Macrophyte community changes related to water level fluctuation and anthropogenic pressure in a floodplain lake in lower Huanghe River Basin, China since the 19th century

Decades of species composition changes can lead to the eutrophication-driven loss of submerged macrophytes in shallow lakes. Investigating the mechanisms of these nature- and human-driven changes is crucial for the restoration and management of such lakes. To investigate the changes in aquatic macrophyte communities over the past two centuries, we analyzed macrofossils in sediments from a 210Pb-dated core obtained in Dongping Lake in the lower Huanghe (Yellow) River Basin, eastern China. Multiple factor analysis (MFA) revealed an association between macrophyte shifts and changes in various environmental stressors (invertebrates, grain size, geochemistry, and documented records), indicating that macrophyte community changes before 1960 were predominately driven by flood disturbances. Ever since, anthropogenic pollution and the construction of water conservancy projects have caused variations in hydrology and nutrients, leading to significant changes in the composition of macrophyte communities. Macrofossil data reveal a decline in diversity and pollution-intolerant species during the late 1980s and the early 2000s, which is indicative of eutrophication. We also found that the current environment of Dongping Lake exhibits a clear degeneration in emergent plants and a proliferation of macrophyte species associated with eutrophic conditions, which could be attributed to water level fluctuation and nutrient input due to the water supply from the eastern route of the South-to-North Water Diversion Project as well as climate warming. Our results provide valuable insights for assessing ecosystem health and the restoration and management of Dongping Lake and similar lakes in the Huanghe River region and elsewhere.