporal scales.The results indicate that the wind field over Lake Chaohu is controlled by the East Asian monsoon circulation and exhibits pronounced seasonal transition characteristics. In 2024, the basin-wide mean wind speed was approximately 3.4 m/s, with easterly winds prevailing in spring, southerly winds in summer, northeasterly winds in autumn, and northerly winds in winter. The current field in Lake Chaohu generally exhibited a weak “west-in–east-out” transport pattern, with mean current velocities at individual stations ranging from 3.75 to 9.27 cm/s and a basin-wide mean of 5.18 cm/s. High-velocity zones were mainly distributed in river inflow and outflow estuaries and flow passages on both sides of Laoshan Island, whereas the northwestern lake region, central lake area, and some nearshore zones remained under low-velocity conditions.Vertical current velocities in Lake Chaohu were only on the order of mm/s, indicating limited vertical exchange capacity. The current field exhibited significant fluctuations across seasonal, monthly, and daily scales. Basin-wide vector-averaged current velocities in spring and summer were 0.92 cm/s and 0.89 cm/s, respectively, both substantially higher than the 0.53 cm/s observed in autumn and winter. During the “Yangtze River-to-Lake Chaohu Water Diversion Project” period, daily mean current velocities in the Zhao River inflow region remained between 9.69 and 14.82 cm/s. At eight national monitoring stations, the mean coefficient of variation of current velocity reached 94.06%, the directional dispersion coefficient ranged from 73.5% to 95.8%, and the mean composite current velocity ratio was only 0.28, indicating that the Lake Chaohu current field is characterized by “low velocity, high variability, and strong directional dispersion.”Wind speed and current velocity showed a significant positive correlation overall (p < 0.01), indicating that wind forcing is the primary driver controlling current variability in Lake Chaohu. However, substantial differences were observed in the response intensity of currents to wind forcing among different sites, suggesting that the current field structure is jointly influenced by multiple factors, including lake basin morphology and inflow–outflow discharge conditions. These findings provide a scientific basis for hydrodynamic regulation, identification of weak-flow retention zones, and the prevention and control of eutrophication and algal blooms in shallow lakes.
Available online: July 13, 2026
Abstract:
Studying water-level amplitude in plateau shallow lakes provides a critical perspective for understanding human–environment interactions and associated ecological risks. However, long-term continuous records of lake-level variation are scarce due to the relatively late establishment of modern monitoring. Using Qilu Lake in Yunnan Province as a case study, this research synthesizes multiple lines of evidence—including settlement distribution, palaeoshoreline geomorphology, historical documents, early maps, and remote sensing—to reconstruct seasonal lake extents (wet and dry seasons) for six representative years (1284, 1523, 1691, 1798, 1894, and 1937). Combined with documentary records, we further derive a characteristic series of water-level amplitude for the period 1284–1955. The results show that the main basin morphology remained generally stable under topographic constraints, while changes in lake extent were concentrated in reclamation-prone areas such as the shoals and deltaic margins along the western shore and the southern and northern shores. These changes are manifested as outward advancement of embankment lines and progressive enclosure of bays, with a gradual reduction in the space available for wet-season lake expansion. Over the past 600 years, the water-level amplitude of Qilu Lake exhibits a step-like decline superimposed on internal variability. Two notable downward shifts occurred around 1523 and 1691, marking phase changes in amplitude, whereas strong human intervention in outflow channels around 1894 did not trigger such a shift. Mechanism analysis indicates that variations in water-level amplitude were jointly driven by climatic windows and engineered interventions, with governance capacity acting as a key mediator. Specifically, warm–dry climatic phases provided implementation windows for reclamation, dredging, and outlet modification by lowering lake levels and promoting the stabilization of exposed lakebeds. Whether a downward shift in amplitude occurred depended on whether institutions could translate such short-term interventions into sustained engineering practices and maintain their effects over time. This study offers a traceable, process-based framework for identifying historical phase shifts and evaluating governance pathways in plateau shallow lakes.
Studying water-level amplitude in plateau shallow lakes provides a critical perspective for understanding human–environment interactions and associated ecological risks. However, long-term continuous records of lake-level variation are scarce due to the relatively late establishment of modern monitoring. Using Qilu Lake in Yunnan Province as a case study, this research synthesizes multiple lines of evidence—including settlement distribution, palaeoshoreline geomorphology, historical documents, early maps, and remote sensing—to reconstruct seasonal lake extents (wet and dry seasons) for six representative years (1284, 1523, 1691, 1798, 1894, and 1937). Combined with documentary records, we further derive a characteristic series of water-level amplitude for the period 1284–1955. The results show that the main basin morphology remained generally stable under topographic constraints, while changes in lake extent were concentrated in reclamation-prone areas such as the shoals and deltaic margins along the western shore and the southern and northern shores. These changes are manifested as outward advancement of embankment lines and progressive enclosure of bays, with a gradual reduction in the space available for wet-season lake expansion. Over the past 600 years, the water-level amplitude of Qilu Lake exhibits a step-like decline superimposed on internal variability. Two notable downward shifts occurred around 1523 and 1691, marking phase changes in amplitude, whereas strong human intervention in outflow channels around 1894 did not trigger such a shift. Mechanism analysis indicates that variations in water-level amplitude were jointly driven by climatic windows and engineered interventions, with governance capacity acting as a key mediator. Specifically, warm–dry climatic phases provided implementation windows for reclamation, dredging, and outlet modification by lowering lake levels and promoting the stabilization of exposed lakebeds. Whether a downward shift in amplitude occurred depended on whether institutions could translate such short-term interventions into sustained engineering practices and maintain their effects over time. This study offers a traceable, process-based framework for identifying historical phase shifts and evaluating governance pathways in plateau shallow lakes.
Available online: July 13, 2026
Abstract:
Potential evapotranspiration (PET) is a key parameter in hydrological cycle and ecological process research, and is currently mostly calculated using the Penman-Monteith (P-M) equation. However, direct measurement of PET is usually difficult, resulting in a lack of empirical verification for calculation results and unknown uncertainty. Based on the underlying surface characteristics of the Poyang Lake floodplain wetland, this study used latent heat flux observation data from an eddy covariance system, drew on Granger"s (1989) conceptual analysis of potential evapotranspiration, and combined multiple accuracy evaluation indicators to test the calculation results of the P-M equation under different temperature input conditions. Comprehensive analysis shows that the PET values calculated by different methods are highly consistent with the measured data, but the PET using surface temperature as input is closest to the observed latent heat flux and can better reflect the temporal variation characteristics of potential evapotranspiration. This research result helps to further clarify the sensitivity of potential evapotranspiration to temperature, improve the reliability of calculation results, and has positive theoretical significance and practical reference value.
Potential evapotranspiration (PET) is a key parameter in hydrological cycle and ecological process research, and is currently mostly calculated using the Penman-Monteith (P-M) equation. However, direct measurement of PET is usually difficult, resulting in a lack of empirical verification for calculation results and unknown uncertainty. Based on the underlying surface characteristics of the Poyang Lake floodplain wetland, this study used latent heat flux observation data from an eddy covariance system, drew on Granger"s (1989) conceptual analysis of potential evapotranspiration, and combined multiple accuracy evaluation indicators to test the calculation results of the P-M equation under different temperature input conditions. Comprehensive analysis shows that the PET values calculated by different methods are highly consistent with the measured data, but the PET using surface temperature as input is closest to the observed latent heat flux and can better reflect the temporal variation characteristics of potential evapotranspiration. This research result helps to further clarify the sensitivity of potential evapotranspiration to temperature, improve the reliability of calculation results, and has positive theoretical significance and practical reference value.
Ke Senfan, ZHU Shilong, LI Dongqing, Duan Xinbin, Yu Lixiong, Gao Shenghui, JIAO Yilin, HU Yizhong, Cheng Bixin, Shi Xiaotao
Available online: July 13, 2026
Abstract:
The upstream post-dam movement strategies of fish constitute an important basis for evaluating habitat suitability in dam-affected river reaches. In particular, how the typical abrupt hydraulic characteristics of mountainous rivers influence post-dam upstream migration behaviour remains an urgent question to be addressed. In this study, two representative loach species from the Heishui River in the Jinsha River basin, the red-tailed loach Paracobitis variegatus and the short-bodied loach Paracobitis potanini, were selected as target species. Fish resources of the target species were investigated using net-capture surveys, and radio frequency identification (RFID) technology was applied to evaluate the post-dam upstream migration performance of the two loach species. A quantitative evaluation model of post-dam upstream migration performance for loaches was developed by coupling hydrological and hydrodynamic factors of the reservoir area, in order to identify the key factors influencing post-dam upstream migration performance and to establish response curves between upstream migration success and these key factors. The results showed that: (1) the fishway passage rates of the two loach species in 2022, 2023, and 2024 were 22.92%, 9.01%, and 7.00%, respectively; (2) after dam passage, loaches exhibited different proportions of habitat selection, with 85% remaining in the near-dam reservoir area, 15% continuing upstream to 0.7 km above the dam, and no loaches migrating to 1.3 km above the dam; (3) the dominant factors affecting post-dam upstream migration performance were fish species, river discharge, and river water temperature; (4) post-dam upstream migration success was significantly negatively correlated with river discharge and water temperature (P < 0.05), and the upstream migration success of P. potanini was significantly higher than that of P. variegatus (P < 0.05); and (5) surveys of post-dam loach distribution and substrate characteristics indicated that loaches were mainly distributed in areas characterized by mixed cobble and silt substrates. This study provides an important reference for ecological operation of small hydropower stations and post-dam habitat restoration in the Jinsha River basin.
The upstream post-dam movement strategies of fish constitute an important basis for evaluating habitat suitability in dam-affected river reaches. In particular, how the typical abrupt hydraulic characteristics of mountainous rivers influence post-dam upstream migration behaviour remains an urgent question to be addressed. In this study, two representative loach species from the Heishui River in the Jinsha River basin, the red-tailed loach Paracobitis variegatus and the short-bodied loach Paracobitis potanini, were selected as target species. Fish resources of the target species were investigated using net-capture surveys, and radio frequency identification (RFID) technology was applied to evaluate the post-dam upstream migration performance of the two loach species. A quantitative evaluation model of post-dam upstream migration performance for loaches was developed by coupling hydrological and hydrodynamic factors of the reservoir area, in order to identify the key factors influencing post-dam upstream migration performance and to establish response curves between upstream migration success and these key factors. The results showed that: (1) the fishway passage rates of the two loach species in 2022, 2023, and 2024 were 22.92%, 9.01%, and 7.00%, respectively; (2) after dam passage, loaches exhibited different proportions of habitat selection, with 85% remaining in the near-dam reservoir area, 15% continuing upstream to 0.7 km above the dam, and no loaches migrating to 1.3 km above the dam; (3) the dominant factors affecting post-dam upstream migration performance were fish species, river discharge, and river water temperature; (4) post-dam upstream migration success was significantly negatively correlated with river discharge and water temperature (P < 0.05), and the upstream migration success of P. potanini was significantly higher than that of P. variegatus (P < 0.05); and (5) surveys of post-dam loach distribution and substrate characteristics indicated that loaches were mainly distributed in areas characterized by mixed cobble and silt substrates. This study provides an important reference for ecological operation of small hydropower stations and post-dam habitat restoration in the Jinsha River basin.
Available online: July 08, 2026
Abstract:
Intense climate change and intensified human activities have profoundly altered river hydrological processes, exerting significant impacts on the health and security of fluvial aquatic ecosystems. Following the research paradigm of “spatiotemporal evolution?driving mechanism?causal pathways”, this study systematically analyzes the spatiotemporal variation characteristics and driving mechanisms of hydrological regime indices at 18 hydrological stations across the Nan?Beipan River Basin. The Bayesian Estimation of Abrupt change, Seasonality and Trend (BEAST) method is employed to identify non?stationarity and abrupt changes in runoff series, while the Indicators of Hydrologic Alteration?Range of Variability Approach (IHA?RVA) is used to quantify the degree of hydrological regime alteration before and after dam construction. Combined with Extreme Gradient Boosting?SHapley Additive exPlanations (XGBoost?SHAP), Optimal Multivariate Stratified Geodetector (OMGD) and Partial Least Squares?Structural Equation Modeling (PLS?SEM), this study further distinguishes single?factor, multi?factor effects and impact pathways of natural factors and human activities across the whole basin, regulated basins and natural basins. The results show that: (1) Abrupt runoff changes are highly consistent with regional drought and flood events; (2) Reservoir dams induce hydrological regime shifts characterized by decreased high?flow magnitudes and increased low?flow magnitudes, with dam?induced impacts gradually weakening with increasing distance; (3) XGBoost?SHAP results reveal that climatic factors dominate hydrological regime variations in different basins, whereas both OMGD and PLS?SEM indicate that coupled interactions between climate and river network/landscape/human activities are the primary controlling factors for the whole basin, regulated basins and natural basins respectively. Topography, lithology, soil and other factors only affect partial hydrological regime indices. Overall, hydrological regime indices in the karst Nan?Beipan River Basin exhibit nonlinear responses to climatic and underlying surface factors. Regulated basins are mainly governed by the “climate?landscape” coupling mode, while natural basins are dominated by the “climate?human activity” coupling mode. Both modes demonstrate high sensitivity to climate change. Enhanced human disturbances may increase vulnerability risks in natural basins, highlighting the urgent need to monitor and regulate anthropogenic impacts. Future basin water resource management should prioritize extreme hydrological events triggered by climate change, and pay close attention to potential ecological impacts of reservoir regulation and land?use changes (human activities).
Intense climate change and intensified human activities have profoundly altered river hydrological processes, exerting significant impacts on the health and security of fluvial aquatic ecosystems. Following the research paradigm of “spatiotemporal evolution?driving mechanism?causal pathways”, this study systematically analyzes the spatiotemporal variation characteristics and driving mechanisms of hydrological regime indices at 18 hydrological stations across the Nan?Beipan River Basin. The Bayesian Estimation of Abrupt change, Seasonality and Trend (BEAST) method is employed to identify non?stationarity and abrupt changes in runoff series, while the Indicators of Hydrologic Alteration?Range of Variability Approach (IHA?RVA) is used to quantify the degree of hydrological regime alteration before and after dam construction. Combined with Extreme Gradient Boosting?SHapley Additive exPlanations (XGBoost?SHAP), Optimal Multivariate Stratified Geodetector (OMGD) and Partial Least Squares?Structural Equation Modeling (PLS?SEM), this study further distinguishes single?factor, multi?factor effects and impact pathways of natural factors and human activities across the whole basin, regulated basins and natural basins. The results show that: (1) Abrupt runoff changes are highly consistent with regional drought and flood events; (2) Reservoir dams induce hydrological regime shifts characterized by decreased high?flow magnitudes and increased low?flow magnitudes, with dam?induced impacts gradually weakening with increasing distance; (3) XGBoost?SHAP results reveal that climatic factors dominate hydrological regime variations in different basins, whereas both OMGD and PLS?SEM indicate that coupled interactions between climate and river network/landscape/human activities are the primary controlling factors for the whole basin, regulated basins and natural basins respectively. Topography, lithology, soil and other factors only affect partial hydrological regime indices. Overall, hydrological regime indices in the karst Nan?Beipan River Basin exhibit nonlinear responses to climatic and underlying surface factors. Regulated basins are mainly governed by the “climate?landscape” coupling mode, while natural basins are dominated by the “climate?human activity” coupling mode. Both modes demonstrate high sensitivity to climate change. Enhanced human disturbances may increase vulnerability risks in natural basins, highlighting the urgent need to monitor and regulate anthropogenic impacts. Future basin water resource management should prioritize extreme hydrological events triggered by climate change, and pay close attention to potential ecological impacts of reservoir regulation and land?use changes (human activities).
Available online: July 08, 2026
Abstract:
Benthic diatoms are important primary producers in river ecosystems and serve as sensitive indicators of nutrient dynamics and ecological health. To elucidate the spatiotemporal distribution patterns of benthic diatom communities and their responses to environmental factors in the mainstream of the Fenhe River, seasonal surveys were conducted at 25 sampling sites along the mainstream during four seasons from April 2021 to January 2022. Community composition, diversity, and relationships with physicochemical variables were systematically investigated. The results indicated pronounced seasonal and spatial variations in benthic diatom communities. Diatoma moniliformis dominated in spring, autumn, and winter, whereas the abundance of Cyclotella meneghiniana increased markedly in summer. Although α-diversity indices showed no significant overall differences among seasons, clear spatial patterns were observed, with significantly higher values in the upstream reaches than in the middle and downstream reaches. β-diversity analyses demonstrated that both season (R2 = 0.143, P = 0.001) and river reach (R2 = 0.136, P = 0.001) exerted significant effects on community structure. Redundancy analysis (RDA) further revealed that water temperature, pH, dissolved oxygen, total dissolved solids, and total phosphorus were the principal environmental factors driving the distribution of benthic diatom communities.
Benthic diatoms are important primary producers in river ecosystems and serve as sensitive indicators of nutrient dynamics and ecological health. To elucidate the spatiotemporal distribution patterns of benthic diatom communities and their responses to environmental factors in the mainstream of the Fenhe River, seasonal surveys were conducted at 25 sampling sites along the mainstream during four seasons from April 2021 to January 2022. Community composition, diversity, and relationships with physicochemical variables were systematically investigated. The results indicated pronounced seasonal and spatial variations in benthic diatom communities. Diatoma moniliformis dominated in spring, autumn, and winter, whereas the abundance of Cyclotella meneghiniana increased markedly in summer. Although α-diversity indices showed no significant overall differences among seasons, clear spatial patterns were observed, with significantly higher values in the upstream reaches than in the middle and downstream reaches. β-diversity analyses demonstrated that both season (R2 = 0.143, P = 0.001) and river reach (R2 = 0.136, P = 0.001) exerted significant effects on community structure. Redundancy analysis (RDA) further revealed that water temperature, pH, dissolved oxygen, total dissolved solids, and total phosphorus were the principal environmental factors driving the distribution of benthic diatom communities.
Available online: July 02, 2026
Abstract:
This study investigates whether environmental stress alters the mechanisms by which biodiversity sustains ecosystem functioning and stability. To address this question, we established 48 freshwater mesocosms with submerged macrophyte communities and exposed them to two stressors: warming and pulsed surface runoff pollution. Results show that warming significantly increased the net biodiversity effect (NBE), whereas runoff pollution had no significant impact on functioning or its components. Complementarity effects remained the primary mechanism driving ecosystem functioning, with their positive relationship to functioning being unaffected by either stressor. Selection effects played a similarly important role in driving ecosystem functioning, but their correlation with functioning showed a weakening trend under pollution. Regarding stability, warming maintained overall ecosystem stability by reducing species asynchrony while simultaneously increasing average species stability, without altering the positive relationships between overall stability and these two components. Further analysis revealed that average species stability contributed more strongly to overall stability than species asynchrony, highlighting the dominant role of key species in stability maintenance. Path analysis indicated that warming indirectly buffered its potential negative effects on stability primarily by enhancing ecosystem functioning. While pollution induced a certain degree of species asynchrony, this positive regulatory effect was overridden by the pronounced biomass dominance of key species within the experimental scale. Overall, these findings suggest that the mechanisms by which biodiversity maintains ecosystem functioning and stability may shift under environmental stress, although these mechanisms still exhibited strong robustness under relatively moderate stress intensities. This study advances the understanding of how freshwater ecosystems respond to global change in terms of functioning and stability mechanisms, and provides a theoretical basis for ecosystem management and ecological risk assessment.
This study investigates whether environmental stress alters the mechanisms by which biodiversity sustains ecosystem functioning and stability. To address this question, we established 48 freshwater mesocosms with submerged macrophyte communities and exposed them to two stressors: warming and pulsed surface runoff pollution. Results show that warming significantly increased the net biodiversity effect (NBE), whereas runoff pollution had no significant impact on functioning or its components. Complementarity effects remained the primary mechanism driving ecosystem functioning, with their positive relationship to functioning being unaffected by either stressor. Selection effects played a similarly important role in driving ecosystem functioning, but their correlation with functioning showed a weakening trend under pollution. Regarding stability, warming maintained overall ecosystem stability by reducing species asynchrony while simultaneously increasing average species stability, without altering the positive relationships between overall stability and these two components. Further analysis revealed that average species stability contributed more strongly to overall stability than species asynchrony, highlighting the dominant role of key species in stability maintenance. Path analysis indicated that warming indirectly buffered its potential negative effects on stability primarily by enhancing ecosystem functioning. While pollution induced a certain degree of species asynchrony, this positive regulatory effect was overridden by the pronounced biomass dominance of key species within the experimental scale. Overall, these findings suggest that the mechanisms by which biodiversity maintains ecosystem functioning and stability may shift under environmental stress, although these mechanisms still exhibited strong robustness under relatively moderate stress intensities. This study advances the understanding of how freshwater ecosystems respond to global change in terms of functioning and stability mechanisms, and provides a theoretical basis for ecosystem management and ecological risk assessment.
Available online: June 30, 2026
Abstract:
he lakes in the Qinghai-Tibet Plateau are greatly affected by climate change. The lake expansion and salinity decline caused by rapid warming are changing the physical environment inside the lake, which in turn affects its ecological process. However, the differences in the vertical distribution of phytoplankton biomass between the thermal stratification period and the mixing period in plateau lakes are still not fully understood. Based on the comprehensive observation data of 10 large lakes in the plateau during the thermal stratification period and the mixing period from 2024 to 2025, combined with the historical high-resolution and continuous lake water temperature profile, this study analyzed the difference of phytoplankton biomass ( represented by chlorophyll a ) between the thermal stratification period and the mixing period, and discussed the regulation mechanism of thermal stability and density barrier driven by salinity gradient on the temporal and spatial displacement of chlorophyll a. The results showed that the change of lake thermal structure dominated the vertical differentiation of chlorophyll a, and the concentration of chlorophyll a in most lakes during the thermal mixing period was significantly lower than that during the thermal stratification period. During the thermal stratification period, the chlorophyll a in the lakes of Bamu Co, Selin Co and Zhari Namco showed a typical deep chlorophyll maximum ( DCM ) phenomenon in the vertical direction ( the peak concentration of chlorophyll a in Bamu Co was 6.15 μg / L and 4.10 μg / L in 2024 and 2025, respectively ). In 2024, the peak concentration of chlorophyll a in Zhari Namco was 7.10 μg / L ; in 2024, the peak concentration of chlorophyll a in Selin Co was 3.97 μg / L ), that is, the surface concentration was low, and a significant peak was formed in the thermocline with the increase of depth and reached the maximum value, and then gradually decreased in the deep water layer. Not all lakes follow this rule. For example, although there is thermal stratification in Peiku Co and Tangra Yumco, there is no significant difference in the vertical distribution of chlorophyll a concentration. In the thermal mixing period, the vertical distribution of chlorophyll a concentration in the lake was in a uniform distribution state, and the overall chlorophyll a concentration was at a low level ( the maximum chlorophyll a concentration in the mixing period of Zhari Namco in 2025 was 2.61 μg / L, and the maximum chlorophyll a concentration in Selin Co was 2.40 μg / L ). In addition, the high-salinity water in the lower layer ( below 20 m ) of Dagze Co formed a stable salinity thermocline, resulting in the lake maintaining a density stratification state throughout the year. This unique physical structure makes the vertical distribution pattern of chlorophyll a significantly different from other lakes only controlled by thermal stratification. The results of this study show that the change of thermal structure controls the vertical distribution pattern of chlorophyll a in plateau lakes, while the stable salinity stratification of Dagze Co can form a perennial effective physical barrier and dominate its unique vertical distribution pattern. Therefore, the vertical distribution characteristics of phytoplankton biomass in plateau lakes are determined by the thermal stratification and high salinity of lakes.
he lakes in the Qinghai-Tibet Plateau are greatly affected by climate change. The lake expansion and salinity decline caused by rapid warming are changing the physical environment inside the lake, which in turn affects its ecological process. However, the differences in the vertical distribution of phytoplankton biomass between the thermal stratification period and the mixing period in plateau lakes are still not fully understood. Based on the comprehensive observation data of 10 large lakes in the plateau during the thermal stratification period and the mixing period from 2024 to 2025, combined with the historical high-resolution and continuous lake water temperature profile, this study analyzed the difference of phytoplankton biomass ( represented by chlorophyll a ) between the thermal stratification period and the mixing period, and discussed the regulation mechanism of thermal stability and density barrier driven by salinity gradient on the temporal and spatial displacement of chlorophyll a. The results showed that the change of lake thermal structure dominated the vertical differentiation of chlorophyll a, and the concentration of chlorophyll a in most lakes during the thermal mixing period was significantly lower than that during the thermal stratification period. During the thermal stratification period, the chlorophyll a in the lakes of Bamu Co, Selin Co and Zhari Namco showed a typical deep chlorophyll maximum ( DCM ) phenomenon in the vertical direction ( the peak concentration of chlorophyll a in Bamu Co was 6.15 μg / L and 4.10 μg / L in 2024 and 2025, respectively ). In 2024, the peak concentration of chlorophyll a in Zhari Namco was 7.10 μg / L ; in 2024, the peak concentration of chlorophyll a in Selin Co was 3.97 μg / L ), that is, the surface concentration was low, and a significant peak was formed in the thermocline with the increase of depth and reached the maximum value, and then gradually decreased in the deep water layer. Not all lakes follow this rule. For example, although there is thermal stratification in Peiku Co and Tangra Yumco, there is no significant difference in the vertical distribution of chlorophyll a concentration. In the thermal mixing period, the vertical distribution of chlorophyll a concentration in the lake was in a uniform distribution state, and the overall chlorophyll a concentration was at a low level ( the maximum chlorophyll a concentration in the mixing period of Zhari Namco in 2025 was 2.61 μg / L, and the maximum chlorophyll a concentration in Selin Co was 2.40 μg / L ). In addition, the high-salinity water in the lower layer ( below 20 m ) of Dagze Co formed a stable salinity thermocline, resulting in the lake maintaining a density stratification state throughout the year. This unique physical structure makes the vertical distribution pattern of chlorophyll a significantly different from other lakes only controlled by thermal stratification. The results of this study show that the change of thermal structure controls the vertical distribution pattern of chlorophyll a in plateau lakes, while the stable salinity stratification of Dagze Co can form a perennial effective physical barrier and dominate its unique vertical distribution pattern. Therefore, the vertical distribution characteristics of phytoplankton biomass in plateau lakes are determined by the thermal stratification and high salinity of lakes.
Available online: June 30, 2026
Abstract:
Huayang Lake Complex is a typical wetland system in the middle and lower reaches of the Yangtze River, with core ecological functions including waterbird protection, hydrological connectivity and water quality purification, as well as social production guarantee functions such as water supply and flood control. Current water level regulation focuses on single factors and lacks an annual dynamic process curve, which is difficult to fully support the stable exertion of its core ecological functions. Based on nearly 50 years of hydrological, topographic, water quality and habitat data, this study establishes a multi-factor collaborative calculation framework of “hydrology–morphology–water quality–habitat” by using the IHA-RVA method, ArcGIS spatial analysis, hydrodynamic-water quality model and habitat suitability area method, and proposes an annual optimal ecological water level hydrograph to satisfy the hydrological stability and ecological health of the lake complex. The results show that the optimal ecological water level ranges from 11.86 m (April) to 13.53 m (September), with a threshold range of 11.56 m (March) to 14.87 m (August). It presents a temporal distribution characteristic of "convergence in winter and spring, expansion in summer and autumn", and the seasonal water levels adapt to the demands of biological habitats, hydrological rhythms and water quality improvement. This scheme can guarantee the overwintering of key waterbirds, inhabitation of aquatic organisms and water quality purification, and provide a scientific reference for ecological water level regulation of similar gate-controlled lakes or lake groups in the middle and lower reaches of the Yangtze River.
Huayang Lake Complex is a typical wetland system in the middle and lower reaches of the Yangtze River, with core ecological functions including waterbird protection, hydrological connectivity and water quality purification, as well as social production guarantee functions such as water supply and flood control. Current water level regulation focuses on single factors and lacks an annual dynamic process curve, which is difficult to fully support the stable exertion of its core ecological functions. Based on nearly 50 years of hydrological, topographic, water quality and habitat data, this study establishes a multi-factor collaborative calculation framework of “hydrology–morphology–water quality–habitat” by using the IHA-RVA method, ArcGIS spatial analysis, hydrodynamic-water quality model and habitat suitability area method, and proposes an annual optimal ecological water level hydrograph to satisfy the hydrological stability and ecological health of the lake complex. The results show that the optimal ecological water level ranges from 11.86 m (April) to 13.53 m (September), with a threshold range of 11.56 m (March) to 14.87 m (August). It presents a temporal distribution characteristic of "convergence in winter and spring, expansion in summer and autumn", and the seasonal water levels adapt to the demands of biological habitats, hydrological rhythms and water quality improvement. This scheme can guarantee the overwintering of key waterbirds, inhabitation of aquatic organisms and water quality purification, and provide a scientific reference for ecological water level regulation of similar gate-controlled lakes or lake groups in the middle and lower reaches of the Yangtze River.
He Shufeng, She Xingyuan, Feng Tao, Ma Yiming, Wu Biqiong, Du Mingcheng, Sun Huimin, He Mengnan, Chen Qiuwen
Available online: June 29, 2026
Abstract:
Abstract: Dongting Lake, as the second largest natural lake connected to the Yangtze River in the middle and lower reaches, is an important habitat for the four major Chinese carps in the Yangtze River and possesses irreplaceable ecological functions and economic value. Based on the hydrological and topographic data of Dongting Lake from 2016 to 2020, this study constructed a two-dimensional hydrodynamic model of Dongting Lake, simulated the flow velocity and water depth distribution of Dongting Lake from 2016 to 2020, and established the flow velocity and water depth suitability curves for the fattening of juvenile and adult fish of the four major Chinese carps in combination with literature data. The changes of Habitat Suitability Index (HSI) and Weighted Usable Area (WUA) from July to October 2016-2020 were calculated, and the relationship between WUA and the water level of Chenglingji in Dongting Lake was fitted. The suitable ecological water level of Dongting Lake has been determined. The results show that: (1) The optimal flow rate for fattening juvenile fish of the four major Chinese carps in Dongting Lake by rope feed is 0.1-0.2 m/s, and the optimal water depth is 0.7-1.6 m. The optimal flow rate for fattening adult fish by rope feed is 0.1-0.3 m/s, and the optimal water depth is 2.0-4.0 m. (2) From 2016 to 2020, the average monthly flow velocity and water depth of Dongting Lake from July to October basically showed a gradually decreasing trend. The flow velocity of South Dongting Lake was relatively high, while that of East Dongting Lake was relatively high. In 2020, the overall average monthly flow velocity and water depth were relatively high compared with other years. (3) From 2016 to 2020, the average monthly HSI and WUA ranges of juvenile fish of the four major Chinese carps in Dongting Lake during July and August were 0.004-0.14 and 12-402 km2 respectively, and those of adult fish during September and October were 0.05-0.23 and 146-683 km2 respectively. Juvenile and adult fish have the highest suitability in the non-mainstream area of South Dongting Lake. (4) The suitable ecological water level for fattening juvenile fish of the four major Chinese carps in Dongting Lake by using bait is 26.9-28.0 m, corresponding to a WUA of 342 km2, accounting for 13% of the total area. The suitable ecological water level for fattening adult fish by using bait is 29.0-30.0 m, corresponding to a WUA of 832 km2, accounting for 32% of the total area. The research results provide a reference for the protection of the Dongting Lake ecosystem. Key words: Dongting Lake; The four major Chinese carps; Feeding and Fattening of Juvenile fish; Feeding and Fattening of adult fish; Ecological water level
Abstract: Dongting Lake, as the second largest natural lake connected to the Yangtze River in the middle and lower reaches, is an important habitat for the four major Chinese carps in the Yangtze River and possesses irreplaceable ecological functions and economic value. Based on the hydrological and topographic data of Dongting Lake from 2016 to 2020, this study constructed a two-dimensional hydrodynamic model of Dongting Lake, simulated the flow velocity and water depth distribution of Dongting Lake from 2016 to 2020, and established the flow velocity and water depth suitability curves for the fattening of juvenile and adult fish of the four major Chinese carps in combination with literature data. The changes of Habitat Suitability Index (HSI) and Weighted Usable Area (WUA) from July to October 2016-2020 were calculated, and the relationship between WUA and the water level of Chenglingji in Dongting Lake was fitted. The suitable ecological water level of Dongting Lake has been determined. The results show that: (1) The optimal flow rate for fattening juvenile fish of the four major Chinese carps in Dongting Lake by rope feed is 0.1-0.2 m/s, and the optimal water depth is 0.7-1.6 m. The optimal flow rate for fattening adult fish by rope feed is 0.1-0.3 m/s, and the optimal water depth is 2.0-4.0 m. (2) From 2016 to 2020, the average monthly flow velocity and water depth of Dongting Lake from July to October basically showed a gradually decreasing trend. The flow velocity of South Dongting Lake was relatively high, while that of East Dongting Lake was relatively high. In 2020, the overall average monthly flow velocity and water depth were relatively high compared with other years. (3) From 2016 to 2020, the average monthly HSI and WUA ranges of juvenile fish of the four major Chinese carps in Dongting Lake during July and August were 0.004-0.14 and 12-402 km2 respectively, and those of adult fish during September and October were 0.05-0.23 and 146-683 km2 respectively. Juvenile and adult fish have the highest suitability in the non-mainstream area of South Dongting Lake. (4) The suitable ecological water level for fattening juvenile fish of the four major Chinese carps in Dongting Lake by using bait is 26.9-28.0 m, corresponding to a WUA of 342 km2, accounting for 13% of the total area. The suitable ecological water level for fattening adult fish by using bait is 29.0-30.0 m, corresponding to a WUA of 832 km2, accounting for 32% of the total area. The research results provide a reference for the protection of the Dongting Lake ecosystem. Key words: Dongting Lake; The four major Chinese carps; Feeding and Fattening of Juvenile fish; Feeding and Fattening of adult fish; Ecological water level
Available online: June 25, 2026
Abstract:
The Tianshan Mountains serve as a crucial water resource formation zone in China"s arid northwest region. Understanding the hydrological processes within this area holds significant implications for water resource management in arid zones. The northern slope of the Tianshan Mountains lies at the heart of the Eurasian continent, encompassing primarily the region north of the Tianshan range and the southern edge of the Junggar Basin. It exhibits a typical temperate continental climate. While previous studies have primarily focused on precipitation and groundwater isotopes in arid regions, systematic investigations of river water hydrogen and oxygen stable isotopes across the entire northern slope of the Tianshan Mountains remain scarce. To reveal the stable isotope characteristics of river water on the northern slope of the Tianshan Mountains in the arid northwest region and their implications for the hydrological cycle, this study systematically collected river water samples from major rivers on the northern slope of the Tianshan Mountains between 2022 and 2025. Based on hydrogen and oxygen stable isotope data from 225 samples, it combined isotope analysis with remote sensing technology to elucidate the spatiotemporal variation characteristics of hydrogen and oxygen stable isotope compositions in river water. The study also analyzed the influence of river water physicochemical properties and environmental factors on these isotope compositions. The results indicate:(1) River water hydrogen and oxygen stable isotope compositions exhibit distinct spatiotemporal variation patterns. The ranges of δ2H and δ1?O values for rivers on the northern slope of the Tianshan Mountains were ?117.2‰ to ?46.4‰ and ?17.84‰ to?7.10‰, respectively, with regional averages of ?78.3‰ and ?13.27‰. The temporal variability in the stable hydrogen and oxygen isotope composition is relatively small. Spatially, significant regional differentiation is evident: the western, central, and eastern regions exhibit average δ2H and δ18O values of ?85.8‰,?14.16‰ and ?71.0‰,?12.28‰ and ?81.0‰, ?13.74‰, respectively, forming a spatial distribution pattern with higher values in the central area and lower values in the eastern and western wings.(2) The regional river water line (EL) equation is δ2H = 4.31δ18O? 21.94 (R2=0.72, n=225), with a slope (4.31) significantly lower than that of the local atmospheric precipitation line (slope 7.51) and the global atmospheric precipitation line (slope 8); The hydrogen and oxygen stable isotope compositions of rivers in the western and central regions are primarily dominated by precipitation recharge, while eastern rivers exhibit a strong signal of evaporative fractionation.(3) Hydrogen and oxygen stable isotope compositions in rivers on the northern slope of the Tianshan Mountains are influenced by multiple factors. The physicochemical properties of the river water itself contribute to its isotopic characteristics. Additionally, environmental factors such as precipitation, evapotranspiration, surface temperature, and vegetation cover influence river isotope compositions by regulating local hydrological processes. This study elucidates the spatiotemporal variation patterns of stable hydrogen and oxygen isotopes in river water along the northern slope of the Tianshan Mountains. Through field sampling and remote sensing techniques, it quantitatively identifies the primary factors influencing the stable hydrogen and oxygen isotope composition of regional river water. This research fills a gap in studies using stable hydrogen and oxygen isotopes in river water to indicate hydrological processes across the entire mountain range scale of the northern Tianshan slope, providing isotopic evidence for a deeper understanding of water cycle processes in the Tianshan region"s watersheds.
The Tianshan Mountains serve as a crucial water resource formation zone in China"s arid northwest region. Understanding the hydrological processes within this area holds significant implications for water resource management in arid zones. The northern slope of the Tianshan Mountains lies at the heart of the Eurasian continent, encompassing primarily the region north of the Tianshan range and the southern edge of the Junggar Basin. It exhibits a typical temperate continental climate. While previous studies have primarily focused on precipitation and groundwater isotopes in arid regions, systematic investigations of river water hydrogen and oxygen stable isotopes across the entire northern slope of the Tianshan Mountains remain scarce. To reveal the stable isotope characteristics of river water on the northern slope of the Tianshan Mountains in the arid northwest region and their implications for the hydrological cycle, this study systematically collected river water samples from major rivers on the northern slope of the Tianshan Mountains between 2022 and 2025. Based on hydrogen and oxygen stable isotope data from 225 samples, it combined isotope analysis with remote sensing technology to elucidate the spatiotemporal variation characteristics of hydrogen and oxygen stable isotope compositions in river water. The study also analyzed the influence of river water physicochemical properties and environmental factors on these isotope compositions. The results indicate:(1) River water hydrogen and oxygen stable isotope compositions exhibit distinct spatiotemporal variation patterns. The ranges of δ2H and δ1?O values for rivers on the northern slope of the Tianshan Mountains were ?117.2‰ to ?46.4‰ and ?17.84‰ to?7.10‰, respectively, with regional averages of ?78.3‰ and ?13.27‰. The temporal variability in the stable hydrogen and oxygen isotope composition is relatively small. Spatially, significant regional differentiation is evident: the western, central, and eastern regions exhibit average δ2H and δ18O values of ?85.8‰,?14.16‰ and ?71.0‰,?12.28‰ and ?81.0‰, ?13.74‰, respectively, forming a spatial distribution pattern with higher values in the central area and lower values in the eastern and western wings.(2) The regional river water line (EL) equation is δ2H = 4.31δ18O? 21.94 (R2=0.72, n=225), with a slope (4.31) significantly lower than that of the local atmospheric precipitation line (slope 7.51) and the global atmospheric precipitation line (slope 8); The hydrogen and oxygen stable isotope compositions of rivers in the western and central regions are primarily dominated by precipitation recharge, while eastern rivers exhibit a strong signal of evaporative fractionation.(3) Hydrogen and oxygen stable isotope compositions in rivers on the northern slope of the Tianshan Mountains are influenced by multiple factors. The physicochemical properties of the river water itself contribute to its isotopic characteristics. Additionally, environmental factors such as precipitation, evapotranspiration, surface temperature, and vegetation cover influence river isotope compositions by regulating local hydrological processes. This study elucidates the spatiotemporal variation patterns of stable hydrogen and oxygen isotopes in river water along the northern slope of the Tianshan Mountains. Through field sampling and remote sensing techniques, it quantitatively identifies the primary factors influencing the stable hydrogen and oxygen isotope composition of regional river water. This research fills a gap in studies using stable hydrogen and oxygen isotopes in river water to indicate hydrological processes across the entire mountain range scale of the northern Tianshan slope, providing isotopic evidence for a deeper understanding of water cycle processes in the Tianshan region"s watersheds.
Available online: June 22, 2026
Abstract:
Phytoplankton in cold-region lakes are key carriers of material cycling and energy flow in lake ecosystems. Compared with phytoplankton in lakes at mid-to-low latitudes, their community structure exhibits higher sensitivity to climate change and anthropogenic stress. To elucidate the spatio-temporal characteristics of phytoplankton community structure and its key driving forces in cold-region lakes, this study used samples from January, May, July and September to represent winter, spring, summer and autumn, respectively. Plankton community and water quality samples were collected from Lake Chagan in 2024 and subjected to laboratory analysis.The results showed that the water trophic state of Chagan Lake was mesotrophic in spring, summer, and winter (34.20≤TLI≤47.16), while it was eutrophic in autumn (48.85≤TLI≤59.56). A total of 175 phytoplankton species belonging to 8 phyla were identified, with Bacillariophyta having the highest biomass and Cyanophyta the highest cell density. There were 12 dominant phytoplankton species from 5 phyla; the absolute dominant species (with the highest dominance) in spring, summer, autumn, and winter were Synedra acus (Bacillariophyta), Tribonema ulothrichoides (Xanthophyta), Dolichospermum spiroides (Cyanophyta), and Synedra acus var. angustissima (Bacillariophyta), respectively. The Shannon-Wiener diversity index, Simpson diversity index, Pielou evenness index, and Margalef richness index of the phytoplankton community were generally low, indicating weak resistance to external and internal environmental changes. Based on Pearson correlation analysis, redundancy analysis (RDA), and Mantel tests, it was clarified that WT, TP, TN, NH??-N, NO??-N, and DO were the main controlling factors affecting phytoplankton cell density in Chagan Lake. Among these, WT, TN, TP, and NO??-N were the main factors influencing phytoplankton dominance, while TN, NH??-N, and DO dominated changes in phytoplankton community structure. Notably, low temperature, low light (ice cover) and weakened hydrodynamic mixing in winter and spring promoted Bacillariophyta to become the absolute dominant species, whereas high TN and NO??-N in summer and autumn facilitated Xanthophyta and Cyanophyta to become the absolute dominant species. To effectively prevent Cyanophyta from becoming the absolute dominant species across all seasons in Chagan Lake, it is urgent to reduce the concentration of nutrient salts (TN and NO??-N) input in summer and autumn to address the threats posed by climate warming. This study reveals the driving mechanism of phytoplankton community structure in northern cold-region lakes, providing a scientific basis for the aquatic ecological protection of Chagan Lake and similar cold-region lakes.
Phytoplankton in cold-region lakes are key carriers of material cycling and energy flow in lake ecosystems. Compared with phytoplankton in lakes at mid-to-low latitudes, their community structure exhibits higher sensitivity to climate change and anthropogenic stress. To elucidate the spatio-temporal characteristics of phytoplankton community structure and its key driving forces in cold-region lakes, this study used samples from January, May, July and September to represent winter, spring, summer and autumn, respectively. Plankton community and water quality samples were collected from Lake Chagan in 2024 and subjected to laboratory analysis.The results showed that the water trophic state of Chagan Lake was mesotrophic in spring, summer, and winter (34.20≤TLI≤47.16), while it was eutrophic in autumn (48.85≤TLI≤59.56). A total of 175 phytoplankton species belonging to 8 phyla were identified, with Bacillariophyta having the highest biomass and Cyanophyta the highest cell density. There were 12 dominant phytoplankton species from 5 phyla; the absolute dominant species (with the highest dominance) in spring, summer, autumn, and winter were Synedra acus (Bacillariophyta), Tribonema ulothrichoides (Xanthophyta), Dolichospermum spiroides (Cyanophyta), and Synedra acus var. angustissima (Bacillariophyta), respectively. The Shannon-Wiener diversity index, Simpson diversity index, Pielou evenness index, and Margalef richness index of the phytoplankton community were generally low, indicating weak resistance to external and internal environmental changes. Based on Pearson correlation analysis, redundancy analysis (RDA), and Mantel tests, it was clarified that WT, TP, TN, NH??-N, NO??-N, and DO were the main controlling factors affecting phytoplankton cell density in Chagan Lake. Among these, WT, TN, TP, and NO??-N were the main factors influencing phytoplankton dominance, while TN, NH??-N, and DO dominated changes in phytoplankton community structure. Notably, low temperature, low light (ice cover) and weakened hydrodynamic mixing in winter and spring promoted Bacillariophyta to become the absolute dominant species, whereas high TN and NO??-N in summer and autumn facilitated Xanthophyta and Cyanophyta to become the absolute dominant species. To effectively prevent Cyanophyta from becoming the absolute dominant species across all seasons in Chagan Lake, it is urgent to reduce the concentration of nutrient salts (TN and NO??-N) input in summer and autumn to address the threats posed by climate warming. This study reveals the driving mechanism of phytoplankton community structure in northern cold-region lakes, providing a scientific basis for the aquatic ecological protection of Chagan Lake and similar cold-region lakes.
Available online: June 22, 2026
Abstract:
Molecular species identification and environmental DNA (eDNA) technologies have developed rapidly in recent years. They are widely used in biodiversity surveys and environmental monitoring because they are efficient and non-invasive. However, their performance and accuracy depend strongly on the completeness and reliability of reference databases, especially DNA barcode libraries. In China, most river basins still lack systematic, standardized, and comprehensive barcode resources. This limitation restricts the application of molecular methods in ecological assessment and biodiversity conservation. The Yarlung Tsangpo River is one of the highest-altitude large transboundary rivers in the world. Its unique climate and complex hydrological and geomorphological conditions support rich and distinctive freshwater fish diversity. However, a basin-wide DNA barcode reference library for fish is still lacking. Systematic genetic data remain insufficient, which limits the use of molecular monitoring approaches in this region. In this study, we compiled DNA sequences from fish specimens collected by our research team across the Yarlung Tsangpo River basin from 1998 to 2024. We also incorporated sequences from public databases. All data were processed using standardized methods, followed by strict quality control and reliability assessment based on genetic distances. Based on these steps, we established the first comprehensive DNA barcode reference dataset covering the entire basin. The dataset contains 3,174 high-quality DNA sequences. Among them, 2,890 sequences (91.1%) were newly generated, and 284 sequences (8.9%) were obtained from public databases. Samples were collected from 82 sites, including the main stem, major tributaries, and associated lakes and wetlands. The elevation range spans from 155 to 4,600 m. The dataset includes 78 species from 49 genera, 21 families, and 8 orders. These species comprise 62 native species and 16 non-native species. The dataset covers 69% of endemic fish species in the basin and 100% of fish species in the reach upstream of the Lhagu River confluence. The average sequence length is approximately 813 bp. The main molecular markers are cytochrome c oxidase subunit I (COI) and cytochrome b (Cyt b). Their sequence length ranges are 461-1779 bp and 798-1390 bp, respectively. Most species show clear DNA barcode gaps, which support reliable species-level identification. The dataset adopts a “metadata-sequence data” separation framework. It follows the FAIR (Findable, Accessible, Interoperable, Reusable) and CARE (Collective Benefit, Authority to Control, Responsibility, Ethics) principles. It includes standardized information on taxonomy, voucher specimens, distribution, sampling time, collectors, and sequence sources. Color photographs are available for some species. The dataset is openly accessible through the Science Data Bank(ScienceDB; DOI：10.57760/sciencedb.36688). This dataset fills a key gap in DNA barcode reference resources for fish in the Yarlung Tsangpo River basin. It supports species identification, biodiversity inventory, non-native species monitoring, and eDNA metabarcoding studies. It also provides essential data support for the conservation and management of plateau river ecosystems.
Molecular species identification and environmental DNA (eDNA) technologies have developed rapidly in recent years. They are widely used in biodiversity surveys and environmental monitoring because they are efficient and non-invasive. However, their performance and accuracy depend strongly on the completeness and reliability of reference databases, especially DNA barcode libraries. In China, most river basins still lack systematic, standardized, and comprehensive barcode resources. This limitation restricts the application of molecular methods in ecological assessment and biodiversity conservation. The Yarlung Tsangpo River is one of the highest-altitude large transboundary rivers in the world. Its unique climate and complex hydrological and geomorphological conditions support rich and distinctive freshwater fish diversity. However, a basin-wide DNA barcode reference library for fish is still lacking. Systematic genetic data remain insufficient, which limits the use of molecular monitoring approaches in this region. In this study, we compiled DNA sequences from fish specimens collected by our research team across the Yarlung Tsangpo River basin from 1998 to 2024. We also incorporated sequences from public databases. All data were processed using standardized methods, followed by strict quality control and reliability assessment based on genetic distances. Based on these steps, we established the first comprehensive DNA barcode reference dataset covering the entire basin. The dataset contains 3,174 high-quality DNA sequences. Among them, 2,890 sequences (91.1%) were newly generated, and 284 sequences (8.9%) were obtained from public databases. Samples were collected from 82 sites, including the main stem, major tributaries, and associated lakes and wetlands. The elevation range spans from 155 to 4,600 m. The dataset includes 78 species from 49 genera, 21 families, and 8 orders. These species comprise 62 native species and 16 non-native species. The dataset covers 69% of endemic fish species in the basin and 100% of fish species in the reach upstream of the Lhagu River confluence. The average sequence length is approximately 813 bp. The main molecular markers are cytochrome c oxidase subunit I (COI) and cytochrome b (Cyt b). Their sequence length ranges are 461-1779 bp and 798-1390 bp, respectively. Most species show clear DNA barcode gaps, which support reliable species-level identification. The dataset adopts a “metadata-sequence data” separation framework. It follows the FAIR (Findable, Accessible, Interoperable, Reusable) and CARE (Collective Benefit, Authority to Control, Responsibility, Ethics) principles. It includes standardized information on taxonomy, voucher specimens, distribution, sampling time, collectors, and sequence sources. Color photographs are available for some species. The dataset is openly accessible through the Science Data Bank(ScienceDB; DOI：10.57760/sciencedb.36688). This dataset fills a key gap in DNA barcode reference resources for fish in the Yarlung Tsangpo River basin. It supports species identification, biodiversity inventory, non-native species monitoring, and eDNA metabarcoding studies. It also provides essential data support for the conservation and management of plateau river ecosystems.
Available online: June 16, 2026
Abstract:
Since the impoundment of the Three Gorges Reservoir (TGR) and the joint regulation of upstream cascade reservoirs, the sediment transport environment of the TGR, particularly within the variable backwater zone, has undergone significant changes. As a sensitive reach subject to alternating river–reservoir influences, the evolution of suspended sediment vertical distribution in this zone directly affects sediment management strategies at the reservoir tail and navigational maintenance. Based on long-term field observations from 2009 to 2020, this study systematically identifies suspended sediment vertical distribution patterns in the variable backwater zone using the K-means clustering algorithm and quantitatively evaluates the applicability of the classical Rouse equation and the Han Qiangwei non-equilibrium sediment transport formula. A total of 267 measured vertical profiles are classified into three typical patterns: low-concentration weak-gradient pattern (Pattern 0, 67.8%), medium-concentration positive-gradient pattern (Pattern 1, 28.8%), and high-concentration quasi-uniform pattern (Pattern 2, 3.4%). The results reveal pronounced temporal differentiation among the distribution patterns. On the intra-annual scale, the patterns are closely associated with flood-season hydrological processes: Pattern 0 predominates during the pre- and post-flood periods, whereas the other patterns mainly occur during the main flood season (July–August). On the interannual scale, the low-concentration pattern increased steadily during 2009–2020 and became the dominant distribution in the variable backwater zone after 2014 under cascade reservoir regulation. This evolution is consistent with the intensified clear-water release effect induced by the operation of the TGR and the Jinsha River cascade reservoirs, indicating a persistent non-equilibrium sediment transport regime in which sediment transport capacity substantially exceeds sediment supply. In terms of formula performance, the Rouse equation and the Han formula yield comparable results for calculating depth-averaged suspended sediment concentration. However, for unit-width sediment discharge, the Han formula effectively corrects the systematic underestimation under Pattern 0 by introducing a non-equilibrium coefficient, showing significantly higher accuracy and stability than the Rouse equation. Both formulas exhibit limited capability in representing near-bed high-concentration layers. Future studies should focus on improving diffusion coefficient parameterization under unsteady flow conditions in variable backwater zones and incorporating fine-sediment flocculation processes to enhance sediment transport predictions under complex hydraulic conditions. The findings provide important theoretical support for understanding sediment transport mechanisms and optimizing regulation strategies in variable backwater zones of large reservoirs.
Since the impoundment of the Three Gorges Reservoir (TGR) and the joint regulation of upstream cascade reservoirs, the sediment transport environment of the TGR, particularly within the variable backwater zone, has undergone significant changes. As a sensitive reach subject to alternating river–reservoir influences, the evolution of suspended sediment vertical distribution in this zone directly affects sediment management strategies at the reservoir tail and navigational maintenance. Based on long-term field observations from 2009 to 2020, this study systematically identifies suspended sediment vertical distribution patterns in the variable backwater zone using the K-means clustering algorithm and quantitatively evaluates the applicability of the classical Rouse equation and the Han Qiangwei non-equilibrium sediment transport formula. A total of 267 measured vertical profiles are classified into three typical patterns: low-concentration weak-gradient pattern (Pattern 0, 67.8%), medium-concentration positive-gradient pattern (Pattern 1, 28.8%), and high-concentration quasi-uniform pattern (Pattern 2, 3.4%). The results reveal pronounced temporal differentiation among the distribution patterns. On the intra-annual scale, the patterns are closely associated with flood-season hydrological processes: Pattern 0 predominates during the pre- and post-flood periods, whereas the other patterns mainly occur during the main flood season (July–August). On the interannual scale, the low-concentration pattern increased steadily during 2009–2020 and became the dominant distribution in the variable backwater zone after 2014 under cascade reservoir regulation. This evolution is consistent with the intensified clear-water release effect induced by the operation of the TGR and the Jinsha River cascade reservoirs, indicating a persistent non-equilibrium sediment transport regime in which sediment transport capacity substantially exceeds sediment supply. In terms of formula performance, the Rouse equation and the Han formula yield comparable results for calculating depth-averaged suspended sediment concentration. However, for unit-width sediment discharge, the Han formula effectively corrects the systematic underestimation under Pattern 0 by introducing a non-equilibrium coefficient, showing significantly higher accuracy and stability than the Rouse equation. Both formulas exhibit limited capability in representing near-bed high-concentration layers. Future studies should focus on improving diffusion coefficient parameterization under unsteady flow conditions in variable backwater zones and incorporating fine-sediment flocculation processes to enhance sediment transport predictions under complex hydraulic conditions. The findings provide important theoretical support for understanding sediment transport mechanisms and optimizing regulation strategies in variable backwater zones of large reservoirs.
Available online: June 16, 2026
Abstract:
Varved lake sediments serve as a crucial archive for high-resolution paleoclimate and paleoenvironmental research. Owing to their interannual to even seasonal temporal resolution, they provide a high-precision chronological framework for climate reconstruction. Investigating the formation mechanism of varves is essential for understanding their depositional processes and for accurately interpreting the climatic and environmental information they record. This study focuses on the laminated sediments of Rena Co in the central Tibetan Plateau. By integratingS210Pb/137Cs dating with varve counting results, it confirms that these laminations are varves. Based on microscopic observations of varve thin sections, micro-X-ray fluorescence (μ-XRF) elemental mapping of varve thin sections, X-ray diffraction (XRD) analysis of core sediments, and scanning electron microscopy (SEM) observations of surface microtextures on coarse-grained particles, we systematically analyzed the structural, compositional, and morphological characteristics of the varves from Rena Co, and further explored their formation processes and underlying mechanisms. The results indicate that the varves of Rena Co consist of alternating light and dark layers. The light-colored layers form during summer and are mainly composed of fine-grained, Ca-rich authigenic carbonate (such as aragonite), together with abundant cladoceran fragments remains. In contrast, the dark-colored layers develop during winter following lake ice formation and comprise fine-grained, Fe-rich clay minerals that slowly settle beneath the ice, along with coarse-grained, Si-rich aeolian materials (e.g., quartz and feldspar) that accumulate on the ice surface and are subsequently deposited on the lakebed during ice melt.
Varved lake sediments serve as a crucial archive for high-resolution paleoclimate and paleoenvironmental research. Owing to their interannual to even seasonal temporal resolution, they provide a high-precision chronological framework for climate reconstruction. Investigating the formation mechanism of varves is essential for understanding their depositional processes and for accurately interpreting the climatic and environmental information they record. This study focuses on the laminated sediments of Rena Co in the central Tibetan Plateau. By integratingS210Pb/137Cs dating with varve counting results, it confirms that these laminations are varves. Based on microscopic observations of varve thin sections, micro-X-ray fluorescence (μ-XRF) elemental mapping of varve thin sections, X-ray diffraction (XRD) analysis of core sediments, and scanning electron microscopy (SEM) observations of surface microtextures on coarse-grained particles, we systematically analyzed the structural, compositional, and morphological characteristics of the varves from Rena Co, and further explored their formation processes and underlying mechanisms. The results indicate that the varves of Rena Co consist of alternating light and dark layers. The light-colored layers form during summer and are mainly composed of fine-grained, Ca-rich authigenic carbonate (such as aragonite), together with abundant cladoceran fragments remains. In contrast, the dark-colored layers develop during winter following lake ice formation and comprise fine-grained, Fe-rich clay minerals that slowly settle beneath the ice, along with coarse-grained, Si-rich aeolian materials (e.g., quartz and feldspar) that accumulate on the ice surface and are subsequently deposited on the lakebed during ice melt.
Available online: June 16, 2026
Abstract:
River network routing is a crucial component of watershed hydrological modeling, with the Muskingum method being one of the most widely used approaches. However, traditional applications of the Muskingum method typically rely on discrete difference equations, which not only introduce numerical errors but also hinder seamless temporal-scale coupling with hydrological models formulated in differential form. To address this limitation, this study develops a differential form of the Muskingum river routing method by assembling the governing ordinary differential equations (ODEs) for all river segments using a matrix-based approach. A connectivity matrix is introduced to identify upstream inflows for each channel, leading to the formulation of the Muskingum-based Ordinary Differential Equation River-network Routing method (ODE-MR). The ODE-MR is further coupled with the differential form of the Xinanjiang hydrological model to construct a fully differential hydrological modeling framework.Comparative experiments between differential and difference forms demonstrate that, with analytical solutions as reference, the root mean square error of ODE-MR is on the order of 10??, significantly reducing the numerical inaccuracies of the traditional difference-based Muskingum method. Additional experiments comparing the coupling strategies with differential hydrological models show that, as the time step decreases, the results of the hybrid differential-difference coupling approach gradually converge toward those of the fully differential coupling method, indicating superior modeling accuracy of the fully differential coupling method approach. Real-world application in the Tunxi River Basin further validates the model, at the daily scale, with the ODE-MR-based fully differential coupling model improving the multi-year average Nash-Sutcliffe efficiency coefficient by 0.04, demonstrating enhanced predictive performance. This study provides a valuable reference for hydrological modeling and cross-disciplinary model integration within a unified differential equation framework.
River network routing is a crucial component of watershed hydrological modeling, with the Muskingum method being one of the most widely used approaches. However, traditional applications of the Muskingum method typically rely on discrete difference equations, which not only introduce numerical errors but also hinder seamless temporal-scale coupling with hydrological models formulated in differential form. To address this limitation, this study develops a differential form of the Muskingum river routing method by assembling the governing ordinary differential equations (ODEs) for all river segments using a matrix-based approach. A connectivity matrix is introduced to identify upstream inflows for each channel, leading to the formulation of the Muskingum-based Ordinary Differential Equation River-network Routing method (ODE-MR). The ODE-MR is further coupled with the differential form of the Xinanjiang hydrological model to construct a fully differential hydrological modeling framework.Comparative experiments between differential and difference forms demonstrate that, with analytical solutions as reference, the root mean square error of ODE-MR is on the order of 10??, significantly reducing the numerical inaccuracies of the traditional difference-based Muskingum method. Additional experiments comparing the coupling strategies with differential hydrological models show that, as the time step decreases, the results of the hybrid differential-difference coupling approach gradually converge toward those of the fully differential coupling method, indicating superior modeling accuracy of the fully differential coupling method approach. Real-world application in the Tunxi River Basin further validates the model, at the daily scale, with the ODE-MR-based fully differential coupling model improving the multi-year average Nash-Sutcliffe efficiency coefficient by 0.04, demonstrating enhanced predictive performance. This study provides a valuable reference for hydrological modeling and cross-disciplinary model integration within a unified differential equation framework.
Available online: June 16, 2026
Abstract:
After the completion and operation of Quanzhou Bailai Water Control Project, the water supply capacity of Jinji sluice will be improved, resulting in the decrease of downstream water volume. In order to analyze the impact of the project on the estuary water environment, a two-dimensional unsteady water environment mathematical model of Jinjiang estuary is constructed by using MIKE21, and the tidal current field, salinity upstream distance, along-the-way change and diluted water area of the estuary before and after the construction of Bailai Reservoir are simulated. After analysis, the discharge of Jinji Gate is reduced by 53.4% at the maximum after the construction of the reservoir, and the prediction results show that the basic shape of tidal current field in Jinjiang estuary and coastal waters has not changed before and after the construction of the reservoir. The maximum increment of the upstream distance of the saltwater tide in Jinjiang Estuary is 0.66km, and the areas with obvious changes are mainly 2.6~12.3km in the upper reaches of Jinjiang Estuary, and the salinity variation is basically below 3.4‰. The area of diluted water in the experimental area of Quanzhou Bay Estuary Wetland Nature Reserve decreased by 3.4% at the maximum, but the core area and buffer area basically had no effect. Generally speaking, the Bailai Reservoir has little influence on tidal current field and salinity field in Jinjiang estuary after the reservoir is built. The research results can provide a basis for the protection and management of water environment in Jinjiang estuary, and can also provide some reference for the impact analysis of water environment in other estuary projects.
After the completion and operation of Quanzhou Bailai Water Control Project, the water supply capacity of Jinji sluice will be improved, resulting in the decrease of downstream water volume. In order to analyze the impact of the project on the estuary water environment, a two-dimensional unsteady water environment mathematical model of Jinjiang estuary is constructed by using MIKE21, and the tidal current field, salinity upstream distance, along-the-way change and diluted water area of the estuary before and after the construction of Bailai Reservoir are simulated. After analysis, the discharge of Jinji Gate is reduced by 53.4% at the maximum after the construction of the reservoir, and the prediction results show that the basic shape of tidal current field in Jinjiang estuary and coastal waters has not changed before and after the construction of the reservoir. The maximum increment of the upstream distance of the saltwater tide in Jinjiang Estuary is 0.66km, and the areas with obvious changes are mainly 2.6~12.3km in the upper reaches of Jinjiang Estuary, and the salinity variation is basically below 3.4‰. The area of diluted water in the experimental area of Quanzhou Bay Estuary Wetland Nature Reserve decreased by 3.4% at the maximum, but the core area and buffer area basically had no effect. Generally speaking, the Bailai Reservoir has little influence on tidal current field and salinity field in Jinjiang estuary after the reservoir is built. The research results can provide a basis for the protection and management of water environment in Jinjiang estuary, and can also provide some reference for the impact analysis of water environment in other estuary projects.
Available online: June 16, 2026
Abstract:
Riverbed armoring in gravel-sand rivers involves complex interactions among suspended load, bed load, and bed material, forming a non-steady “scour–armoring–exchange” process. Traditional prediction methods often oversimplify these mechanisms and neglect sediment exchange, leading to limited accuracy and applicability. This study aims to develop a new riverbed armoring calculation method that explicitly incorporates sediment exchange between suspended load, bed load, and bed material to improve prediction performance. Four representative domestic and international riverbed armoring models were first compared under different hydraulic and sediment conditions to identify their limitations. Based on sediment transport statistical theory and an improved active-layer sediment mass conservation equation, a new method was proposed that considers the coupled “suspended load–bed load–bed material” exchange process. The model was validated against both flume experiments and field data from the downstream reaches of the Danjiangkou and Three Gorges Reservoirs. The results show that compared with the traditional methods, the proposed method significantly improves the prediction accuracy. The calculation accuracy of the new method is considerably higher than that of conventional approaches in both natural rivers and flume experiments. When applied to natural rivers, the RMSE and MAE values are 4.9% and 3.3%, respectively, while for flume tests they are 5.5% and 2.5%, respectively. It effectively reproduced the dynamic feedback between flow scour and bed armoring, accurately simulating both the gradation of the armoring layer and the depth of bed scour. Sensitivity analyses demonstrated that dynamic variation of the active-layer thickness and appropriate definition of armoring stability are essential for accurate modeling. The newly developed method, grounded in sediment transport statistics and active-layer balance theory, provides a physically-based and reliable approach for predicting armoring in gravel-sand beds. It addresses key limitations of conventional models by coupling multiple sediment transport modes and dynamic bed evolution. The results enhance understanding of riverbed armoring mechanisms and offer a robust tool for forecasting downstream channel adjustment below large dams.
Riverbed armoring in gravel-sand rivers involves complex interactions among suspended load, bed load, and bed material, forming a non-steady “scour–armoring–exchange” process. Traditional prediction methods often oversimplify these mechanisms and neglect sediment exchange, leading to limited accuracy and applicability. This study aims to develop a new riverbed armoring calculation method that explicitly incorporates sediment exchange between suspended load, bed load, and bed material to improve prediction performance. Four representative domestic and international riverbed armoring models were first compared under different hydraulic and sediment conditions to identify their limitations. Based on sediment transport statistical theory and an improved active-layer sediment mass conservation equation, a new method was proposed that considers the coupled “suspended load–bed load–bed material” exchange process. The model was validated against both flume experiments and field data from the downstream reaches of the Danjiangkou and Three Gorges Reservoirs. The results show that compared with the traditional methods, the proposed method significantly improves the prediction accuracy. The calculation accuracy of the new method is considerably higher than that of conventional approaches in both natural rivers and flume experiments. When applied to natural rivers, the RMSE and MAE values are 4.9% and 3.3%, respectively, while for flume tests they are 5.5% and 2.5%, respectively. It effectively reproduced the dynamic feedback between flow scour and bed armoring, accurately simulating both the gradation of the armoring layer and the depth of bed scour. Sensitivity analyses demonstrated that dynamic variation of the active-layer thickness and appropriate definition of armoring stability are essential for accurate modeling. The newly developed method, grounded in sediment transport statistics and active-layer balance theory, provides a physically-based and reliable approach for predicting armoring in gravel-sand beds. It addresses key limitations of conventional models by coupling multiple sediment transport modes and dynamic bed evolution. The results enhance understanding of riverbed armoring mechanisms and offer a robust tool for forecasting downstream channel adjustment below large dams.
Available online: June 15, 2026
Abstract:
To elucidate the spatiotemporal succession patterns and environmental driving mechanisms of bacterial communities across different habitats in reservoirs within the semi-arid region of southern Ningxia, water and sediment samples were collected from eight typical reservoirs in Guyuan City during April, July, and October 2025. By integrating 16S rRNA gene high-throughput sequencing with the Trophic Level Index (TLI), Mantel tests, and Redundancy Analysis (RDA), this study investigated community structure, seasonal dynamics, and their relationships with environmental factors.The results indicated that the eight reservoirs exhibited a complete environmental gradient ranging from mesotrophic (Site S6) to hyper-eutrophic (Site S1) status based on TLI evaluation. Proteobacteria was the predominant phylum in both water (31.68%–36.49%) and sediment (38.16%–43.48%) habitats. In July, high temperatures and strong irradiance drove an explosive enrichment of Cyanobacteriota and its constituent order Synechococcales in the water column, resulting in a simplified community structure and a decline in α-diversity. In contrast, the sediment habitat remained relatively stable, enriching benthic-specific taxa such as Acidobacteriota and Chloroflexi, with α-diversity exhibiting a trend of seasonal accumulation.The environmental driving mechanisms demonstrated distinct habitat specificity. Water bacterial communities were significantly influenced by Total Nitrogen (TN), Total Phosphorus (TP), Permanganate Index (CODMn), and Nitrate Nitrogen (NO3-N) (P<0.01), while high summer temperatures and pH were identified as key physical factors reshaping community structure. Conversely, the succession of sediment communities was primarily regulated by Ammonium Nitrogen (NH4+-N), TP, and Salinity (SAL). This study systematically elucidates the seasonal variations in microbial community structures across different habitats in arid-region reservoirs, providing a scientific basis for regional water environment management.
To elucidate the spatiotemporal succession patterns and environmental driving mechanisms of bacterial communities across different habitats in reservoirs within the semi-arid region of southern Ningxia, water and sediment samples were collected from eight typical reservoirs in Guyuan City during April, July, and October 2025. By integrating 16S rRNA gene high-throughput sequencing with the Trophic Level Index (TLI), Mantel tests, and Redundancy Analysis (RDA), this study investigated community structure, seasonal dynamics, and their relationships with environmental factors.The results indicated that the eight reservoirs exhibited a complete environmental gradient ranging from mesotrophic (Site S6) to hyper-eutrophic (Site S1) status based on TLI evaluation. Proteobacteria was the predominant phylum in both water (31.68%–36.49%) and sediment (38.16%–43.48%) habitats. In July, high temperatures and strong irradiance drove an explosive enrichment of Cyanobacteriota and its constituent order Synechococcales in the water column, resulting in a simplified community structure and a decline in α-diversity. In contrast, the sediment habitat remained relatively stable, enriching benthic-specific taxa such as Acidobacteriota and Chloroflexi, with α-diversity exhibiting a trend of seasonal accumulation.The environmental driving mechanisms demonstrated distinct habitat specificity. Water bacterial communities were significantly influenced by Total Nitrogen (TN), Total Phosphorus (TP), Permanganate Index (CODMn), and Nitrate Nitrogen (NO3-N) (P<0.01), while high summer temperatures and pH were identified as key physical factors reshaping community structure. Conversely, the succession of sediment communities was primarily regulated by Ammonium Nitrogen (NH4+-N), TP, and Salinity (SAL). This study systematically elucidates the seasonal variations in microbial community structures across different habitats in arid-region reservoirs, providing a scientific basis for regional water environment management.
Available online: June 12, 2026
Abstract:
The dynamics of total phosphorus (TP) concentrations in shallow lakes are collectively driven by multiple environmental factors. The complexity of these underlying mechanisms is closely related to the lake"s physicochemical properties. Based on high-frequency data from national water quality, hydrological, and meteorological monitoring stations in the Lake Chaohu basin from 2021 to 2024, this study employed principal component analysis (PCA) and time-lag correlation analysis to elucidate the variation patterns of TP concentrations, identify the primary driving factors, and determine the risk threshold grades of environmental factors associated with TP exceedance or abrupt changes. The results indicated that water temperature (WT), dissolved oxygen (DO), and algal density (AD) were the dominant environmental drivers governing TP fluctuations in Lake Chaohu, with a cumulative contribution rate exceeding 50%. Wind speed (WD) was identified as a key meteorological factor. Furthermore, this study identified a cascading driving process of TP dynamics with distinct time-lag effects in Lake Chaohu. Specifically, a rise in WT during summer was followed by an increase in algal biomass after 4 days, accompanied by a significant decline in DO. The decrease in DO rapidly induced an elevation in water TP concentration within 24 hours, indicating a rapid response of phosphorus release at the sediment-water microinterface. The peak impact of AD on TP concentration occurred with a 3-day lag, attributable to both direct phosphorus release during algal growth and senescence, and indirect effects via DO consumption. Based on these findings, risk threshold grades for DO (7.69, 7.08, 6.72 mg/L) and AD (9.80, 15.64, 21.14 × 10? cells/L) were established for different TP concentration intervals in Lake Chaohu: (0.05, 0.075], (0.075, 0.1], and >0.1 mg/L. These results provide a crucial temporal decision-making basis for TP risk early warning and precision management in Lake Chaohu.
The dynamics of total phosphorus (TP) concentrations in shallow lakes are collectively driven by multiple environmental factors. The complexity of these underlying mechanisms is closely related to the lake"s physicochemical properties. Based on high-frequency data from national water quality, hydrological, and meteorological monitoring stations in the Lake Chaohu basin from 2021 to 2024, this study employed principal component analysis (PCA) and time-lag correlation analysis to elucidate the variation patterns of TP concentrations, identify the primary driving factors, and determine the risk threshold grades of environmental factors associated with TP exceedance or abrupt changes. The results indicated that water temperature (WT), dissolved oxygen (DO), and algal density (AD) were the dominant environmental drivers governing TP fluctuations in Lake Chaohu, with a cumulative contribution rate exceeding 50%. Wind speed (WD) was identified as a key meteorological factor. Furthermore, this study identified a cascading driving process of TP dynamics with distinct time-lag effects in Lake Chaohu. Specifically, a rise in WT during summer was followed by an increase in algal biomass after 4 days, accompanied by a significant decline in DO. The decrease in DO rapidly induced an elevation in water TP concentration within 24 hours, indicating a rapid response of phosphorus release at the sediment-water microinterface. The peak impact of AD on TP concentration occurred with a 3-day lag, attributable to both direct phosphorus release during algal growth and senescence, and indirect effects via DO consumption. Based on these findings, risk threshold grades for DO (7.69, 7.08, 6.72 mg/L) and AD (9.80, 15.64, 21.14 × 10? cells/L) were established for different TP concentration intervals in Lake Chaohu: (0.05, 0.075], (0.075, 0.1], and >0.1 mg/L. These results provide a crucial temporal decision-making basis for TP risk early warning and precision management in Lake Chaohu.
Available online: June 12, 2026
Abstract:
The operation of the Three Gorges Reservoir (TGR) has altered water and sediment processes in the middle and lower reaches of the Yangtze River, affecting the adjustment characteristics of scouring and sedimentation in the branch channels as well as the flow distribution relationships among relatively balanced channels. Thereby exerting a cascading impact on flood control, navigation, and river management. Given the current limitations in understanding the adjustment patterns of branch channels under the influence of water and sediment conditions altered by the operation of cascade reservoi, this study utilizes measured hydrological and topographic data from 2003 to 2023. Taking eleven typical distributary channels in the Chenglingji to Jiujiang section as examples, it employs a distributary channel classification method based on dynamic diversion ratios to investigate channel type conversion phenomena and analyze their driving mechanisms. The study reveals：（1）The method for classifying branch channels based on dynamic diversion ratios demonstrates good adaptability in classifying branch channels in the middle and lower reaches of the Yangtze River and identifying their typological transitions under different operating modes of the TGR（2）Following the TGR impoundment, the branch channels exhibited different adjustment patterns during various periods. Since 2013, the section from Chenglingji to Jiujiang has been dominated by Type I branch channels (where the main channel corresponds to a low-flow-dominant branch channel), while in Type II branch channels (where the main channel corresponds to a low-flow-prone branch), the Jiepaoxin Sandbar branch section, Luxi Kou, Jiayu, and Yanzowo channels have transitioned to Type I branch channels, shifting from a “main channel shortening, branch channel lengthening” pattern to a “main channel lengthening, branch channel shortening” pattern;（3）For the transformation of Type II distributary channels into Type I channels, altered hydrological and sediment conditions were the primary driver. Navigation improvement projects demonstrated a promoting effect on this transformation in most distributary channels. After 2013, the frequency and duration of flow levels between 20,000 and 30,000 m3/s increased, leading to intensified scouring in the main channel branch at these flow levels. with some branches evolving into Class I distributary channels. It is foreseeable that branched river systems in the middle and lower reaches of the Yangtze River will predominantly shift toward Class I, characterized by an adjustment pattern where the main channel grows while tributaries diminish.
The operation of the Three Gorges Reservoir (TGR) has altered water and sediment processes in the middle and lower reaches of the Yangtze River, affecting the adjustment characteristics of scouring and sedimentation in the branch channels as well as the flow distribution relationships among relatively balanced channels. Thereby exerting a cascading impact on flood control, navigation, and river management. Given the current limitations in understanding the adjustment patterns of branch channels under the influence of water and sediment conditions altered by the operation of cascade reservoi, this study utilizes measured hydrological and topographic data from 2003 to 2023. Taking eleven typical distributary channels in the Chenglingji to Jiujiang section as examples, it employs a distributary channel classification method based on dynamic diversion ratios to investigate channel type conversion phenomena and analyze their driving mechanisms. The study reveals：（1）The method for classifying branch channels based on dynamic diversion ratios demonstrates good adaptability in classifying branch channels in the middle and lower reaches of the Yangtze River and identifying their typological transitions under different operating modes of the TGR（2）Following the TGR impoundment, the branch channels exhibited different adjustment patterns during various periods. Since 2013, the section from Chenglingji to Jiujiang has been dominated by Type I branch channels (where the main channel corresponds to a low-flow-dominant branch channel), while in Type II branch channels (where the main channel corresponds to a low-flow-prone branch), the Jiepaoxin Sandbar branch section, Luxi Kou, Jiayu, and Yanzowo channels have transitioned to Type I branch channels, shifting from a “main channel shortening, branch channel lengthening” pattern to a “main channel lengthening, branch channel shortening” pattern;（3）For the transformation of Type II distributary channels into Type I channels, altered hydrological and sediment conditions were the primary driver. Navigation improvement projects demonstrated a promoting effect on this transformation in most distributary channels. After 2013, the frequency and duration of flow levels between 20,000 and 30,000 m3/s increased, leading to intensified scouring in the main channel branch at these flow levels. with some branches evolving into Class I distributary channels. It is foreseeable that branched river systems in the middle and lower reaches of the Yangtze River will predominantly shift toward Class I, characterized by an adjustment pattern where the main channel grows while tributaries diminish.
Available online: June 12, 2026
Abstract:
In river ecosystems, environmental filtering selects for aquatic biological functional traits that exhibit specific responses to catchment-scale land use patterns. To elucidate the mechanisms by which spatial land use configurations influence the distribution of aquatic biological functional traits, this study conducted systematic surveys at 30 sampling sites in the Chishui River Basin from 2022 to 2024. Four macroinvertebrate functional groups were identified through functional trait matrix analysis and cluster analysis. Significant traits for each functional group were screened using Gini coefficients derived from random forest models. Multiple linear regression analysis was employed to examine the variation in explanatory power (R2) of habitat factors within buffer zones of 50, 100, 250, 500, 1000, and 2000 m. Based on the principle of R2 maximization, a 500-m circular buffer zone was determined as the optimal spatial scale for each sampling site. Generalized additive models were subsequently applied to identify the response intervals of buffer zone land use structure that maintain stability of each functional assemblage: forest land 15.21%–44.89%, cropland <5.29%, built-up land 1.21%–9.00%, bare land >32.49%, and water body 0.64%–10.89%, along with critical habitat parameter ranges (water temperature 15–24℃, pH 5.02–8.81, NH?-N 0.31–0.45 mg/L, substrate particle size 36–188 mm). This study further quantified the effects of natural land proportion on the suitability of each functional group: a 10% increase in natural land corresponded to suitability increases of 0.33 and 0.34 units for scrapers and predators, respectively; filters and collectors also exhibited significant suitability improvements with elevated natural land proportion. These findings reveal the response relationships and underlying mechanisms among land use, habitat factors, and macroinvertebrate functional groups, providing quantitative foundations for catchment ecological conservation and land management.
In river ecosystems, environmental filtering selects for aquatic biological functional traits that exhibit specific responses to catchment-scale land use patterns. To elucidate the mechanisms by which spatial land use configurations influence the distribution of aquatic biological functional traits, this study conducted systematic surveys at 30 sampling sites in the Chishui River Basin from 2022 to 2024. Four macroinvertebrate functional groups were identified through functional trait matrix analysis and cluster analysis. Significant traits for each functional group were screened using Gini coefficients derived from random forest models. Multiple linear regression analysis was employed to examine the variation in explanatory power (R2) of habitat factors within buffer zones of 50, 100, 250, 500, 1000, and 2000 m. Based on the principle of R2 maximization, a 500-m circular buffer zone was determined as the optimal spatial scale for each sampling site. Generalized additive models were subsequently applied to identify the response intervals of buffer zone land use structure that maintain stability of each functional assemblage: forest land 15.21%–44.89%, cropland <5.29%, built-up land 1.21%–9.00%, bare land >32.49%, and water body 0.64%–10.89%, along with critical habitat parameter ranges (water temperature 15–24℃, pH 5.02–8.81, NH?-N 0.31–0.45 mg/L, substrate particle size 36–188 mm). This study further quantified the effects of natural land proportion on the suitability of each functional group: a 10% increase in natural land corresponded to suitability increases of 0.33 and 0.34 units for scrapers and predators, respectively; filters and collectors also exhibited significant suitability improvements with elevated natural land proportion. These findings reveal the response relationships and underlying mechanisms among land use, habitat factors, and macroinvertebrate functional groups, providing quantitative foundations for catchment ecological conservation and land management.
Available online: June 11, 2026
Abstract:
Lakes are vital ecosystems providing essential functions such as water conservation, climate regulation, and biodiversity maintenance. Jiangsu Province, located in the lower reaches of the Yangtze and Huaihe rivers, is a typical region of shallow lakes in China where eutrophication remains a prominent issue. Due to the distinct natural geographical backgrounds and socio-economic development levels between Northern and Southern Jiangsu, the trophic states and driving mechanisms of these lakes exhibit significant regional heterogeneity. Based on long-term monthly monitoring data from 2011 to 2023, this study systematically analyzed the spatiotemporal evolution of water quality indicators and the comprehensive Trophic Level Index (TLI) in seven typical lakes: Lake Luoma, Lake Hongze, Lake Baima, and Lake Gaoyou in Northern Jiangsu, and Lake Ge, Lake Changdang, and Lake Gucheng in Southern Jiangsu. The driving mechanisms were further quantified using Random Forest (RF) models and Pearson correlation analysis. The results showed that over the past decade, the water quality of typical lakes in Jiangsu exhibited a distinct regional divergence. In terms of trophic status, Lake Ge and Lake Changdang exhibited the highest degree of eutrophication, ranging from light to moderate eutrophic states. Lake Baima, Lake Hongze, and Lake Gaoyou were categorized as lightly eutrophic, while Lake Luoma and Lake Gucheng were positioned within the critical transition range from mesotrophic to lightly eutrophic states. Trend analysis revealed that lakes in Southern Jiangsu exhibited significant water quality improvements, particularly Lake Ge and Lake Changdang, which were historically moderately eutrophic. Specifically, TN and TP concentrations in Lake Ge decreased by 1.96 mg/L and 0.087 mg/L (a 48.3% reduction), respectively, with its TLI dropping by 9.4. Conversely, lakes in Northern Jiangsu experienced a deteriorating trend. Lake Luoma transitioned from mesotrophic to lightly eutrophic as its TLI rose by 7.4, while Lake Hongze and Lake Gaoyou TLI increased 6.6 and 5.4, respectively. TLI values ranged across the study area from 47.36 to 61.01, with Southern lakes generally maintaining higher absolute trophic levels but showing better remediation progress. In terms of seasonal variation, Northern lakes exhibited significant differences between flood and non-flood seasons, with TLI values significantly higher during the flood season, whereas Southern lakes remained relatively stable throughout the year. Driver analysis revealed that water quality in Northern lakes was highly sensitive to hydrometeorological fluctuations. Increased precipitation and the resulting surge in inflow volume acted as the primary drivers of exogenous nutrient loading, further exacerbated by internal release under high temperatures and wind disturbances. In contrast, the improvement in Southern lakes was mainly attributed to landuse optimization and strict pollution control. The reduction in farmland (acting as a "source") and the restoration of forests and wetlands (acting as "sinks") effectively intercepted runoff pollution. These findings highlight the complexity of lake management under climate change and non-point source pressures, providing a scientific basis for differentiated eutrophication control and regional water security strategies in Jiangsu Province.
Lakes are vital ecosystems providing essential functions such as water conservation, climate regulation, and biodiversity maintenance. Jiangsu Province, located in the lower reaches of the Yangtze and Huaihe rivers, is a typical region of shallow lakes in China where eutrophication remains a prominent issue. Due to the distinct natural geographical backgrounds and socio-economic development levels between Northern and Southern Jiangsu, the trophic states and driving mechanisms of these lakes exhibit significant regional heterogeneity. Based on long-term monthly monitoring data from 2011 to 2023, this study systematically analyzed the spatiotemporal evolution of water quality indicators and the comprehensive Trophic Level Index (TLI) in seven typical lakes: Lake Luoma, Lake Hongze, Lake Baima, and Lake Gaoyou in Northern Jiangsu, and Lake Ge, Lake Changdang, and Lake Gucheng in Southern Jiangsu. The driving mechanisms were further quantified using Random Forest (RF) models and Pearson correlation analysis. The results showed that over the past decade, the water quality of typical lakes in Jiangsu exhibited a distinct regional divergence. In terms of trophic status, Lake Ge and Lake Changdang exhibited the highest degree of eutrophication, ranging from light to moderate eutrophic states. Lake Baima, Lake Hongze, and Lake Gaoyou were categorized as lightly eutrophic, while Lake Luoma and Lake Gucheng were positioned within the critical transition range from mesotrophic to lightly eutrophic states. Trend analysis revealed that lakes in Southern Jiangsu exhibited significant water quality improvements, particularly Lake Ge and Lake Changdang, which were historically moderately eutrophic. Specifically, TN and TP concentrations in Lake Ge decreased by 1.96 mg/L and 0.087 mg/L (a 48.3% reduction), respectively, with its TLI dropping by 9.4. Conversely, lakes in Northern Jiangsu experienced a deteriorating trend. Lake Luoma transitioned from mesotrophic to lightly eutrophic as its TLI rose by 7.4, while Lake Hongze and Lake Gaoyou TLI increased 6.6 and 5.4, respectively. TLI values ranged across the study area from 47.36 to 61.01, with Southern lakes generally maintaining higher absolute trophic levels but showing better remediation progress. In terms of seasonal variation, Northern lakes exhibited significant differences between flood and non-flood seasons, with TLI values significantly higher during the flood season, whereas Southern lakes remained relatively stable throughout the year. Driver analysis revealed that water quality in Northern lakes was highly sensitive to hydrometeorological fluctuations. Increased precipitation and the resulting surge in inflow volume acted as the primary drivers of exogenous nutrient loading, further exacerbated by internal release under high temperatures and wind disturbances. In contrast, the improvement in Southern lakes was mainly attributed to landuse optimization and strict pollution control. The reduction in farmland (acting as a "source") and the restoration of forests and wetlands (acting as "sinks") effectively intercepted runoff pollution. These findings highlight the complexity of lake management under climate change and non-point source pressures, providing a scientific basis for differentiated eutrophication control and regional water security strategies in Jiangsu Province.
Available online: June 11, 2026
Abstract:
Sediment nitrogen and phosphorus pollution has become a critical factor limiting the sustained improvement of lake water quality in China. To address this issue, this study reviewed domestic and international literature and monitoring data from 2000 to 2022, obtaining surface sediment data from 131 lakes within China"s five major lake zones—Eastern Plain Lakes (EPL), Northeast Plain & Mountain Lakes (NPML), Inner Mongolia-Xinjiang Plateau Lakes (IXML), Yunnan-Guizhou Plateau Lakes (YGPL), and Tibetan Plateau Lakes (TPL). The Single Pollution Index (Pi) method was employed to evaluate the pollution status and spatial differentiation characteristics of Total Nitrogen (TN) and Total Phosphorus (TP). Furthermore, by incorporating case studies, this research systematically reviews the nearly 70-year evolution of management paradigms for lake sediments in China. The key findings are as follows: (1) TN pollution in lake sediments is relatively severe overall (Average Pi = 4.54), reaching a heavy pollution level, with a spatial pattern showing higher levels in the northeast and southwest and lower levels in central and western regions. The pollution degree across lake zones, in descending order, is: NPML Pi = 6.90 > YGPL (5.89) > IXML (5.08) > EPL (4.09) > TPL (4.08). In contrast, TP pollution is relatively lighter overall (Average Pi = 1.41), with the order YGPL Pi = 2.26 > NPML (1.96) > IXML (1.32) > EPL (1.27) > TPL (0.94), at a light pollution level. This indicates that the relatively severe TN pollution and the TP pollution in Chinese lakes are primarily influenced by localized anthropogenic inputs and regional natural backgrounds. (2) The management of sediment pollution in China has undergone a clear three-stage developmental progression: from engineering dredging (1950–1998) to environmental dredging (1998–2015), and then to the current stage of systematic governance (2015–present). (3) For future management, a systematic approach guided by the principle of "zoning, classification, and gradation" must be implemented. Efforts should focus on strengthening foundational surveys and database construction, promoting the classified recycling and utilization of sediments based on pollution characteristics, and establishing long-term guarantee mechanisms, to achieve effective internal pollution control and the long-term restoration of lake ecosystems in China.
Sediment nitrogen and phosphorus pollution has become a critical factor limiting the sustained improvement of lake water quality in China. To address this issue, this study reviewed domestic and international literature and monitoring data from 2000 to 2022, obtaining surface sediment data from 131 lakes within China"s five major lake zones—Eastern Plain Lakes (EPL), Northeast Plain & Mountain Lakes (NPML), Inner Mongolia-Xinjiang Plateau Lakes (IXML), Yunnan-Guizhou Plateau Lakes (YGPL), and Tibetan Plateau Lakes (TPL). The Single Pollution Index (Pi) method was employed to evaluate the pollution status and spatial differentiation characteristics of Total Nitrogen (TN) and Total Phosphorus (TP). Furthermore, by incorporating case studies, this research systematically reviews the nearly 70-year evolution of management paradigms for lake sediments in China. The key findings are as follows: (1) TN pollution in lake sediments is relatively severe overall (Average Pi = 4.54), reaching a heavy pollution level, with a spatial pattern showing higher levels in the northeast and southwest and lower levels in central and western regions. The pollution degree across lake zones, in descending order, is: NPML Pi = 6.90 > YGPL (5.89) > IXML (5.08) > EPL (4.09) > TPL (4.08). In contrast, TP pollution is relatively lighter overall (Average Pi = 1.41), with the order YGPL Pi = 2.26 > NPML (1.96) > IXML (1.32) > EPL (1.27) > TPL (0.94), at a light pollution level. This indicates that the relatively severe TN pollution and the TP pollution in Chinese lakes are primarily influenced by localized anthropogenic inputs and regional natural backgrounds. (2) The management of sediment pollution in China has undergone a clear three-stage developmental progression: from engineering dredging (1950–1998) to environmental dredging (1998–2015), and then to the current stage of systematic governance (2015–present). (3) For future management, a systematic approach guided by the principle of "zoning, classification, and gradation" must be implemented. Efforts should focus on strengthening foundational surveys and database construction, promoting the classified recycling and utilization of sediments based on pollution characteristics, and establishing long-term guarantee mechanisms, to achieve effective internal pollution control and the long-term restoration of lake ecosystems in China.
Available online: June 10, 2026
Abstract:
The global attention to the pollution of nutrients and per-and polyfluoroalkyl substances (PFAS) is increasing, which requires the development of more efficient and low-cost remediation strategies. This study focuses on the remediation of nitrogen, phosphorus, and various PFAS components by aquatic plants, representing a sustainable alternative to traditional physical and chemical methods. In order to overcome the limitations of traditional experimental methods, we constructed a comprehensive dataset by systematically searching for literature in databases such as CNKI, Science Direct, and Web of Science from 2015 to 2025. The final database contains 128 independent experimental records, covering pollutant remediation data under different experimental conditions, ensuring the universality of research conclusions. The input features cover 14 dimensions, including aquatic plant types (submerged, emergent, and floating), planting density, environmental temperature, and initial concentrations of nitrogen, phosphorus, and eight specific PFAS components (such as PFOS, PFOA, PFBA). In order to mitigate inherent systematic biases in multi-source literature data, this study implemented strict quality control protocols. For missing values of secondary environmental parameters, RF-based imputation is used for processing, which can better preserve the nonlinear structure of the data than simple mean replacement. All numerical features are standardized using StandardScaler to eliminate dimensional deviations. In addition, data heterogeneity was quantitatively evaluated using one-way analysis of variance (ANOVA) and effect measures (η2). The results indicate that planting density and temperature are the main sources of statistical heterogeneity, explaining 41.67% and 41.47% of the total variation, respectively (P<0.001). We comprehensively evaluated the impact of various factors on the removal rate of PFAS using Multi-objective Random Forest (MTRF), Multilayer Perceptron (MLP), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) algorithms.?Use R2 and Root Mean Square Err (RMSE) as evaluation metrics for different models.The MTRF model achieved average R2 values of 0.68 and 0.72 in nitrogen removal and PFNA prediction, respectively, demonstrating substantial predictive ability significantly better than the MLP model with negative R2 values and inability to capture complex patterns. The in-depth mechanism explanation using the SHAP framework reveals that initial phosphorus concentration has a positive effect on nitrogen absorption, and phosphorus can promote nitrogen absorption by improving plant metabolic capacity. For PFAS, a threshold suppression effect was observed; Due to oxidative stress and enzyme activity inhibition caused by reactive oxygen species (ROS), high initial concentrations and extreme temperatures are negatively correlated with removal efficiency. Through virtual screening, Vallisneria natans was identified as the dominant species, possibly due to its strong root to stem transport ability and high bioaccumulation factor for PFAS. By optimizing the operating conditions, the optimal planting density for removing nutrients from Vallisneria natans is 19 plants/m2, and the optimal restoration time is 69 days; The optimal planting density for removing PFAS is 59 plants/m2, and the optimal restoration time is 34 days. The machine learning model established in this study not only provides accurate predictions for plant remediation efficiency under complex water quality conditions, but also provides theoretical basis and engineering decision support for low-cost and systematic treatment of water composite pollution.
The global attention to the pollution of nutrients and per-and polyfluoroalkyl substances (PFAS) is increasing, which requires the development of more efficient and low-cost remediation strategies. This study focuses on the remediation of nitrogen, phosphorus, and various PFAS components by aquatic plants, representing a sustainable alternative to traditional physical and chemical methods. In order to overcome the limitations of traditional experimental methods, we constructed a comprehensive dataset by systematically searching for literature in databases such as CNKI, Science Direct, and Web of Science from 2015 to 2025. The final database contains 128 independent experimental records, covering pollutant remediation data under different experimental conditions, ensuring the universality of research conclusions. The input features cover 14 dimensions, including aquatic plant types (submerged, emergent, and floating), planting density, environmental temperature, and initial concentrations of nitrogen, phosphorus, and eight specific PFAS components (such as PFOS, PFOA, PFBA). In order to mitigate inherent systematic biases in multi-source literature data, this study implemented strict quality control protocols. For missing values of secondary environmental parameters, RF-based imputation is used for processing, which can better preserve the nonlinear structure of the data than simple mean replacement. All numerical features are standardized using StandardScaler to eliminate dimensional deviations. In addition, data heterogeneity was quantitatively evaluated using one-way analysis of variance (ANOVA) and effect measures (η2). The results indicate that planting density and temperature are the main sources of statistical heterogeneity, explaining 41.67% and 41.47% of the total variation, respectively (P<0.001). We comprehensively evaluated the impact of various factors on the removal rate of PFAS using Multi-objective Random Forest (MTRF), Multilayer Perceptron (MLP), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) algorithms.?Use R2 and Root Mean Square Err (RMSE) as evaluation metrics for different models.The MTRF model achieved average R2 values of 0.68 and 0.72 in nitrogen removal and PFNA prediction, respectively, demonstrating substantial predictive ability significantly better than the MLP model with negative R2 values and inability to capture complex patterns. The in-depth mechanism explanation using the SHAP framework reveals that initial phosphorus concentration has a positive effect on nitrogen absorption, and phosphorus can promote nitrogen absorption by improving plant metabolic capacity. For PFAS, a threshold suppression effect was observed; Due to oxidative stress and enzyme activity inhibition caused by reactive oxygen species (ROS), high initial concentrations and extreme temperatures are negatively correlated with removal efficiency. Through virtual screening, Vallisneria natans was identified as the dominant species, possibly due to its strong root to stem transport ability and high bioaccumulation factor for PFAS. By optimizing the operating conditions, the optimal planting density for removing nutrients from Vallisneria natans is 19 plants/m2, and the optimal restoration time is 69 days; The optimal planting density for removing PFAS is 59 plants/m2, and the optimal restoration time is 34 days. The machine learning model established in this study not only provides accurate predictions for plant remediation efficiency under complex water quality conditions, but also provides theoretical basis and engineering decision support for low-cost and systematic treatment of water composite pollution.
Available online: June 10, 2026
Abstract:
As global climate change intensifies, hydrological cycles are exhibiting increasingly pronounced non-stationary, multi-scale, and highly nonlinear behaviors. Traditional mechanistic models face significant challenges in fully capturing the meteorological–runoff response mechanisms, while deep learning approaches still struggle with long-term dependency modeling, spatial correlations, and sequence decoupling. To address these issues, we propose a hybrid forecasting model, JMD-Gformer, which combines Jump plus AM-FM Mode Decomposition (JMD), sparse directed graph networks, and Transformer-based architectures. In this framework, JMD decomposes the non-stationary runoff time series into jump components (representing abrupt runoff events) and periodic components (capturing seasonal and inter-annual fluctuations), effectively mitigating noise and mode aliasing. Additionally, we construct a sparse directed graph based on meteorology-hydrology nodes to represent the upstream-downstream interactions. The model further incorporates a multi-head self-attention mechanism for long-range temporal dependencies. Experiments conducted on multi-time-scale runoff predictions in the Daliao River Basin demonstrate that, compared to the second-best benchmark model, JMD-Gformer reduces MAPE and RMSE by 36.4% and 41.2%, respectively, and shows strong robustness and predictive accuracy under complex hydrological conditions. This model provides a promising new approach for smart watershed management.
As global climate change intensifies, hydrological cycles are exhibiting increasingly pronounced non-stationary, multi-scale, and highly nonlinear behaviors. Traditional mechanistic models face significant challenges in fully capturing the meteorological–runoff response mechanisms, while deep learning approaches still struggle with long-term dependency modeling, spatial correlations, and sequence decoupling. To address these issues, we propose a hybrid forecasting model, JMD-Gformer, which combines Jump plus AM-FM Mode Decomposition (JMD), sparse directed graph networks, and Transformer-based architectures. In this framework, JMD decomposes the non-stationary runoff time series into jump components (representing abrupt runoff events) and periodic components (capturing seasonal and inter-annual fluctuations), effectively mitigating noise and mode aliasing. Additionally, we construct a sparse directed graph based on meteorology-hydrology nodes to represent the upstream-downstream interactions. The model further incorporates a multi-head self-attention mechanism for long-range temporal dependencies. Experiments conducted on multi-time-scale runoff predictions in the Daliao River Basin demonstrate that, compared to the second-best benchmark model, JMD-Gformer reduces MAPE and RMSE by 36.4% and 41.2%, respectively, and shows strong robustness and predictive accuracy under complex hydrological conditions. This model provides a promising new approach for smart watershed management.
Ye Zili, Zhi Mingqiang, Zhang Wenyu, Li Yuanhe, Shi Yuanzhi, Zhang Chunmin, Zhang Huajun, Huang Wei, Liu Cheng, Yin Hongbin
Available online: June 09, 2026
Abstract:
Taking East Taihu Lake as the research object, this study systematically investigated the physicochemical properties, nutrient distribution and pollutant release characteristics of sediments in historical aquaculture areas and aquatic vegetation zones. The single–factor pollution index method and comprehensive pollution index method were adopted to evaluate sediment pollution, so as to clarify the sediment pollution and release characteristics in the historical aquaculture areas of East Taihu Lake. The results showed that there were significant differences in the physicochemical properties, nutrient contents and distribution of sediments between the historical aquaculture areas and the aquatic vegetation zones. The pH values (7.19 and 7.23, respectively) and moisture contents (65.84% and 54.31%, respectively) of surface sediments at 0–10 cm and 10–20 cm in the aquaculture areas were significantly higher than those in the aquatic vegetation zones (p < 0.05). Moreover, the pH value increased with sediment depth, while the moisture content decreased with depth. The average contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in surface sediments at 0–10 cm in the aquaculture areas were 1610 mg/kg, 665 mg/kg and 4.26%, respectively, which were 1.22, 1.43 and 1.51 times those in the aquatic vegetation zones, and nutrients in the aquaculture areas were mainly accumulated in the surface sediment layer.The average total nitrogen release rate in the aquaculture areas (31.63 mg·m-2·d-1) was much higher than that in the aquatic vegetation zones (-3.99 mg·m-2·d-1), showing a continuous release state, whereas no significant difference was observed in the total phosphorus release rate between the two zones. The concentrations of ammonia nitrogen and ferrous iron in pore water, as well as the release fluxes calculated by Fick"s Law, were significantly higher in the aquaculture areas than in the aquatic vegetation zones (p < 0.05). The average concentration of diffusive gradients in thin films–extractable phosphorus (DGT–P) in the aquaculture areas (0.026 mg/L) was 1.5 times that in the aquatic vegetation zones (0.017 mg/L), indicating a stronger release capacity of labile phosphorus.The sediment pollution assessment revealed that sediment pollution exhibited the characteristics of "vertical decrease and regional differentiation".The proportion of heavily polluted sites for total nitrogen (TN) in the 0–10 cm layer was 17.4%, and that for the comprehensive pollution index (FF) was 35.5%; this proportion for FF decreased to 26.1% in the 10–20 cm layer. The 20–30 cm layer was dominated by light pollution for FF (accounting for 37.4%). The pollution indices of the aquaculture areas were significantly higher than those of the aquatic vegetation zones at all depth layers, and heavily polluted sites were concentrated in the historical aquaculture areas. The results of this study can provide scientific support for the precise control of internal pollution in the aquaculture areas of East Taihu Lake.
Taking East Taihu Lake as the research object, this study systematically investigated the physicochemical properties, nutrient distribution and pollutant release characteristics of sediments in historical aquaculture areas and aquatic vegetation zones. The single–factor pollution index method and comprehensive pollution index method were adopted to evaluate sediment pollution, so as to clarify the sediment pollution and release characteristics in the historical aquaculture areas of East Taihu Lake. The results showed that there were significant differences in the physicochemical properties, nutrient contents and distribution of sediments between the historical aquaculture areas and the aquatic vegetation zones. The pH values (7.19 and 7.23, respectively) and moisture contents (65.84% and 54.31%, respectively) of surface sediments at 0–10 cm and 10–20 cm in the aquaculture areas were significantly higher than those in the aquatic vegetation zones (p < 0.05). Moreover, the pH value increased with sediment depth, while the moisture content decreased with depth. The average contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in surface sediments at 0–10 cm in the aquaculture areas were 1610 mg/kg, 665 mg/kg and 4.26%, respectively, which were 1.22, 1.43 and 1.51 times those in the aquatic vegetation zones, and nutrients in the aquaculture areas were mainly accumulated in the surface sediment layer.The average total nitrogen release rate in the aquaculture areas (31.63 mg·m-2·d-1) was much higher than that in the aquatic vegetation zones (-3.99 mg·m-2·d-1), showing a continuous release state, whereas no significant difference was observed in the total phosphorus release rate between the two zones. The concentrations of ammonia nitrogen and ferrous iron in pore water, as well as the release fluxes calculated by Fick"s Law, were significantly higher in the aquaculture areas than in the aquatic vegetation zones (p < 0.05). The average concentration of diffusive gradients in thin films–extractable phosphorus (DGT–P) in the aquaculture areas (0.026 mg/L) was 1.5 times that in the aquatic vegetation zones (0.017 mg/L), indicating a stronger release capacity of labile phosphorus.The sediment pollution assessment revealed that sediment pollution exhibited the characteristics of "vertical decrease and regional differentiation".The proportion of heavily polluted sites for total nitrogen (TN) in the 0–10 cm layer was 17.4%, and that for the comprehensive pollution index (FF) was 35.5%; this proportion for FF decreased to 26.1% in the 10–20 cm layer. The 20–30 cm layer was dominated by light pollution for FF (accounting for 37.4%). The pollution indices of the aquaculture areas were significantly higher than those of the aquatic vegetation zones at all depth layers, and heavily polluted sites were concentrated in the historical aquaculture areas. The results of this study can provide scientific support for the precise control of internal pollution in the aquaculture areas of East Taihu Lake.
Chen Weijing, Fu Yu, Teng Jiakun, Xie Tian, Lu Xiuming, Yu Hailing, Che Chunguang, Duan Houlang, Yu Xiubo
Available online: June 09, 2026
Abstract:
Hydrology and vegetation are important components of the landscape structure of freshwater wetlands. Changes in the water and sediment regimes of the Yellow River, along with reduced freshwater input, have impacted waterbird diversity in the Shandong Yellow River Delta National Nature Reserve (hereinafter referred to as the "Nature Reserve"). In response, the Nature Reserve has implemented consecutive years of freshwater wetland ecological water supplement projects, regulating the distribution area of open water and shallow water, and improving plant community composition. However, quantitative research on waterbird diversity and its relationship with wetland landscape patterns following this ecological intervention has been lacking. This study utilizes waterbird survey data, Sentinel-2 satellite remote sensing data, and water level monitoring data collected during field investigations in 2023 and 2024. The aim is to elucidate the composition and numerical changes of waterbird communities in the wetland restoration area and to reveal the quantitative relationships between waterbird diversity and the areal extent of key wetland landscape elements. The results showed that a total of 126 waterbird species belonging to 15 families and 7 orders were recorded in the study area. Waterbird species richness and individual abundance exhibited significant monthly fluctuations, with peaks during migration periods in March and November. During migration seasons, ducks and shorebirds dominated in terms of species proportion, while ducks, cranes, and storks dominated in terms of individual abundance. Within the 10,000-mu wetland restoration area of the Nature Reserve, the areas of shallow water (water depth 0-30 cm) and open water were largest. Specifically, the shallow water area was greatest in winter (1888 m2), while the open water area was relatively larger in spring and autumn (2933 m2). The vegetation area exhibited a trend of "expansion in summer, contraction in winter," increasing by 26% in 2024 compared to 2023. The abundance of geese and ducks showed a unimodal relationship with the proportions of both open water area and vegetation area. Goose abundance peaked when the ratio of water area to vegetation area was approximately 2:1 (n = 44, df = 40, p < 0.01, R2 = 0.14; n = 44, df = 40, p < 0.01, R2 = 0.28). Duck abundance peaked when this ratio was approximately 1.5:1 (n = 118, df = 114, p < 0.01, R2 = 0.02; n = 118, df = 114, p < 0.01, R2 = 0.002). The abundance of shorebirds was significantly positively correlated with the proportion of shallow water area (n = 24, df = 22, p < 0.05, R2 = 0.29) but significantly negatively correlated with the proportion of vegetation area (n = 24, df = 22, p < 0.05, R2 = 0.17).
Hydrology and vegetation are important components of the landscape structure of freshwater wetlands. Changes in the water and sediment regimes of the Yellow River, along with reduced freshwater input, have impacted waterbird diversity in the Shandong Yellow River Delta National Nature Reserve (hereinafter referred to as the "Nature Reserve"). In response, the Nature Reserve has implemented consecutive years of freshwater wetland ecological water supplement projects, regulating the distribution area of open water and shallow water, and improving plant community composition. However, quantitative research on waterbird diversity and its relationship with wetland landscape patterns following this ecological intervention has been lacking. This study utilizes waterbird survey data, Sentinel-2 satellite remote sensing data, and water level monitoring data collected during field investigations in 2023 and 2024. The aim is to elucidate the composition and numerical changes of waterbird communities in the wetland restoration area and to reveal the quantitative relationships between waterbird diversity and the areal extent of key wetland landscape elements. The results showed that a total of 126 waterbird species belonging to 15 families and 7 orders were recorded in the study area. Waterbird species richness and individual abundance exhibited significant monthly fluctuations, with peaks during migration periods in March and November. During migration seasons, ducks and shorebirds dominated in terms of species proportion, while ducks, cranes, and storks dominated in terms of individual abundance. Within the 10,000-mu wetland restoration area of the Nature Reserve, the areas of shallow water (water depth 0-30 cm) and open water were largest. Specifically, the shallow water area was greatest in winter (1888 m2), while the open water area was relatively larger in spring and autumn (2933 m2). The vegetation area exhibited a trend of "expansion in summer, contraction in winter," increasing by 26% in 2024 compared to 2023. The abundance of geese and ducks showed a unimodal relationship with the proportions of both open water area and vegetation area. Goose abundance peaked when the ratio of water area to vegetation area was approximately 2:1 (n = 44, df = 40, p < 0.01, R2 = 0.14; n = 44, df = 40, p < 0.01, R2 = 0.28). Duck abundance peaked when this ratio was approximately 1.5:1 (n = 118, df = 114, p < 0.01, R2 = 0.02; n = 118, df = 114, p < 0.01, R2 = 0.002). The abundance of shorebirds was significantly positively correlated with the proportion of shallow water area (n = 24, df = 22, p < 0.05, R2 = 0.29) but significantly negatively correlated with the proportion of vegetation area (n = 24, df = 22, p < 0.05, R2 = 0.17).
Available online: June 08, 2026
Abstract:
To explore the spatiotemporal coupling mechanism of the water network in the Erhai Basin under the combined influence of natural and social drivers, and to reveal the mediating role of topological features between driving factors and water system elements, this study integrates four phases of remote sensing and geographic data within the framework of complex network theory. Nine topological indicators were selected to characterize the structural features of the basin’s water network，to overcome the limitation of traditional regression that it is difficult to simultaneously handle driver collinearity, spatial overflow and mechanism decomposition, this paper constructs a （Partial Least Squares）PLS-（Spatial Durbin Model）SDM-（Mediation effect）MED framework that can handle multi-driver collinearity, simultaneously characterize spatial overflow, and decompose the total effect into direct effects and indirect effects conducted through topological structure, thereby more accurately identifying key intermediate paths. The results show that:(1) From 2001 to 2023, the Erhai water network evolved from a multi-source redundant configuration to a stable state characterized by a clear mainstem and relatively high efficiency.(2) Among a total of 216 paths, 68 significant X-M-Y paths were identified, with mediation efficiencies mainly ranging between 40% and 80%. Betweenness centrality of edges, compactness, global efficiency, and algebraic connectivity were identified as the core mediating indicators.(3) Social factors primarily exerted high-proportion negative effects on hydrological elements through the mediating role of network topology, while natural factors generally displayed moderately strong and stable positive effects, with a few pathways showing structural suppressing effects.The proposed PLS–SDM–Med analytical framework provides a transferable approach for identifying key structural units and risk pathways in plateau lake basins, offering a theoretical basis for zoning control and ecological restoration in the Erhai Basin and other similar highland lake watersheds.
To explore the spatiotemporal coupling mechanism of the water network in the Erhai Basin under the combined influence of natural and social drivers, and to reveal the mediating role of topological features between driving factors and water system elements, this study integrates four phases of remote sensing and geographic data within the framework of complex network theory. Nine topological indicators were selected to characterize the structural features of the basin’s water network，to overcome the limitation of traditional regression that it is difficult to simultaneously handle driver collinearity, spatial overflow and mechanism decomposition, this paper constructs a （Partial Least Squares）PLS-（Spatial Durbin Model）SDM-（Mediation effect）MED framework that can handle multi-driver collinearity, simultaneously characterize spatial overflow, and decompose the total effect into direct effects and indirect effects conducted through topological structure, thereby more accurately identifying key intermediate paths. The results show that:(1) From 2001 to 2023, the Erhai water network evolved from a multi-source redundant configuration to a stable state characterized by a clear mainstem and relatively high efficiency.(2) Among a total of 216 paths, 68 significant X-M-Y paths were identified, with mediation efficiencies mainly ranging between 40% and 80%. Betweenness centrality of edges, compactness, global efficiency, and algebraic connectivity were identified as the core mediating indicators.(3) Social factors primarily exerted high-proportion negative effects on hydrological elements through the mediating role of network topology, while natural factors generally displayed moderately strong and stable positive effects, with a few pathways showing structural suppressing effects.The proposed PLS–SDM–Med analytical framework provides a transferable approach for identifying key structural units and risk pathways in plateau lake basins, offering a theoretical basis for zoning control and ecological restoration in the Erhai Basin and other similar highland lake watersheds.
Available online: June 08, 2026
Abstract:
PME (Phosphate monoesters) are key components of dissolved organic phosphorus, characterized by relatively high abundance and pronounced photoactivity; however, their photochemical dephosphorylation mechanisms in aquatic systems remain to be systematically elucidated. The study systematically investigated the photochemical behavior of the phosphate monoester G6P (Glucose-6-phosphate) by combining experimental investigations with DFT (Density Functional Theory) calculations. The results indicated that the light absorption of G6P is primarily in the 200–290?nm range, with higher photolysis efficiency under shorter-wavelength irradiation. Analysis of energy and electron transfer processes revealed that interactions between G6P and DO (Dissolved Oxygen), DOM (Dissolved Organic Matter), and major anions (e.g., NO3-, HCO3-) do not serve as the main pathways driving its photolysis. Instead, photodegradation relies more on the attack of RIs (Reactive Intermediates) on electron-rich sites, such as the extended region of the glycosyl–phosphate linkage, which triggers molecular destabilization and ultimately leads to IP (Inorganic Phosphate) release. Photolysis experiments further confirmed this mechanism, showing that 3DOM* plays a predominant role in promoting G6P degradation in DOM-containing systems. From an environmental perspective, significant differences were observed in the photolysis of PME between freshwater and seawater systems. The photolysis rate constants of G6P were determined to be (2.00–5.60)?×10-3?h-1 in freshwater and (1.60–3.30)?×10-3?h-1 in seawater. Freshwater systems favor oxidation-dominated pathways with higher thermodynamic driving force, whereas seawater systems, under high salinity and halide-rich conditions, exhibit more pronounced halogen substitution and addition characteristics. Overall, this study demonstrates that the photolysis of PME is co-determined by its molecular structure and ambient aqueous conditions, which collectively govern the pathways and efficiency of its photochemical transformation. These findings provide a new mechanistic perspective for understanding the abiotic mineralization and environmental behavior of DOP (Dissolved Organic Phosphorus) in aquatic systems.
PME (Phosphate monoesters) are key components of dissolved organic phosphorus, characterized by relatively high abundance and pronounced photoactivity; however, their photochemical dephosphorylation mechanisms in aquatic systems remain to be systematically elucidated. The study systematically investigated the photochemical behavior of the phosphate monoester G6P (Glucose-6-phosphate) by combining experimental investigations with DFT (Density Functional Theory) calculations. The results indicated that the light absorption of G6P is primarily in the 200–290?nm range, with higher photolysis efficiency under shorter-wavelength irradiation. Analysis of energy and electron transfer processes revealed that interactions between G6P and DO (Dissolved Oxygen), DOM (Dissolved Organic Matter), and major anions (e.g., NO3-, HCO3-) do not serve as the main pathways driving its photolysis. Instead, photodegradation relies more on the attack of RIs (Reactive Intermediates) on electron-rich sites, such as the extended region of the glycosyl–phosphate linkage, which triggers molecular destabilization and ultimately leads to IP (Inorganic Phosphate) release. Photolysis experiments further confirmed this mechanism, showing that 3DOM* plays a predominant role in promoting G6P degradation in DOM-containing systems. From an environmental perspective, significant differences were observed in the photolysis of PME between freshwater and seawater systems. The photolysis rate constants of G6P were determined to be (2.00–5.60)?×10-3?h-1 in freshwater and (1.60–3.30)?×10-3?h-1 in seawater. Freshwater systems favor oxidation-dominated pathways with higher thermodynamic driving force, whereas seawater systems, under high salinity and halide-rich conditions, exhibit more pronounced halogen substitution and addition characteristics. Overall, this study demonstrates that the photolysis of PME is co-determined by its molecular structure and ambient aqueous conditions, which collectively govern the pathways and efficiency of its photochemical transformation. These findings provide a new mechanistic perspective for understanding the abiotic mineralization and environmental behavior of DOP (Dissolved Organic Phosphorus) in aquatic systems.
Available online: June 05, 2026
Abstract:
Rivers entering the lake constitute the primary pathways for external nutrient inputs, and variations in nitrogen (N) and phosphorus (P) fluxes directly influence lake eutrophication and the risk of algal blooms. To accurately assess the pollutant export characteristics and driving mechanisms of typical inflow rivers in the Chaohu Basin, this study focuses on the Hangbu River, the largest tributary discharging into Chaohu Lake. Using the period-average flux method, the Load Estimator (LOADEST) model, and the WRTDS model, fluxes and long-term trends were estimated for hydrological and water-quality data from 2019 to 2024 at four stations along the river: Yaojiahe (upstream), Hekou Bridge (midstream), Sanhe Town Bridge (mid-downstream), and Beizhadukou (downstream). The period-average method is computationally simple but produces large errors. In comparison, the LOADEST model performs better in the Chaohu Basin and achieves substantially higher agreement with observed daily fluxes than the WRTDS model. The results show that LOADEST performs best under conditions of continuous discharge records and relatively sparse water-quality measurements, with R2 values of 0.89 to 0.97 and NSE values of 0.84 to 0.98, allowing stable reconstruction of continuous flux series. Based on LOADEST, the estimated total nitrogen (TN) and total phosphorus (TP) fluxes exhibit strong temporal and spatial variability. At the lake-inlet section, the wet season from May to September contributes 68 to 77 percent of annual TN flux and 72 to 81 percent of annual TP flux. A single storm event with 61.8 mm of rainfall can generate as much as 73 percent of the monthly flux, revealing a pronounced pulse-like export pattern. Spatially, TN and TP fluxes increase progressively from upstream to downstream, and the annual fluxes at the Beizhadukou section reach 4.24×106 kg N per year and 2.25×105 kg P per year, which are 10 to 17 times higher than those upstream. Trend decomposition indicates that TN flux into the lake has continued to rise over the past five years, whereas TP flux shows a slight decline, suggesting persistent nitrogen accumulation but a temporary easing of phosphorus export. Overall, flux variations are jointly driven by hydrological processes and human activities. Intense rainfall events amplify the contributions of agricultural and urban pollution to nutrient loading at downstream sections. These findings provide scientific support for external load assessment, pollution control, and algal bloom risk management in the Chaohu Basin under current environmental conditions.
Rivers entering the lake constitute the primary pathways for external nutrient inputs, and variations in nitrogen (N) and phosphorus (P) fluxes directly influence lake eutrophication and the risk of algal blooms. To accurately assess the pollutant export characteristics and driving mechanisms of typical inflow rivers in the Chaohu Basin, this study focuses on the Hangbu River, the largest tributary discharging into Chaohu Lake. Using the period-average flux method, the Load Estimator (LOADEST) model, and the WRTDS model, fluxes and long-term trends were estimated for hydrological and water-quality data from 2019 to 2024 at four stations along the river: Yaojiahe (upstream), Hekou Bridge (midstream), Sanhe Town Bridge (mid-downstream), and Beizhadukou (downstream). The period-average method is computationally simple but produces large errors. In comparison, the LOADEST model performs better in the Chaohu Basin and achieves substantially higher agreement with observed daily fluxes than the WRTDS model. The results show that LOADEST performs best under conditions of continuous discharge records and relatively sparse water-quality measurements, with R2 values of 0.89 to 0.97 and NSE values of 0.84 to 0.98, allowing stable reconstruction of continuous flux series. Based on LOADEST, the estimated total nitrogen (TN) and total phosphorus (TP) fluxes exhibit strong temporal and spatial variability. At the lake-inlet section, the wet season from May to September contributes 68 to 77 percent of annual TN flux and 72 to 81 percent of annual TP flux. A single storm event with 61.8 mm of rainfall can generate as much as 73 percent of the monthly flux, revealing a pronounced pulse-like export pattern. Spatially, TN and TP fluxes increase progressively from upstream to downstream, and the annual fluxes at the Beizhadukou section reach 4.24×106 kg N per year and 2.25×105 kg P per year, which are 10 to 17 times higher than those upstream. Trend decomposition indicates that TN flux into the lake has continued to rise over the past five years, whereas TP flux shows a slight decline, suggesting persistent nitrogen accumulation but a temporary easing of phosphorus export. Overall, flux variations are jointly driven by hydrological processes and human activities. Intense rainfall events amplify the contributions of agricultural and urban pollution to nutrient loading at downstream sections. These findings provide scientific support for external load assessment, pollution control, and algal bloom risk management in the Chaohu Basin under current environmental conditions.
Available online: June 05, 2026
Abstract:
Semi-arid closed lakes are critical nodes where ecological, climate, and human factors intertwine. Their multifunctionality plays an important supporting role in regional sustainable development. This study focuses on the ecological function maintenance of closed lakes in semi-arid regions, with Lake Daihai, a typical inland closed saline lake in the Mongolian Plateau, as the research subject. Given the ongoing deterioration of its water environment, this study conducts a systematic analysis based on continuous monitoring data from 2020 to 2024. Using Principal Component Analysis/Factor Analysis (PCA/FA), five key water quality parameters—dissolved oxygen (DO), chemical oxygen demand (CODCr), total nitrogen (TN), total phosphorus (TP), and salinity (Sal)—were selected from the multidimensional water quality dataset. The spatiotemporal variation patterns of the water environment parameters in Lake Daihai were systematically analyzed, and the Water Quality Index (WQI) was used for quantitative assessment. Pollution source apportionment was carried out using a comparative analysis of the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) models. The results show that the PMF model exhibited better performance in pollution source identification. The source apportionment results revealed that the main pollution sources in Lake Daihai are as follows, with their contribution rates: rural domestic pollution (23.5%), planktonic endogenous release (22.5%), livestock farming pollution (20.1%), surface runoff pollution (19.6%), and agricultural cultivation pollution (14.4%). This study quantifies the contribution rates of pollution sources in Lake Daihai, providing a theoretical basis for targeted management and ecological restoration of Daihai and similar lakes in semi-arid regions.
Semi-arid closed lakes are critical nodes where ecological, climate, and human factors intertwine. Their multifunctionality plays an important supporting role in regional sustainable development. This study focuses on the ecological function maintenance of closed lakes in semi-arid regions, with Lake Daihai, a typical inland closed saline lake in the Mongolian Plateau, as the research subject. Given the ongoing deterioration of its water environment, this study conducts a systematic analysis based on continuous monitoring data from 2020 to 2024. Using Principal Component Analysis/Factor Analysis (PCA/FA), five key water quality parameters—dissolved oxygen (DO), chemical oxygen demand (CODCr), total nitrogen (TN), total phosphorus (TP), and salinity (Sal)—were selected from the multidimensional water quality dataset. The spatiotemporal variation patterns of the water environment parameters in Lake Daihai were systematically analyzed, and the Water Quality Index (WQI) was used for quantitative assessment. Pollution source apportionment was carried out using a comparative analysis of the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) models. The results show that the PMF model exhibited better performance in pollution source identification. The source apportionment results revealed that the main pollution sources in Lake Daihai are as follows, with their contribution rates: rural domestic pollution (23.5%), planktonic endogenous release (22.5%), livestock farming pollution (20.1%), surface runoff pollution (19.6%), and agricultural cultivation pollution (14.4%). This study quantifies the contribution rates of pollution sources in Lake Daihai, providing a theoretical basis for targeted management and ecological restoration of Daihai and similar lakes in semi-arid regions.
Available online: June 04, 2026
Abstract:
Over the past half-century of evolution in the Yangtze River-Dongting Lake water network, the regulating and storage function of Dongting Lake over the Yangtze River and the Xiang, Zi, Yuan, and Li Rivers in Hunan has gradually shifted from flood retention and sedimentation to flood regulation and sediment replenishment. This transition marks a new phase in the relationship between rivers and lakes, necessitating updated perspectives for their governance and protection. This study, based on comprehensive prototype observation data of the Yangtze River main stream and the Dongting Lake water system, thoroughly analyzes the developmental process, distribution characteristics, and driving factors of sedimentation to sediment replenishment in Dongting Lake. It reveals the macroscopic response of hydrological conditions (flood and dry seasons) in the lake region to changes in sediment deposition status. Results indicate that Dongting Lake has sequentially undergone three developmental stages: the sediment retention weakening phase, the sediment retention stabilization phase, and the sediment replenishment enhancement phase. Sediment deposition progresses from west to east, while sediment replenishment moves from east to west, maintaining the seasonal pattern of deposition during flood periods and replenishment during non-flood periods. Sediment replenishment is primarily dominated by extremely fine particles, which do not contribute to bed formation in the Yangtze River main stream but facilitate the replenishment of nutrient materials. High sediment inflow and weak hydrodynamic conditions are the primary causes of sediment deposition. The sustained decline in sediment concentration of lake inflow, driven by the operation of controlling reservoir groups and soil conservation projects, serves as the core driving factor for sediment replenishment. However, the level of sediment replenishment in the lake region remains low and shows limited potential for further development. Sediment deposition is one of the main factors behind the widespread elevation of the highest water levels in the lake region prior to the impoundment of the Three Gorges Reservoir. The water replenishment regulation of the Three Gorges Reservoir downstream of the dam struggles to mitigate the declining trend of the lowest water levels in the Dongting Lake region. While changes in sediment deposition status will improve flood control conditions in Dongting Lake, the hydrological situation during dry seasons in the lake region is becoming increasingly strained.
Over the past half-century of evolution in the Yangtze River-Dongting Lake water network, the regulating and storage function of Dongting Lake over the Yangtze River and the Xiang, Zi, Yuan, and Li Rivers in Hunan has gradually shifted from flood retention and sedimentation to flood regulation and sediment replenishment. This transition marks a new phase in the relationship between rivers and lakes, necessitating updated perspectives for their governance and protection. This study, based on comprehensive prototype observation data of the Yangtze River main stream and the Dongting Lake water system, thoroughly analyzes the developmental process, distribution characteristics, and driving factors of sedimentation to sediment replenishment in Dongting Lake. It reveals the macroscopic response of hydrological conditions (flood and dry seasons) in the lake region to changes in sediment deposition status. Results indicate that Dongting Lake has sequentially undergone three developmental stages: the sediment retention weakening phase, the sediment retention stabilization phase, and the sediment replenishment enhancement phase. Sediment deposition progresses from west to east, while sediment replenishment moves from east to west, maintaining the seasonal pattern of deposition during flood periods and replenishment during non-flood periods. Sediment replenishment is primarily dominated by extremely fine particles, which do not contribute to bed formation in the Yangtze River main stream but facilitate the replenishment of nutrient materials. High sediment inflow and weak hydrodynamic conditions are the primary causes of sediment deposition. The sustained decline in sediment concentration of lake inflow, driven by the operation of controlling reservoir groups and soil conservation projects, serves as the core driving factor for sediment replenishment. However, the level of sediment replenishment in the lake region remains low and shows limited potential for further development. Sediment deposition is one of the main factors behind the widespread elevation of the highest water levels in the lake region prior to the impoundment of the Three Gorges Reservoir. The water replenishment regulation of the Three Gorges Reservoir downstream of the dam struggles to mitigate the declining trend of the lowest water levels in the Dongting Lake region. While changes in sediment deposition status will improve flood control conditions in Dongting Lake, the hydrological situation during dry seasons in the lake region is becoming increasingly strained.
Available online: June 04, 2026
Abstract:
Runoff simulation and forecasting are essential for watershed flood hazard mitigation and optimal utilization of regional water resources. A key factor affecting these processes is the structural heterogeneity of precipitation inputs. As the primary source of precipitation data derived from ground observations, rain gauges can substantially improve rainfall-runoff modeling accuracy when deployed with appropriate density and spatial distribution. This study constructs a spatio-temporal graph neural network framework that integrates Long Short-Term Memory (LSTM) and Graph Neural Network (GNN) approaches to jointly capture the temporal dynamics of hydrological variables and the spatial topological structure among stations for watershed runoff simulation. Meanwhile, the effects of rain gauge density and spatial distribution on model performance are systematically assessed using multiple mean areal precipitation (MAP) estimation methods. The results revealed that: (1) Rain gauge samples selected through clustering form four density distribution scenarios, representing 100%, 72.22%, 50%, and 27.78% of the full network respectively. Across four distributions, the average Nash-Sutcliffe efficiency (NSE) values exceeded 0.93. The runoff simulation associated with Distribution 3 yielded the best performance (NSE=0.967, mean absolute error MAE=175.5m3/s, relative bias BIAS=0.01, and coefficient of determination R2=0.98) under both high-flow and low-flow conditions; (2) Among all the MAP methods, the clustering weight method produced the most robust results, achieving the highest NSE, relatively low MAE, and BIAS closest to 0. Additionally, Distribution 3 maintained the best overall performance, with the smallest simulation errors and biases. The optimization of the rain gauge network combined with the selection of appropriate MAP approaches can enhance the efficiency and adaptability and simulation accuracy of runoff simulation models, offering a solid scientific foundation for hydrological forecasting.
Runoff simulation and forecasting are essential for watershed flood hazard mitigation and optimal utilization of regional water resources. A key factor affecting these processes is the structural heterogeneity of precipitation inputs. As the primary source of precipitation data derived from ground observations, rain gauges can substantially improve rainfall-runoff modeling accuracy when deployed with appropriate density and spatial distribution. This study constructs a spatio-temporal graph neural network framework that integrates Long Short-Term Memory (LSTM) and Graph Neural Network (GNN) approaches to jointly capture the temporal dynamics of hydrological variables and the spatial topological structure among stations for watershed runoff simulation. Meanwhile, the effects of rain gauge density and spatial distribution on model performance are systematically assessed using multiple mean areal precipitation (MAP) estimation methods. The results revealed that: (1) Rain gauge samples selected through clustering form four density distribution scenarios, representing 100%, 72.22%, 50%, and 27.78% of the full network respectively. Across four distributions, the average Nash-Sutcliffe efficiency (NSE) values exceeded 0.93. The runoff simulation associated with Distribution 3 yielded the best performance (NSE=0.967, mean absolute error MAE=175.5m3/s, relative bias BIAS=0.01, and coefficient of determination R2=0.98) under both high-flow and low-flow conditions; (2) Among all the MAP methods, the clustering weight method produced the most robust results, achieving the highest NSE, relatively low MAE, and BIAS closest to 0. Additionally, Distribution 3 maintained the best overall performance, with the smallest simulation errors and biases. The optimization of the rain gauge network combined with the selection of appropriate MAP approaches can enhance the efficiency and adaptability and simulation accuracy of runoff simulation models, offering a solid scientific foundation for hydrological forecasting.
Available online: June 02, 2026
Abstract:
While there is a wealth of research on the water quality improvement effects of lake ecological restoration projects, a systematic assessment of the dynamic changes in endogenous pollution in sediments and the mechanisms of nitrogen and phosphorus release is lacking. In particular, the seasonal characteristics of nutrient release at the sediment-water interface after ecological restoration of eutrophic lakes in the plateau region remain unclear. This study takes Dapokou, a typical eutrophic water area in the Caohai Lake of Dianchi Lake, as the research object. By comparing the water environment characteristics, sediment nitrogen and phosphorus occurrence forms, and interface release fluxes in the ecological restoration area and the unrestored area during the rainy season (peak growth period of submerged plants) and the dry season (decline period of submerged plants), the study systematically elucidates the spatiotemporal distribution characteristics of nitrogen and phosphorus in the overlying water-sediment system and the seasonal evolution of interface release fluxes in the ecological restoration area. The results show that ecological restoration improved the quality of the overlying water environment, with the water structure exhibiting a transformation from algal to grass-like patterns. During the rainy season, the total nitrogen (TN) and total phosphorus (TP) concentrations in the restored area decreased by 53.9% and 43.2%, respectively, compared to the unrestored area, while transparency (SD) significantly improved, and dissolved oxygen (DO) returned from supersaturation to normal levels. Regarding sediment occurrence, the remediation area exhibited differentiated evolutionary characteristics: total sediment nitrogen (STN) was significantly reduced by about 50% compared to the unremediation area, and convertible nitrogen (TTN) accounted for only 0.01%–0.02% of total nitrogen, with nitrogen mainly in stable form; however, bioavailable phosphorus (BAP) was enriched in the surface layer of the remediation area (reaching 468.72–534.35 mg/kg), forming a high potential releasable phosphorus reservoir. Regarding nitrogen and phosphorus release characteristics, the release flux at the sediment-water interface exhibits a clear seasonal shift: during the rainy season, when submerged plants are thriving, the interface is dominated by net adsorption, with a sediment-phosphorus (SRP) release flux of -1.08 mg/(m2·d). During the dry season, the decomposition of plant remains alters the sediment microenvironment, significantly increasing the interfacial release flux. At some sites, the ammonia nitrogen (NH4+-N) release flux reaches 86.31–91.53 mg/(m2·d), more than seven times that of the unrestored area, and SRP also shifts to a release state. In summary, the Dapokou ecological restoration project demonstrates improved water quality and net adsorption at the interface during the plant growth period, but there is a risk of nitrogen and phosphorus re-release due to remains decomposition during the dry season. Given the significant fluctuations in water levels and the concentrated seasonal decline of vegetation in shallow plateau lakes, submerged plant restoration measures should be combined with management methods such as dry season debris removal, water level regulation, and bottom sediment oxidation maintenance to control the intensity of seasonal endogenous release and provide a scientific basis and engineering reference for the treatment of endogenous pollution in Dianchi Lake and similar plateau lakes.
While there is a wealth of research on the water quality improvement effects of lake ecological restoration projects, a systematic assessment of the dynamic changes in endogenous pollution in sediments and the mechanisms of nitrogen and phosphorus release is lacking. In particular, the seasonal characteristics of nutrient release at the sediment-water interface after ecological restoration of eutrophic lakes in the plateau region remain unclear. This study takes Dapokou, a typical eutrophic water area in the Caohai Lake of Dianchi Lake, as the research object. By comparing the water environment characteristics, sediment nitrogen and phosphorus occurrence forms, and interface release fluxes in the ecological restoration area and the unrestored area during the rainy season (peak growth period of submerged plants) and the dry season (decline period of submerged plants), the study systematically elucidates the spatiotemporal distribution characteristics of nitrogen and phosphorus in the overlying water-sediment system and the seasonal evolution of interface release fluxes in the ecological restoration area. The results show that ecological restoration improved the quality of the overlying water environment, with the water structure exhibiting a transformation from algal to grass-like patterns. During the rainy season, the total nitrogen (TN) and total phosphorus (TP) concentrations in the restored area decreased by 53.9% and 43.2%, respectively, compared to the unrestored area, while transparency (SD) significantly improved, and dissolved oxygen (DO) returned from supersaturation to normal levels. Regarding sediment occurrence, the remediation area exhibited differentiated evolutionary characteristics: total sediment nitrogen (STN) was significantly reduced by about 50% compared to the unremediation area, and convertible nitrogen (TTN) accounted for only 0.01%–0.02% of total nitrogen, with nitrogen mainly in stable form; however, bioavailable phosphorus (BAP) was enriched in the surface layer of the remediation area (reaching 468.72–534.35 mg/kg), forming a high potential releasable phosphorus reservoir. Regarding nitrogen and phosphorus release characteristics, the release flux at the sediment-water interface exhibits a clear seasonal shift: during the rainy season, when submerged plants are thriving, the interface is dominated by net adsorption, with a sediment-phosphorus (SRP) release flux of -1.08 mg/(m2·d). During the dry season, the decomposition of plant remains alters the sediment microenvironment, significantly increasing the interfacial release flux. At some sites, the ammonia nitrogen (NH4+-N) release flux reaches 86.31–91.53 mg/(m2·d), more than seven times that of the unrestored area, and SRP also shifts to a release state. In summary, the Dapokou ecological restoration project demonstrates improved water quality and net adsorption at the interface during the plant growth period, but there is a risk of nitrogen and phosphorus re-release due to remains decomposition during the dry season. Given the significant fluctuations in water levels and the concentrated seasonal decline of vegetation in shallow plateau lakes, submerged plant restoration measures should be combined with management methods such as dry season debris removal, water level regulation, and bottom sediment oxidation maintenance to control the intensity of seasonal endogenous release and provide a scientific basis and engineering reference for the treatment of endogenous pollution in Dianchi Lake and similar plateau lakes.
Available online: June 02, 2026
Abstract:
Per- and polyfluoroalkyl substances (PFASs) in peri-urban shallow lakes have attracted increasing scientific attention due to their complex environmental behavior and potential health risks. This study investigated the occurrence, bioaccumulation, and trophic magnification of 15 PFASs in water and tissues (muscle and viscera) of 11 fish species from Luoma Lake (a representative peri-urban shallow lake in eastern China), and conducted a preliminary human health risk assessment associated with fish consumption. Results showed that nine PFASs were detected in surface water (∑PFASs: 58.80~90.59 ng/L), while all 15 target compounds were present in both muscle and visceral tissues (∑PFASs: 166.59~417.65 ng/g dw in muscle; 76.04~897.83 ng/g dw in viscera). PFBA, PFOA, and PFHpA were the predominant congeners in water, muscle, and viscera, respectively. PFASs exhibited pronounced tissue-specific accumulation, with concentrations following the order: kidney > liver > gill > muscle > intestine > brain, indicating preferential enrichment in excretory and metabolic organs. A significant urban-rural gradient was observed: PFASs concentrations in muscle, kidney, liver, and gill of fish from urban zone were significantly higher than those from rural zone, whereas no significant differences were found in brain and intestine. Long-chain PFASs generally displayed higher bioaccumulation factors (BAFs) than short-chain analogues. Trophic transfer analysis revealed that long-chain PFASs underwent significant biomagnification (trophic magnification factor, TMF > 1), whereas short-chain PFASs tended to be biodiluted (TMF < 1). Health risk assessment indicated that current dietary exposure to PFASs via consumption of Luoma Lake fish is within acceptable limits (HR < 1). Nevertheless, potential risks from long-term low-dose exposure and the relatively high cumulative toxicity in rural zones warrant further attention. These findings provide valuable insights into the environmental fate, ecological effects, and health risk management of PFASs in peri-urban shallow lake ecosystems.
Per- and polyfluoroalkyl substances (PFASs) in peri-urban shallow lakes have attracted increasing scientific attention due to their complex environmental behavior and potential health risks. This study investigated the occurrence, bioaccumulation, and trophic magnification of 15 PFASs in water and tissues (muscle and viscera) of 11 fish species from Luoma Lake (a representative peri-urban shallow lake in eastern China), and conducted a preliminary human health risk assessment associated with fish consumption. Results showed that nine PFASs were detected in surface water (∑PFASs: 58.80~90.59 ng/L), while all 15 target compounds were present in both muscle and visceral tissues (∑PFASs: 166.59~417.65 ng/g dw in muscle; 76.04~897.83 ng/g dw in viscera). PFBA, PFOA, and PFHpA were the predominant congeners in water, muscle, and viscera, respectively. PFASs exhibited pronounced tissue-specific accumulation, with concentrations following the order: kidney > liver > gill > muscle > intestine > brain, indicating preferential enrichment in excretory and metabolic organs. A significant urban-rural gradient was observed: PFASs concentrations in muscle, kidney, liver, and gill of fish from urban zone were significantly higher than those from rural zone, whereas no significant differences were found in brain and intestine. Long-chain PFASs generally displayed higher bioaccumulation factors (BAFs) than short-chain analogues. Trophic transfer analysis revealed that long-chain PFASs underwent significant biomagnification (trophic magnification factor, TMF > 1), whereas short-chain PFASs tended to be biodiluted (TMF < 1). Health risk assessment indicated that current dietary exposure to PFASs via consumption of Luoma Lake fish is within acceptable limits (HR < 1). Nevertheless, potential risks from long-term low-dose exposure and the relatively high cumulative toxicity in rural zones warrant further attention. These findings provide valuable insights into the environmental fate, ecological effects, and health risk management of PFASs in peri-urban shallow lake ecosystems.
Zhang Wenting, Zhang Xia, Yan Xingcheng, Feng Tao, Qiao Ruxia, Wang Li, Chen Qiuwen, Zhang Xin, Cao Rui
Available online: June 01, 2026
Abstract:
Dissolved inorganic phosphorus (DIP) is a key limiting nutrient in freshwater ecosystems, and its excessive input poses a serious threat to lake water quality and ecological stability. Previous studies have primarily focused on identifying DIP sources in surface waters such as rivers and lakes, while systematic understanding of the spatiotemporal distribution and source contributions of groundwater DIP remains limited. In this study, the Taihu Basin was selected as a representative case. Groundwater samples were systematically collected during the normal, wet, and dry water period in 2024 to analyze DIP concentrations, hydrochemical characteristics, and phosphate oxygen isotope compositions for source apportionment. The results showed that groundwater levels across the basin generally exhibited a spatial pattern of higher values in the west and lower values in the east, with a central depression zone. During the wet water period, groundwater levels were higher and primarily discharged into Lake Taihu, whereas during the dry water period, groundwater levels declined and the flow direction reversed toward discharge-dominated conditions. Spatially, groundwater DIP concentrations were higher in the central and southern regions of the basin and lower in the western and eastern regions. Temporally, DIP concentrations followed the order wet > normal > dry water period. Hydrochemical analyses indicated that groundwater was mainly affected by agricultural activities and domestic sewage during the wet and normal water period, while industrial activities exerted stronger influence during the dry water period. Source apportionment based on phosphate oxygen isotopes revealed that, during the normal season, the contributions of industrial effluents, domestic sewage, and agricultural wastewater were comparable, accounting for 34%, 31%, and 30%, respectively, while forest runoff contributed the least (5%). During the wet water period, agricultural wastewater became the dominant source, accounting for 37%, whereas domestic sewage and industrial effluents decreased to 28% and 25%, respectively, and forest runoff slightly increased to 10%. In contrast, during the dry water period, the agricultural contribution further increased to 42%, followed by domestic sewage (31%), while forest runoff rose significantly to 18% and industrial effluents declined to 9%. Overall, this study provides the comprehensive characterization of the spatiotemporal patterns and seasonal variations in groundwater DIP sources across the Taihu Basin. The findings offer new insights into identifying dominant groundwater phosphorus sources and provide a scientific basis for developing differentiated strategies for water quality management and eutrophication control in large lake basins.
Dissolved inorganic phosphorus (DIP) is a key limiting nutrient in freshwater ecosystems, and its excessive input poses a serious threat to lake water quality and ecological stability. Previous studies have primarily focused on identifying DIP sources in surface waters such as rivers and lakes, while systematic understanding of the spatiotemporal distribution and source contributions of groundwater DIP remains limited. In this study, the Taihu Basin was selected as a representative case. Groundwater samples were systematically collected during the normal, wet, and dry water period in 2024 to analyze DIP concentrations, hydrochemical characteristics, and phosphate oxygen isotope compositions for source apportionment. The results showed that groundwater levels across the basin generally exhibited a spatial pattern of higher values in the west and lower values in the east, with a central depression zone. During the wet water period, groundwater levels were higher and primarily discharged into Lake Taihu, whereas during the dry water period, groundwater levels declined and the flow direction reversed toward discharge-dominated conditions. Spatially, groundwater DIP concentrations were higher in the central and southern regions of the basin and lower in the western and eastern regions. Temporally, DIP concentrations followed the order wet > normal > dry water period. Hydrochemical analyses indicated that groundwater was mainly affected by agricultural activities and domestic sewage during the wet and normal water period, while industrial activities exerted stronger influence during the dry water period. Source apportionment based on phosphate oxygen isotopes revealed that, during the normal season, the contributions of industrial effluents, domestic sewage, and agricultural wastewater were comparable, accounting for 34%, 31%, and 30%, respectively, while forest runoff contributed the least (5%). During the wet water period, agricultural wastewater became the dominant source, accounting for 37%, whereas domestic sewage and industrial effluents decreased to 28% and 25%, respectively, and forest runoff slightly increased to 10%. In contrast, during the dry water period, the agricultural contribution further increased to 42%, followed by domestic sewage (31%), while forest runoff rose significantly to 18% and industrial effluents declined to 9%. Overall, this study provides the comprehensive characterization of the spatiotemporal patterns and seasonal variations in groundwater DIP sources across the Taihu Basin. The findings offer new insights into identifying dominant groundwater phosphorus sources and provide a scientific basis for developing differentiated strategies for water quality management and eutrophication control in large lake basins.
minjialing, yujinxiang, raorongcheng, huanyi, liufangning, meizhigang, yangying, weilingxia, yinheng, zhangyun, lindanqing, chenyukuan, huaqi, licaigang, quejianglong
Available online: May 28, 2026
Abstract:
To investigate the distribution dynamics of Yangtze finless porpoises (YFPs) in Poyang Lake and its tributaries during the middle of the fishing ban, we conducted ten surveys at different water levels between 2022 and 2025. The results indicate that the YFP population is primarily concentrated in the Laoye Temple-Zhuxi Estuary-Piaotou and Duchang-Piaoshan-Meixizui waters. The high water level period is scattered and widely distributed in the lake area, with less distribution in the waterway connecting the Yangtze River and tributaries; The low water level period is concentrated in the main channel and increases in the distribution of sand pits, the waterway connecting the Yangtze River, and tributary tails. The tributaries Gan River, Xin River, Rao River, Fu River, and Xiu River all have distribution of YFPs. Stable, year-round populations were observed in the Gan River (Yangzizhou) and Xin River (Xiniuwan). Migration activities of YFPs are related to seasons and water levels. During winter/low water periods, they migrate from the lake area to the tail of tributaries, while during summer/high water periods, they migrate from the tail of tributaries to the lake area. And as the low water level continues, the distance of migration towards the tail of the tributary may increase for search of resources and space. The KDE model results indicate that the 50% KDE distribution of the YFPs is mainly continuous in the central part of the lake area during the high water level period, while it is fragmented in the lake area and tributary tails during the low water level period. The 50% KDE area decreases with declining water levels, exhibiting a significant positive linear correlation (R=0.721, P<0.05). The fishing ban has led to an expanded distribution range for the YFPs in Poyang Lake. However, the habitat area has decreased and become fragmented due to the normalization of low water levels which may be an important risk factor for the population. The research results suggest that the protection of YFPs in Poyang Lake should focus on the protection of core home range and the connectivity of ecological corridors under the background of normalized low water levels.
To investigate the distribution dynamics of Yangtze finless porpoises (YFPs) in Poyang Lake and its tributaries during the middle of the fishing ban, we conducted ten surveys at different water levels between 2022 and 2025. The results indicate that the YFP population is primarily concentrated in the Laoye Temple-Zhuxi Estuary-Piaotou and Duchang-Piaoshan-Meixizui waters. The high water level period is scattered and widely distributed in the lake area, with less distribution in the waterway connecting the Yangtze River and tributaries; The low water level period is concentrated in the main channel and increases in the distribution of sand pits, the waterway connecting the Yangtze River, and tributary tails. The tributaries Gan River, Xin River, Rao River, Fu River, and Xiu River all have distribution of YFPs. Stable, year-round populations were observed in the Gan River (Yangzizhou) and Xin River (Xiniuwan). Migration activities of YFPs are related to seasons and water levels. During winter/low water periods, they migrate from the lake area to the tail of tributaries, while during summer/high water periods, they migrate from the tail of tributaries to the lake area. And as the low water level continues, the distance of migration towards the tail of the tributary may increase for search of resources and space. The KDE model results indicate that the 50% KDE distribution of the YFPs is mainly continuous in the central part of the lake area during the high water level period, while it is fragmented in the lake area and tributary tails during the low water level period. The 50% KDE area decreases with declining water levels, exhibiting a significant positive linear correlation (R=0.721, P<0.05). The fishing ban has led to an expanded distribution range for the YFPs in Poyang Lake. However, the habitat area has decreased and become fragmented due to the normalization of low water levels which may be an important risk factor for the population. The research results suggest that the protection of YFPs in Poyang Lake should focus on the protection of core home range and the connectivity of ecological corridors under the background of normalized low water levels.
Available online: May 22, 2026
Abstract:
The Qarhan Salt Lake plays a crucial role in China"s potassium fertilizer production, highlighting the essential relationship of water-salt (Here, the term “water-salt” refers to the coupled mass balance of water (liquid) and potash (solid + dissolved) in the Qarhan playa-lake system)for sustainable resource management and potassium fertilizer supply. This research investigates the complex evolutionary mechanisms governing the water-salt relationship in the mining region, influenced by climate change and human activities. This study utilised a comprehensive set of hydrometeorological data collected over a period of nearly three decades (1990–2024) to identify the evolving trends in the key factors influencing the water-salt relationship in the Qarhan Salt Lake mining area. Pearson correlation analysis was employed to reveal the evolution patterns and driving factors of the water-salt system in this region. The results indicate that over the past two decades (2000-2024), the climate in the mining area has transitioned from "warm and dry" to a "warm and humid". The volume of runoff of the recharged river has increased by more than 20%, accompanied by a temperature increasing of 1.5-2.0 °C. Conversely, a reduction of 18.5% has been noted in evaporation rates. Large-scale resource development activities have adversely affected water replenishment in the mining area, leading to a significant decline in the level of confined brine and a reduction in KCl grade. The implementation of artificial water replenishment and mineral dissolution has been shown to alleviate the severity of these negative impacts. The evolution of water-mineral interactions can be divided into three distinct stages. Initially, there is a transition from a naturally "hydrometeorological-dominated" state to a phase characterized by "combined natural and human influences." This is subsequently followed by a shift to a "human-dominated" trajectory. The key drivers of this transformation include climate warming, brine mining, and artificial water recharge for mineral dissolution. It is clear that brine extraction and artificial water recharge serve as the essential conditions for regulating the water-salt balance. These findings offer a scientific foundation for achieving effective water-salt balance and management in the Qarhan Salt Lake mining area.
The Qarhan Salt Lake plays a crucial role in China"s potassium fertilizer production, highlighting the essential relationship of water-salt (Here, the term “water-salt” refers to the coupled mass balance of water (liquid) and potash (solid + dissolved) in the Qarhan playa-lake system)for sustainable resource management and potassium fertilizer supply. This research investigates the complex evolutionary mechanisms governing the water-salt relationship in the mining region, influenced by climate change and human activities. This study utilised a comprehensive set of hydrometeorological data collected over a period of nearly three decades (1990–2024) to identify the evolving trends in the key factors influencing the water-salt relationship in the Qarhan Salt Lake mining area. Pearson correlation analysis was employed to reveal the evolution patterns and driving factors of the water-salt system in this region. The results indicate that over the past two decades (2000-2024), the climate in the mining area has transitioned from "warm and dry" to a "warm and humid". The volume of runoff of the recharged river has increased by more than 20%, accompanied by a temperature increasing of 1.5-2.0 °C. Conversely, a reduction of 18.5% has been noted in evaporation rates. Large-scale resource development activities have adversely affected water replenishment in the mining area, leading to a significant decline in the level of confined brine and a reduction in KCl grade. The implementation of artificial water replenishment and mineral dissolution has been shown to alleviate the severity of these negative impacts. The evolution of water-mineral interactions can be divided into three distinct stages. Initially, there is a transition from a naturally "hydrometeorological-dominated" state to a phase characterized by "combined natural and human influences." This is subsequently followed by a shift to a "human-dominated" trajectory. The key drivers of this transformation include climate warming, brine mining, and artificial water recharge for mineral dissolution. It is clear that brine extraction and artificial water recharge serve as the essential conditions for regulating the water-salt balance. These findings offer a scientific foundation for achieving effective water-salt balance and management in the Qarhan Salt Lake mining area.
Deng Guoping, Fang Dian, Ding Yuting, Yuan Jia, Zhang Xizhao, Zhou Yanfeng, Xu Dongpo, Tang Fujiang, You Yang
Available online: May 22, 2026
Abstract:
In the 1980s, a fishery transplant was carried out nationwide using the H. nipponensis from the Yalu River system as the source population, which achieved significant economic benefits. However, the genetic diversity of the initial small population established by transplantation has not received due attention due to the subsequent effects of different transplantation behaviors (repeated introduction, mixing of other sources, and unintentional transplantation) and adaptation to the habitat. In this study, 439 individuals were collected from 15 transplanted populations across China’s main production regions (Northeast, North, Northwest and Southwest). Mitochondrial cytochrome c oxidase I (CO I) sequences were used to assess genetic diversity and differentiation. The analysis results showed that a total of 47 haplotypes were detected in 15 populations, Overall haplotype diversity (Hd=0.690) and nucleotide diversity (Pi=0.00290) exhibit species characteristics of high haplotype diversity (Hd) and low nucleotide diversity (Pi). Group Evolutionary Tree, haplotype networks and AMOVA showed that most molecular variance occurred within populations (65.06 %, versus 34.94 % among populations). Populations from Miyun Reservoir (MY) and Panjiakou Reservoir (PJK) in North China formed a separate clade and were highly differentiated from all others (Fst > 0.5), probably reflecting repeated introductions from native Japanese sources. The Dahushi Reservoir (DHS) population showed marked diversity loss, likely attributable to accidental transplantation of a very small founder group. The diversity levels of the four populations in Northeast China, which are connected to the water system of their source areas, are relatively balanced. The populations in Northwest and Southwest China, exhibit moderate to high levels of diversity, which demonstrated the potential adaptation of fish species to the new habitat. Neutrality tests, mismatch distributions and Bayesian skyline plots all indicated a historical population expansion. Based on the current research results, it is recommended to identify the biological management units and core population germplasm resources in China as soon as possible, implement necessary genetic monitoring in a timely manner, and then carry out orderly germplasm use strategies, block based resource management, and fishery production management measures to promote the sustainable and healthy development of the industry.
In the 1980s, a fishery transplant was carried out nationwide using the H. nipponensis from the Yalu River system as the source population, which achieved significant economic benefits. However, the genetic diversity of the initial small population established by transplantation has not received due attention due to the subsequent effects of different transplantation behaviors (repeated introduction, mixing of other sources, and unintentional transplantation) and adaptation to the habitat. In this study, 439 individuals were collected from 15 transplanted populations across China’s main production regions (Northeast, North, Northwest and Southwest). Mitochondrial cytochrome c oxidase I (CO I) sequences were used to assess genetic diversity and differentiation. The analysis results showed that a total of 47 haplotypes were detected in 15 populations, Overall haplotype diversity (Hd=0.690) and nucleotide diversity (Pi=0.00290) exhibit species characteristics of high haplotype diversity (Hd) and low nucleotide diversity (Pi). Group Evolutionary Tree, haplotype networks and AMOVA showed that most molecular variance occurred within populations (65.06 %, versus 34.94 % among populations). Populations from Miyun Reservoir (MY) and Panjiakou Reservoir (PJK) in North China formed a separate clade and were highly differentiated from all others (Fst > 0.5), probably reflecting repeated introductions from native Japanese sources. The Dahushi Reservoir (DHS) population showed marked diversity loss, likely attributable to accidental transplantation of a very small founder group. The diversity levels of the four populations in Northeast China, which are connected to the water system of their source areas, are relatively balanced. The populations in Northwest and Southwest China, exhibit moderate to high levels of diversity, which demonstrated the potential adaptation of fish species to the new habitat. Neutrality tests, mismatch distributions and Bayesian skyline plots all indicated a historical population expansion. Based on the current research results, it is recommended to identify the biological management units and core population germplasm resources in China as soon as possible, implement necessary genetic monitoring in a timely manner, and then carry out orderly germplasm use strategies, block based resource management, and fishery production management measures to promote the sustainable and healthy development of the industry.
Available online: May 20, 2026
Abstract:
: This study investigated the driving mechanisms of methane (CH?) emission flux (FCH?) through controlled laboratory experiments simulating the decomposition process of submerged plant (Potamogeton pectinatus) residues in a eutrophic lake. Four treatment groups were established: a no-plant control (CK), and low (300 g), medium (500 g), and high (1000 g) plant residue addition groups. Constant-temperature incubation was used to simulate environments during both the ice-covered period (0–4°C) and the ice-melt period (10–15°C), with continuous monitoring employed to reveal the dynamics of FCH? and key environmental parameters.The results indicated that plant residue decomposition released dissolved organic carbon (DOC) and total organic carbon (TOC) into the water-sediment system. Their subsequent mineralization produced dissolved inorganic carbon (DIC) and total inorganic carbon (TIC). The decomposition process concurrently consumed dissolved oxygen (DO), causing DO concentrations to rapidly decline below 2 mg/L and forming a strongly reducing anaerobic environment, which significantly increased the abundance of methanogens. During the ice-covered period, FCH? increased significantly with the amount of plant residues added, with the FCH? in the high plant group being 3.7 times that of the control group. This confirms that the synergistic effect of “carbon source input–anoxic environment”drove the increase in FCH? during the ice-covered period.Rising temperatures further accelerated organic matter mineralization and CH? production. During this period, FCH? remained significantly positively correlated with the amount of plant residue added (r = 0.86, p<0.001), indicating that climate warming may amplify the promoting effect of plant input on CH? emissions. In conclusion, the decomposition of plant residues in macrophyte-dominated eutrophic lakes jointly promotes CH? production by supplying organic carbon sources and creating anaerobic conditions, while global climate warming—leading to shorter ice-covered periods and higher temperatures—further exacerbates CH? emissions. This study provides an important theoretical basis for the management of eutrophic lakes under global climate change.
: This study investigated the driving mechanisms of methane (CH?) emission flux (FCH?) through controlled laboratory experiments simulating the decomposition process of submerged plant (Potamogeton pectinatus) residues in a eutrophic lake. Four treatment groups were established: a no-plant control (CK), and low (300 g), medium (500 g), and high (1000 g) plant residue addition groups. Constant-temperature incubation was used to simulate environments during both the ice-covered period (0–4°C) and the ice-melt period (10–15°C), with continuous monitoring employed to reveal the dynamics of FCH? and key environmental parameters.The results indicated that plant residue decomposition released dissolved organic carbon (DOC) and total organic carbon (TOC) into the water-sediment system. Their subsequent mineralization produced dissolved inorganic carbon (DIC) and total inorganic carbon (TIC). The decomposition process concurrently consumed dissolved oxygen (DO), causing DO concentrations to rapidly decline below 2 mg/L and forming a strongly reducing anaerobic environment, which significantly increased the abundance of methanogens. During the ice-covered period, FCH? increased significantly with the amount of plant residues added, with the FCH? in the high plant group being 3.7 times that of the control group. This confirms that the synergistic effect of “carbon source input–anoxic environment”drove the increase in FCH? during the ice-covered period.Rising temperatures further accelerated organic matter mineralization and CH? production. During this period, FCH? remained significantly positively correlated with the amount of plant residue added (r = 0.86, p<0.001), indicating that climate warming may amplify the promoting effect of plant input on CH? emissions. In conclusion, the decomposition of plant residues in macrophyte-dominated eutrophic lakes jointly promotes CH? production by supplying organic carbon sources and creating anaerobic conditions, while global climate warming—leading to shorter ice-covered periods and higher temperatures—further exacerbates CH? emissions. This study provides an important theoretical basis for the management of eutrophic lakes under global climate change.
Available online: May 20, 2026
Abstract:
Arid-zone lakes serve as key indicators of watershed ecological and environmental changes, playing vital hydrological and ecological roles in maintaining regional water-cycle balance and ecosystem stability. This study examines lake dynamics and their climatic responses in the Hunshandake Sandy Land, a climate-sensitive region in northern China characterized by pronounced aridification and ecological fragility. By integrating multi-source datasets including Landsat, Sentinel, Global Surface Water (GSW), and Global Land Analysis and Discovery (GLAD), water extent was mapped applying the water-index method, water classification enhancement approach, and random-forest classification. Changes in water storage were estimated by combining stage-area relationships and volume-area empirical curves. Based on these methods, we quantified monthly and annual changes in lake area (＞0.01 km2) and water storage from 2003 to 2023, while analyzing relevant meteorological factors. Results indicate significant intra-annual seasonality, exhibiting a single-peak trend in lake extent from May to October. At the interannual scale, the lake system has undergone persistent degradation trend over the 21-year record. Total lake area had decreased by 37.17% compared to 2003. The number of lakes declined from 1,198 to 466, primarily driven by losses of small, shallow lakes and widespread drying. Under regional climatic aridity conditions, 8% of formerly permanent water bodies converted to seasonal status, while 86% of seasonal water bodies experienced episodic drying. Net water storage decreased at a rate of -0.005 km3·yr?1, with medium-to-large lakes (≥1km2) accounting for 60% of the storage loss. Climate-driven mechanisms indicate that precipitation, vapor pressure deficit (VPD), and air temperature exhibit spatiotemporal lags of 0-2 months, with precipitation and VPD both peaking at a 1-month lag. VPD emerges as primary negative factor influencing annual and monthly water body area, while precipitation dominates the interannual regulation of seasonal water body area and, jointly governs positively monthly fluctuations with potential evapotranspiration (ET). Temperature indirectly affects lake dynamics by increasing the VPD and evapotranspiration demand. This regional-scale study elucidates the response mechanisms and spatiotemporal heterogeneity of arid-region lakes under climate change, providing data support for adaptive water-resource management in ecologically fragile areas.
Arid-zone lakes serve as key indicators of watershed ecological and environmental changes, playing vital hydrological and ecological roles in maintaining regional water-cycle balance and ecosystem stability. This study examines lake dynamics and their climatic responses in the Hunshandake Sandy Land, a climate-sensitive region in northern China characterized by pronounced aridification and ecological fragility. By integrating multi-source datasets including Landsat, Sentinel, Global Surface Water (GSW), and Global Land Analysis and Discovery (GLAD), water extent was mapped applying the water-index method, water classification enhancement approach, and random-forest classification. Changes in water storage were estimated by combining stage-area relationships and volume-area empirical curves. Based on these methods, we quantified monthly and annual changes in lake area (＞0.01 km2) and water storage from 2003 to 2023, while analyzing relevant meteorological factors. Results indicate significant intra-annual seasonality, exhibiting a single-peak trend in lake extent from May to October. At the interannual scale, the lake system has undergone persistent degradation trend over the 21-year record. Total lake area had decreased by 37.17% compared to 2003. The number of lakes declined from 1,198 to 466, primarily driven by losses of small, shallow lakes and widespread drying. Under regional climatic aridity conditions, 8% of formerly permanent water bodies converted to seasonal status, while 86% of seasonal water bodies experienced episodic drying. Net water storage decreased at a rate of -0.005 km3·yr?1, with medium-to-large lakes (≥1km2) accounting for 60% of the storage loss. Climate-driven mechanisms indicate that precipitation, vapor pressure deficit (VPD), and air temperature exhibit spatiotemporal lags of 0-2 months, with precipitation and VPD both peaking at a 1-month lag. VPD emerges as primary negative factor influencing annual and monthly water body area, while precipitation dominates the interannual regulation of seasonal water body area and, jointly governs positively monthly fluctuations with potential evapotranspiration (ET). Temperature indirectly affects lake dynamics by increasing the VPD and evapotranspiration demand. This regional-scale study elucidates the response mechanisms and spatiotemporal heterogeneity of arid-region lakes under climate change, providing data support for adaptive water-resource management in ecologically fragile areas.
Available online: May 20, 2026
Abstract:
Submerged macrophytes are critical component in ecological restoration of lakes, which harbor epiphytic microbes that play important roles in nutrient cycling and water quality improvement in aquatic ecosystems. However, the responses of planktonic and epiphytic microbial communities to different restoration strategies, as well as the underlying mechanisms, remain largely unknown. To address this gap, we investigated bacterial and microeukaryotic communities in both water column and phyllosphere of Vallisneria natans (V. natans) across three areas of the urban Lake Xuanwu: a near-natural restoration (NR) area, an enclosure restoration (ER) area, and an unrestored (UR) area, to uncover how ecological restoration shapes microbial communities and their potential functions. The results showed that the NR area exhibited higher coverage and greater species richness of submerged macrophytes, along with lower concentrations of total nitrogen (TN), total phosphorus (TP), turbidity (Turb), and chlorophyll a (Chl a). The diversity of both planktonic and phyllosphere microbial communities was significantly higher in the NR area than in the ER and UR areas. The dominant microbial taxa in the phyllosphere of V. natans differed from those in the surrounding water, with obvious compositional differences among the three restoration areas. Variations in microbial community structure were primarily driven by differences in TN, TP, Turb, and Chl a, with bacterial communities being more strongly influenced by environmental factors than microeukaryotic communities. Functional bacterial groups involved in nitrification and nitrate ammonification were selectively enriched in the phyllosphere of V. natans, and the abundance of nitrogen-cycling populations was significantly correlated with ambient nitrogen concentrations in the water. The microbial co-occurrence networks in the NR area displayed greater complexity and stability than those in the ER and UR areas. Compared with the microeukaryotic network, the bacterial network contained more nodes and edges connecting nodes with environmental factors, reflecting a stronger susceptible to environmental influence for the bacterial community. Moreover, based on functional predictions, the key bacterial genera within the phyllosphere network of Vallisneria natans may play important roles in carbon and nitrogen cycling. This study elucidates the mechanisms by which submerged macrophytes regulate microbial community structure, interaction networks, and keystone functional taxa during ecological restoration to improve water quality, thereby providing scientific support for the ecological restoration of eutrophic lakes.
Submerged macrophytes are critical component in ecological restoration of lakes, which harbor epiphytic microbes that play important roles in nutrient cycling and water quality improvement in aquatic ecosystems. However, the responses of planktonic and epiphytic microbial communities to different restoration strategies, as well as the underlying mechanisms, remain largely unknown. To address this gap, we investigated bacterial and microeukaryotic communities in both water column and phyllosphere of Vallisneria natans (V. natans) across three areas of the urban Lake Xuanwu: a near-natural restoration (NR) area, an enclosure restoration (ER) area, and an unrestored (UR) area, to uncover how ecological restoration shapes microbial communities and their potential functions. The results showed that the NR area exhibited higher coverage and greater species richness of submerged macrophytes, along with lower concentrations of total nitrogen (TN), total phosphorus (TP), turbidity (Turb), and chlorophyll a (Chl a). The diversity of both planktonic and phyllosphere microbial communities was significantly higher in the NR area than in the ER and UR areas. The dominant microbial taxa in the phyllosphere of V. natans differed from those in the surrounding water, with obvious compositional differences among the three restoration areas. Variations in microbial community structure were primarily driven by differences in TN, TP, Turb, and Chl a, with bacterial communities being more strongly influenced by environmental factors than microeukaryotic communities. Functional bacterial groups involved in nitrification and nitrate ammonification were selectively enriched in the phyllosphere of V. natans, and the abundance of nitrogen-cycling populations was significantly correlated with ambient nitrogen concentrations in the water. The microbial co-occurrence networks in the NR area displayed greater complexity and stability than those in the ER and UR areas. Compared with the microeukaryotic network, the bacterial network contained more nodes and edges connecting nodes with environmental factors, reflecting a stronger susceptible to environmental influence for the bacterial community. Moreover, based on functional predictions, the key bacterial genera within the phyllosphere network of Vallisneria natans may play important roles in carbon and nitrogen cycling. This study elucidates the mechanisms by which submerged macrophytes regulate microbial community structure, interaction networks, and keystone functional taxa during ecological restoration to improve water quality, thereby providing scientific support for the ecological restoration of eutrophic lakes.
Available online: May 20, 2026
Abstract:
As one of the most advanced ensemble learning technologies, Stacking is an important way to improve the performance of runoff prediction. The existing researches of Stacking-based runoff prediction mostly focus on the accuracy evaluation under few basins and few lead times. Applicability evaluation and influencing factors analysis under multiple basins and multiple lead times remains unexplored. In this study, Support Vector Regression (SVR) and Random Forest (RF) were used as individual learners, and Ridge Regression was used as a meta-learner, and runoff prediction models based on Stacking were constructed. Taking 200 basins in CAMELS dataset as the study area, and taking 1~7 days as the lead times, the accuracy, stability and applicability of Stacking-based runoff prediction were systematically evaluated, and the correlation between the effectiveness of Stacking and the characteristics of basins and the accuracy of individual learners were analyzed. The main results are as follows: (1) The overall accuracy and stability of Stacking are higher than those of the individual learners. (2) Stacking can improve the accuracy of runoff prediction in most basins in the continental United States. The improvement effect is more significant in the basins with heavy precipitation and high temperature, but the effect is relatively limited in the basins with light precipitation and low temperature. (3) Stacking tends to improve prediction accuracy in the basins with low accuracy of the individual learners, but it is difficult to improve the prediction accuracy in the basins with high accuracy of the individual learners. This study can provide a reference for the application of Stacking in runoff prediction.
As one of the most advanced ensemble learning technologies, Stacking is an important way to improve the performance of runoff prediction. The existing researches of Stacking-based runoff prediction mostly focus on the accuracy evaluation under few basins and few lead times. Applicability evaluation and influencing factors analysis under multiple basins and multiple lead times remains unexplored. In this study, Support Vector Regression (SVR) and Random Forest (RF) were used as individual learners, and Ridge Regression was used as a meta-learner, and runoff prediction models based on Stacking were constructed. Taking 200 basins in CAMELS dataset as the study area, and taking 1~7 days as the lead times, the accuracy, stability and applicability of Stacking-based runoff prediction were systematically evaluated, and the correlation between the effectiveness of Stacking and the characteristics of basins and the accuracy of individual learners were analyzed. The main results are as follows: (1) The overall accuracy and stability of Stacking are higher than those of the individual learners. (2) Stacking can improve the accuracy of runoff prediction in most basins in the continental United States. The improvement effect is more significant in the basins with heavy precipitation and high temperature, but the effect is relatively limited in the basins with light precipitation and low temperature. (3) Stacking tends to improve prediction accuracy in the basins with low accuracy of the individual learners, but it is difficult to improve the prediction accuracy in the basins with high accuracy of the individual learners. This study can provide a reference for the application of Stacking in runoff prediction.
luosi, zhoushangrong, zhoujunjie, JinShiyu, quxiao, 葛超, shizhining, wangzexin, zhangzhen, FAMUREW A Janet A
Available online: May 11, 2026
Abstract:
To investigate the trophic niche characteristics of fish in regulated lakes under water level fluctuations, Hongze Lake was selected as the study area. Carbon and nitrogen stable isotope techniques were used to analyze the trophic levels, trophic niche widths, niche overlap, and major food sources of six common benthic fish species—Cyprinus carpio, Pelteobagrus nitidus, Hemibarbus maculatus, Pelteobagrus fulvidraco, Saurogobio dabryi, and Paracanthobrama guichenoti—during the low-water period (July) and the high-water period (November). The results showed that the average trophic levels of all six benthic fish species ranged from 2.43 to 3.65, placing them at mid-trophic levels. However, their δ13C–δ1?N spatial distributions, trophic levels, and resource use patterns differed significantly between species and water-level periods. Distinct trophic niche characteristics were observed for the six fish species across the two periods. Specifically, the trophic niches of S. dabryi and P. guichenoti expanded significantly during the high-water period, indicating trophic niche expansion; the trophic niches of P. nitidus and P. fulvidraco contracted overall, showing trophic niche compression; whereas H. maculatus exhibited relatively stable trophic niche widths between the two periods but demonstrated trophic niche shifts. Niche overlap analysis revealed that trophic niche overlap among benthic fishes was highly asymmetric during the low-water period, suggesting stronger potential interspecific competition, while niche overlap became more symmetric during the high-water period, indicating a reduction in competitive pressure. These findings suggest that water level fluctuations, by altering habitat conditions and food resource patterns, significantly impact the trophic niche structure and interspecific relationships of benthic fishes in Hongze Lake. This study provides valuable insights into fish resource use and coexistence mechanisms under water level fluctuations, and offers scientific guidance for fish resource conservation in regulated lakes.
To investigate the trophic niche characteristics of fish in regulated lakes under water level fluctuations, Hongze Lake was selected as the study area. Carbon and nitrogen stable isotope techniques were used to analyze the trophic levels, trophic niche widths, niche overlap, and major food sources of six common benthic fish species—Cyprinus carpio, Pelteobagrus nitidus, Hemibarbus maculatus, Pelteobagrus fulvidraco, Saurogobio dabryi, and Paracanthobrama guichenoti—during the low-water period (July) and the high-water period (November). The results showed that the average trophic levels of all six benthic fish species ranged from 2.43 to 3.65, placing them at mid-trophic levels. However, their δ13C–δ1?N spatial distributions, trophic levels, and resource use patterns differed significantly between species and water-level periods. Distinct trophic niche characteristics were observed for the six fish species across the two periods. Specifically, the trophic niches of S. dabryi and P. guichenoti expanded significantly during the high-water period, indicating trophic niche expansion; the trophic niches of P. nitidus and P. fulvidraco contracted overall, showing trophic niche compression; whereas H. maculatus exhibited relatively stable trophic niche widths between the two periods but demonstrated trophic niche shifts. Niche overlap analysis revealed that trophic niche overlap among benthic fishes was highly asymmetric during the low-water period, suggesting stronger potential interspecific competition, while niche overlap became more symmetric during the high-water period, indicating a reduction in competitive pressure. These findings suggest that water level fluctuations, by altering habitat conditions and food resource patterns, significantly impact the trophic niche structure and interspecific relationships of benthic fishes in Hongze Lake. This study provides valuable insights into fish resource use and coexistence mechanisms under water level fluctuations, and offers scientific guidance for fish resource conservation in regulated lakes.
Available online: May 11, 2026
Abstract:
To investigate the effect of temperature on the immobilization of phosphorus (P) and arsenic (As) by lanthanum-modified bentonite (LMB) at the sediment-water interface (SWI) and determine the optimal remediation temperature for maximizing its efficacy, laboratory-scale simulation experiments were performed using SWI samples collected from eutrophic shallow lakes. Microelectrode profiling, high-resolution porewater sampling, and inductively coupled plasma mass spectrometry (ICP-MS) were employed to characterize the spatiotemporal dynamics of dissolved oxygen (DO), pH, iron (Fe), manganese (Mn), and dissolved organic matter (DOM) under three controlled temperature conditions (10?℃, 20?℃, and 30?℃). Concurrently, high-precision analytical methods were utilized to quantify the speciation and distribution of dissolved P and As. Results showed that elevated temperatures decreased DO concentrations, increased pH values, and elevated DOM content in the SWI. These changes facilitated the formation of anaerobic conditions, promoting the reductive dissolution of Fe and Mn oxides and thereby enhancing the release of dissolved P and As. The immobilization efficiency of LMB was clearly temperature-dependent, with maximal efficacy observed at 20?℃. At this temperature, the concentrations of dissolved P and As decreased by 85.97% and 41.43%, respectively, on day 7, and remained significantly suppressed on day 50, with reduction rates of 82.10% and 20.35%. Furthermore, LMB application facilitated the transformation of mobile fractions of P and As into more stable chemical forms in the sediment matrix. Specifically, at 20?℃, the proportion of stable P increased from 48.55% to 51.05%, whereas that of stable As rose from 62.20% to 68.92%. This study demonstrates that the effectiveness of LMB in mitigating the release of P and As at the SWI is strongly temperature-dependent. The optimal restoration temperature of 20?℃ identified by the study can be applied to address endogenous pollution in shallow lakes of temperate and subtropical regions during the spring and autumn seasons when water temperatures are suitable. Keyword: Temperature; lanthanum-modified bentonite; sediment-water interface; phosphorus; arsenic
To investigate the effect of temperature on the immobilization of phosphorus (P) and arsenic (As) by lanthanum-modified bentonite (LMB) at the sediment-water interface (SWI) and determine the optimal remediation temperature for maximizing its efficacy, laboratory-scale simulation experiments were performed using SWI samples collected from eutrophic shallow lakes. Microelectrode profiling, high-resolution porewater sampling, and inductively coupled plasma mass spectrometry (ICP-MS) were employed to characterize the spatiotemporal dynamics of dissolved oxygen (DO), pH, iron (Fe), manganese (Mn), and dissolved organic matter (DOM) under three controlled temperature conditions (10?℃, 20?℃, and 30?℃). Concurrently, high-precision analytical methods were utilized to quantify the speciation and distribution of dissolved P and As. Results showed that elevated temperatures decreased DO concentrations, increased pH values, and elevated DOM content in the SWI. These changes facilitated the formation of anaerobic conditions, promoting the reductive dissolution of Fe and Mn oxides and thereby enhancing the release of dissolved P and As. The immobilization efficiency of LMB was clearly temperature-dependent, with maximal efficacy observed at 20?℃. At this temperature, the concentrations of dissolved P and As decreased by 85.97% and 41.43%, respectively, on day 7, and remained significantly suppressed on day 50, with reduction rates of 82.10% and 20.35%. Furthermore, LMB application facilitated the transformation of mobile fractions of P and As into more stable chemical forms in the sediment matrix. Specifically, at 20?℃, the proportion of stable P increased from 48.55% to 51.05%, whereas that of stable As rose from 62.20% to 68.92%. This study demonstrates that the effectiveness of LMB in mitigating the release of P and As at the SWI is strongly temperature-dependent. The optimal restoration temperature of 20?℃ identified by the study can be applied to address endogenous pollution in shallow lakes of temperate and subtropical regions during the spring and autumn seasons when water temperatures are suitable. Keyword: Temperature; lanthanum-modified bentonite; sediment-water interface; phosphorus; arsenic
Available online: May 11, 2026
Abstract:
Microcystis, the most frequently observed genus among cyanobacterial blooms, exhibits significant morphological diversity and pronounced spatio-tempo variation. However, the seasonal distribution patterns of its distinct morphological characteristics remain unclear. This study systematically analyzed the morphological features, spatio-temporal distribution patterns, and coupling relationships with environmental factors (temperature, nutrients, etc.) of Microcystis in Chaohu Lake from 2022 to 2024. Results indicate: Significant differences exist among Microcystis species in colony size and single-cell diameter. M. panniformis and M. aeruginosa exhibit the largest colony sizes, significantly exceeding those of M. flos-aquae and M. botrys. M. wesenbergii possesses the largest cell diameter, significantly exceeding M. botrys, M. aeruginosa, and M. viridis, while M. flos-aquae and M. ichthyoblabe exhibit the smallest diameters. These phenomenon exhibited distinct differences in response to nutrients (nitrogen, phosphorus) and temperature. Nitrogen and phosphorus were key nutrients influencing Microcystis population size and cell diameter, with significant differences in the distribution proportions of different species across total nitrogen and temperature ranges. During the cold season, M. viridis and M. pseudofilamentosa exhibited higher frequencies. As water temperatures rose into the warm season, the community shifted toward higher frequencies of M. wesenbergii, M. novacekii, and M. aeruginosa. In the hot season, M. botrys and M. smithii became the most frequent species. Correlation analysis and regression models further revealed the regulatory effects of environmental factors on Microcystis cell diameter. Temperature and phosphorus show significant correlations (p<0.05) with cell diameter in most species. This study aims to provide scientific basis for understanding the ecological adaptation mechanisms of Microcystis in Chaohu Lake and for managing cyanobacteria in eutrophic lakes.
Microcystis, the most frequently observed genus among cyanobacterial blooms, exhibits significant morphological diversity and pronounced spatio-tempo variation. However, the seasonal distribution patterns of its distinct morphological characteristics remain unclear. This study systematically analyzed the morphological features, spatio-temporal distribution patterns, and coupling relationships with environmental factors (temperature, nutrients, etc.) of Microcystis in Chaohu Lake from 2022 to 2024. Results indicate: Significant differences exist among Microcystis species in colony size and single-cell diameter. M. panniformis and M. aeruginosa exhibit the largest colony sizes, significantly exceeding those of M. flos-aquae and M. botrys. M. wesenbergii possesses the largest cell diameter, significantly exceeding M. botrys, M. aeruginosa, and M. viridis, while M. flos-aquae and M. ichthyoblabe exhibit the smallest diameters. These phenomenon exhibited distinct differences in response to nutrients (nitrogen, phosphorus) and temperature. Nitrogen and phosphorus were key nutrients influencing Microcystis population size and cell diameter, with significant differences in the distribution proportions of different species across total nitrogen and temperature ranges. During the cold season, M. viridis and M. pseudofilamentosa exhibited higher frequencies. As water temperatures rose into the warm season, the community shifted toward higher frequencies of M. wesenbergii, M. novacekii, and M. aeruginosa. In the hot season, M. botrys and M. smithii became the most frequent species. Correlation analysis and regression models further revealed the regulatory effects of environmental factors on Microcystis cell diameter. Temperature and phosphorus show significant correlations (p<0.05) with cell diameter in most species. This study aims to provide scientific basis for understanding the ecological adaptation mechanisms of Microcystis in Chaohu Lake and for managing cyanobacteria in eutrophic lakes.
Available online: May 09, 2026
Abstract:
To elucidate the trophic ecological characteristics of the fish community in the Jiangjin section of the National Nature Reserve for Rare and Endemic Fishes in the Upper Yangtze River, this study analyzed 246 individuals across 42 fish species using stable isotope analysis (SIA) of carbon (δ13C) and nitrogen (δ1?N) during the flood and dry seasons of 2024. The results revealed that: (1) At the fish community level, the δ13C values ranged from -28.76‰ to -19.05‰, showing no significant difference between the flood and dry seasons; meanwhile, the δ1?N values ranged from 3.73‰ to 13.01‰, exhibiting significant seasonal differences and reflecting clear trophic differentiation. (2) The trophic level (TL) of the fish community ranged from 1.17 to 3.82, with a mean value of 2.37 ± 0.45, illustrating multi-level trophic relationships. (3) Significant seasonal hydrological differences were observed in the community trophic structure, with overall δ1?N values and the trophic levels of major feeding guilds being significantly higher in the dry season than in the flood season(P<0.05). (4) The community trophic niche width, measured by the Standard Ellipse Area (SEAc), was significantly larger in the flood season than in the dry season, indicating seasonal hydrological differences in food resource utilization patterns. This study provides a critical perspective for understanding the food web structure, seasonal hydrological dynamics, and resource utilization strategies of the fish community in this protected area, thereby offering a scientific basis for fish biodiversity conservation and ecosystem management in the region.
To elucidate the trophic ecological characteristics of the fish community in the Jiangjin section of the National Nature Reserve for Rare and Endemic Fishes in the Upper Yangtze River, this study analyzed 246 individuals across 42 fish species using stable isotope analysis (SIA) of carbon (δ13C) and nitrogen (δ1?N) during the flood and dry seasons of 2024. The results revealed that: (1) At the fish community level, the δ13C values ranged from -28.76‰ to -19.05‰, showing no significant difference between the flood and dry seasons; meanwhile, the δ1?N values ranged from 3.73‰ to 13.01‰, exhibiting significant seasonal differences and reflecting clear trophic differentiation. (2) The trophic level (TL) of the fish community ranged from 1.17 to 3.82, with a mean value of 2.37 ± 0.45, illustrating multi-level trophic relationships. (3) Significant seasonal hydrological differences were observed in the community trophic structure, with overall δ1?N values and the trophic levels of major feeding guilds being significantly higher in the dry season than in the flood season(P<0.05). (4) The community trophic niche width, measured by the Standard Ellipse Area (SEAc), was significantly larger in the flood season than in the dry season, indicating seasonal hydrological differences in food resource utilization patterns. This study provides a critical perspective for understanding the food web structure, seasonal hydrological dynamics, and resource utilization strategies of the fish community in this protected area, thereby offering a scientific basis for fish biodiversity conservation and ecosystem management in the region.
Available online: May 09, 2026
Abstract:
With climate change, the increasing frequency and intensity of extreme climate events have intensified the outbreak and expansion of cyanobacterial blooms in shallow eutrophic lakes, posing severe threats to the security and water supply safety of lake ecosystems. However, how extreme climate events drive the long-term dynamics of cyanobacterial blooms, as well as the dominant factors and underlying mechanisms, remain unclear. Taking Lake Hongze as a case study, Mann-Kendall trend analysis based on 64 years of meteorological observations revealed a significant warming trend in extreme temperature indices. Since 1991, the total duration and frequency of extreme heat events has increased by approximately 5.33 days and 2 events per decade, respectively. Meanwhile, the Simple Daily Intensity Index (SDII) and the annual total precipitation from very wet days (R95p) have increased by 0.38 mm d-1and 15.18 mm per decade, respectively. Based on remote-sensing observations from 2003 to 2020, the bloom occurrence rate in Lake Hongze has increased by 1.15%, while the maximum bloom extent has expanded by 154.69 km². The bloom onset has advanced by 24.56 days, and the potential bloom duration has extended by an average of 27.20 days. Further attribution analysis using the SHAP method indicated that the bloom occurrence rate and the maximum bloom extent are the cyanobacterial bloom metrics most sensitive to extreme climate events, with the mean intensity of extreme heat events playing a dominant role. The continued intensification of extreme heat events is expected to further advance the bloom onset and expand the bloom extent. Notably, when temperatures exceed a certain threshold, algal growth may be inhibited due to thermal stress, suggesting a dual “promoting-inhibiting” effect of extreme heat events on cyanobacterial bloom dynamics. This study elucidates the response mechanisms and threshold behaviors of cyanobacterial blooms under extreme climate forcing, providing a theoretical basis and scientific support for the early warning of bloom risks and adaptive watershed management.
With climate change, the increasing frequency and intensity of extreme climate events have intensified the outbreak and expansion of cyanobacterial blooms in shallow eutrophic lakes, posing severe threats to the security and water supply safety of lake ecosystems. However, how extreme climate events drive the long-term dynamics of cyanobacterial blooms, as well as the dominant factors and underlying mechanisms, remain unclear. Taking Lake Hongze as a case study, Mann-Kendall trend analysis based on 64 years of meteorological observations revealed a significant warming trend in extreme temperature indices. Since 1991, the total duration and frequency of extreme heat events has increased by approximately 5.33 days and 2 events per decade, respectively. Meanwhile, the Simple Daily Intensity Index (SDII) and the annual total precipitation from very wet days (R95p) have increased by 0.38 mm d-1and 15.18 mm per decade, respectively. Based on remote-sensing observations from 2003 to 2020, the bloom occurrence rate in Lake Hongze has increased by 1.15%, while the maximum bloom extent has expanded by 154.69 km². The bloom onset has advanced by 24.56 days, and the potential bloom duration has extended by an average of 27.20 days. Further attribution analysis using the SHAP method indicated that the bloom occurrence rate and the maximum bloom extent are the cyanobacterial bloom metrics most sensitive to extreme climate events, with the mean intensity of extreme heat events playing a dominant role. The continued intensification of extreme heat events is expected to further advance the bloom onset and expand the bloom extent. Notably, when temperatures exceed a certain threshold, algal growth may be inhibited due to thermal stress, suggesting a dual “promoting-inhibiting” effect of extreme heat events on cyanobacterial bloom dynamics. This study elucidates the response mechanisms and threshold behaviors of cyanobacterial blooms under extreme climate forcing, providing a theoretical basis and scientific support for the early warning of bloom risks and adaptive watershed management.
Available online: May 09, 2026
Abstract:
Lake ecosystems in cold and arid regions are highly sensitive to climate change and anthropogenic disturbances, with phytoplankton community dynamics serving as a key indicator of aquatic ecological changes. Hulun Lake, a typical shallow lake in the arid and semi-arid region of northern China, has experienced significant alterations in its hydrological cycle and pollution patterns following the implementation of the "River Water Diversion to Lake" project, leading to eutrophication. Against this backdrop, investigating the assembly mechanisms of its phytoplankton community and identifying the key environmental drivers are crucial for lake ecological restoration and algal bloom prevention. This study conducted systematic ecological surveys at 26 sampling sites in the main body of Hulun Lake and its major inflow rivers during spring and summer of 2024 and 2025. The aim was to analyze the seasonal succession patterns of the phytoplankton community, its taxonomic beta diversity characteristics, and its coupling relationship with environmental factors. The results showed that: The phytoplankton community structure exhibited significant seasonal succession. Bacillariophyta dominated in spring, with Cyclotella menaquinone as the key dominant species, while the community shifted to absolute dominance by Cyanobacteria in summer, led by Microcystis aeruginosa and Anabaenopsis oscillarioides. Although species richness was higher in summer, the Shannon-Wiener diversity index was significantly lower than in spring. Canonical Correspondence Analysis (CCA) indicated that the key environmental drivers of community succession differed between seasons. The spring community was primarily influenced by Total Phosphorus (TP), Turbidity (Turb), and Chemical Oxygen Demand (BOD<sub>5</sub>), whereas the summer community was mainly driven by Water Temperature (WT), Total Nitrogen (TN), Five-day Biochemical Oxygen Demand (BOD<sub>5</sub>), and Chlorophyll-a (Chl-a). Decomposition of taxonomic beta diversity revealed that the total β-diversity between seasons and across years was primarily driven by the turnover component, with a limited contribution from the nestedness component. This indicates that species replacement is the core process structuring the phytoplankton community in Hulun Lake, reflecting strong environmental filtering and habitat heterogeneity. This study, from the dual perspectives of species composition and community assembly mechanisms, reveals that environmental filtering is the core driving force shaping the seasonal dynamics of the phytoplankton community in Hulun Lake. The research findings not only identify key regulatory factors in the eutrophication process of Hulun Lake but also provide important scientific evidence and a case study for the aquatic ecological health assessment, cyanobacterial bloom early warning, and ecological restoration practices for Hulun Lake and similar lakes in cold and arid regions of northern China.
Lake ecosystems in cold and arid regions are highly sensitive to climate change and anthropogenic disturbances, with phytoplankton community dynamics serving as a key indicator of aquatic ecological changes. Hulun Lake, a typical shallow lake in the arid and semi-arid region of northern China, has experienced significant alterations in its hydrological cycle and pollution patterns following the implementation of the "River Water Diversion to Lake" project, leading to eutrophication. Against this backdrop, investigating the assembly mechanisms of its phytoplankton community and identifying the key environmental drivers are crucial for lake ecological restoration and algal bloom prevention. This study conducted systematic ecological surveys at 26 sampling sites in the main body of Hulun Lake and its major inflow rivers during spring and summer of 2024 and 2025. The aim was to analyze the seasonal succession patterns of the phytoplankton community, its taxonomic beta diversity characteristics, and its coupling relationship with environmental factors. The results showed that: The phytoplankton community structure exhibited significant seasonal succession. Bacillariophyta dominated in spring, with Cyclotella menaquinone as the key dominant species, while the community shifted to absolute dominance by Cyanobacteria in summer, led by Microcystis aeruginosa and Anabaenopsis oscillarioides. Although species richness was higher in summer, the Shannon-Wiener diversity index was significantly lower than in spring. Canonical Correspondence Analysis (CCA) indicated that the key environmental drivers of community succession differed between seasons. The spring community was primarily influenced by Total Phosphorus (TP), Turbidity (Turb), and Chemical Oxygen Demand (BOD<sub>5</sub>), whereas the summer community was mainly driven by Water Temperature (WT), Total Nitrogen (TN), Five-day Biochemical Oxygen Demand (BOD<sub>5</sub>), and Chlorophyll-a (Chl-a). Decomposition of taxonomic beta diversity revealed that the total β-diversity between seasons and across years was primarily driven by the turnover component, with a limited contribution from the nestedness component. This indicates that species replacement is the core process structuring the phytoplankton community in Hulun Lake, reflecting strong environmental filtering and habitat heterogeneity. This study, from the dual perspectives of species composition and community assembly mechanisms, reveals that environmental filtering is the core driving force shaping the seasonal dynamics of the phytoplankton community in Hulun Lake. The research findings not only identify key regulatory factors in the eutrophication process of Hulun Lake but also provide important scientific evidence and a case study for the aquatic ecological health assessment, cyanobacterial bloom early warning, and ecological restoration practices for Hulun Lake and similar lakes in cold and arid regions of northern China.
Available online: May 08, 2026
Abstract:
To address the limitations of data-driven model, which lack physical constraints, and to enable rapid prediction of reservoir thermal structure under future non-stationary climate scenarios, this study proposes a hybrid framework that integrates physical mechanisms with data-driven modeling for predicting reservoir water temperature profiles. Utilizing observed data from the Sanbanxi Reservoir (2007-2016), a one-dimensional hydrodynamic-water temperature model (GLM), a Random Forest-Bidirectional Long Short-Term Memory (RF-BILSTM) machine learning model, and Global Climate Models (GCMs), we reconstructed the historical thermal structure of the reservoir and projected its evolution under future climate scenarios from 2023 to 2100. The results indicate that: (1) A physically constrained training data set generated by combining the GLM model with measured data effectively mitigates spurious correlations inherent in purely data-driven approaches. The RF-BILSTM prediction framework achieved high simulation accuracy, with R2> 0.9. (2) Projections from GCMs show a significant increasing trend in future air temperature at the Sanbanxi Reservoir (p < 0.01). The temperature increase under the SSP5-8.5 scenario is substantially greater than under SSP2-4.5, while precipitation also exhibits a significant upward trend. (3) By 2100, the average water temperature in the reservoir is projected to rise by 0.39 ℃ and 0.87 ℃ under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, showing pronounced vertical differentiation. Surface warming is more significant, with projected increases of 0.94℃ and 2.04℃, respectively. The annual mean surface-bottom temperature difference is expected to increase by 1.32℃ and 1.55℃, with the maximum vertical difference occurring in August. Annual water column stability (Schmidt stability, St) is projected to increase by 643.41 J/m2(+7.85%) and 1829.47 J/m2(+22.31%), respectively, indicating intensified thermal stratification. This could elevate the risks of surface algal blooms and nutrient stratification enrichment, while also advancing the spawning timing of downstream fish. This study presents a novel approach that deeply integrates physical mechanisms with data-driven techniques, providing technical support for reservoir water temperature management.
To address the limitations of data-driven model, which lack physical constraints, and to enable rapid prediction of reservoir thermal structure under future non-stationary climate scenarios, this study proposes a hybrid framework that integrates physical mechanisms with data-driven modeling for predicting reservoir water temperature profiles. Utilizing observed data from the Sanbanxi Reservoir (2007-2016), a one-dimensional hydrodynamic-water temperature model (GLM), a Random Forest-Bidirectional Long Short-Term Memory (RF-BILSTM) machine learning model, and Global Climate Models (GCMs), we reconstructed the historical thermal structure of the reservoir and projected its evolution under future climate scenarios from 2023 to 2100. The results indicate that: (1) A physically constrained training data set generated by combining the GLM model with measured data effectively mitigates spurious correlations inherent in purely data-driven approaches. The RF-BILSTM prediction framework achieved high simulation accuracy, with R2> 0.9. (2) Projections from GCMs show a significant increasing trend in future air temperature at the Sanbanxi Reservoir (p < 0.01). The temperature increase under the SSP5-8.5 scenario is substantially greater than under SSP2-4.5, while precipitation also exhibits a significant upward trend. (3) By 2100, the average water temperature in the reservoir is projected to rise by 0.39 ℃ and 0.87 ℃ under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, showing pronounced vertical differentiation. Surface warming is more significant, with projected increases of 0.94℃ and 2.04℃, respectively. The annual mean surface-bottom temperature difference is expected to increase by 1.32℃ and 1.55℃, with the maximum vertical difference occurring in August. Annual water column stability (Schmidt stability, St) is projected to increase by 643.41 J/m2(+7.85%) and 1829.47 J/m2(+22.31%), respectively, indicating intensified thermal stratification. This could elevate the risks of surface algal blooms and nutrient stratification enrichment, while also advancing the spawning timing of downstream fish. This study presents a novel approach that deeply integrates physical mechanisms with data-driven techniques, providing technical support for reservoir water temperature management.
Available online: May 08, 2026
Abstract:
Exploring the temporal variation characteristics of phytoplankton community structure is of great significance for understanding the evolution of aquatic ecological environment; The automatic monitoring of phytoplankton communities provides fundamental data for revealing the multi-scale changes in phytoplankton community structure. However, the multi periodicity of high-frequency monitoring data also poses challenges to traditional time series analysis methods. This study takes the Jiangdong Reservoir in Beixi, Jiulong River as a case study, and obtains hourly automatic monitoring data of the biomass of four groups of green algae, blue-green algae, diatoms, and cryptoalgae from 2017 to 2022. Using Multiple Seasonal-Trend decomposition using LOESS, the biomass of each group is decomposed into four components: trend, annual period, daily period, and residual. The multi time scale variation characteristics of community structure are analyzed. The results showed that: (1) The biomass of the green algae group rapidly increased from 2020 and reached its peak in 2021, becoming the dominant group; The overall trend of other groups is declining. (2) The seasonal fluctuations of various groups are relatively stable, with cryptic algae having the largest amplitude, followed by green algae and blue-green algae, and diatoms having the smallest amplitude. (3) All types of groups have stable diurnal rhythms, reaching their peak before 12-16 pm, with green algae showing the largest amplitude and blue-green algae showing the smoothest changes. (4) Seasonal cycles and long-term trends jointly explain the main part of community abundance variation, while the contribution of daily cycles is relatively small. The research results indicate that the changes in green algae and diatom groups are driven by both multi-year background and seasonal factors, while the fluctuations in blue-green algae and cryptoalgae groups are more dependent on seasonal temperature light cycles. This study reveals the dominant substitution and niche segregation phenomena of phytoplankton at multiple scales including interannual, seasonal, and diurnal, which can provide scientific basis for early warning of harmful algal blooms and management of aquatic ecosystems.
Exploring the temporal variation characteristics of phytoplankton community structure is of great significance for understanding the evolution of aquatic ecological environment; The automatic monitoring of phytoplankton communities provides fundamental data for revealing the multi-scale changes in phytoplankton community structure. However, the multi periodicity of high-frequency monitoring data also poses challenges to traditional time series analysis methods. This study takes the Jiangdong Reservoir in Beixi, Jiulong River as a case study, and obtains hourly automatic monitoring data of the biomass of four groups of green algae, blue-green algae, diatoms, and cryptoalgae from 2017 to 2022. Using Multiple Seasonal-Trend decomposition using LOESS, the biomass of each group is decomposed into four components: trend, annual period, daily period, and residual. The multi time scale variation characteristics of community structure are analyzed. The results showed that: (1) The biomass of the green algae group rapidly increased from 2020 and reached its peak in 2021, becoming the dominant group; The overall trend of other groups is declining. (2) The seasonal fluctuations of various groups are relatively stable, with cryptic algae having the largest amplitude, followed by green algae and blue-green algae, and diatoms having the smallest amplitude. (3) All types of groups have stable diurnal rhythms, reaching their peak before 12-16 pm, with green algae showing the largest amplitude and blue-green algae showing the smoothest changes. (4) Seasonal cycles and long-term trends jointly explain the main part of community abundance variation, while the contribution of daily cycles is relatively small. The research results indicate that the changes in green algae and diatom groups are driven by both multi-year background and seasonal factors, while the fluctuations in blue-green algae and cryptoalgae groups are more dependent on seasonal temperature light cycles. This study reveals the dominant substitution and niche segregation phenomena of phytoplankton at multiple scales including interannual, seasonal, and diurnal, which can provide scientific basis for early warning of harmful algal blooms and management of aquatic ecosystems.
Available online: May 07, 2026
Abstract:
To understand the changes in fish community structure and diversity in the Zhenjiang section of the Yangtze River since the implementation of the ten-year fishing ban, this study conducted surveys once during the fish breeding period (April–July) and once during the fattening period (September–November) each year from 2021 to 2024. Over the four-year period, a total of 792 net hauls were conducted in the Zhenjiang section, collecting 3,908 fish weighing 575.62?kg. A total of 66 fish species were identified, belonging to 9 orders, 16 families, and 47 genera. During the study period, the fish assemblage in the Zhenjiang reach of the Yangtze River was dominated by omnivorous (carnivorous) species, freshwater resident species, and benthic fish, accounting for 40.91% (40.91%), 69.70%, and 43.94% of the total species, respectively. The dominant species were Parabramis pekinensis, Hemiculter bleekeri, and Saurogobio dabryi. The highest number of fish species was recorded in 2024, with 48 species, significantly higher than the 39 species recorded in 2023. One-way ANOVA results indicated significant interannual differences in fish community diversity. In 2024, the fish diversity, richness, evenness, and dominance indices were the highest. The diversity index in 2024 (3.04) was significantly higher (P < 0.05) than in the previous three years. The richness index (6.86) was significantly higher (P < 0.05) than in 2023, and the evenness index (0.79) was significantly higher (P < 0.05) than in 2022. The abundance/biomass curve results showed that after the implementation of the fishing ban, the fish community structure in the Zhenjiang section was generally less disturbed. However, in 2022, the fish community was moderately disturbed due to abnormally low water levels, leading to decreased stability. By 2024, the fish community had preliminarily reached a stable state. Cluster and NMDS analyses indicated that the fish community in the Zhenjiang section was grouped into two clusters: 2021 and 2022–2024. Compared with 2021, the relative abundances of small fish such as Pelteobagrus nitidus, Hemiculter bleekeri, and Xenocypris argentea decreased from 2022 to 2024, while the relative abundance of Coilia nasus increased, reflecting certain successional characteristics in the community structure. After the ten-year fishing ban in the Yangtze River, fish resources in the Zhenjiang section showed a gradual recovery trend, and the community remained relatively stable. However, the recovery of the fish community was not a simple linear progression but was simultaneously influenced by both the “fishing ban (positive)” and “extremely low water levels (negative)” factors. This study clarifies the basic characteristics and trends of the fish community in the Zhenjiang section since the implementation of the ten-year fishing ban, providing support for evaluating the effectiveness of the fishing ban and assessing the aquatic biological integrity index. It also contributes to the steady and long-term implementation of the ten-year fishing ban policy in the Yangtze River.
To understand the changes in fish community structure and diversity in the Zhenjiang section of the Yangtze River since the implementation of the ten-year fishing ban, this study conducted surveys once during the fish breeding period (April–July) and once during the fattening period (September–November) each year from 2021 to 2024. Over the four-year period, a total of 792 net hauls were conducted in the Zhenjiang section, collecting 3,908 fish weighing 575.62?kg. A total of 66 fish species were identified, belonging to 9 orders, 16 families, and 47 genera. During the study period, the fish assemblage in the Zhenjiang reach of the Yangtze River was dominated by omnivorous (carnivorous) species, freshwater resident species, and benthic fish, accounting for 40.91% (40.91%), 69.70%, and 43.94% of the total species, respectively. The dominant species were Parabramis pekinensis, Hemiculter bleekeri, and Saurogobio dabryi. The highest number of fish species was recorded in 2024, with 48 species, significantly higher than the 39 species recorded in 2023. One-way ANOVA results indicated significant interannual differences in fish community diversity. In 2024, the fish diversity, richness, evenness, and dominance indices were the highest. The diversity index in 2024 (3.04) was significantly higher (P < 0.05) than in the previous three years. The richness index (6.86) was significantly higher (P < 0.05) than in 2023, and the evenness index (0.79) was significantly higher (P < 0.05) than in 2022. The abundance/biomass curve results showed that after the implementation of the fishing ban, the fish community structure in the Zhenjiang section was generally less disturbed. However, in 2022, the fish community was moderately disturbed due to abnormally low water levels, leading to decreased stability. By 2024, the fish community had preliminarily reached a stable state. Cluster and NMDS analyses indicated that the fish community in the Zhenjiang section was grouped into two clusters: 2021 and 2022–2024. Compared with 2021, the relative abundances of small fish such as Pelteobagrus nitidus, Hemiculter bleekeri, and Xenocypris argentea decreased from 2022 to 2024, while the relative abundance of Coilia nasus increased, reflecting certain successional characteristics in the community structure. After the ten-year fishing ban in the Yangtze River, fish resources in the Zhenjiang section showed a gradual recovery trend, and the community remained relatively stable. However, the recovery of the fish community was not a simple linear progression but was simultaneously influenced by both the “fishing ban (positive)” and “extremely low water levels (negative)” factors. This study clarifies the basic characteristics and trends of the fish community in the Zhenjiang section since the implementation of the ten-year fishing ban, providing support for evaluating the effectiveness of the fishing ban and assessing the aquatic biological integrity index. It also contributes to the steady and long-term implementation of the ten-year fishing ban policy in the Yangtze River.
Available online: May 07, 2026
Abstract:
The full open discharge scouring during flood season is important for the scouring of Sanmenxia reservoir, and often presents a scouring-equilibrium process. But the current related research is still insufficient. Using the combination methods of field data analysis, theory research, experiment study and model simulation, the sediment transport law and scouring-equilibrium process of full open discharge are studied. Data analysis show that the sediment transport rate of full open discharge during flood season can be calculated by the power law relationship model by addition of the upstream sediment supply function, in which the sediment transport coefficient decrease with the increase of accumulated scouring time and volume. The decrease of sediment transport coefficient is a fundamental reason for the formation of the scouring-equilibrium process, and is an important reason for the unreasonable phenomenon of the power law index of discharge being less than 1.0 in previous calibrations. Furthermore, considering the difference of incipient motion condition for upper layer new deposited sediment and lower layer consolidated sediment, the power law relationship model is improved and the sediment transport coefficient is revised. It shows that the variation of revised sediment transport coefficient becomes more smooth and reasonable. Scouring experiment for the consolidated sediment proves that if the dry density of consolidated sediment increases slightly, the incipient motion condition (velocity, shear stress and discharge) will increase significantly. Finally, according to the principle of self-adjustment of alluvial river and using the delayed response model theory, the delayed response model for sediment transport coefficient and accumulated scouring volume are established and applied to simulate the scouring-equilibrium process of full open discharge for Sanmenxia reservoir. The simulation results show that the calculated curve of sediment transport coefficient varied with the accumulated scouring time are in agreement with the measured values, the calculated curve of accumulated scouring volume varied with the accumulated incoming water are in good agreement with the measured values. The values of determination coefficient and Nash-Sutcliffe efficiency are 0.98 and 0.98, which preliminarily illustrate the rationality of the proposed model.
The full open discharge scouring during flood season is important for the scouring of Sanmenxia reservoir, and often presents a scouring-equilibrium process. But the current related research is still insufficient. Using the combination methods of field data analysis, theory research, experiment study and model simulation, the sediment transport law and scouring-equilibrium process of full open discharge are studied. Data analysis show that the sediment transport rate of full open discharge during flood season can be calculated by the power law relationship model by addition of the upstream sediment supply function, in which the sediment transport coefficient decrease with the increase of accumulated scouring time and volume. The decrease of sediment transport coefficient is a fundamental reason for the formation of the scouring-equilibrium process, and is an important reason for the unreasonable phenomenon of the power law index of discharge being less than 1.0 in previous calibrations. Furthermore, considering the difference of incipient motion condition for upper layer new deposited sediment and lower layer consolidated sediment, the power law relationship model is improved and the sediment transport coefficient is revised. It shows that the variation of revised sediment transport coefficient becomes more smooth and reasonable. Scouring experiment for the consolidated sediment proves that if the dry density of consolidated sediment increases slightly, the incipient motion condition (velocity, shear stress and discharge) will increase significantly. Finally, according to the principle of self-adjustment of alluvial river and using the delayed response model theory, the delayed response model for sediment transport coefficient and accumulated scouring volume are established and applied to simulate the scouring-equilibrium process of full open discharge for Sanmenxia reservoir. The simulation results show that the calculated curve of sediment transport coefficient varied with the accumulated scouring time are in agreement with the measured values, the calculated curve of accumulated scouring volume varied with the accumulated incoming water are in good agreement with the measured values. The values of determination coefficient and Nash-Sutcliffe efficiency are 0.98 and 0.98, which preliminarily illustrate the rationality of the proposed model.
Available online: May 07, 2026
Abstract:
Abstract: To investigate the spatiotemporal dynamics of fish resources downstream of the Wudongde Hydropower Station, hydroacoustic surveys were conducted using a Simrad EK80 echosounder (200 kHz) from May 2024 to April 2025. These surveys were integrated with fish catch sampling conducted in May and November and monthly monitoring data from a fixed fish aggregation station located on the right bank downstream of the dam. The fish catch surveys collected 250 individuals representing 31 species across 24 genera and 6 families, with Carassius auratus dominating the assemblage (44.4%), followed by Coreius guichenoti (5.6%) and Hemiculter leucisculus (5.2%). Both species richness and abundance were higher in May than in November. The fixed aggregation station recorded a total of 35,026 individuals representing 55 species from 40 genera and 11 families. The assemblage was numerically dominated by Hemiculter leucisculus (54.90%), Culter alburnus (32.98%), and Lepturichthys fimbriata (5.11%), with daily catches exhibiting pronounced seasonal peaks between June and September. Hydroacoustic target strength corresponded to fish body lengths ranging from 10.1 to 117.4 cm, and monthly fish densities varied between 3.07 and 53.43 individuals per 1000 m3. Temporal trends in fish length and density derived from hydroacoustic data were consistent with those from catch surveys and showed significant monthly correlations with aggregation station data (density: R = 0.73, p < 0.01; body length during May–October: R = 0.82, p = 0.047), demonstrating strong complementarity between the two monitoring approaches in terms of spatial coverage (hydroacoustics) and temporal continuity (aggregation station). Hydroacoustic observations further revealed distinct seasonal spatial patterns of fish distribution downstream of the dam. During spring and early summer (March–June), spawning-driven aggregations dominated, with spawning grounds of different species shifting longitudinally within 1.8–12.0 km downstream of the dam across months. In contrast, during autumn and winter (September–March), fish distributions became increasingly dispersed, characterized by downstream diffusion, low-density conditions, and intermittent return movements. Overall, fish distribution dynamics downstream of the dam can be summarized as a seasonal cycle of reproduction-driven aggregation, dispersal, low-density persistence, and return migration. These findings provide a scientific basis for optimizing the operation of fish aggregation systems and ecological regulation downstream of large dams and highlight the value of integrating hydroacoustic monitoring with fish tracking, hydrological observations, and environmental data to further elucidate underlying driving mechanisms.
Abstract: To investigate the spatiotemporal dynamics of fish resources downstream of the Wudongde Hydropower Station, hydroacoustic surveys were conducted using a Simrad EK80 echosounder (200 kHz) from May 2024 to April 2025. These surveys were integrated with fish catch sampling conducted in May and November and monthly monitoring data from a fixed fish aggregation station located on the right bank downstream of the dam. The fish catch surveys collected 250 individuals representing 31 species across 24 genera and 6 families, with Carassius auratus dominating the assemblage (44.4%), followed by Coreius guichenoti (5.6%) and Hemiculter leucisculus (5.2%). Both species richness and abundance were higher in May than in November. The fixed aggregation station recorded a total of 35,026 individuals representing 55 species from 40 genera and 11 families. The assemblage was numerically dominated by Hemiculter leucisculus (54.90%), Culter alburnus (32.98%), and Lepturichthys fimbriata (5.11%), with daily catches exhibiting pronounced seasonal peaks between June and September. Hydroacoustic target strength corresponded to fish body lengths ranging from 10.1 to 117.4 cm, and monthly fish densities varied between 3.07 and 53.43 individuals per 1000 m3. Temporal trends in fish length and density derived from hydroacoustic data were consistent with those from catch surveys and showed significant monthly correlations with aggregation station data (density: R = 0.73, p < 0.01; body length during May–October: R = 0.82, p = 0.047), demonstrating strong complementarity between the two monitoring approaches in terms of spatial coverage (hydroacoustics) and temporal continuity (aggregation station). Hydroacoustic observations further revealed distinct seasonal spatial patterns of fish distribution downstream of the dam. During spring and early summer (March–June), spawning-driven aggregations dominated, with spawning grounds of different species shifting longitudinally within 1.8–12.0 km downstream of the dam across months. In contrast, during autumn and winter (September–March), fish distributions became increasingly dispersed, characterized by downstream diffusion, low-density conditions, and intermittent return movements. Overall, fish distribution dynamics downstream of the dam can be summarized as a seasonal cycle of reproduction-driven aggregation, dispersal, low-density persistence, and return migration. These findings provide a scientific basis for optimizing the operation of fish aggregation systems and ecological regulation downstream of large dams and highlight the value of integrating hydroacoustic monitoring with fish tracking, hydrological observations, and environmental data to further elucidate underlying driving mechanisms.
Available online: May 06, 2026
Abstract:
Poyang Lake is a key habitat for waterbirds along the East Asian–Australasian Flyway. Understanding the spatiotemporal dynamics of wintering waterbird diversity is critical for optimizing regional wetland conservation. Using waterbird survey data from 44 sites during 2013–2023, we quantified species richness, abundance, Shannon diversity and Pielou evenness to assess interannual trends, feeding-guild responses, contrasts inside versus outside protected areas, and spatial patterns of diversity. We recorded 109 wintering waterbird species from 7 orders and 16 families. Total abundance showed no significant long-term change, but community structure shifted markedly. Feeding guilds responded differently: diversity increased in guilds feeding on sedges and grasses, whereas the abundance of invertebrate-feeding guilds declined and tuber-feeding guilds showed a weak declining trend that was not statistically significant. Diversity was generally higher inside protected areas, yet abundance decreased inside reserves and increased outside, suggesting a redistribution of birds towards surrounding habitats. Based on mean Shannon diversity and its temporal change, sites were classified into diversity core, degradation-warning, recovery-potential and vulnerable areas, revealing strong spatial differentiation in wintering waterbird diversity across the lake. Against a backdrop of overall numerical stability, our results indicate substantial structural and functional reorganization of wintering waterbird communities and support tiered, spatially differentiated management that integrates feeding-guild responses and protected-area versus non-protected patterns to enhance population and habitat resilience in Poyang Lake.
Poyang Lake is a key habitat for waterbirds along the East Asian–Australasian Flyway. Understanding the spatiotemporal dynamics of wintering waterbird diversity is critical for optimizing regional wetland conservation. Using waterbird survey data from 44 sites during 2013–2023, we quantified species richness, abundance, Shannon diversity and Pielou evenness to assess interannual trends, feeding-guild responses, contrasts inside versus outside protected areas, and spatial patterns of diversity. We recorded 109 wintering waterbird species from 7 orders and 16 families. Total abundance showed no significant long-term change, but community structure shifted markedly. Feeding guilds responded differently: diversity increased in guilds feeding on sedges and grasses, whereas the abundance of invertebrate-feeding guilds declined and tuber-feeding guilds showed a weak declining trend that was not statistically significant. Diversity was generally higher inside protected areas, yet abundance decreased inside reserves and increased outside, suggesting a redistribution of birds towards surrounding habitats. Based on mean Shannon diversity and its temporal change, sites were classified into diversity core, degradation-warning, recovery-potential and vulnerable areas, revealing strong spatial differentiation in wintering waterbird diversity across the lake. Against a backdrop of overall numerical stability, our results indicate substantial structural and functional reorganization of wintering waterbird communities and support tiered, spatially differentiated management that integrates feeding-guild responses and protected-area versus non-protected patterns to enhance population and habitat resilience in Poyang Lake.
Available online: May 06, 2026
Abstract:
Freshwater lakes are hotspots in the global carbon cycle and significant sources of surface carbon emissions. This study focuses on the satellite lakes within the Poyang Lake Basin, the largest throughflow freshwater lake in China. By integrating cavity ring-down spectroscopy, stable isotope analysis, and organic matter spectroscopic analysis, we systematically investigate the spatiotemporal characteristics, methane (CH4) prduction pathways, and key driving factors of carbon dioxide (CO2) and CH4 emissions under different hydrological conditions. The results reveal that carbon emission fluxes from the satellite lakes in the Poyang Lake Basin exhibit significant spatiotemporal heterogeneity driven primarily by hydrological conditions. The seasonal patterns of CO2 emission fluxes varied across lakes of different scales. Large and medium-sized lakes exhibited higher emissions during the wet season due to enhanced terrestrial inputs and heterotrophic respiration, with a mean of 13.68 ± 26.77 mmol m-2 d-1.Conversely, small lakes (<10 km2) displayed higher emissions during the dry season, with an average flux of 18.23 ± 28.72 mmol m-2 d-1. Hotspots of CO2 emission remained concentrated in river inlets and shallow zones, which are strongly influenced by terrestrial inputs, with peak fluxes reaching up to 127.80 mmol m-2 d-1 during the wet season. Concurrently, CH4 emissions were consistently higher during the wet season than the dry season across all lakes. This seasonal difference was particularly pronounced in medium-sized lakes, where the average flux increased from 0.07 ± 0.12 mmol m-2 d-1 in the dry season to 0.27 ± 0.23 mmol m-2 d-1 in the wet season; however, localized peak emissions in the dry season could reach as high as 2.6 mmol m-2d-1. Stable isotope analysis revealed a shift in methanogenic pathways from the wet to the dry season. The overall range of αC narrowed, with the maximum value decreasing from 1.07 to 1.05, indicating a transition from coexisting hydrogenotrophic and acetoclastic methanogenesis during the wet season to a predominance of acetoclastic methanogenesis during the dry season. Further analysis indicated that the primary drivers of CO2 emissions shifted from allochthonous inputs and respiration in the wet season to autochthonous photochemical and biological degradation in the dry season. Similarly, CH4 production transitioned from benthic methanogenesis fueled by allochthonous substrates to the decomposition of autochthonous matter in local microenvironments. These findings demonstrate that catchment processes significantly affect throughflow lakes carbon emissions, contributing to a deeper understanding of the dynamics of lake carbon cycling.
Freshwater lakes are hotspots in the global carbon cycle and significant sources of surface carbon emissions. This study focuses on the satellite lakes within the Poyang Lake Basin, the largest throughflow freshwater lake in China. By integrating cavity ring-down spectroscopy, stable isotope analysis, and organic matter spectroscopic analysis, we systematically investigate the spatiotemporal characteristics, methane (CH4) prduction pathways, and key driving factors of carbon dioxide (CO2) and CH4 emissions under different hydrological conditions. The results reveal that carbon emission fluxes from the satellite lakes in the Poyang Lake Basin exhibit significant spatiotemporal heterogeneity driven primarily by hydrological conditions. The seasonal patterns of CO2 emission fluxes varied across lakes of different scales. Large and medium-sized lakes exhibited higher emissions during the wet season due to enhanced terrestrial inputs and heterotrophic respiration, with a mean of 13.68 ± 26.77 mmol m-2 d-1.Conversely, small lakes (<10 km2) displayed higher emissions during the dry season, with an average flux of 18.23 ± 28.72 mmol m-2 d-1. Hotspots of CO2 emission remained concentrated in river inlets and shallow zones, which are strongly influenced by terrestrial inputs, with peak fluxes reaching up to 127.80 mmol m-2 d-1 during the wet season. Concurrently, CH4 emissions were consistently higher during the wet season than the dry season across all lakes. This seasonal difference was particularly pronounced in medium-sized lakes, where the average flux increased from 0.07 ± 0.12 mmol m-2 d-1 in the dry season to 0.27 ± 0.23 mmol m-2 d-1 in the wet season; however, localized peak emissions in the dry season could reach as high as 2.6 mmol m-2d-1. Stable isotope analysis revealed a shift in methanogenic pathways from the wet to the dry season. The overall range of αC narrowed, with the maximum value decreasing from 1.07 to 1.05, indicating a transition from coexisting hydrogenotrophic and acetoclastic methanogenesis during the wet season to a predominance of acetoclastic methanogenesis during the dry season. Further analysis indicated that the primary drivers of CO2 emissions shifted from allochthonous inputs and respiration in the wet season to autochthonous photochemical and biological degradation in the dry season. Similarly, CH4 production transitioned from benthic methanogenesis fueled by allochthonous substrates to the decomposition of autochthonous matter in local microenvironments. These findings demonstrate that catchment processes significantly affect throughflow lakes carbon emissions, contributing to a deeper understanding of the dynamics of lake carbon cycling.
Available online: May 06, 2026
Abstract:
Fuxian Lake, China"s largest deep freshwater lake in terms of water storage capacity, has seen its water level decline since 2010 due to reduced inflow and other reasons, affecting the natural reproduction of its indigenous fish species. To protect the rare fish resources and biodiversity of Fuxian Lake, and to ensure the healthy and sustainable development of its ecosystem, it is imperative to determine a suitable ecological water level that promotes the habitat protection and restoration of its endemic fish species. This study focused on the endemic fish, Anabarilius grahami, of Fuxian Lake, taking it as the target species for analysis. Based on the habitat requirements of Anabarilius grahami during its growth period, three crucial habitat factors were identified: water temperature, flow velocity, and dissolved oxygen (DO). Given Fuxian Lake’s characteristic as a deep lake, a three-dimensional hydrodynamic and water quality model was constructed using the Environmental Fluid Dynamics Code (EFDC). The Vertical Cumulative Weighted Usable Area (VCWUA) tailored for deep lakes was proposed, leveraging the habitat simulation method to calculate the suitable ecological water level for Fuxian Lake and assess its feasibility. The study yielded several key findings: ①The spatial distribution characteristics of the Suitability Index(SI) for the three key habitat factors — water temperature, flow velocity, and DO — exhibit differences. The SI for water temperature and flow velocity show minimal variation at different depths and have little impact on the comprehensive HSI. However, the SI for DO decreases significantly when the water depth exceeds 15 meters, which is the main factor affecting the vertical distribution of suitable habitat space. ②The variation of the Weighted Usable Area (WUA) in the living space (0-20m underwater range) of Anabarilius grahami is the same under different water level schemes. As the water depth increases, the WUA first increases and then decreases, peaking at a depth of 15 meters underwater. ③By analyzing the relationship between the water level of Fuxian Lake and the VCWUA of Anabarilius grahami, it is observed that the VCWUA increases initially and then decreases as the water level rises. The target value of the suitable ecological water level corresponding to the maximum value of the curve is 1722.29 m. Considering predictions of water level changes driven by climate change and human activities, as well as the scale of water diversion projects implemented in the Fuxian Lake basin, it is deemed achievable to attain this target water level.
Fuxian Lake, China"s largest deep freshwater lake in terms of water storage capacity, has seen its water level decline since 2010 due to reduced inflow and other reasons, affecting the natural reproduction of its indigenous fish species. To protect the rare fish resources and biodiversity of Fuxian Lake, and to ensure the healthy and sustainable development of its ecosystem, it is imperative to determine a suitable ecological water level that promotes the habitat protection and restoration of its endemic fish species. This study focused on the endemic fish, Anabarilius grahami, of Fuxian Lake, taking it as the target species for analysis. Based on the habitat requirements of Anabarilius grahami during its growth period, three crucial habitat factors were identified: water temperature, flow velocity, and dissolved oxygen (DO). Given Fuxian Lake’s characteristic as a deep lake, a three-dimensional hydrodynamic and water quality model was constructed using the Environmental Fluid Dynamics Code (EFDC). The Vertical Cumulative Weighted Usable Area (VCWUA) tailored for deep lakes was proposed, leveraging the habitat simulation method to calculate the suitable ecological water level for Fuxian Lake and assess its feasibility. The study yielded several key findings: ①The spatial distribution characteristics of the Suitability Index(SI) for the three key habitat factors — water temperature, flow velocity, and DO — exhibit differences. The SI for water temperature and flow velocity show minimal variation at different depths and have little impact on the comprehensive HSI. However, the SI for DO decreases significantly when the water depth exceeds 15 meters, which is the main factor affecting the vertical distribution of suitable habitat space. ②The variation of the Weighted Usable Area (WUA) in the living space (0-20m underwater range) of Anabarilius grahami is the same under different water level schemes. As the water depth increases, the WUA first increases and then decreases, peaking at a depth of 15 meters underwater. ③By analyzing the relationship between the water level of Fuxian Lake and the VCWUA of Anabarilius grahami, it is observed that the VCWUA increases initially and then decreases as the water level rises. The target value of the suitable ecological water level corresponding to the maximum value of the curve is 1722.29 m. Considering predictions of water level changes driven by climate change and human activities, as well as the scale of water diversion projects implemented in the Fuxian Lake basin, it is deemed achievable to attain this target water level.
Available online: April 29, 2026
Abstract:
To elucidate the hydrological evolution patterns of Lake Taihu, this study utilized compiled hydrological data from 1986–2024, employing inflow/outflow volumes and water retention time as key indicators. Mann-Kendall trend tests and other statistical methods were applied to analyze trend and periodic characteristics, identify abrupt change points, and investigate driving factors. The results shows that: (1) Both the inflow and outflow of water have shown a significant upward trend and experienced a sudden change in 2007, with main cycles at 23-25 years, 14 years, and 9 years. (2) Spatially, the spatial structure of the inflow of water has been reconstructed. The inflow and proportion in Huxi area of the lake have shown a significant upward trend, while the inflow in Zhexi area has slightly increased. The inflow from the Yangtze River to Taihu Lake has risen to the third place. The inflow in the Wuchengxiyu area and the Hangjiahu area has sharply decreased in 2009 and 2004, respectively. In terms of outflow, the WanYu River, Zhexi area, and the Hangjiahu area have shown a significant upward trend. (3) showed a significant decreasing trend with a synchronous abrupt change in 2007, dropping from 227 days annually before the change to 195 days; when accounting for peripheral water withdrawal, it decreased more sharply from 226 days to 172 days. After the 2007 change, water withdrawal caused an average reduction of 23 days in the retention time. Further analysis revealed that watershed precipitation was the primary driver in the early period (1986–2006), but after the 2007 change, engineering regulation significantly altered the inflow mechanisms in Huxi, Zhexi, and Wucheng-Xiyu areas. Consequently, total inflow around the lake (a composite of rainfall-runoff and artificial regulation) replaced precipitation as the dominant driving factor of the retention time.
To elucidate the hydrological evolution patterns of Lake Taihu, this study utilized compiled hydrological data from 1986–2024, employing inflow/outflow volumes and water retention time as key indicators. Mann-Kendall trend tests and other statistical methods were applied to analyze trend and periodic characteristics, identify abrupt change points, and investigate driving factors. The results shows that: (1) Both the inflow and outflow of water have shown a significant upward trend and experienced a sudden change in 2007, with main cycles at 23-25 years, 14 years, and 9 years. (2) Spatially, the spatial structure of the inflow of water has been reconstructed. The inflow and proportion in Huxi area of the lake have shown a significant upward trend, while the inflow in Zhexi area has slightly increased. The inflow from the Yangtze River to Taihu Lake has risen to the third place. The inflow in the Wuchengxiyu area and the Hangjiahu area has sharply decreased in 2009 and 2004, respectively. In terms of outflow, the WanYu River, Zhexi area, and the Hangjiahu area have shown a significant upward trend. (3) showed a significant decreasing trend with a synchronous abrupt change in 2007, dropping from 227 days annually before the change to 195 days; when accounting for peripheral water withdrawal, it decreased more sharply from 226 days to 172 days. After the 2007 change, water withdrawal caused an average reduction of 23 days in the retention time. Further analysis revealed that watershed precipitation was the primary driver in the early period (1986–2006), but after the 2007 change, engineering regulation significantly altered the inflow mechanisms in Huxi, Zhexi, and Wucheng-Xiyu areas. Consequently, total inflow around the lake (a composite of rainfall-runoff and artificial regulation) replaced precipitation as the dominant driving factor of the retention time.
Available online: April 29, 2026
Abstract:
To clarify the current situation of water resources reserved for exceptional drought in the water network area is the premise of improving the regional water network pattern and enhancing regional drought resistance. Aiming at the problems of unclear concept of water source reserve and lack of calculation method of reserve scale, this paper puts forward the definition of water source reserved for exceptional drought on the basis of analyzing existing concepts of water source reserve, and gives the calculation method of water source reserve scale for four types of water sources: lake and reservoir water, river water, groundwater and external water. The method was applied to the intake area of the middle route of the South-to-North Water Transfer project. The results showed that the total water reserved for exceptional drought of the intake area reached 12.252 billion m3, among which the water reserved by lake and reservoir, river, groundwater and transferred water accounted for 10.86%, 15.7%, 56.31% and 17.12% respectively. Among the 20 cities in the water receiving area, only 7 cities have the above 4 types of water sources in their water reserves to cope with severe drought, and 13 cities have groundwater reserves that account for more than 50%, and the type of water reserves is single. There are four cities with small reserve amount and single reserve type, so it is urgent to further improve the water resources reserve system for exceptional drought in the intake area of the middle route of the South-to-North Water Transfer project.
To clarify the current situation of water resources reserved for exceptional drought in the water network area is the premise of improving the regional water network pattern and enhancing regional drought resistance. Aiming at the problems of unclear concept of water source reserve and lack of calculation method of reserve scale, this paper puts forward the definition of water source reserved for exceptional drought on the basis of analyzing existing concepts of water source reserve, and gives the calculation method of water source reserve scale for four types of water sources: lake and reservoir water, river water, groundwater and external water. The method was applied to the intake area of the middle route of the South-to-North Water Transfer project. The results showed that the total water reserved for exceptional drought of the intake area reached 12.252 billion m3, among which the water reserved by lake and reservoir, river, groundwater and transferred water accounted for 10.86%, 15.7%, 56.31% and 17.12% respectively. Among the 20 cities in the water receiving area, only 7 cities have the above 4 types of water sources in their water reserves to cope with severe drought, and 13 cities have groundwater reserves that account for more than 50%, and the type of water reserves is single. There are four cities with small reserve amount and single reserve type, so it is urgent to further improve the water resources reserve system for exceptional drought in the intake area of the middle route of the South-to-North Water Transfer project.
Available online: April 29, 2026
Abstract:
The Qaidam Basin, located on the northeastern margin of the Tibetan Plateau, is characterized by a “mountain–deep basin” structural framework and Cenozoic sedimentary fill exceeding 10 km, which has given rise to China’s largest continental saline-lake potash metallogenic belt, containing over 80% of the nation’s proven reserves. Since the Neogene, the basin has undergone multiple phases of tectonic deformation. Under the combined influence of plateau uplift and extreme regional aridification, secondary depressions such as Qarhan, Dalangtan–Heibei, Kunteyi, and Mahai developed, forming a composite mineralization system dominated by brine-type deposits with coexisting solid–liquid mineralization. The potash-forming process is jointly controlled by four-dimensional factors: tectonics, climate, provenance, and sedimentation. Based on a systematic review of tectono-sedimentary evolution and paleoclimate changes, this study reconstructs the spatiotemporal distribution and controlling mechanisms of potash mineralization. The results indicate that tectonic differentiation determined the framework of brine accumulation and storage, climatic aridification drove evaporation concentration and mineralization rhythms, while sustained provenance supply provided sufficient material input. Combined with lithofacies–paleogeographic differentiation, the sedimentary center of the basin migrated repeatedly from the Early Pleistocene to the Holocene. On the basis of integrated analysis of metallogenic factors, the evolution of potash mineralization in the Qaidam Basin can be divided into five stages: unified paleolake subsidence, multi-depression differentiation, extreme aridification and concentration, fault-controlled inheritance and metallogenic climax, and the modern saline-lake cluster. Furthermore, three metallogenic models are identified: central sedimentary-center type, foreland thrust-belt-controlled type, and northwestern tectonically controlled type. This evolutionary sequence and model framework not only reveal the dynamic essence of saline-lake potash mineralization under the uplift of the Tibetan Plateau, but also provide a theoretical basis and practical guidance for deep brine exploration and the refinement of metallogenic models in China.
The Qaidam Basin, located on the northeastern margin of the Tibetan Plateau, is characterized by a “mountain–deep basin” structural framework and Cenozoic sedimentary fill exceeding 10 km, which has given rise to China’s largest continental saline-lake potash metallogenic belt, containing over 80% of the nation’s proven reserves. Since the Neogene, the basin has undergone multiple phases of tectonic deformation. Under the combined influence of plateau uplift and extreme regional aridification, secondary depressions such as Qarhan, Dalangtan–Heibei, Kunteyi, and Mahai developed, forming a composite mineralization system dominated by brine-type deposits with coexisting solid–liquid mineralization. The potash-forming process is jointly controlled by four-dimensional factors: tectonics, climate, provenance, and sedimentation. Based on a systematic review of tectono-sedimentary evolution and paleoclimate changes, this study reconstructs the spatiotemporal distribution and controlling mechanisms of potash mineralization. The results indicate that tectonic differentiation determined the framework of brine accumulation and storage, climatic aridification drove evaporation concentration and mineralization rhythms, while sustained provenance supply provided sufficient material input. Combined with lithofacies–paleogeographic differentiation, the sedimentary center of the basin migrated repeatedly from the Early Pleistocene to the Holocene. On the basis of integrated analysis of metallogenic factors, the evolution of potash mineralization in the Qaidam Basin can be divided into five stages: unified paleolake subsidence, multi-depression differentiation, extreme aridification and concentration, fault-controlled inheritance and metallogenic climax, and the modern saline-lake cluster. Furthermore, three metallogenic models are identified: central sedimentary-center type, foreland thrust-belt-controlled type, and northwestern tectonically controlled type. This evolutionary sequence and model framework not only reveal the dynamic essence of saline-lake potash mineralization under the uplift of the Tibetan Plateau, but also provide a theoretical basis and practical guidance for deep brine exploration and the refinement of metallogenic models in China.
zhuoyu, lijunle, likemao, jianshenglong, suixiaoyun, zhoushijia, zhangwanjing, jiayintao, chenyifeng
Available online: April 29, 2026
Abstract:
The indicator species approach is an important tool for assessing the health of aquatic ecosystems. Its effectiveness depends on the selection of species that are both sensitive to environmental changes and representative of the local ecological community. This study aimed to establish a fish-based indicator species framework suitable for the upper reaches of the Yellow River. Drawing on field survey data collected from 2022 to 2023, we integrated fish community distribution patterns with species-environment relationships using a multi-faceted analytical approach and validated the results via the indicator value (IndVal) method. First, redundancy analysis (RDA) was employed to explore the associations between fish distributions and environmental variables, and to assess species-specific responses to individual environmental gradients. Subsequently, RLQ and fourth-corner analyses were used to quantify the coupling between fish functional traits and environmental gradients. Species that exhibited significant responses in both analyses were selected as candidate indicator species. Ultimately, six key indicator species were identified for the upper reaches of the Yellow River: Schizopygopsis pylzovi, Chuanchia labiosa, Gymnocypris eckloni, Platypharodon extremus, Gymnodiptychus pachycheilus, and Triplophysa siluroides. The IndVal method was then used to evaluate the indicator strength of these species for specific habitats. Among them, five species—S. pylzovi, C. labiosa, P. extremus, G. pachycheilus, and T. siluroides—exhibited statistically significant indicator values. Furthermore, the random forest model was applied to examine the relationships between the occurrence of indicator species and environmental factors. The results revealed that reservoir age, aquaculture age, and the cumulative number of dams were the most important predictors of species presence or absence. Indicator species occurrence frequency declined markedly as reservoir age and aquaculture duration grew, whereas dam quantity showed a nonlinear correlation with the probability of indicator species loss. This study provides a methodological reference for the selection of indicator fish species and offers a scientific basis for the ecological protection and management of river basins. In addition, these findings provide a methodological basis for the identification of indicator species and valuable insights to support ecological monitoring, conservation planning, and watershed management in the Yellow River Basin.
The indicator species approach is an important tool for assessing the health of aquatic ecosystems. Its effectiveness depends on the selection of species that are both sensitive to environmental changes and representative of the local ecological community. This study aimed to establish a fish-based indicator species framework suitable for the upper reaches of the Yellow River. Drawing on field survey data collected from 2022 to 2023, we integrated fish community distribution patterns with species-environment relationships using a multi-faceted analytical approach and validated the results via the indicator value (IndVal) method. First, redundancy analysis (RDA) was employed to explore the associations between fish distributions and environmental variables, and to assess species-specific responses to individual environmental gradients. Subsequently, RLQ and fourth-corner analyses were used to quantify the coupling between fish functional traits and environmental gradients. Species that exhibited significant responses in both analyses were selected as candidate indicator species. Ultimately, six key indicator species were identified for the upper reaches of the Yellow River: Schizopygopsis pylzovi, Chuanchia labiosa, Gymnocypris eckloni, Platypharodon extremus, Gymnodiptychus pachycheilus, and Triplophysa siluroides. The IndVal method was then used to evaluate the indicator strength of these species for specific habitats. Among them, five species—S. pylzovi, C. labiosa, P. extremus, G. pachycheilus, and T. siluroides—exhibited statistically significant indicator values. Furthermore, the random forest model was applied to examine the relationships between the occurrence of indicator species and environmental factors. The results revealed that reservoir age, aquaculture age, and the cumulative number of dams were the most important predictors of species presence or absence. Indicator species occurrence frequency declined markedly as reservoir age and aquaculture duration grew, whereas dam quantity showed a nonlinear correlation with the probability of indicator species loss. This study provides a methodological reference for the selection of indicator fish species and offers a scientific basis for the ecological protection and management of river basins. In addition, these findings provide a methodological basis for the identification of indicator species and valuable insights to support ecological monitoring, conservation planning, and watershed management in the Yellow River Basin.
Available online: April 29, 2026
Abstract:
The increasing global demand for biodiversity conservation has made the accurate acquisition of biodiversity data a pressing challenge worldwide. Essential Biodiversity Variables (EBVs), as core indicators for biodiversity monitoring, provide a scientific foundation for both global and regional conservation policies. While traditional monitoring methods have contributed valuable data, they remain limited by high costs, low efficiency, and sampling difficulties. Remote sensing technology offers an effective global solution for the derivation of EBVs, but its application to aquatic biodiversity monitoring remains constrained, particularly with respect to genetic diversity. Environmental DNA (eDNA), as an emerging tool, enables efficient and precise detection of diverse species within environmental samples, thereby supplying richer datasets for the development of EBVs. This paper highlights the potential of eDNA technology in advancing EBV construction and examines its prospects in biodiversity conservation in China, with the goal of fostering stronger integration between scientific research and policy-making. Using the six classes of EBVs as an analytical framework, this study reviewed 23 national and regional guidelines for aquatic biodiversity monitoring in China. The results revealed a strong dominance of community-level indicators, with approximately 95% of guidelines focusing on community composition, while genetic diversity, quantitative population dynamics, and ecosystem structure and function remain poorly represented. Considerable inconsistencies also existed among guidelines issued by different administrative sectors, limiting long-term comparability. Environmental DNA, with its high sensitivity, non-invasive sampling, and broad taxonomic coverage, offers a promising approach to address these structural gaps and support the development of EBV-aligned aquatic biodiversity monitoring systems.
The increasing global demand for biodiversity conservation has made the accurate acquisition of biodiversity data a pressing challenge worldwide. Essential Biodiversity Variables (EBVs), as core indicators for biodiversity monitoring, provide a scientific foundation for both global and regional conservation policies. While traditional monitoring methods have contributed valuable data, they remain limited by high costs, low efficiency, and sampling difficulties. Remote sensing technology offers an effective global solution for the derivation of EBVs, but its application to aquatic biodiversity monitoring remains constrained, particularly with respect to genetic diversity. Environmental DNA (eDNA), as an emerging tool, enables efficient and precise detection of diverse species within environmental samples, thereby supplying richer datasets for the development of EBVs. This paper highlights the potential of eDNA technology in advancing EBV construction and examines its prospects in biodiversity conservation in China, with the goal of fostering stronger integration between scientific research and policy-making. Using the six classes of EBVs as an analytical framework, this study reviewed 23 national and regional guidelines for aquatic biodiversity monitoring in China. The results revealed a strong dominance of community-level indicators, with approximately 95% of guidelines focusing on community composition, while genetic diversity, quantitative population dynamics, and ecosystem structure and function remain poorly represented. Considerable inconsistencies also existed among guidelines issued by different administrative sectors, limiting long-term comparability. Environmental DNA, with its high sensitivity, non-invasive sampling, and broad taxonomic coverage, offers a promising approach to address these structural gaps and support the development of EBV-aligned aquatic biodiversity monitoring systems.
Available online: April 29, 2026
Abstract:
Urban lakes serve multiple functions including flood storage, water supply, landscape tourism, and ecological maintenance, possessing significant ecological, environmental, and socio-economic value. Yangtze River Basin hosts approximately 355,000 urban lakes, accounting for over 65% of the nation"s total water area. These lakes exhibit strong ecological functions. Currently, urban lakes in the Yangtze River Basin face prominent challenges such as high non-point source pollution loads during flood seasons, pollution risks associated with ecological water supplementation safety, and weak resilience of aquatic ecosystems. Addressing these issues requires an integrated approach that considers the holistic nature of urban lake ecosystems and the systemic characteristics of the river basin. Advancing coordinated water environment and aquatic ecosystem management under a source–sewer–treatment plant–river–lake integrated framework. This study provides a systematic review of the research status and development needs related to the coordinated governance of water environment and aquatic ecosystems in urban lakes of the Yangtze River Basin. It synthesizes recent progress in domestic and international research as well as practical engineering applications, and offers an in-depth analysis of the major challenges currently constraining coordinated governance: (1) In certain urban areas, the issues of pollutant accumulation during dry seasons and the episodic release of contaminants during rainfall events remain prominent. Notably, storm-induced non-point source pollution has increasingly become a key constraint on the sustained improvement of urban water environments; (2) The critical challenge for using effluents from municipal wastewater treatment plants as ecological replenishment for urban lakes lies in achieving water quality and aquatic ecosystem compatibility between reclaimed water and receiving lake bodies; (3) The ecological resilience of lake ecosystems remains weak, and watershed-level systematic governance is still insufficient. Based on this analysis, we summarize targeted strategies and key tasks centered on "pollution source identification and perception - efficient external source control - water supplementation safety - habitat restoration and reconstruction - system optimization and configuration - integrated platform management," aiming to accelerate new achievements in the ecological environment governance of urban lakes in the Yangtze River Basin and provide scientific and technological support for national ecological civilization construction and green development strategy implementation.
Urban lakes serve multiple functions including flood storage, water supply, landscape tourism, and ecological maintenance, possessing significant ecological, environmental, and socio-economic value. Yangtze River Basin hosts approximately 355,000 urban lakes, accounting for over 65% of the nation"s total water area. These lakes exhibit strong ecological functions. Currently, urban lakes in the Yangtze River Basin face prominent challenges such as high non-point source pollution loads during flood seasons, pollution risks associated with ecological water supplementation safety, and weak resilience of aquatic ecosystems. Addressing these issues requires an integrated approach that considers the holistic nature of urban lake ecosystems and the systemic characteristics of the river basin. Advancing coordinated water environment and aquatic ecosystem management under a source–sewer–treatment plant–river–lake integrated framework. This study provides a systematic review of the research status and development needs related to the coordinated governance of water environment and aquatic ecosystems in urban lakes of the Yangtze River Basin. It synthesizes recent progress in domestic and international research as well as practical engineering applications, and offers an in-depth analysis of the major challenges currently constraining coordinated governance: (1) In certain urban areas, the issues of pollutant accumulation during dry seasons and the episodic release of contaminants during rainfall events remain prominent. Notably, storm-induced non-point source pollution has increasingly become a key constraint on the sustained improvement of urban water environments; (2) The critical challenge for using effluents from municipal wastewater treatment plants as ecological replenishment for urban lakes lies in achieving water quality and aquatic ecosystem compatibility between reclaimed water and receiving lake bodies; (3) The ecological resilience of lake ecosystems remains weak, and watershed-level systematic governance is still insufficient. Based on this analysis, we summarize targeted strategies and key tasks centered on "pollution source identification and perception - efficient external source control - water supplementation safety - habitat restoration and reconstruction - system optimization and configuration - integrated platform management," aiming to accelerate new achievements in the ecological environment governance of urban lakes in the Yangtze River Basin and provide scientific and technological support for national ecological civilization construction and green development strategy implementation.
Zhang Yaning, He Xinlin, Dong Ying, Wu Xijun, Liu Jing, Peng Yan, Zhang Fuchu, Song Weihao, Zhao Jian
Available online: April 28, 2026
Abstract:
To clarify the impact of different pollution sources on the ecological environment and human health risks, the typical river in the northern Shaanxi Energy and Chemical Industry Base was taken as the research object. The contents of heavy metals (Cu, Zn, Pb, Cd, Ni, Cr, Hg and As) in 59 sediment samples were collected and measured during the wet and dry seasons. The Geo-accumulation Index (Igeo) and Nemerow Index (P) were used to assess the heavy metal pollution level; the Positive Matrix Factorization model (PMF) was applied to quantitatively identify the sources of heavy metals. Furthermore, the contribution of each pollution sources to potential ecological risks and human health risks was quantitatively analyzed by combining PMF with the potential ecological risk model (RI) and the human health risk assessment model (HRA). The results showed that the average concentration of Hg in the sediment decreased from 0.10 mg·kg?1 in the wet season to 0.01 mg·kg?1 in the dry season, while the concentrations of the other seven heavy metals in the dry season were significantly higher than those in the wet season. The average content of eight heavy metals was at the non-pollution or low-pollution level, while the overall pollution level was relatively high. The PMF results based on receptor concentration indicated that heavy metal pollution during the wet season mainly came from industrial sources (48.23%), transportation sources (31.06%), agricultural sources (11.84%), and coal mining sources (8.87%); During the dry season, heavy metals are mainly affected by industrial sources (58.83%), coal mining sources (28.12%), and transportation sources (13.05%). Results from the PMF-RI/HRA coupling model based on pollution sources showed that the average comprehensive ecological risk indices (RI) in the wet season and dry season were 160.27 and 147.00, respectively, corresponding to "moderate risk" and "low risk" levels. The wet-season risk was mainly driven by Hg emissions (98.46%) from coal mining sources (48.27%), while the dry-season risk was mainly driven by Cd emissions (69.52%) from industrial sources (46.87%). Carcinogenic risks were evident in all populations, with boys facing the highest risk, which was mainly attributed to Ni exposure (≥80.13%) from industrial source pollution (≥51.47%). The results of the pollution source-oriented ecological and health risk assessment provide a scientific basis for pollution prevention and control in such areas.
To clarify the impact of different pollution sources on the ecological environment and human health risks, the typical river in the northern Shaanxi Energy and Chemical Industry Base was taken as the research object. The contents of heavy metals (Cu, Zn, Pb, Cd, Ni, Cr, Hg and As) in 59 sediment samples were collected and measured during the wet and dry seasons. The Geo-accumulation Index (Igeo) and Nemerow Index (P) were used to assess the heavy metal pollution level; the Positive Matrix Factorization model (PMF) was applied to quantitatively identify the sources of heavy metals. Furthermore, the contribution of each pollution sources to potential ecological risks and human health risks was quantitatively analyzed by combining PMF with the potential ecological risk model (RI) and the human health risk assessment model (HRA). The results showed that the average concentration of Hg in the sediment decreased from 0.10 mg·kg?1 in the wet season to 0.01 mg·kg?1 in the dry season, while the concentrations of the other seven heavy metals in the dry season were significantly higher than those in the wet season. The average content of eight heavy metals was at the non-pollution or low-pollution level, while the overall pollution level was relatively high. The PMF results based on receptor concentration indicated that heavy metal pollution during the wet season mainly came from industrial sources (48.23%), transportation sources (31.06%), agricultural sources (11.84%), and coal mining sources (8.87%); During the dry season, heavy metals are mainly affected by industrial sources (58.83%), coal mining sources (28.12%), and transportation sources (13.05%). Results from the PMF-RI/HRA coupling model based on pollution sources showed that the average comprehensive ecological risk indices (RI) in the wet season and dry season were 160.27 and 147.00, respectively, corresponding to "moderate risk" and "low risk" levels. The wet-season risk was mainly driven by Hg emissions (98.46%) from coal mining sources (48.27%), while the dry-season risk was mainly driven by Cd emissions (69.52%) from industrial sources (46.87%). Carcinogenic risks were evident in all populations, with boys facing the highest risk, which was mainly attributed to Ni exposure (≥80.13%) from industrial source pollution (≥51.47%). The results of the pollution source-oriented ecological and health risk assessment provide a scientific basis for pollution prevention and control in such areas.
Available online: April 28, 2026
Abstract:
Abstract:To systematically reveal the sediment pollution characteristics, endogenous release risks, and primary pollution sources in Qilu Lake, a heavily polluted plateau lake in Yunnan, and to provide a scientific basis for its precise and effective management, a comprehensive sediment investigation was conducted across the entire lake from 2024 to 2025. This study involved collecting samples from 20 sites to determine the concentrations of total nitrogen (TN), total phosphorus (TP), organic matter (OM), and various heavy metals, with their spatial distribution patterns analyzed using GIS. Concurrently, laboratory static incubation experiments were performed on sediments from three typical areas—the western estuary, the lake"s center, and the northeastern region—to quantify the release fluxes and transformation patterns of nitrogen and phosphorus. Finally, methods such as Nemerow"s comprehensive pollution index and Principal Component Analysis (PCA) were employed to assess the pollution degree and identify the main sources. The results indicated that the sediments of Qilu Lake act as a massive "pollution reservoir" and are extremely polluted, with surface sediment concentrations of TN, TP, and OM ranging from 2120–11300 mg/kg, 270–2280 mg/kg, and 41.4–260 g/kg, respectively. The Nemerow"s index assessment revealed that 70% of the sampling sites reached moderate to severe pollution levels (PN > 2.0), with TN being the primary determining factor for the pollution. The pollutant distribution exhibited significant spatial heterogeneity, forming "pollution hotspots" in the southwestern estuary area, which receives terrestrial inputs, and in the central lake area, which serves as a deposition center for endogenous biomass. PCA clearly distinguished two major categories of pollution sources: (1) a composite source of agricultural non-point and industrial pollution, characterized by TP and various heavy metals (especially Cd, Pb, Cu, Zn); and (2) an organic pollution source, characterized by TN and OM, originating from domestic sewage and endogenous biological contributions. The static release experiments confirmed that the sediment is a strong internal source of nitrogen and phosphorus. The central and northeastern parts of the lake were identified as the main "high-efficiency release zones," with a maximum TP release flux of up to 2.80 mg/(m2·d) and an ammonia nitrogen release flux as high as 146.1 mg/(m2·d). In contrast, the western estuary area exhibited a unique net absorption of total nitrogen, suggesting its potential as a "denitrification functional zone." The core innovation of this study lies in revealing, for the first time, the spatial heterogeneity and functional differentiation between the "stock" (pollutant storage) and "risk" (release potential) of internal pollution in Qilu Lake. The study found that the western estuary area, despite having the highest pollutant stock, exhibited unique net total nitrogen absorption in its release mechanisms, identifying it as a potential "denitrification functional zone." Conversely, the central and northeastern areas, although some parts do not have the highest pollutant stock, function as the "high-efficiency release zones" for nitrogen and phosphorus. This finding not only deepens the understanding of the complexity of biogeochemical processes in heavily polluted shallow lakes but, more importantly, This provides the critical scientific evidence for evolving endogenous pollution remediation in lakes, moving away from conventional, simplistic, holistic approaches to a precision, zone-based management and control strategy informed by "source-sink" patterns and functional differentiation.
Abstract:To systematically reveal the sediment pollution characteristics, endogenous release risks, and primary pollution sources in Qilu Lake, a heavily polluted plateau lake in Yunnan, and to provide a scientific basis for its precise and effective management, a comprehensive sediment investigation was conducted across the entire lake from 2024 to 2025. This study involved collecting samples from 20 sites to determine the concentrations of total nitrogen (TN), total phosphorus (TP), organic matter (OM), and various heavy metals, with their spatial distribution patterns analyzed using GIS. Concurrently, laboratory static incubation experiments were performed on sediments from three typical areas—the western estuary, the lake"s center, and the northeastern region—to quantify the release fluxes and transformation patterns of nitrogen and phosphorus. Finally, methods such as Nemerow"s comprehensive pollution index and Principal Component Analysis (PCA) were employed to assess the pollution degree and identify the main sources. The results indicated that the sediments of Qilu Lake act as a massive "pollution reservoir" and are extremely polluted, with surface sediment concentrations of TN, TP, and OM ranging from 2120–11300 mg/kg, 270–2280 mg/kg, and 41.4–260 g/kg, respectively. The Nemerow"s index assessment revealed that 70% of the sampling sites reached moderate to severe pollution levels (PN > 2.0), with TN being the primary determining factor for the pollution. The pollutant distribution exhibited significant spatial heterogeneity, forming "pollution hotspots" in the southwestern estuary area, which receives terrestrial inputs, and in the central lake area, which serves as a deposition center for endogenous biomass. PCA clearly distinguished two major categories of pollution sources: (1) a composite source of agricultural non-point and industrial pollution, characterized by TP and various heavy metals (especially Cd, Pb, Cu, Zn); and (2) an organic pollution source, characterized by TN and OM, originating from domestic sewage and endogenous biological contributions. The static release experiments confirmed that the sediment is a strong internal source of nitrogen and phosphorus. The central and northeastern parts of the lake were identified as the main "high-efficiency release zones," with a maximum TP release flux of up to 2.80 mg/(m2·d) and an ammonia nitrogen release flux as high as 146.1 mg/(m2·d). In contrast, the western estuary area exhibited a unique net absorption of total nitrogen, suggesting its potential as a "denitrification functional zone." The core innovation of this study lies in revealing, for the first time, the spatial heterogeneity and functional differentiation between the "stock" (pollutant storage) and "risk" (release potential) of internal pollution in Qilu Lake. The study found that the western estuary area, despite having the highest pollutant stock, exhibited unique net total nitrogen absorption in its release mechanisms, identifying it as a potential "denitrification functional zone." Conversely, the central and northeastern areas, although some parts do not have the highest pollutant stock, function as the "high-efficiency release zones" for nitrogen and phosphorus. This finding not only deepens the understanding of the complexity of biogeochemical processes in heavily polluted shallow lakes but, more importantly, This provides the critical scientific evidence for evolving endogenous pollution remediation in lakes, moving away from conventional, simplistic, holistic approaches to a precision, zone-based management and control strategy informed by "source-sink" patterns and functional differentiation.
Available online: April 28, 2026
Abstract:
Dissolved gases are key byproducts of biogeochemical reactions and serve as critical indicators for the evolution of aquatic ecosystems. However, traditional headspace equilibrium sampling methods are prone to air contamination, decompression-induced degassing, and limited measurement precision. To address these challenges, this study developed an in-situ system for the simultaneous determination of multiple dissolved gases in deep waters. The method was applied to characterize the distribution of dissolved gases in the Three Gorges Reservoir. Results demonstrated that the proposed method achieves high-precision, simultaneous in-situ measurements of five key gases—methane (CH4), nitrogen (N2), oxygen (O2), argon (Ar), and carbon dioxide (CO2)—at depths of up to 100 meters. High-precision calibration models were established for these five gases through systematic multi-temperature and multi-concentration calibration, achieving a measurement resolution of 1 ppm. Compared to traditional headspace sampling, this approach effectively eliminates air interference and decompression degassing, significantly enhancing data fidelity. Field validation against commercial high-precision instruments (Picarro greenhouse gas analyzer and multi-parameter water quality sondes) demonstrated exceptional consistency (R2 > 0.96; Concordance Correlation Coefficient [CCC] > 0.98), confirming the accuracy and reliability of the measurements. Furthermore, the proposed method surpasses traditional techniques in terms of real-time performance, spatial resolution, and monitoring efficiency. Field application in the Pengxi River Bay of the Three Gorges Reservoir successfully generated high-resolution two-dimensional distribution profiles along a 42-km longitudinal section. The results clearly revealed distinct vertical stratification, extensive bottom water hypoxia, and coupled accumulation of CO2 and CH4 during summer and autumn, effectively identifying hotspots of intense biogeochemical activity. This in-situ monitoring technology matches the accuracy of traditional laboratory methods while offering superior data fidelity, spatiotemporal resolution, and monitoring efficiency. It provides innovative technical support for greenhouse gas emission assessment, water quality management, aquatic nitrogen cycling, and the study of material cycling and ecological evolution in complex aquatic environments.
Dissolved gases are key byproducts of biogeochemical reactions and serve as critical indicators for the evolution of aquatic ecosystems. However, traditional headspace equilibrium sampling methods are prone to air contamination, decompression-induced degassing, and limited measurement precision. To address these challenges, this study developed an in-situ system for the simultaneous determination of multiple dissolved gases in deep waters. The method was applied to characterize the distribution of dissolved gases in the Three Gorges Reservoir. Results demonstrated that the proposed method achieves high-precision, simultaneous in-situ measurements of five key gases—methane (CH4), nitrogen (N2), oxygen (O2), argon (Ar), and carbon dioxide (CO2)—at depths of up to 100 meters. High-precision calibration models were established for these five gases through systematic multi-temperature and multi-concentration calibration, achieving a measurement resolution of 1 ppm. Compared to traditional headspace sampling, this approach effectively eliminates air interference and decompression degassing, significantly enhancing data fidelity. Field validation against commercial high-precision instruments (Picarro greenhouse gas analyzer and multi-parameter water quality sondes) demonstrated exceptional consistency (R2 > 0.96; Concordance Correlation Coefficient [CCC] > 0.98), confirming the accuracy and reliability of the measurements. Furthermore, the proposed method surpasses traditional techniques in terms of real-time performance, spatial resolution, and monitoring efficiency. Field application in the Pengxi River Bay of the Three Gorges Reservoir successfully generated high-resolution two-dimensional distribution profiles along a 42-km longitudinal section. The results clearly revealed distinct vertical stratification, extensive bottom water hypoxia, and coupled accumulation of CO2 and CH4 during summer and autumn, effectively identifying hotspots of intense biogeochemical activity. This in-situ monitoring technology matches the accuracy of traditional laboratory methods while offering superior data fidelity, spatiotemporal resolution, and monitoring efficiency. It provides innovative technical support for greenhouse gas emission assessment, water quality management, aquatic nitrogen cycling, and the study of material cycling and ecological evolution in complex aquatic environments.
zhao rui, Lu Mansheng, Huang Junteng, Li Shengping, Liu Wanxin, Zhang Shulin, Tang Jiaxin, Zheng Jiazhong, Yong Bin, Wang Weiguang
Available online: April 28, 2026
Abstract:
River discharge serves as a critical variable in basin hydrological processes, playing a vital role in flood control, water resource planning, and management. Due to harsh natural environments and climatic conditions, discharge observation stations are scarce in the Yangtze River source region located on the eastern edge of the Qinghai-Tibet Plateau, making it a typical data-deficient area. Therefore, conducting discharge estimation in this region is of significant importance for ensuring water security in the Yangtze River basin and protecting regional ecosystems. This study establishes virtual stations upstream and downstream of the Zhimenda hydrological station in the Yangtze headwaters (ZMD_1 and ZMD_2) as reference points. Utilizing Sentinel-2 and Jason-3, and Sentinel-3A satellite remote sensing data. A novel quantile matching approach was employed to fuse remotely sensed water level and river width data. The Manning"s equation was modified based on generalized cross-section profiles to conduct quantitative discharge estimation for the Yangtze headwaters. Results indicate that the new method achieves high esti-mation accuracy at both virtual stations, with Nash"s efficiency coefficients (NSE) exceeding 0.74. The root mean square error (RMSE) of estimated discharges was 302.13 m3/s and 316.46 m3/s, respectively, with relative root mean square errors (RRMSE) of 30.0% and 32.8%. Overall, discharge estimation accuracy at the ZMD_1 virtual station outperformed that at ZMD_2. The ZMD_2 virtual station results exhibited significant fluctuations, primarily due to the presence of mid-channel bars within the ZMD_2 buffer zone, which compromised the accuracy of flow inversion at the virtual station. This study, based on multi-source satellite remote sensing for estimating river flows in the Yangtze River source region, provides theoretical methods and technical references for flow estimation in data-scarce areas.
River discharge serves as a critical variable in basin hydrological processes, playing a vital role in flood control, water resource planning, and management. Due to harsh natural environments and climatic conditions, discharge observation stations are scarce in the Yangtze River source region located on the eastern edge of the Qinghai-Tibet Plateau, making it a typical data-deficient area. Therefore, conducting discharge estimation in this region is of significant importance for ensuring water security in the Yangtze River basin and protecting regional ecosystems. This study establishes virtual stations upstream and downstream of the Zhimenda hydrological station in the Yangtze headwaters (ZMD_1 and ZMD_2) as reference points. Utilizing Sentinel-2 and Jason-3, and Sentinel-3A satellite remote sensing data. A novel quantile matching approach was employed to fuse remotely sensed water level and river width data. The Manning"s equation was modified based on generalized cross-section profiles to conduct quantitative discharge estimation for the Yangtze headwaters. Results indicate that the new method achieves high esti-mation accuracy at both virtual stations, with Nash"s efficiency coefficients (NSE) exceeding 0.74. The root mean square error (RMSE) of estimated discharges was 302.13 m3/s and 316.46 m3/s, respectively, with relative root mean square errors (RRMSE) of 30.0% and 32.8%. Overall, discharge estimation accuracy at the ZMD_1 virtual station outperformed that at ZMD_2. The ZMD_2 virtual station results exhibited significant fluctuations, primarily due to the presence of mid-channel bars within the ZMD_2 buffer zone, which compromised the accuracy of flow inversion at the virtual station. This study, based on multi-source satellite remote sensing for estimating river flows in the Yangtze River source region, provides theoretical methods and technical references for flow estimation in data-scarce areas.
Available online: April 23, 2026
Abstract:
Phytoplankton, as the primary producers in lake ecosystems, influence material cycling and energy flow within water bodies. Their community structure and dynamic changes directly reflect the nutrient status and ecological health of the water body. To comprehensively understand phytoplankton variations and influencing factors in tailwater lakes of northern arid-cold regions, the representative Daihai Lake was selected as the study site. Water and sediment samples were collected across all four seasons in 2024 to systematically analyse phytoplankton community structure and its response to environmental factors. Results indicate that during the study period, water body total nitrogen (TN) and total phosphorus (TP) concentrations exceeded Class V and Class IV water standards, respectively, while sediment TN and TP contents surpassed the national sediment average. A total of 95 phytoplankton species belonging to 8 phyla were identified, dominated by Chlorophyta, Cyanobacteria, and Diatomeae. Phytoplankton cell density, biomass, and Chl.a concentration peaked in winter. Ten dominant species across 5 phyla were identified, primarily from Chlorophyta and Diatomeae, with Microcystis and Chromomonas serving as key dominant species throughout the year. Results from Shannon diversity index, Pielou evenness index, Margalef richness index, and Simpson dominance index indicated higher phytoplankton community diversity and greater ecosystem stability in spring and summer compared to autumn and winter. Phytoplankton communities in Daihai Lake exhibited low spatial heterogeneity, suggesting that diversity and richness are primarily influenced by seasonal variations. Statistical analysis indicates that water temperature (WT), pH, dissolved oxygen (DO), total nitrogen (TN), and dissolved inorganic phosphorus (DIP) are key factors influencing phytoplankton community structure. Multi-year surveys reveal that the dominant phytoplankton species in Daihai Lake have shifted from diatoms and green algae to cyanobacteria and cryptophytes. This study uncovers the key mechanisms driving seasonal succession in phytoplankton communities of northern cold-arid lakes, providing a scientific basis for ecological management and conservation of Daihai Lake.
Phytoplankton, as the primary producers in lake ecosystems, influence material cycling and energy flow within water bodies. Their community structure and dynamic changes directly reflect the nutrient status and ecological health of the water body. To comprehensively understand phytoplankton variations and influencing factors in tailwater lakes of northern arid-cold regions, the representative Daihai Lake was selected as the study site. Water and sediment samples were collected across all four seasons in 2024 to systematically analyse phytoplankton community structure and its response to environmental factors. Results indicate that during the study period, water body total nitrogen (TN) and total phosphorus (TP) concentrations exceeded Class V and Class IV water standards, respectively, while sediment TN and TP contents surpassed the national sediment average. A total of 95 phytoplankton species belonging to 8 phyla were identified, dominated by Chlorophyta, Cyanobacteria, and Diatomeae. Phytoplankton cell density, biomass, and Chl.a concentration peaked in winter. Ten dominant species across 5 phyla were identified, primarily from Chlorophyta and Diatomeae, with Microcystis and Chromomonas serving as key dominant species throughout the year. Results from Shannon diversity index, Pielou evenness index, Margalef richness index, and Simpson dominance index indicated higher phytoplankton community diversity and greater ecosystem stability in spring and summer compared to autumn and winter. Phytoplankton communities in Daihai Lake exhibited low spatial heterogeneity, suggesting that diversity and richness are primarily influenced by seasonal variations. Statistical analysis indicates that water temperature (WT), pH, dissolved oxygen (DO), total nitrogen (TN), and dissolved inorganic phosphorus (DIP) are key factors influencing phytoplankton community structure. Multi-year surveys reveal that the dominant phytoplankton species in Daihai Lake have shifted from diatoms and green algae to cyanobacteria and cryptophytes. This study uncovers the key mechanisms driving seasonal succession in phytoplankton communities of northern cold-arid lakes, providing a scientific basis for ecological management and conservation of Daihai Lake.
Available online: April 13, 2026
Abstract:
The operation of cascade reservoirs has a significant impact on river water temperature. This study constructs a quantitative attribution framework to distinguish the impacts of climate change and reservoir operation on river water temperature by integrating the Maximal Overlap Discrete Wavelet Transform (MODWT), Multiresolution Analysis (MRA), ERA5-Land reanalysis data, and a Bi-LSTM model. Taking the Xiangjiaba Station in the lower Jinsha River as a case study, the multi-scale effects of cascade reservoir operation on water temperature were investigated. The results indicate that: (1) The joint operation of the cascade reservoirs significantly dampens water temperature fluctuations at medium-to-high frequencies (daily, weekly, monthly scales), exhibiting a "smoothing effect"; (2) At low frequencies (seasonal and inter-annual scales), reservoir operation leads to a significant "attenuation effect" and "lag effect" on water temperature, and these effects intensify with an increasing number of reservoirs in operation; (3) Reservoir operation is the dominant factor driving water temperature changes at the seasonal scale, while climate change primarily drives the changes at the annual scale during the four-reservoir joint operation period. This study reveals the multi-temporal scale characteristics of the impact of cascade reservoirs on water temperature, proposes a novel attribution analysis method, and provides a scientific basis for the ecological operation of reservoirs and watershed water temperature management.
The operation of cascade reservoirs has a significant impact on river water temperature. This study constructs a quantitative attribution framework to distinguish the impacts of climate change and reservoir operation on river water temperature by integrating the Maximal Overlap Discrete Wavelet Transform (MODWT), Multiresolution Analysis (MRA), ERA5-Land reanalysis data, and a Bi-LSTM model. Taking the Xiangjiaba Station in the lower Jinsha River as a case study, the multi-scale effects of cascade reservoir operation on water temperature were investigated. The results indicate that: (1) The joint operation of the cascade reservoirs significantly dampens water temperature fluctuations at medium-to-high frequencies (daily, weekly, monthly scales), exhibiting a "smoothing effect"; (2) At low frequencies (seasonal and inter-annual scales), reservoir operation leads to a significant "attenuation effect" and "lag effect" on water temperature, and these effects intensify with an increasing number of reservoirs in operation; (3) Reservoir operation is the dominant factor driving water temperature changes at the seasonal scale, while climate change primarily drives the changes at the annual scale during the four-reservoir joint operation period. This study reveals the multi-temporal scale characteristics of the impact of cascade reservoirs on water temperature, proposes a novel attribution analysis method, and provides a scientific basis for the ecological operation of reservoirs and watershed water temperature management.
Available online: April 08, 2026
Abstract:
In order to reveal the distribution patterns and causes of microplastics (MPs) in the surface water of plateau lakes with different degrees of human interference, this study selected Shudu Lake, which has relatively weak human interference, and Xingyun Lake, which has relatively strong human interference, as the research areas. Through sample collection and the separation, extraction, and identification of MPs, the distribution characteristics and source differences of MPs in the surface water of the two lakes were compared and analyzed, providing a theoretical basis for the prevention and protection restoration of MPs in different plateau lakes. The results indicate that: (1) The average abundance of MPs was 1.82 particles/m3 in Shudu Lake and 2.14 ± 1.25 particles/m3 in Xingyun Lake. The average number of MPs was 478 ± 57 particles/individual in Shudu Lake and 558 ± 314 particles/individual in Xingyun Lake. As the intensity of human disturbance increases, both the average abundance and average count of MPs in the surface waters of these two plateau lakes show a gradual upward trend. (2) The MPs in Shudu Lake are mainly black and blue (with an average total count of 295 ± 12 particles/individual), while those in Xingyun Lake are mainly blue and black (with an average total count of 403 ± 106 particles/individual). The shapes of MPs in both Xingyun Lake and Shudu Lake are mainly line, with an average number of 462 particles/individual in Shudu Lake and 481 ± 239 particles/individual in Xingyun Lake. The average number of MPs with a size of ≤ 200 μm is 86 ± 30 particles/individual in Shudu Lake and 280 ± 167 particles/individual in Xingyun Lake. The main polymer types in Shudu Lake are 4 types (rayon (RY), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET)), while in Xingyun Lake there are 7 types (RY, PE, PET, low-density styrene-butadiene-styrene (SBS), polyethylenimine ephchlorohydrin modified (PEM), polyester (PES), and polyvinyl alcohol (PVA)). Shudu Lake has fewer polymer types than Xingyun Lake, indicating that the sources of MPs in Xingyun Lake are more diverse. With the increase in the intensity of human interference, the average quantities of the main colors (black and blue), main shapes (line), and size range (≤ 200 μm) of MPs in the surface water of the two plateau lakes have all shown a gradual increase trend, and the number of main polymer types has also shown a gradual increase trend. (3) Shudu Lake is oligotrophic and subject to limited anthropogenic disturbance; the main sources of microplastic pollution are tourism activities, grazing, and atmospheric deposition. Xingyun Lake is mildly eutrophic and experiences stronger human interference; MPs pollution originates from domestic sewage, agricultural cultivation, transportation, fish farming, fishing operations, industrial production, tourism activities, atmospheric deposition, and grazing activities. The distribution and sources of MPs in the surface waters of the two plateau lakes differ, and the level of anthropogenic disturbance is the key factor determining MPs abundance.
In order to reveal the distribution patterns and causes of microplastics (MPs) in the surface water of plateau lakes with different degrees of human interference, this study selected Shudu Lake, which has relatively weak human interference, and Xingyun Lake, which has relatively strong human interference, as the research areas. Through sample collection and the separation, extraction, and identification of MPs, the distribution characteristics and source differences of MPs in the surface water of the two lakes were compared and analyzed, providing a theoretical basis for the prevention and protection restoration of MPs in different plateau lakes. The results indicate that: (1) The average abundance of MPs was 1.82 particles/m3 in Shudu Lake and 2.14 ± 1.25 particles/m3 in Xingyun Lake. The average number of MPs was 478 ± 57 particles/individual in Shudu Lake and 558 ± 314 particles/individual in Xingyun Lake. As the intensity of human disturbance increases, both the average abundance and average count of MPs in the surface waters of these two plateau lakes show a gradual upward trend. (2) The MPs in Shudu Lake are mainly black and blue (with an average total count of 295 ± 12 particles/individual), while those in Xingyun Lake are mainly blue and black (with an average total count of 403 ± 106 particles/individual). The shapes of MPs in both Xingyun Lake and Shudu Lake are mainly line, with an average number of 462 particles/individual in Shudu Lake and 481 ± 239 particles/individual in Xingyun Lake. The average number of MPs with a size of ≤ 200 μm is 86 ± 30 particles/individual in Shudu Lake and 280 ± 167 particles/individual in Xingyun Lake. The main polymer types in Shudu Lake are 4 types (rayon (RY), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET)), while in Xingyun Lake there are 7 types (RY, PE, PET, low-density styrene-butadiene-styrene (SBS), polyethylenimine ephchlorohydrin modified (PEM), polyester (PES), and polyvinyl alcohol (PVA)). Shudu Lake has fewer polymer types than Xingyun Lake, indicating that the sources of MPs in Xingyun Lake are more diverse. With the increase in the intensity of human interference, the average quantities of the main colors (black and blue), main shapes (line), and size range (≤ 200 μm) of MPs in the surface water of the two plateau lakes have all shown a gradual increase trend, and the number of main polymer types has also shown a gradual increase trend. (3) Shudu Lake is oligotrophic and subject to limited anthropogenic disturbance; the main sources of microplastic pollution are tourism activities, grazing, and atmospheric deposition. Xingyun Lake is mildly eutrophic and experiences stronger human interference; MPs pollution originates from domestic sewage, agricultural cultivation, transportation, fish farming, fishing operations, industrial production, tourism activities, atmospheric deposition, and grazing activities. The distribution and sources of MPs in the surface waters of the two plateau lakes differ, and the level of anthropogenic disturbance is the key factor determining MPs abundance.
Available online: March 31, 2026
Abstract:
Accurate prediction of sediment concentration processes is crucial for effective reservoir flood regulation, sediment management, and ecological conservation in river basins with significant sediment loads, such as the Yellow River. The ability to predict sediment concentrations accurately is key to mitigating the negative impacts of sedimentation in reservoirs, optimizing flood control, and ensuring the safety of infrastructure and water quality management. In this study, we focus on the sediment concentration process at the Tongguan Hydrological Station, which is located in the middle and lower reaches of the Yellow River. The Yellow River, known for its high sediment load, plays a vital role in the sediment transport dynamics that influence the river"s water quality and sedimentation patterns. The Tongguan station is a critical monitoring point in the Yellow River basin because it marks the confluence of the Yellow River mainstream with major tributaries such as the Weihe and Beiluohe Rivers, and it is located just before sediment enters the Sanmenxia Reservoir, which significantly influences downstream sedimentation and flood management. This study proposes a Parallel Spatio-Temporal Attention Long Short-Term Memory (PSTA-LSTM) model designed for sediment concentration forecasting, specifically tailored to handle the dynamic and complex flow-sediment conditions of the Yellow River. The PSTA-LSTM model integrates a parallel spatio-temporal attention mechanism that allows it to jointly capture multiscale temporal dependencies and spatial correlations among different watershed sites, significantly improving its ability to model sediment transport processes. In addition, the model incorporates an adaptive segmented rectified linear unit (SReLU) in the hidden layers to enhance the model’s capacity to learn complex nonlinear features and better handle rapid fluctuations in sediment concentrations, particularly during peak sediment events. This adaptive function helps the model manage the large variability in sediment loads commonly observed in rivers like the Yellow River, which is subject to varying flow conditions, tributary contributions, and local erosion-deposition dynamics. Experiments were conducted using measured hydrological and sediment data from 2000 to 2024. The results show that compared to the traditional serial LSTM structure, introducing the parallel spatio-temporal attention mechanism reduces the overall Root Mean Square Error (RMSE) by approximately 25.6%, and improves Peak Sediment Prediction Accuracy (PRE) by about 12.7%. Incorporating the SReLU activation function significantly enhances peak prediction accuracy, with the Nash-Sutcliffe Efficiency (NSE) improving by over 9%, showing that SReLU can more effectively handle peak sediment values. The study focuses on the sediment concentration process at the Tongguan hydrological station, located in the confluence area of the middle Yellow River. Tongguan Station is situated at the junction of the Yellow River mainstream and major tributaries such as the Weihe and Beiluohe Rivers. It serves as a critical sediment control section before the Yellow River enters the Sanmenxia Reservoir, playing an important role in reservoir regulation and downstream sediment transport. The upstream water and sediment mainly originate from the Yellow River basin above the Longmen Station, as well as the Weihe River basin at Huaxian Station and the Beiluohe River basin at Zhuangtou Station. Among these, the mainstream floods are characterized by sharp rises and falls with high sediment concentration; the Weihe River floods have a longer duration and a more blunt peak, while the Beiluohe River floods have sharp, narrow peaks, high sediment concentration, and rapid sediment wave propagation. The confluence and superposition of floods from different sources at the Tongguan confluence area not only affect sediment transport intensity but also determine the temporal variation characteristics of the sediment concentration process at Tongguan Station. Experiments were conducted using long-term observed hydrological and sediment data from 2000 to 2024, with the samples classified into five flow-sediment regimes: high-flow/high-sediment, medium-flow/medium-sediment, low-flow/low-sediment, high-flow/low-sediment, and low-flow/high-sediment. The PSTA-LSTM model was trained and evaluated separately under each regime and further compared between flood and non-flood seasons to examine its adaptability to varying hydrological conditions. The results show that introducing the parallel spatio-temporal attention mechanism improves the model’s performance significantly, with the Root Mean Square Error (RMSE) decreasing by approximately 25.6% and Peak Sediment Prediction Accuracy (PRE) improving by about 12.7%. Additionally, incorporating the SReLU activation function led to an increase in Nash-Sutcliffe Efficiency (NSE) by 6-11% compared to the traditional ReLU and softplus activation functions, showing its enhanced capability to handle peak sediment values effectively. The results also demonstrate that regime-based training based on flow-sediment types improves the prediction accuracy, with RMSE decreasing by approximately 15.7%, and NSE reaching over 80%. The comparison between flood and non-flood seasons shows that the PSTA-LSTM model exhibits stronger responsiveness during the flood season, especially during periods with significant peak sediment concentrations and rapid short-term fluctuations. These results highlight the model"s ability to adapt to dynamic and complex sediment transport conditions and its potential for real-time sediment concentration forecasting in large river systems like the Yellow River.
Accurate prediction of sediment concentration processes is crucial for effective reservoir flood regulation, sediment management, and ecological conservation in river basins with significant sediment loads, such as the Yellow River. The ability to predict sediment concentrations accurately is key to mitigating the negative impacts of sedimentation in reservoirs, optimizing flood control, and ensuring the safety of infrastructure and water quality management. In this study, we focus on the sediment concentration process at the Tongguan Hydrological Station, which is located in the middle and lower reaches of the Yellow River. The Yellow River, known for its high sediment load, plays a vital role in the sediment transport dynamics that influence the river"s water quality and sedimentation patterns. The Tongguan station is a critical monitoring point in the Yellow River basin because it marks the confluence of the Yellow River mainstream with major tributaries such as the Weihe and Beiluohe Rivers, and it is located just before sediment enters the Sanmenxia Reservoir, which significantly influences downstream sedimentation and flood management. This study proposes a Parallel Spatio-Temporal Attention Long Short-Term Memory (PSTA-LSTM) model designed for sediment concentration forecasting, specifically tailored to handle the dynamic and complex flow-sediment conditions of the Yellow River. The PSTA-LSTM model integrates a parallel spatio-temporal attention mechanism that allows it to jointly capture multiscale temporal dependencies and spatial correlations among different watershed sites, significantly improving its ability to model sediment transport processes. In addition, the model incorporates an adaptive segmented rectified linear unit (SReLU) in the hidden layers to enhance the model’s capacity to learn complex nonlinear features and better handle rapid fluctuations in sediment concentrations, particularly during peak sediment events. This adaptive function helps the model manage the large variability in sediment loads commonly observed in rivers like the Yellow River, which is subject to varying flow conditions, tributary contributions, and local erosion-deposition dynamics. Experiments were conducted using measured hydrological and sediment data from 2000 to 2024. The results show that compared to the traditional serial LSTM structure, introducing the parallel spatio-temporal attention mechanism reduces the overall Root Mean Square Error (RMSE) by approximately 25.6%, and improves Peak Sediment Prediction Accuracy (PRE) by about 12.7%. Incorporating the SReLU activation function significantly enhances peak prediction accuracy, with the Nash-Sutcliffe Efficiency (NSE) improving by over 9%, showing that SReLU can more effectively handle peak sediment values. The study focuses on the sediment concentration process at the Tongguan hydrological station, located in the confluence area of the middle Yellow River. Tongguan Station is situated at the junction of the Yellow River mainstream and major tributaries such as the Weihe and Beiluohe Rivers. It serves as a critical sediment control section before the Yellow River enters the Sanmenxia Reservoir, playing an important role in reservoir regulation and downstream sediment transport. The upstream water and sediment mainly originate from the Yellow River basin above the Longmen Station, as well as the Weihe River basin at Huaxian Station and the Beiluohe River basin at Zhuangtou Station. Among these, the mainstream floods are characterized by sharp rises and falls with high sediment concentration; the Weihe River floods have a longer duration and a more blunt peak, while the Beiluohe River floods have sharp, narrow peaks, high sediment concentration, and rapid sediment wave propagation. The confluence and superposition of floods from different sources at the Tongguan confluence area not only affect sediment transport intensity but also determine the temporal variation characteristics of the sediment concentration process at Tongguan Station. Experiments were conducted using long-term observed hydrological and sediment data from 2000 to 2024, with the samples classified into five flow-sediment regimes: high-flow/high-sediment, medium-flow/medium-sediment, low-flow/low-sediment, high-flow/low-sediment, and low-flow/high-sediment. The PSTA-LSTM model was trained and evaluated separately under each regime and further compared between flood and non-flood seasons to examine its adaptability to varying hydrological conditions. The results show that introducing the parallel spatio-temporal attention mechanism improves the model’s performance significantly, with the Root Mean Square Error (RMSE) decreasing by approximately 25.6% and Peak Sediment Prediction Accuracy (PRE) improving by about 12.7%. Additionally, incorporating the SReLU activation function led to an increase in Nash-Sutcliffe Efficiency (NSE) by 6-11% compared to the traditional ReLU and softplus activation functions, showing its enhanced capability to handle peak sediment values effectively. The results also demonstrate that regime-based training based on flow-sediment types improves the prediction accuracy, with RMSE decreasing by approximately 15.7%, and NSE reaching over 80%. The comparison between flood and non-flood seasons shows that the PSTA-LSTM model exhibits stronger responsiveness during the flood season, especially during periods with significant peak sediment concentrations and rapid short-term fluctuations. These results highlight the model"s ability to adapt to dynamic and complex sediment transport conditions and its potential for real-time sediment concentration forecasting in large river systems like the Yellow River.
Li Qiao, Wang Xiaoxiao, Yi Xuemei, Ma Xiaoling, Cai Yunlong, Wu Tianyou, Yang Nairui, Li Dasong, Wu Shengjun
Available online: March 31, 2026
Abstract:
The spatial distribution patterns, phenotypic responses, and environmental driving mechanisms of dominant plants in the riparian zone of large reservoirs are key to understanding plant adaptation mechanisms and the community succession to the alternating terrestrial and aquatic habitats. This study focuses on Cynodon dactylon (L.) Pers.), a typical dominant plant in the drawdown zone of the Three Gorges Reservoir.. Through comprehensive vegetation and soil surveys, and using methods such as spatial interpolation, analysis of variance, and regression analysis, we analyzed its spatial distribution, phenotypic variation, and environmental drivers. The results showed that the coverage of C. dactylon exhibited a horizontal spatial pattern, characterized as high in the mid-section yet low in both the upper and lower sections of the reservoir. with its coverage and density in the mainstream significantly lower than in the tributaries. Along the elevation gradient, both the coverage and density of C. dactylon in the 165–175 m elevation zone were significantly lower. Analysis of environmental factors revealed that the coverage and density were primarily regulated by soil bulk density and phosphorus content, while high nitrogen environments drove preferential biomass investment into leaves to enhance photosynthetic capacity. The study demonstrates that C. dactylon adapts to environmental heterogeneity in the hydro-fluctuation zone by adjusting biomass allocation strategies and exhibiting phenotypic plasticity, providing a theoretical basis for near-natural restoration of reservoir riparian zones.
The spatial distribution patterns, phenotypic responses, and environmental driving mechanisms of dominant plants in the riparian zone of large reservoirs are key to understanding plant adaptation mechanisms and the community succession to the alternating terrestrial and aquatic habitats. This study focuses on Cynodon dactylon (L.) Pers.), a typical dominant plant in the drawdown zone of the Three Gorges Reservoir.. Through comprehensive vegetation and soil surveys, and using methods such as spatial interpolation, analysis of variance, and regression analysis, we analyzed its spatial distribution, phenotypic variation, and environmental drivers. The results showed that the coverage of C. dactylon exhibited a horizontal spatial pattern, characterized as high in the mid-section yet low in both the upper and lower sections of the reservoir. with its coverage and density in the mainstream significantly lower than in the tributaries. Along the elevation gradient, both the coverage and density of C. dactylon in the 165–175 m elevation zone were significantly lower. Analysis of environmental factors revealed that the coverage and density were primarily regulated by soil bulk density and phosphorus content, while high nitrogen environments drove preferential biomass investment into leaves to enhance photosynthetic capacity. The study demonstrates that C. dactylon adapts to environmental heterogeneity in the hydro-fluctuation zone by adjusting biomass allocation strategies and exhibiting phenotypic plasticity, providing a theoretical basis for near-natural restoration of reservoir riparian zones.
Available online: March 19, 2026
Abstract:
This study investigated five typical wetland plants in Dongting Lake—Acorus calamus, Zizania latifolia, Phragmites australis, Carex brevicuspis, and Typha orientalis—under different flooding durations (30, 60, 90, and 120 days), systematically analyzing their morphological and physiological responses as well as nitrogen and phosphorus removal efficiency. The results showed that flooding duration significantly influenced plant morphology, physiological responses, and nutrient removal efficiency. Morphologically, with increasing flooding time, the biomass and plant height of A. calamus decreased significantly; the biomass and root length of C. brevicuspis remained relatively stable while plant height slightly decreased; whereas the plant heights of P. australis, Z. latifolia, and T. orientalis continued to increase with prolonged flooding. Physiologically, markers of oxidative stress and osmoregulation showed species-specific trends. For instance, in Z. latifolia, contents of malondialdehyde (MDA) and soluble sugars decreased significantly, while antioxidant enzyme activity and chlorophyll content increased. In contrast, T. orientalis displayed a dynamic change in MDA, superoxide dismutase (SOD), and proline, which decreased initially, peaked at 90 days, and then declined again, whereas its chlorophyll content continuously decreased. Regarding purification capacity, the nitrogen and phosphorus removal rates of P. australis and T. orientalis continuously improved with prolonged flooding. In contrast, A. calamus, Z. latifolia, and C. brevicuspis reached peak removal efficiency at 60–90 days of treatment before declining. In summary, different plants exhibited significant species-specific and time-dependent responses in morphology, physiology, and function under flooding conditions. P. australis and T. orientalis can maintain high purification efficiency under prolonged flooding, making them more suitable as dominant species for long-term flooded wetland ecosystems.
This study investigated five typical wetland plants in Dongting Lake—Acorus calamus, Zizania latifolia, Phragmites australis, Carex brevicuspis, and Typha orientalis—under different flooding durations (30, 60, 90, and 120 days), systematically analyzing their morphological and physiological responses as well as nitrogen and phosphorus removal efficiency. The results showed that flooding duration significantly influenced plant morphology, physiological responses, and nutrient removal efficiency. Morphologically, with increasing flooding time, the biomass and plant height of A. calamus decreased significantly; the biomass and root length of C. brevicuspis remained relatively stable while plant height slightly decreased; whereas the plant heights of P. australis, Z. latifolia, and T. orientalis continued to increase with prolonged flooding. Physiologically, markers of oxidative stress and osmoregulation showed species-specific trends. For instance, in Z. latifolia, contents of malondialdehyde (MDA) and soluble sugars decreased significantly, while antioxidant enzyme activity and chlorophyll content increased. In contrast, T. orientalis displayed a dynamic change in MDA, superoxide dismutase (SOD), and proline, which decreased initially, peaked at 90 days, and then declined again, whereas its chlorophyll content continuously decreased. Regarding purification capacity, the nitrogen and phosphorus removal rates of P. australis and T. orientalis continuously improved with prolonged flooding. In contrast, A. calamus, Z. latifolia, and C. brevicuspis reached peak removal efficiency at 60–90 days of treatment before declining. In summary, different plants exhibited significant species-specific and time-dependent responses in morphology, physiology, and function under flooding conditions. P. australis and T. orientalis can maintain high purification efficiency under prolonged flooding, making them more suitable as dominant species for long-term flooded wetland ecosystems.
Available online: March 19, 2026
Abstract:
Under global warming, the increasing frequency of high-temperature events in lakes, combined with the implementation of the "Cessation of Aquaculture and Return to Lake" ecological restoration project in the eastern Lake Taihu region since 2019, has created complex interactions that complicate the dynamic processes of methane (CH4) emissions from lakes. This study aims to elucidate the impacts of high-temperature events and ecological restoration on CH4 emissions in Lake Taihu and their underlying mechanisms. Based on high-frequency observational data from the Dongtaihu site of the Taihu Eddy Flux Network from 2018 to 2020, the seasonal threshold method was employed to identify high-temperature events, and their effects on CH4 fluxes, as well as the regulatory effects of the "Cessation of Aquaculture and Return to Lake" project, were systematically analyzed. The results indicated that the seasonal threshold method effectively captured short-term high-temperature processes driving CH4 emissions, accommodating seasonal water-temperature fluctuations and high-frequency temporal variations in CH4 emissions. A total of 23 high-temperature events were identified from 2018 to 2020. The promoting effect of high-temperature events on CH4 emissions showed clear seasonal differences, being stronger in spring and autumn than in summer and winter. During individual events, CH4 fluxes typically exhibited a three-phase pattern: remaining stable in the pre-heatwave period, increasing sharply during the heatwave, and decreasing in the post-heatwave period. The "Cessation of Aquaculture and Return to Lake" project effectively suppressed CH4 emissions during high-temperature periods. During the ecological restoration period, the median CH4 fluxes before, during, and after high-temperature events were 0.05–0.17, 0.07–0.25, and 0.04–0.15 μg·m?2·s?1, respectively, representing reductions of approximately 72%–95% compared to the aquaculture period (0.42–0.62, 1.05–5.26, and 0.71–4.60 μg·m?2·s?1, respectively). This study provides a theoretical basis for understanding the response mechanisms of carbon cycling in shallow lakes to climate warming and ecological management.
Under global warming, the increasing frequency of high-temperature events in lakes, combined with the implementation of the "Cessation of Aquaculture and Return to Lake" ecological restoration project in the eastern Lake Taihu region since 2019, has created complex interactions that complicate the dynamic processes of methane (CH4) emissions from lakes. This study aims to elucidate the impacts of high-temperature events and ecological restoration on CH4 emissions in Lake Taihu and their underlying mechanisms. Based on high-frequency observational data from the Dongtaihu site of the Taihu Eddy Flux Network from 2018 to 2020, the seasonal threshold method was employed to identify high-temperature events, and their effects on CH4 fluxes, as well as the regulatory effects of the "Cessation of Aquaculture and Return to Lake" project, were systematically analyzed. The results indicated that the seasonal threshold method effectively captured short-term high-temperature processes driving CH4 emissions, accommodating seasonal water-temperature fluctuations and high-frequency temporal variations in CH4 emissions. A total of 23 high-temperature events were identified from 2018 to 2020. The promoting effect of high-temperature events on CH4 emissions showed clear seasonal differences, being stronger in spring and autumn than in summer and winter. During individual events, CH4 fluxes typically exhibited a three-phase pattern: remaining stable in the pre-heatwave period, increasing sharply during the heatwave, and decreasing in the post-heatwave period. The "Cessation of Aquaculture and Return to Lake" project effectively suppressed CH4 emissions during high-temperature periods. During the ecological restoration period, the median CH4 fluxes before, during, and after high-temperature events were 0.05–0.17, 0.07–0.25, and 0.04–0.15 μg·m?2·s?1, respectively, representing reductions of approximately 72%–95% compared to the aquaculture period (0.42–0.62, 1.05–5.26, and 0.71–4.60 μg·m?2·s?1, respectively). This study provides a theoretical basis for understanding the response mechanisms of carbon cycling in shallow lakes to climate warming and ecological management.
Available online: March 19, 2026
Abstract:
The Yarlung Tsangpo River is one of the world"s major international rivers and also one of the most sensitive and fragile ecosystems globally. Eukaryotic phytoplankton play a vital role in maintaining the ecological balance of this river ecosystem. To reveal the diversity, spatiotemporal distribution characteristics, and key driving factors of eukaryotic phytoplankton communities in the Nyang River and Palong Tsangpo, representative primary tributaries of the lower Yarlung Tsangpo River, this study employed high-throughput amplicon sequencing technology to investigate the diversity patterns and driving factors of eukaryotic phytoplankton across three seasons spring, summer, and autumn—in this watershed. Results revealed that 6,723 ASVs of eukaryotic phytoplankton were identified across the three seasons, belonging to 8 phyla, 39 classes, 87 orders, 100 families, and 265 genera. The Phaeophyceae phylum exhibited the highest abundance in species composition throughout all seasons. Overall, Shannon diversity, Simpson diversity, and Pielou"s evenness index exhibited a pattern of spring > summer > autumn, with highly significant seasonal differences (P < 0.001). Eukaryotic phytoplankton communities showed highly significant seasonal differences (P < 0.001). Summer eukaryotic phytoplankton community assembly was dominated by stochastic processes, while spring and autumn communities were dominated by deterministic processes. All three seasons exhibited highly significant geographic decay trends (P < 0.001), elevation decay trends (P < 0.001), and environmental decay trends (P < 0.001). Interactions among eukaryotic phytoplankton communities were predominantly cooperative. Environmental factors significantly explained more community variation than geographic and altitude factors across all seasons. Key environmental drivers for spring eukaryotic phytoplankton communities were pH, dissolved oxygen (DO), water temperature (WT), turbidity (TUR), ammonium nitrogen (NH??-N), and altitude (ALT); summer: electrical conductivity (EC) and water temperature (WT); autumn: water temperature (WT), dissolved oxygen (DO), and electrical conductivity (EC). Water temperature exerted a highly significant influence on eukaryotic phytoplankton communities across all three seasons. This study employed high-throughput amplicon sequencing to analyze the spatiotemporal structure of eukaryotic phytoplankton communities in the river basin. It revealed the distribution patterns and variation characteristics of eukaryotic phytoplankton communities in plateau rivers, providing crucial evidence for microbial diversity conservation and aquatic ecosystem health management in plateau regions.
The Yarlung Tsangpo River is one of the world"s major international rivers and also one of the most sensitive and fragile ecosystems globally. Eukaryotic phytoplankton play a vital role in maintaining the ecological balance of this river ecosystem. To reveal the diversity, spatiotemporal distribution characteristics, and key driving factors of eukaryotic phytoplankton communities in the Nyang River and Palong Tsangpo, representative primary tributaries of the lower Yarlung Tsangpo River, this study employed high-throughput amplicon sequencing technology to investigate the diversity patterns and driving factors of eukaryotic phytoplankton across three seasons spring, summer, and autumn—in this watershed. Results revealed that 6,723 ASVs of eukaryotic phytoplankton were identified across the three seasons, belonging to 8 phyla, 39 classes, 87 orders, 100 families, and 265 genera. The Phaeophyceae phylum exhibited the highest abundance in species composition throughout all seasons. Overall, Shannon diversity, Simpson diversity, and Pielou"s evenness index exhibited a pattern of spring > summer > autumn, with highly significant seasonal differences (P < 0.001). Eukaryotic phytoplankton communities showed highly significant seasonal differences (P < 0.001). Summer eukaryotic phytoplankton community assembly was dominated by stochastic processes, while spring and autumn communities were dominated by deterministic processes. All three seasons exhibited highly significant geographic decay trends (P < 0.001), elevation decay trends (P < 0.001), and environmental decay trends (P < 0.001). Interactions among eukaryotic phytoplankton communities were predominantly cooperative. Environmental factors significantly explained more community variation than geographic and altitude factors across all seasons. Key environmental drivers for spring eukaryotic phytoplankton communities were pH, dissolved oxygen (DO), water temperature (WT), turbidity (TUR), ammonium nitrogen (NH??-N), and altitude (ALT); summer: electrical conductivity (EC) and water temperature (WT); autumn: water temperature (WT), dissolved oxygen (DO), and electrical conductivity (EC). Water temperature exerted a highly significant influence on eukaryotic phytoplankton communities across all three seasons. This study employed high-throughput amplicon sequencing to analyze the spatiotemporal structure of eukaryotic phytoplankton communities in the river basin. It revealed the distribution patterns and variation characteristics of eukaryotic phytoplankton communities in plateau rivers, providing crucial evidence for microbial diversity conservation and aquatic ecosystem health management in plateau regions.
Available online: March 19, 2026
Abstract:
Suspended particulate matter (SPM) is a key optically active constituent in lake water. Its concentration governs turbidity, water colour and transparency, and therefore serves as a critical indicator of lake water quality. Taihu, Hongze and Chao—the three largest lakes in the middle–lower Yangtze River basin—exhibit pronounced spatio-temporal SPM variabilitydriven by both natural processes and human activities. Although polar-orbiting satellites have been widely used to characterize seasonal-to-interannual SPM dynamics, the scarcity of cloud-free images severely limits analyses at monthly or daily resolution.Here, 132 620 Level-2 images from the Geostationary Ocean Color Imager (GOCI) acquired between April 2011 and December 2020, together with quasi-synchronous in-situ data collected over the three lakes, were used to evaluate existing SPM algorithms. After selection and optimisation, the best-performing algorithm was applied to the quality-controlled GOCI imagery to generate a long-term hourly SPM concentration dataset.The dataset is provided in GeoTIFF format under the geographic coordinate system GCS_WGS_1984 and consists of 13 262 files. On average, the number of valid observational days per month (defined as the fraction of usable pixels > 85 %) is 9.1 for Taihu, 7.6 for Hongze and 7.5 for Chao. Cross-validation shows excellent agreement between satellite retrievals and field measurements in both spatial patterns and long-term temporal trends (R2 > 0.90, MAPE < 15 %, RMSE < 5 mg L?1), demonstrating the robustness and reliability of the product.Compared with polar-orbiting satellite products, the present dataset offers an order-of-magnitude improvement in temporal resolution, delivering complete SPM dynamics at daily and monthly scales and accurately capturing seasonal and inter-annual variations. The dense time series further enables high-frequency SPM monitoring, allowing short-term, high-magnitude disturbances—such as rainstorm runoff, dredging and water-diversion events—to be resolved. The dataset thus provides essential support for elucidating the short- and long-term mechanisms underlying SPM spatio-temporal variability and is of great value for lake management and scientific research.
Suspended particulate matter (SPM) is a key optically active constituent in lake water. Its concentration governs turbidity, water colour and transparency, and therefore serves as a critical indicator of lake water quality. Taihu, Hongze and Chao—the three largest lakes in the middle–lower Yangtze River basin—exhibit pronounced spatio-temporal SPM variabilitydriven by both natural processes and human activities. Although polar-orbiting satellites have been widely used to characterize seasonal-to-interannual SPM dynamics, the scarcity of cloud-free images severely limits analyses at monthly or daily resolution.Here, 132 620 Level-2 images from the Geostationary Ocean Color Imager (GOCI) acquired between April 2011 and December 2020, together with quasi-synchronous in-situ data collected over the three lakes, were used to evaluate existing SPM algorithms. After selection and optimisation, the best-performing algorithm was applied to the quality-controlled GOCI imagery to generate a long-term hourly SPM concentration dataset.The dataset is provided in GeoTIFF format under the geographic coordinate system GCS_WGS_1984 and consists of 13 262 files. On average, the number of valid observational days per month (defined as the fraction of usable pixels > 85 %) is 9.1 for Taihu, 7.6 for Hongze and 7.5 for Chao. Cross-validation shows excellent agreement between satellite retrievals and field measurements in both spatial patterns and long-term temporal trends (R2 > 0.90, MAPE < 15 %, RMSE < 5 mg L?1), demonstrating the robustness and reliability of the product.Compared with polar-orbiting satellite products, the present dataset offers an order-of-magnitude improvement in temporal resolution, delivering complete SPM dynamics at daily and monthly scales and accurately capturing seasonal and inter-annual variations. The dense time series further enables high-frequency SPM monitoring, allowing short-term, high-magnitude disturbances—such as rainstorm runoff, dredging and water-diversion events—to be resolved. The dataset thus provides essential support for elucidating the short- and long-term mechanisms underlying SPM spatio-temporal variability and is of great value for lake management and scientific research.
Available online: March 18, 2026
Abstract:
Against the backdrop of intensified global warming and the growing importance of carbon cycle research, inland water bodies in karst regions have emerged as efficient carbon sinks, underscoring the necessity for their accurate identification and comprehensive characterization. Guangxi, a representative karst region in China, lacks a systematic classification of its karst and non-karst lakes and reservoirs (collectively referred to as lacustrine systems), posing a critical gap in both regional and national-scale research. This study aims to address this gap by providing foundational data for future studies of karst lacustrine systems and informing evidence-based strategies for aquatic ecological conservation and management. A total of 788 lakes and reservoirs in Guangxi (each with a surface area exceeding 10 ha) were analyzed using multi-source geospatial datasets including Lake-Topo Cat, World Karst Aquifer Map (WOKAM), and the Global Lithological Map (GLiM). Through GIS-based delineation, morphological features (area, storage capacity, shoreline length) and catchment characteristics were extracted. Lacustrine systems were classified into four categories based on the proportion of karst lithologies within their catchment areas: karst (>75%), semi-karst (35–75%), weakly karstic (10–35%), and non-karst (<10%). A random forest model was subsequently applied to quantify the influence of various environmental variables—climatic (annual precipitation), geological (lithology), topographic, and anthropogenic (population density)—on the spatial distribution of karst lakes and reservoirs. The research shows: (1) Karst lakes and reservoirs are abundant, comprising 314 of the total (40%) and predominantly situated in peak cluster depressions and dissolution basins within central, north-western, south-western, and north-eastern Guangxi.; (2) Karst lacustrine systems exhibit the largest individual surface area (98.25 km2), maximum storage capacity (10,260 mcm), and the most complex shoreline morphology (up to 554.97 km), yet their average area (1.07 km2) and median storage (1.30 mcm) suggest a predominance of small to medium-sized water bodies with a few large outliers; (3) Karst catchments are overwhelmingly dominated by carbonate sedimentary rocks (>90%), in contrast to non-karst systems, which are primarily underlain by siliceous clastic lithologies; (4) Variable importance analysis from the random forest model reveals that carbonate rocks (37.0%), siliceous clastic rocks (28.87%), and annual precipitation (28.0%) are the most critical determinants of karst lake and reservoir distribution. This study presents the first comprehensive cartographic inventory and morphometric characterization of karst lakes and reservoirs in Guangxi. The results highlight lithology—particularly carbonate dominance—and climate, especially precipitation, as primary controls on karst lacustrine formation. The findings not only fill a longstanding data gap in regional hydro-karst research but also provide a scientific basis for watershed management and aquatic ecosystem conservation in karst terrains.
Against the backdrop of intensified global warming and the growing importance of carbon cycle research, inland water bodies in karst regions have emerged as efficient carbon sinks, underscoring the necessity for their accurate identification and comprehensive characterization. Guangxi, a representative karst region in China, lacks a systematic classification of its karst and non-karst lakes and reservoirs (collectively referred to as lacustrine systems), posing a critical gap in both regional and national-scale research. This study aims to address this gap by providing foundational data for future studies of karst lacustrine systems and informing evidence-based strategies for aquatic ecological conservation and management. A total of 788 lakes and reservoirs in Guangxi (each with a surface area exceeding 10 ha) were analyzed using multi-source geospatial datasets including Lake-Topo Cat, World Karst Aquifer Map (WOKAM), and the Global Lithological Map (GLiM). Through GIS-based delineation, morphological features (area, storage capacity, shoreline length) and catchment characteristics were extracted. Lacustrine systems were classified into four categories based on the proportion of karst lithologies within their catchment areas: karst (>75%), semi-karst (35–75%), weakly karstic (10–35%), and non-karst (<10%). A random forest model was subsequently applied to quantify the influence of various environmental variables—climatic (annual precipitation), geological (lithology), topographic, and anthropogenic (population density)—on the spatial distribution of karst lakes and reservoirs. The research shows: (1) Karst lakes and reservoirs are abundant, comprising 314 of the total (40%) and predominantly situated in peak cluster depressions and dissolution basins within central, north-western, south-western, and north-eastern Guangxi.; (2) Karst lacustrine systems exhibit the largest individual surface area (98.25 km2), maximum storage capacity (10,260 mcm), and the most complex shoreline morphology (up to 554.97 km), yet their average area (1.07 km2) and median storage (1.30 mcm) suggest a predominance of small to medium-sized water bodies with a few large outliers; (3) Karst catchments are overwhelmingly dominated by carbonate sedimentary rocks (>90%), in contrast to non-karst systems, which are primarily underlain by siliceous clastic lithologies; (4) Variable importance analysis from the random forest model reveals that carbonate rocks (37.0%), siliceous clastic rocks (28.87%), and annual precipitation (28.0%) are the most critical determinants of karst lake and reservoir distribution. This study presents the first comprehensive cartographic inventory and morphometric characterization of karst lakes and reservoirs in Guangxi. The results highlight lithology—particularly carbonate dominance—and climate, especially precipitation, as primary controls on karst lacustrine formation. The findings not only fill a longstanding data gap in regional hydro-karst research but also provide a scientific basis for watershed management and aquatic ecosystem conservation in karst terrains.
Available online: March 18, 2026
Abstract:
Plateau lakes, owing to their distinctive seasonal ice cover, play a special role in global greenhouse gas (GHG) emissions, characterized by under-ice accumulation in winter and pulsed release during ice-off. Focusing on Lake Wuliangsuhai in Inner Mongolia, this study resolves the spatiotemporal dynamics of CH? and N?O in the overlying water during the freeze-thaw period and their correlations with environmental factors. Based on freeze-thaw-induced biogeochemical processes in sediments, we further examine variations in carbon and nitrogen nutrients in the overlying water and in sedimentary electron acceptors, thereby elucidating the mechanisms governing GHG storage and release during freeze-thaw. Results demonstrate that formation of an ice cover drives cumulative increases in dissolved CH? in the overlying water. The highest surface-water CH? concentration occurred in vegetated zones during the stable frozen stage (93,382.76 nmol/L), whereas the peak N?O concentration was recorded in occurred in non-vegetated zones at the end of thawing (181.93 nmol/L). In contrast to N2O, whose behavior is largely controlled by internal sedimentary processes and mass-transfer limitations, CH4 responds more sensitively to variations in DO and ORP of the overlying water. Across the freeze-thaw cycle, total organic carbon (TOC) and total nitrogen (TN) accumulated during freezing but declined during thawing due to decomposition. Inorganic nitrogen species (NH??-N, NO??-N, NO??-N) shifted dynamically and reciprocally, consistent with active nitrification and denitrification. Carbon and nitrogen migration was jointly regulated by sediment biogeochemistry and redox conditions imposed by freeze-thaw. Sedimentary organic-matter degradation to displayed vertical stratification: nitrate/iron reduction dominated in upper-middle layers, while sulfate reduction prevailed at depth. Methanogenesis accompanied these pathways, with CH? migrating upward across the sediment-water interface and ultimately accumulating beneath the ice.
Plateau lakes, owing to their distinctive seasonal ice cover, play a special role in global greenhouse gas (GHG) emissions, characterized by under-ice accumulation in winter and pulsed release during ice-off. Focusing on Lake Wuliangsuhai in Inner Mongolia, this study resolves the spatiotemporal dynamics of CH? and N?O in the overlying water during the freeze-thaw period and their correlations with environmental factors. Based on freeze-thaw-induced biogeochemical processes in sediments, we further examine variations in carbon and nitrogen nutrients in the overlying water and in sedimentary electron acceptors, thereby elucidating the mechanisms governing GHG storage and release during freeze-thaw. Results demonstrate that formation of an ice cover drives cumulative increases in dissolved CH? in the overlying water. The highest surface-water CH? concentration occurred in vegetated zones during the stable frozen stage (93,382.76 nmol/L), whereas the peak N?O concentration was recorded in occurred in non-vegetated zones at the end of thawing (181.93 nmol/L). In contrast to N2O, whose behavior is largely controlled by internal sedimentary processes and mass-transfer limitations, CH4 responds more sensitively to variations in DO and ORP of the overlying water. Across the freeze-thaw cycle, total organic carbon (TOC) and total nitrogen (TN) accumulated during freezing but declined during thawing due to decomposition. Inorganic nitrogen species (NH??-N, NO??-N, NO??-N) shifted dynamically and reciprocally, consistent with active nitrification and denitrification. Carbon and nitrogen migration was jointly regulated by sediment biogeochemistry and redox conditions imposed by freeze-thaw. Sedimentary organic-matter degradation to displayed vertical stratification: nitrate/iron reduction dominated in upper-middle layers, while sulfate reduction prevailed at depth. Methanogenesis accompanied these pathways, with CH? migrating upward across the sediment-water interface and ultimately accumulating beneath the ice.
Available online: March 04, 2026
Abstract:
[Background]Plain reservoirs in arid regions face severe ineffective evaporation loss. Selecting efficient, environmentally friendly, and economically viable physical covering structures to reduce water surface evaporation is a key approach to achieving the sustainable utilization of water resources. [Methods]This study was conducted in Kunyu City, Hotan Prefecture, Xinjiang. A control experiment was established in large evaporation tanks with a diameter of 6 meters. Three types of physical covering materials—homogeneous floating balls, bottom-weighted floating balls, and hexagonal diamond-shaped floating bodies—were used to fully cover the water surface, with an uncovered blank group set as the control. Through long-term continuous monitoring, the evaporation inhibition efficiency of different covering structures under complex meteorological conditions and their impacts on the water environment were systematically evaluated. [Results]The findings revealed that: (1) The water surface evaporation process exhibited significant seasonal fluctuations, and the evaporation inhibition effect of the covering layer was comprehensively driven by meteorological factors; (2) The structural morphology of the covering units had a significant impact on water-saving efficiency. The hexagonal diamond-shaped floating bodies achieved an average evaporation inhibition rate of 75.2% at a coverage rate of 83%; while for the two types of floating balls with a coverage rate of 86%, the bottom-weighted floating balls (70.2%) outperformed the homogeneous floating balls (66.7%); (3) Water quality tests indicated that floating ball coverage did not cause secondary pollution to the water body, and the water quality indicators met the standards for agricultural irrigation. The long-term ecological effects of the hexagonal floating bodies require further quantification;(4) On the premise that the evaporation inhibition efficiency meets the engineering design indicators, the homogeneous floating ball water surface coverage scheme exhibits better economic feasibility and cost-effectiveness.[Conclusions]Different physical covering forms vary in water-saving benefits. In engineering practice, a multi-dimensional trade-off should be made based on water-saving rate, economy, and ecological security. The results of this study can provide theoretical basis and data support for the optimization of evaporation inhibition technologies and efficient water resource management in plain reservoirs of arid regions.
[Background]Plain reservoirs in arid regions face severe ineffective evaporation loss. Selecting efficient, environmentally friendly, and economically viable physical covering structures to reduce water surface evaporation is a key approach to achieving the sustainable utilization of water resources. [Methods]This study was conducted in Kunyu City, Hotan Prefecture, Xinjiang. A control experiment was established in large evaporation tanks with a diameter of 6 meters. Three types of physical covering materials—homogeneous floating balls, bottom-weighted floating balls, and hexagonal diamond-shaped floating bodies—were used to fully cover the water surface, with an uncovered blank group set as the control. Through long-term continuous monitoring, the evaporation inhibition efficiency of different covering structures under complex meteorological conditions and their impacts on the water environment were systematically evaluated. [Results]The findings revealed that: (1) The water surface evaporation process exhibited significant seasonal fluctuations, and the evaporation inhibition effect of the covering layer was comprehensively driven by meteorological factors; (2) The structural morphology of the covering units had a significant impact on water-saving efficiency. The hexagonal diamond-shaped floating bodies achieved an average evaporation inhibition rate of 75.2% at a coverage rate of 83%; while for the two types of floating balls with a coverage rate of 86%, the bottom-weighted floating balls (70.2%) outperformed the homogeneous floating balls (66.7%); (3) Water quality tests indicated that floating ball coverage did not cause secondary pollution to the water body, and the water quality indicators met the standards for agricultural irrigation. The long-term ecological effects of the hexagonal floating bodies require further quantification;(4) On the premise that the evaporation inhibition efficiency meets the engineering design indicators, the homogeneous floating ball water surface coverage scheme exhibits better economic feasibility and cost-effectiveness.[Conclusions]Different physical covering forms vary in water-saving benefits. In engineering practice, a multi-dimensional trade-off should be made based on water-saving rate, economy, and ecological security. The results of this study can provide theoretical basis and data support for the optimization of evaporation inhibition technologies and efficient water resource management in plain reservoirs of arid regions.
Xi Ying, Long Jingzhong, Yu Shuilian, Chen Jingyi, Li Kun, Wang Siting, Xu Tao, Huang Yingping, Lv Yuanfei
Available online: December 30, 2025
Abstract:
Periodic water-level fluctuations in the Three Gorges Reservoir have resulted in differential distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soils across different elevations of the drawdown area. From the perspective of soil colloid–water level coupling, this study compared the colloidal characteristics and PAHs distribution in soils at multiple elevations (155–185 m) in the Xiangxi River bay before and after a complete water-level fluctuation cycle (from June 2022 to June 2023), aiming to reveal the redistribution mechanism of PAHs driven by artificial regulation of water levels. Results indicated that the total PAHs content in soils of the drawdown area decreased by 10.8–59.6% after water-level fluctuation. Soil colloids from different elevations exhibited high stability, which enhanced the transport of the PAH monomer phenanthrene (Phe) in porous media. Among all elevations, soil colloid properties and PAHs distribution at 165 m were the most sensitive to water-level variations. Fluctuations significantly altered soil colloid characteristics at this elevation: after water-level variation, the specific surface area of soil colloids increased by 70.7%, colloid particle size decreased by 13.3%, the absolute value of the Zeta potential increased by 18.8%, and the critical flocculation concentration (CFC) increased fourfold compared to pre-fluctuation values, indicating enhanced colloidal stability and transport capacity. Pearson correlation analysis confirmed that colloid stability and Zeta potential (p < 0.01) were the principal factors controlling PAHs distribution in the drawdown area soils during water-level fluctuations. This suggests that artificial water-level regulation drives the “sink–source” transformation of PAHs in soil by modulating colloid stability and physicochemical properties. These findings provide guidance for understanding the effects of water-level fluctuations on exposed-zone ecosystems and for managing PAH pollution in reservoir waters.
Periodic water-level fluctuations in the Three Gorges Reservoir have resulted in differential distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soils across different elevations of the drawdown area. From the perspective of soil colloid–water level coupling, this study compared the colloidal characteristics and PAHs distribution in soils at multiple elevations (155–185 m) in the Xiangxi River bay before and after a complete water-level fluctuation cycle (from June 2022 to June 2023), aiming to reveal the redistribution mechanism of PAHs driven by artificial regulation of water levels. Results indicated that the total PAHs content in soils of the drawdown area decreased by 10.8–59.6% after water-level fluctuation. Soil colloids from different elevations exhibited high stability, which enhanced the transport of the PAH monomer phenanthrene (Phe) in porous media. Among all elevations, soil colloid properties and PAHs distribution at 165 m were the most sensitive to water-level variations. Fluctuations significantly altered soil colloid characteristics at this elevation: after water-level variation, the specific surface area of soil colloids increased by 70.7%, colloid particle size decreased by 13.3%, the absolute value of the Zeta potential increased by 18.8%, and the critical flocculation concentration (CFC) increased fourfold compared to pre-fluctuation values, indicating enhanced colloidal stability and transport capacity. Pearson correlation analysis confirmed that colloid stability and Zeta potential (p < 0.01) were the principal factors controlling PAHs distribution in the drawdown area soils during water-level fluctuations. This suggests that artificial water-level regulation drives the “sink–source” transformation of PAHs in soil by modulating colloid stability and physicochemical properties. These findings provide guidance for understanding the effects of water-level fluctuations on exposed-zone ecosystems and for managing PAH pollution in reservoir waters.
