Cascade Dams Aggravate Local Environmental Heterogeneity at Watershed Scale, Impacting Taxonomic and Functional Groups of Bacterioplankton Community

Reservoirs and dams are increasingly disrupting natural river systems, yet research on their impact on microbial communities at the watershed scale is limited. Given the essential role of bacterioplankton in aquatic ecosystems, we employed 16S rRNA gene sequencing to explore how these communities respond to locks and dams in the Shaying River water increased nutrient and heavy metal content,basin. Our findings revealed that cascade dams create distinct environments, shaping bacterioplankton communities differently from those in natural rivers. In the upstream of the cascade dams, water quality was superior, resulting in simple bacterioplankton structures with weak community interactions. In the midstream of the dams, water increased nutrient and heavy metal content, making bacterioplankton structures more susceptible to environmental changes. Considered to downstream dams, water quality had a significant effect on the community, while the bacterioplankton community structure was the most stable. Furthermore, the functional groups of bacterioplankton were also primarily influenced by environmental factors, particularly water temperature, ORP, turbidity, and some heavy metal concentrations. However, responded to these variables, as well as interrelationships, significantly differ based on the location of locks and dams. In this study, we have provided insights into the impacts of cascade dams on taxonomic and functional diversity from a watershed perspective, offering novel ways to enhance stability and regulation of aquatic ecosystems in various watershed locations.