Responses of Microbial Communities in River to Atmospheric Deposition

Atmospheric deposition threatens aquatic ecosystems, yet its effects on the microbial diversity, composition, and function in rivers remain unclear. Here, we examined the responses of microbial communities to atmospheric pollutants across 105 Chinese rivers. We found that PM 2.5 and PM 10 were associated with reduced bacterial and fungal diversity and richness. Structural equation modeling revealed that atmospheric deposition (e.g., PM 2.5, SO 2, NO 2, and organic matter aerosol) was directly and indirectly associated with bacterial and fungal community composition through cascading pathways mediated by dissolved oxygen, pH, Mn, inorganic nitrogen, nitrate nitrogen, ammonium nitrogen, and chlorophyll-a. Compared with fungal communities, bacterial communities exhibited broader environmental thresholds and greater sensitivity to atmospheric pollutants. Ecological network analysis further revealed that deposition preferentially disrupted mutualistic motifs in bacterial networks but intensified competitive interactions in fungal networks. Metagenomic analysis revealed that atmospheric pollution is significantly associated with key microbial functional genes involved in carbon degradation (e.g., glucoamylase, pullulanase, and β-glucosidase), nitrogen assimilation and reduction (e.g., nifD, narB, and nirS ), and sulfur reduction (e.g., sat, aprA, and dsrA ) in rivers. Our findings underscore the importance of air quality mitigation in terms of protecting river ecosystem health.