[Structure and Ecological Processes of the Bacterioplankton Community in the Cascade Reservoirs of the Lower Reaches of the Jinsha River].

Bacterioplankton are an important component of freshwater ecosystems and play a crucial role in the biogeochemical cycling of biogenic elements, such as carbon, nitrogen, and phosphorus. The operation of dams can cause notable changes in the hydrological conditions of reservoirs, affecting freshwater ecosystems. Exploring the community structure and ecological processes of bacterioplankton under different hydrological conditions is key to understanding the impact of dams on river ecosystems. Taking the Xiluodu-Xiangjiaba cascade reservoirs in the lower reaches of the Jinsha River as the research object, 16S rRNA amplification sequencing was used to analyze the differences in the community structure and ecological process of bacterioplankton in the water under different scheduling operations of the reservoir. The results indicated that the Simpson index, Chao index, water temperature, dissolved organic carbon （DOC） concentration, and total phosphorus （TP） concentration were higher during the low water level period, whereas the hydraulic retention time, pH, and water level were higher during the high water level period. Significant differences were observed in the composition of bacterioplankton communities between the high and low water level periods. Chloroflexi, Gemmatimonadota, Cyanobacteria, Nitrospirota, and Hydrogenedentes were sensitive to changes in water level environments. Cyanobacteria and Nitrospirota were key species in the bacterioplankton networks. During the low water level period, the diversity and abundance of key species in the bacterioplankton network were higher than those during the high water level period, resulting in a more complex and stable network. During both high and low water level periods, the assembly of bacterioplankton communities were dominated by stochastic processes. Therefore, different scheduling operations of reservoirs affected the community structure and ecological processes of bacterioplankton, thereby affecting the cycling process of carbon and nitrogen elements. The research results have important academic value and scientific importance for understanding the structure and function of aquatic ecosystems in river and reservoir habitats under dam construction and water storage, as well as guiding the management of high dams and large reservoirs.