Sedimentary geochemical evidence for recent eutrophication of Lake Chenghai, Yunnan, China |
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| Authors: | Wu Jinglu Michael K Gagan Jiang Xuezhong Xia Weilan Wang Sumin |
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| Institution: | (1) Chinese Academy of Sciences, Nanjing Institute of Geography and Limnology, Nanjing, 210008, Peoples Republic of China;(2) Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia;(3) Department of Geography, Nanjing University, Nanjing, 210004, Peoples Republic of China |
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| Abstract: | Geochemical anomalies and stable isotope ratios ( 18O, 13C) in authigenic carbonates and organic matter (13C) from a 660-year sediment core from Lake Chenghai, southern China, provide a continuous history of recent lake eutrophication. The multi-proxy geochemical and isotopic record can be divided into a three-part history of contrasting limnological development, including: (1) a clear-water, oligotrophic open lake system (1340 and 1690 AD); (2) an environmentally unstable, hydrologically closed, oligotrophic lake system (1690–1940 AD); and (3) an increasingly eutrophic, closed lake system marked by higher organic matter, nitrogen, CaCO3, and pigment concentrations, and lower 18O and 13C values in authigenic calcite (1940–1999 AD). The unanticipated lowering of 18O and 13C of authigenic calcite during eutrophication is thought to be the result of disequilibrium water–carbonate fractionation of oxygen and carbon isotopes during periods of elevated primary production, pH, and CO3
2–] activities in the water column. The recent eutrophication of Lake Chenghai indicated by these geochemical proxies is essentially simultaneous with large-scale human migration and the application of agricultural fertilizers in the catchment area during the 20th century. |
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| Keywords: | China Eutrophication Lake Chenghai Pigments Productivity Radionuclides Sediments Stable isotopes |
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