Taxonomic and Functional Responses of Sediment Bacterial Community to Anthropogenic Disturbances in the Yarlung Tsangpo River on the Tibetan Plateau

Abstract

River sediments, functioning as sink and source for nutrients, are one of the most diverse bacteria habitats in freshwater ecosystems. Recently, more attention has been paid to the sediment bacteria because of their important roles in biogeochemical cycling. Our study addresses the question of how sediment bacterial community varies taxonomically and functionally along one of the largest plateau river in the world (the Yarlung Tsangpo River) subject to anthropogenic pressures, including wastewater discharge and river damming, as they may lead to adverse impacts on river ecosystems. The results indicated that river damming retained biogeochemical nutrients of carbon, silica and nitrogen in the reservoir, while phosphorus was more sensitive to wastewater discharge. Besides, wastewater discharge resulted in asynchronous change of biomass and diversity in sediment bacteria while they were both inhibited by the construction of dam. Moreover, significant alterations in the community composition were observed in dam-associated sites, while according to exploratory bioinformatics prediction tool of PICRUSt, functional variation was not detected between upstream and downstream of the dam due to functional redundancy. In addition, revealed by General Additive Model (GAM) and Mantel test results, elevation was the endemic driver shaping the sediment bacterial community diversity and composition along with pH, while nutrient concentrations were responsible for functional variation. Furthermore, little synchronized dynamics of co-occurrence was exhibited in the sediment bacteria in the Yarlung Tsangpo River. Therefore, our study proposed that sediment bacterial community should be defined taxonomically and functionally when studying its variation in river ecosystems.

Keywords: 16S rRNA gene sequencing, dam, environmental variable, microbial community taxonomy and function, Plateau river