Tracking recent environmental changes in Lake Wanghu, China: a multivariate analysis of lipid biomarkers in sediments

Abstract

Lipid biomarkers in sediments, which are indicative of biological production, provide important information regarding the environmental conditions in and around lakes, and can be used as proxies to infer past environmental changes. In this study, lipid biomarkers in sediments from Lake Wanghu, along the middle reach of the Yangtze River in China, were used to track environmental variations over the past ~ 100 years. Multiple variables, e.g., terrigenous/aquatic ratios of n-alkanes (TAR), in the lake sediments displayed three distinct periods, associated with changes in hydrologic conditions and human impacts. Prior to the 1950s, Lake Wanghu displayed a lower trophic state, with frequent water exchanges between the Yangtze River and Lake Wanghu during flooding events. During the 1950s–1980s, the lake trophic state increased slightly with the decreasing influence of the Yangtze River flow because of the Fuchi Floodgate, which caused a decline in terrigenous detritus inputs. However there was still relatively low algal abundance. Since the 1980s, especially the 2000s, sediments were characterized by a significant increase in the trophic state and considerable algal productivity. Generally, these changes were mainly a result of flooding impacts, human activities around the lake and fishery production, which showed good agreement with historical, written records.