Seasonal variations of microplastics and plastisphere bacterial communities along Wuhan Reaches of Yangtze River

Abstract Microplastics are widely distributed in aquatic environment and serve as habitats for microbial communities, which pause threats to the ecosystem. In this study, the seasonal variations in microplastic abundance and biogeography of their associated plastisphere were studied from 14 sites along the Wuhan Reaches of Yangtze River across spring and autumn. Significant variability in microplastic abundance was observed in Wuhan reaches of Yangtze River, ranging from 260 to 1540 items/m 3 . The microplastic concentrations were significantly higher in autumn than those in spring. The sizes, colors, and shapes of microplastics detected in two seasons were dominated by less than 1000 µm, black and transparent, and fibers and fragments, respectively. The main composition of microplastic polymers were polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) and polyethylene (PE). Medium risk pollution load index (PLI), high to extremely high polymer risk index (PRI) and medium risk potential ecological risk index (PERI) were observed, with higher risks in spring than in autumn. Significant seasonal differences in richness and composition of bacterial communities in water and plastisphere observed, with higher richness in spring. Proteobacteria and Actinobacteriota were the dominant phyla in both water and plastisphere. Stochastic processes dominated the assembly processes of bacterial communities. Plastisphere had less complex co‐occurrence networks than water, with denser networks in spring than autumn. Environmental factors influenced the composition of bacterial communities, with total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC) and longitude having strong significant effects. This study shed light on the microplastic pollution and their associated bacteria in the Wuhan reaches of Yangtze River.