Compositional variations and the environmental responses of bacterioplankton in the Pengxi River of the Three Gorges Reservoir, China

Abstract

Bacterioplankton communities are closely related to river alterations and biogeochemical processes in freshwater reservoirs. Affected by reservoir regulation and hydrological variation, regulated rivers can create distinctive patterns in bacterioplankton communities. In this study, we conducted 16S rRNA V4 amplicon high-throughput sequencing to investigate compositional changes in the bacterioplankton community and its environmental responses to damming effects in the Pengxi River, the largest tributary on the northern bank of the Three Gorges Reservoir (TGR). The bacterial community was dominated by the phyla Proteobacteria and Actinobacteria, accounting for 51.0% and 13.1% of all sequences, respectively. Distinct differences in the bacterioplankton community composition were observed between the backwater and riverine areas, and the dominant taxa showed clear shifts at the class level between the upper stream and backwater area sites along the Pengxi River. Conductivity, transparency and temperature were considered the major environmental factors driving the bacterioplankton composition variation. Additionally, the functional profiles of the bacterioplankton community corresponded with compositional changes in reservoir regulation by TGR. Therefore, these results provide insights into dam effects on the bacterioplankton community in the Pengxi River, and further research should focus on the potential ecological processes of river regulation by dams or reservoirs.