Phytoplankton in Lakes of Different Nutrient Levels in the Middle Yangtze River: Annual Variations in Community Structure and Key Driving Factors

Phytoplankton communities are highly sensitive to environmental change and serve as key indicators of lake ecosystem health. In this study, four typical lakes in the middle Yangtze River (Xiandao, Bao'an, Wanghu, and Cihu Lake) were investigated through field monitoring to reveal the spatiotemporal patterns of phytoplankton communities and their driving environmental factors. Significant seasonal variation and spatial heterogeneity were observed. Although species composition varied, Chlorophyta, Cyanobacteria, and Bacillariophyta were dominant in all lakes. In the eutrophic Bao'an, Cihu, and Wanghu lakes, Cyanobacteria dominated the annual average abundances. Based on Reynolds' functional group (FG) classification, 27 groups were identified. Dominant FG had seasonal successions. Canonical Correspondence and redundancy analyses indicated that water transparency, suspended solids, phosphate, and water temperature were the key environmental factors driving phytoplankton community succession. This study elucidated the response patterns of phytoplankton communities in lakes with varying nutrient levels to seasonal changes as well as the mechanisms underlying shifts in their growth strategies, thereby providing a theoretical framework for the ecological restoration of eutrophic lakes.