Microbial Source Tracking and Community Assembly Mechanisms in Fenhe Reservoir Wetland.

The structure and assembly of microbial communities are fundamental to regulating biogeochemical processes and maintaining water quality in reservoir ecosystems. In this study, Fenhe Reservoir, a reservoir wetland, and Gonghai Lake, a natural lake, were selected to investigate microbial community sources and assembly mechanisms using high-throughput sequencing combined with source tracking and phylogenetic null modeling. The results demonstrate pronounced spatial variation in both microbial sources and community assembly processes within the reservoir. In the upstream region of reservoir, microbial communities were shaped by riverine inputs, with variable selection as the main assembly driver. In downstream zones, homogeneous dispersal was identified as the predominant assembly mechanism, yielding community structures analogous to those typically observed in the natural lakes, wherein microbial sources were primarily restricted to shoreline sediments and the overlying water column. These findings highlight the unique dual structure of artificial reservoir microbial dynamics: upstream regions dominated by external inputs and strong selection pressures, and downstream zones driven by internal dispersal and localized processes.