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How human activities drive regime shifts in microbial communities in the Yangtze River: Implications for the conservation of the world’s great rivers
Jiahui Shang, Yu Gao, Wenlong Zhang, Yi Li
Under the stress of human activities, the world’s great rivers are undergoing rapid and radical shifts. These shifts are likely to occur abruptly and are difficult to reverse; however, it remains unclear how regime shifts occur and what ecological impacts these shifts will bring. In this study, the Yangtze River was selected as the study area. The alternative stable states theory and high-throughput sequencing were combined to investigate the distribution characteristics of microbial community states, as well as their responses to two human activities (i.e., dam construction and urbanization). Results showed that dams, especially the Three Gorges Dam, along the main stream of the Yangtze River, have significantly altered hydrological conditions (e.g., flow discharge and water levels). The reduction in flow discharge (e.g., flow <12,900 m³/s) upstream due to dam construction was found to drive regime shifts in the microbial community, with cyanobacteria gaining dominance. Further downstream in the Yangtze River is a lower-gradient urban area, where high concentrations of nitrogen and phosphorus were detected in river sediments. The increase in environmental stress, particularly ammonia nitrogen and nitrate concentrations, was found to drive regime shifts in the microbial community, accompanied by the reductions in α-diversity and co-occurrence patterns. Our results provide useful insights for dam operations and ecological conservation of the world’s great rivers.
