Spatiotemporal Patterns and Assembly Mechanisms of Microbial Communities in the Overlying Water at the river confluences

¿p#1 Understanding the complex linkages between biological and ecological processes at the river confluences, as well as the driving factors determining community composition, is critical for river management and conservation in dynamically complex environments. Nonetheless, the knowledge on the spatiotemporal patterns and assembly mechanisms of microbial communities in the overlying water at this region is limited. This study investigated the spatiotemporal patterns of microbial communities at river confluences using high-throughput 16S rRNA gene sequencing and multivariate statistical techniques. We discovered that environmental heterogeneity increased after confluence, with stochastic mechanisms dominating microbial community formation at river confluences, accounting for 81.7–86.0% of variance for samples collected in spring and 82.6–86.9% for samples obtained in autumn. Microbial population interactions showed decreasing modularity but increasing connectivity from warmer to cooler seasons. The predicted predominant metabolic functions exhibited seasonal variations, with denitrification being dominant in spring and nitrate respiration/reduction prevailing in autumn. This study emphasizes the varied roles of stochastic and deterministic processes in shaping the overlying water microbial community at river confluences, resulting in a better understanding of the spatiotemporal patterns, processes, and mechanisms of communities within.