Studies on the food web structure of Lake Donghu using stable carbon and nitrogen isotope ratios

摘要

Food web structure was studied by using carbon and nitrogen isotope ratios in a hypereutrophic subtropical Chinese lake, Lake Donghu. High external nutrient loading and the presence of abundant detritus from submersed macrophytes were responsible for the high sediment delta15N and delta13C, respectively. 13C was significantly higher in submersed macrophytes than in other macrophytes. The similar delta13C values in phytoplankton, zooplankton, zoobenthos, and planktivorous fish indicate that phytoplankton was the major food source for the consumers. By using a delta15N mass balance model, we estimate that the contributions of zooplankton to the diet of silver carp and bighead carp were 54% and 74%, respectively, which is in agreement with previous microscopic observations on intestinal contents of these fishes.