Microbial community composition in urban riverbank sediments: response to municipal effluents over spatial gradient

Municipal effluents have adverse impacts on the aquatic ecosystem and especially the microbial community. This study described the compositions of sediment bacterial communities in the urban riverbank over the spatial gradient. Sediments were collected from seven sampling sites of the Macha River. The physicochemical parameters of sediment samples were determined. The bacterial communities in sediments were analyzed by 16S rRNA gene sequencing. The results showed that these sites were affected by different types of effluents, leading to regional variations in the bacterial community. The higher microbial richness and biodiversity at SM2 and SD1 sites were correlated with the levels of NH₄⁺-N, organic matter, effective sulphur, electrical conductivity, and total dissolved solids (p < 0.01). Organic matter, total nitrogen, NH₄⁺-N, NO₃-N, pH, and effective sulphur were identified to be important drivers for bacterial community distribution. At the phylum level, Proteobacteria (32.8-71.7%) was predominant in sediments, and at the genus level, Serratia appeared at all sampling sites and accounted for the dominant genus. Sulphate-reducing bacteria, nitrifiers, and denitrifiers were detected and closely related to contaminants. This study expanded our understanding of municipal effluents on microbial communities in riverbank sediments, and also provided valuable information for further exploration of microbial community functions.