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Abstract
We compared the stable isotope ratios of δ 13C and δ 15N of four basal food sources and eight fish species collected in spring and summer from the largest freshwater lake in China, Lake Poyang. The aim was to study the temporal variations in the fishes’ energy sources. The δ 13C and δ 15N ratios of all eight species of fish were higher in summer. Employing the IsoSource mixing model, we identified that the terrestrial plant Carex spp. was the most important primary producer supporting fish biomass in spring when the water level was low; meanwhile, the submerged macrophyte Potamogeton malaianus made consistent contributions to fish. However, in summer, when the water level was high, the submerged macrophyte Ceratophyllum demersum was the most important primary production source for fish. Our study indicated that feeding links in floodplain lakes are complex and modified by hydrologic seasonality.
Acknowledgments
We sincerely thank Dr Yuwei Chen, Dr Lu Zhang, and the staff of Lake Poyang Laboratory for Wetland Ecosystem Research, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, for their help in the field work and data collection. This study was supported by National Basic Research Program of China (2009CB421106), the National Science and Technology Support Plan (2006BAC08B05), and the National Natural Science Foundation of China (30870428 to Jun Xu). Funding was also awarded to Jun Xu by the K.C. Wong Education Foundation and the Knowledge Innovation Program of the Chinese Academy of Sciences.