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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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.

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History
  • Received:September 23,2024
  • Revised:January 02,2025
  • Adopted:January 07,2025
  • Online: March 27,2025
  • Published:
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