Agricultural Landscape Structure Alters the Water Quality and Bacterioplankton Community Assembly: Implications in River Management

ABSTRACT The aquatic environments of inland rivers are relatively independent and highly heterogeneous. As the second largest inland river in China, the water resources of the Heihe River are intensively exploited in its middle and downstream sections, while the responses of water quality and the community assembly mechanisms (deterministic or stochastic processes) of bacterioplankton to these intensively anthropogenic disturbances remain poorly characterized. In this study, we integrated niche‐neutrality dynamic balancing to investigate the dispersal dynamics of bacterioplankton communities in the Heihe River along gradients of human activity intensity. We found that the upstream landscape of the Heihe River has greater landscape connectivity and better water quality, whereas the downstream landscape is more fragmented and has poorer water quality. The α‐diversity of bacterial communities decreased significantly from upstream to downstream. Meanwhile, community assembly in the plateau meadow (PM) region was dominated by stochastic processes driven by dispersal limitation, whereas deterministic processes dominated by homogeneous selection drove the assembly and turnover of bacteria in other regions. These results indicated that agricultural disturbances could lead to the deterioration of water quality downstream and affect river microbial community assembly. To protect the microbial diversity of the watershed, therefore, more attention should be paid to landscape configuration parameters in the agricultural oasis (AO) region. Our findings contribute to a deeper understanding of the microbial ecology in inland rivers under different landscape patterns and provide valuable guidance for the protection of inland rivers and the development of landscape ecology in the regions surrounding rivers.