Temporal Variation of Plankton Community in a Typical Lake in the Middle Reaches of the Yangtze River: Structure, Environmental Response and Interactions

Abstract: The Liangzi Lake, a typical shallow lake in the middle reaches of the Yangtze River, is important for water resource and biodiversity conservation. With the development of urbanization, anthropogenic activities have posed serious threats to the water quality and biodiversity of Liangzi Lake. To assess the aquatic ecosystem health of Liangzi Lake, the structure, environmental response, and interactions of plankton were investigated in 2022 and 2023. Results indicated that water temperature was a pivotal factor regulating plankton dynamics, while plankton assemblage patterns were predominantly shaped by phytoplankton species, which was Bacillariophyta in spring and Chlorophyta in summer. In terms of phytoplankton, dissolved oxygen, and N:P ratio significantly affects cyanobacteria distribution, and a high biomass and abundance of them in summer highlighted the potential risk of harmful algal blooms. In contrast to phytoplankton, zooplankton exhibited enhanced resilience to changes of the surrounding environment. Rotifera was the dominant group in summer in terms of both abundance and biomass. Most core genera of plankton were jointly identified by eDNA metabarcoding and microscopical analysis, and eDNA metabarcoding has advantages in revealing a higher diversity. However, some taxa among rotifers, such as Liliferotrocha, were only identified using the microscopical analysis. Therefore, a combination of both methods is recommended to better understand the structuring mechanisms of plankton assemblages in lake ecosystems.