Global meta-analysis of river bacterial communities and responses to human activities

River microorganisms play a pivotal role in ecological and biogeochemical processes. However, human activities, by altering environmental conditions or directly introducing human-related microorganisms, significantly affect the composition and function of river microbial communities. There remains considerable uncertainty about the influences of human activities, particularly land use and wastewater discharge, on river microorganisms, with few studies addressing these issues within a comprehensive framework on the global scale. Our study employed meta-analysis to quantify the global response of river microbial communities to human activities. Urban land use correlated positively with river α diversity, and natural land uses (e.g., forests, grasslands, shrubs) similarly showed positive correlations. In contrast, agricultural land use shows a negative correlation with α-diversity. The reduction in microbial diversity of rivers with high land use intensity (LUI) was primarily attributed to the increase in agricultural land around rivers. In addition, microorganisms in high LUI rivers were more fragmented than low LUI rivers, particularly in tropical regions where land use significantly diminished microbial network complexity. Source tracking results revealed that wastewater treatment plants directly contribute 16.03 % to river microbial communities. This study enhances our understanding of the influence of human activities on river microbial communities and holds significant implications for the management and strategic planning of river ecosystems under future global change scenarios.