Nanoplastic pollution inhibits stream leaf decomposition through modulating microbial metabolic activity and fungal community structure

Many studies have proved the impacts of nanoplastic pollution in freshwaters on aquatic organisms and ecosystems. To explore toxic mechanisms of nanoplastics on stream functioning, we conducted a microcosm experiment to investigate the effects of polystyrene nanoparticles (PS NPs, 1–100 μg L−1) on the process of leaf litter decomposition mediated by the microbial community. The chronic exposure to PS NPs at 1 and 100 μg L−1 caused significant decreases in leaf litter decomposition and nutrient (carbon and nitrogen) releases. During the ecological process, some extracellular enzymes (i.e., β-glucosidase, glycine-aminopeptidase, and phenol oxidase) rather than fungal biomass were suppressed. Besides, decreases in the relative abundance of Anguillospora and Setophaeosphaeria weakened their functions in leaf litter decomposition. Thus, the microcosm experiment showed that PS NPs inhibited stream leaf decomposition by modulating the microbial metabolic activity and fungal community structure. Overall, the results of this study provide evidence for the consequences of nanoplastic pollution on freshwater microbial community and stream ecosystem functioning, which is conducive to evaluate the potential risks of nanoplastics in aquatic environments. [Display omitted] •Nanoplastics at 1 and 100 μg L−1 slowed litter decomposition rate.•Nanoplastics enhanced fungal biomass but suppressed enzyme activities.•Fungal community structure was affected through decreasing hub genera percentage.•Fungal hyphae were damaged by nanoplastic pollution.•Inhibitions on litter decay were due to metabolic activity and fungal community.