[Effects of Damming and Impoundment on Planktonic Microbial Community Structure and Interspecific Interaction...

Microbial communities play an important role in ecological processes through direct or indirect interactions. However, the interspecific interaction pattern of reservoir microorganisms has still received little attention. The Hengshan Reservoir in Jiangsu province was selected as the research area. Surface and deep water samples were collected to respectively explore the response of planktonic microbial community structure and the molecular ecological network to water depth changes, as well as to identify the key species of planktonic microbial communities in different water depths. The results showed that the richness and evenness of planktonic microorganisms in the surface layer were higher than those in the deep layer, and there were significant differences in the community structure of planktonic microorganisms in different depths. Water depth indirectly affected the planktonic microbial community by changing the environmental heterogeneity, among which the indicators such as TOC, NO₃^-, NH₄⁺, and PO₄^3- had the most significant impact on the planktonic microbial community structure. In addition, the number of nodes and edges of the deep planktonic microbial molecular ecological network were significantly higher than those on the surface, and the type and number of key species in the deep planktonic microbial community were significantly higher than those on the surface, indicating that the network scale of the deep planktonic microbial community was larger; however, the interspecific cooperative relationship and network connectivity of the surface planktonic microbial community were stronger. These results will provide a scientific basis for the study of interspecific interactions of reservoir microbial communities and are of great significance for predicting the ecological law of microorganisms in reservoir ecosystems and the impact of global material cycles.