Effects of an Extreme Flooding Event on Zooplankton Diversity in Poyang Lake, China's Largest Freshwater Lake

Abstract

Extreme climate events such as floods and droughts become more often than before, but their ecological impacts on large lakes are still unclear. We studied responses of zooplankton species composition, density, biomass and diversity to an extreme flooding event by comparing zooplankton communities in a flooding year (2020) and a regular water level year (2021) in Poyang Lake, the largest freshwater lake in China. Mean density and biomass of zooplankton were not significantly different between the flooding and regular water level years. Density and biomass of rotifers were significantly lower in the flooding year than in the regular water level year, while the biomass of cladocerans was significantly higher in the flooding year. Species richness, Shannon–Wiener index, and Simpson index were significantly lower in the flooding year. A total of 45 and 60 species were detected in the flooding and regular water level years, respectively. Canonical correspondence analysis showed that water depth, alkalinity, transparency, conductivity, total nitrogen, nitrate, phosphate and turbidity were the main factors affecting the zooplankton community. This study provides evidence of flooding effects on zooplankton, which have implications for the conservation of freshwater lake ecosystems under extreme climate events.