Human activities shaping microbial community structure and diversity in urban river water and riparian soil

Abstract Purpose Human activities drive the input of various pollutants into urban river ecosystems, which in turn induce ecotoxicity that alters the community structure and diversity of environmental microorganisms; however, the ecotoxicological effects of human activities on microorganisms in the environmental media of urban rivers ecosystems remain inadequately investigated, and systematic understanding of bacterial resistance distribution and community assembly pattern differences in urban rivers is still lacking. Methods PacBio third-generation sequencing technology was used to sequence the full-length 16 S rRNA genes of microorganisms extracted from water and riparian soil samples, to analyze the spatial distribution and characteristics of microbial community structure and diversity in urban rivers ecosystems, and to identify the potential microbial sources of microbes using SourceTracker. Results The dominant phyla in water samples were Proteobacteria and Bacteroidota, whereas those in soil samples were Proteobacteria, Acidobacteriota, Bacteroidota and Actinobacteriota. Soil microbial communities exhibited no significant geographical differences, while water microbial communities showed distinct geographical distribution patterns among groups (upstream, midstream, and downstream of the Minxin River, and the City Ring Water System) with up to 51 inter-group biomarkers. SourceTracker was used to identify potential microbial sources for downstream water samples (with upstream water, midstream water, and outfalls as candidate sources). Results showed that microorganisms in downstream Minxin River water primarily originated from outfalls (54.11%) and midstream water (32.27%), demonstrating the significant impact of outfalls on river microbial community structure. Conclusions Thus, human activities (e.g., wastewater discharge) and associated pollutant inputs have significantly altered the microbial community structure of urban rivers, providing valuable insights for the ecological management and restoration of urban river ecosystems under human disturbance.