Coupling effects of environmental factors on the phytoplankton community structure in Ebinur Lake, a brackish lake in China

Studying the coupled effects of environmental factors on the structure of phytoplankton communities can deepen our understanding of the stability of aquatic ecosystems in extreme environments. This study examined the phytoplankton community structure and environmental factors of saline a lake during spring, summer, and autumn in 2019. A total of 95 phytoplankton species (belonging to 47 genera and 7 phyla) were identified in Ebinur Lake, reflecting a species richness lower than those of freshwater lakes while being greater than the levels observed in other saltwater lakes. Bacillariophyta dominated the phytoplankton assemblage, followed by Chlorophyta and Cyanophyta, with lesser diversity in other algal species, suggesting that the species composition was similar to that observed in other saltwater lakes. There was considerable spatiotemporal variation in the structure of the phytoplankton community, with the biomass of phytoplankton displaying notable seasonal variation. In spring, the biomass of Bacillariophyta was dominant; in summer, as the climate warmed, the biomass of phytoplankton reached its peak and the biomass of Chlorophyta was dominant; in autumn, the biomass was the lowest, and Chlorophyta and Bacillariophyta shared dominance. The spatial distribution was relatively consistent, as reflected in the distribution of phytoplankton in the three seasons, with the southeastern area of the lake generally exhibiting higher biomass than other lake areas. Bacillariophyta and Chlorophyta were significantly correlated with water transparency (SD); Cyanophyta was significantly correlated with water temperature (WT), and Cryptophyta was significantly correlated with pH. The interaction effects of various environmental factors, including pH, SD, Chl. a, NH₄+-N, and salinity, jointly affect the dynamics of the phytoplankton community structure in Ebinur Lake. This study investigated the effects of physicochemical factors on the structure of the phytoplankton community in a high-salinity lake, thereby providing a basis for ecological protection and environmental management of aquatic ecosystems in extreme environments.