Variations of Food Web Structure and Energy Availability of Shallow Lake with Long‐Term Eutrophication: A Case Study from Lake Taihu, China

Eutrophication in aquatic ecosystem is known to cause an intensification of primary production, with consequences for the ecosystem degradation. Various researches provided evidences about food web structure variations during eutrophication process, but there were few attempts to empirically investigate the relationship between energy availability and trophic relationships, which is an important goal with relevance for management of eutrophic lakes. As a large shallow lake, Lake Taihu has suffered long‐term eutrophication. Here, the species compositions of Lake Taihu food web in three different trophic periods (oligotrophic stage, beginning of eutrophication, and developed stage of eutrophication) were conducted. Food web matrixes and Ecopath model were used to estimate the dynamic of food web structure and energy availability. The results showed that the number of trophic species, trophic links, and the length of food chain declined during the eutrophication process from 1960s to 2000s, which means food web structure of Lake Taihu was simplified even though entrophication brought sufficient nutrient into ecosystem. Meanwhile, the total transfer efficiency of food web declined from 24.1% in 1960s to 23.3% in 1990s and 21.9% in 2000s. These results suggest that long‐term eutrophication altered the energy availability of food web, and then influenced the food web structure gradually.