Microbial community and potential functions in small urban river of Changzhou, China

Urban rivers receive substantial organic matter and nutrients, which shape microbial assemblages and associated biogeochemical processes. However, the bacterial and fungi communities and potential function across paired water sediment habitats remains limited for small sized urban rivers. In this study, water and sediment samples were collected from four small urban rivers in Changzhou in December and August. 16S rRNA gene, ITS amplicon sequencing and metagenomic analysis were used to characterize microbial composition and its functional potential. The results revealed that habitat type and seasonal environmental filtering jointly shaped the diversity and community structure of bacteria and fungi. Genes associated with carbon, nitrogen, and phosphorus cycling showed a higher TPM-based relative abundance pattern in August, whereas the genes involved in environmental adaptation functions with a higher relative abundance pattern was observed in December. One potential novel candidate MAGs contained genes related to the arsenic transformation, N₂O-reduction and carbohydrate utilization. Collectively, this work highlights the interactive roles of environmental conditions and water‑sediment habitat heterogeneity in structuring microbiomes of small urban rivers, providing insights into element‑cycling microbial functions in human‑disturbed fluvial ecosystems.