Response of bacterial communities to variation in water quality and physicochemical conditions in a river-reservoir system

Abstract The construction of high dams results in changes to the ecohydrology processes of river reaches both upstream and downstream of the dam, in addition to causing stratification of reservoir waters. Changes in these hydrodynamic processes then lead to changes in the habitats and nutrients of the waters that are important for basal food chain organisms, consequently affecting bacterial diversity. Here, the Xiangjiaba Hydropower Station (XJB) was used to investigate the above influences on microbial communities. Here, bacterial community structures were examined in 15 samples from upstream of the XJB (UD section) and 15 samples downstream of the XJB (DD section) using 16 S rRNA gene sequencing. The bacterial community structures significantly differed between the surface water and 70 m of bottom water. Cyanobacteria was the dominant phylum in these communities and exhibited significantly higher abundances in the surface water. VPA (variance partitioning analysis) suggested that bacterial communities were influenced by and structured due to the combined effects of nutrient, hydrological, and environmental factors in addition to reservoir mixing dynamics. The abundance of Armatimonas, Roseomonas, Limonhabitans, and Flavobacterium were positively correlated with pH, flow velocity, and dissolved oxygen (DO). Total phosphorus (TP) was negatively correlated with the abundance of Acinetobacter, Roseomonas, Armatimonas. Burkholderia, Gemmatimonas, Nitrospira, hgcl.clade, and marine. group, all of which were highly sensitive to changes in water temperature. The results of this study can be used to understand the responses of bacterial communities to physicochemical conditions and water quality changes associated with reservoirs in order to provide a scientific basis for the protection of aquatic ecosystem stability.