Geochemical sedimentary records of eutrophication and environmental change in Chaohu Lake, East China

Abstract

Chaohu Lake is a representative lake in China that suffers from severe eutrophication and algal blooms. Understanding the changes in the lake's eutrophic condition over time is essential for its restoration and management under the background of global changes and regional sustainability. In this context, the compositions of carbon and nitrogen isotopes (δ13Corg and δ15N, respectively), total organic carbon (TOC), total nitrogen (TN), and carbon-nitrogen ratio (C/N) were analysed to depict the history of eutrophic state of Chaohu Lake, and its relationship with environmental changes. The result show that before the 1950s, the primary productivity of the lake was low. During the period from the 1950s to the 1970s, primary productivity increased substantially due to eutrophication. From the 1970s to the present, as a result of the construction of the Chaohu Floodgate Station, water replacement in the semi-closed Chaohu Lake gradually slowed and nutrients began to accumulate more rapidly. These conditions led to enhanced lake productivity and rapid eutrophication, mainly caused by intensified human activities and increased exogenous inputs. Our findings suggest that the geochemical records (δ13Corg, δ15N, TOC, TN, and C/N ratios) in sediment for Chaohu Lake are capable of recording important shifts in the temporal evolution of lake-water trophic state.