| 摘要: |
| 对高山湖泊浮游动物（如枝角类）群落和生物量以及食物网碳源的变化研究有助于加深对湖泊生态系统响应区域气候环境变化的认识。本研究对滇西北高山湖泊太极湖钻孔沉积物进行多指标分析，包括枝角类亚化石组合、浮游枝角类Daphnia休眠卵和营底栖生活的摇蚊头壳稳定碳同位素（δ13C）和地球化学指标（TN、TP、δ15N和C/N等），以了解该地区高山湖泊近200年来枝角类对区域环境变化的响应模式以及食物网碳源变化特征。结果表明，湖泊营养水平（如TN含量）在近200年来呈上升趋势，分析显示流域输入和大气氮沉降是湖泊TN含量上升的主要因素，同时区域增温和营养盐富集促进了湖泊初级生产力（沉积物叶绿素a）持续上升。钻孔中枝角类群落以沿岸种美丽尖额溞（Alona affinis）和兼浮游种圆形盘肠溞（Chydorus sphaericus）为主要优势种，1860-1970s期间枝角类群落结构较为稳定，1970s以来A. affinis相对丰度上升，C. sphaericus相对丰度下降。冗余分析（RDA）显示，年均气温和湖泊初级生产力（沉积物叶绿素a）是影响枝角类群落演替的显著环境因子。浮游枝角类溞属（Daphnia）休眠卵δ13C值自1940s来发生了明显变化，1860-1940s期间Daphnia休眠卵δ13C值偏负，而湖泊初级生产力较低，且C/N值较高，表明这一时期湖泊浮游碳源明显受到陆源输入的影响。1940-2020s期间Daphnia休眠卵δ13C值明显富集，可能受到了湖泊初级生产力上升和底栖藻类相对丰度增加的影响。摇蚊头壳δ13C值相较于Daphnia休眠卵变化较小，仅在1990-2010s期间出现偏负趋势，可能是降水增加导致陆源有机质在底栖碳源组成中的占比上升。Daphnia休眠卵δ13C值与摇蚊头壳δ13C值变化存在差异，表明浮游和底栖碳源对两者δ13C信号具有差异性影响。本研究发现区域气候变化和流域输入改变了高山湖泊的生产力水平和食物网碳源组成，最终影响了枝角类群落结构和水生生物的稳定碳同位素特征。 |
| 关键词: 气候变化 营养输入 高山湖泊 枝角类 稳定碳同位素 |
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| 基金项目:国家自然科学基金项目（42267069、42171072）、云南省西南联合研究生院科技专项（202302AP370001）、异龙湖高原浅水湖泊云南省野外科学观测研究站（202305AM070002）、兴滇英才支持计划(XDYC-QNRC-2022-0034)项目2024联合资助 |
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| Long-term Characteristics of Cladoceran and Food Web Carbon Sources in Alpine Lake Taiji （Northwestern Yunnan）during the past 200a in Response to Climate Change |
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Xingda Yin, Lingyang Kong, Guangjie Chen, Linpei Huang, Yunqi Chen, Cuiyue Hu, Jiajie Yang
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Yunnan Key Laboratory of Plateau Geographical Processes and Environmental Changes,Faculty of Geography,Yunnan Normal University
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| Abstract: |
| Studies about changes of zooplankton (e.g., Cladoceran) community and biomass, as well as the carbon sources of food web in alpine lake will helpful for the deeply understanding of the response of lake ecosystem to regional climatic and environmental changes. In this study, multi-index analysis of sediment core was carried out in Taiji Lake, an alpine lake in Northwest Yunnan, including the subfossil assemblage of cladoceran, the stable carbon isotope (δ13C) of Daphnia ephippia and chironomid headshield, and geochemical indicators (TN, TP, δ15N and C/N etc.), in order to understand the response pattern of cladoceran to regional environmental change and the characteristic of carbon sources change in the food web in the alpine lake duirng the past 200 years.Changes of TN suggest that the lake nutrient level was continue increasing in the past 200 years. Analysis suggest that exogenous inputs from the catchment and atmospheric nitrogen deposition are the main factors which driving the nutrient enrichement, regional warming and nutrient enrichment also promoted the enhancing of lake primary productivity (Chlorophyll-a). Cladoceran community was dominated by littoral species Alona affinis and the facultative planktonic species Chydorus sphaericus. Before 1970s, there was no significant change of cladoceran community, after then, the relative abundance of C. sphaericus was decreased, associated with increase abundance of A. affinis. RDA analysis shown that the annual average temperature and primary productivity (Chlorophyll-a) were the main driving factors for the succession of cladoceran community in the past 200 years. For the stable carbon isotope values (δ13C), the δ13C of Daphnia ephippia was negative form 1860 to 1940s, probably attributed by the inputs of exogenous material, which supported by the lower lake primary productivity and higher C/N in this period. From 1940 to 2020s, the δ13C of Daphnia ephippia was significantly enriched, which may be affected by the enhanced primary productivity as well as the increase abundance of benthic algae.The δ13C value of chironomid headshell shown minimal change in the past 200 years, only have a negative trend from 1990 to 2010s, probably related to the increase inputs of terrestrial debris which driving by the increase precipitation in this period. Discrepancy in the variation of δ13C values between the Daphnia ephippia and chironomid headshield, indicate that there are different orgainic carbon composition in the planktonic and littoral zone, and affected by the changes of lake primary productivity and terrestrial inputs. Those founds reveal that regional climate change and catchment inputs changed the productivity and carbon source composition of aquatic food web in alpine lake, and ultimately affected the cladoceran community composition and stable carbon isotope values of aquatic organisms. |
| Key words: climate change nutrient input alpine lake cladoceran stable carbon isotope |
