Abstract
<title>Abstract</title> <p> Urban rivers receive substantial organic matter and nutrients, but seasonal changes in their microbial communities remain poorly understood. In this study, water and sediment samples were collected from four urban rivers in Changzhou during winter and summer. 16S rDNA, ITS amplicon sequencing and metagenomic analysis were used to characterize microbial composition and its functional potential. Microbial communities differed markedly between seasons and habitats. Winter water was characterized by <italic>Arenimonas</italic> , <italic>Novosphingobium</italic> , <italic>Acinetobacter</italic> , and <italic>Candidatus Methylopumilus</italic> , whereas summer water was enriched in <italic>Nitrosomonas</italic> , <italic>Polynucleobacter</italic> , <italic>Synechococcus</italic> , and <italic>Chryseobacterium</italic> . Nutrient-rich sediments showed enrichment of <italic>Anaerolinea</italic> , <italic>Smithella</italic> , <italic>Syntrophus</italic> , <italic>Dechloromonas</italic> , <italic>Penicillium</italic> , and <italic>Trichoderma</italic> . Bacterial-fungal networks contained more positive associations in summer, particularly in sediments, but more negative associations in winter water. Genes associated with carbon, nitrogen, and phosphorus cycling were more abundant in summer, whereas the genes in winter communities were enriched in environmental adaptation functions. Three potential novel candidate MAGs contained genes related to aromatic compound transformation, cofactor uptake, nitrosative-stress response, and N₂O reduction. These findings demonstrate that season and habitat jointly shape microbial composition and functional potential in urban rivers. </p>