[Composition Structure and Influence Factors of Bacterial Communities in the Miyun Reservoir]

As the largest reservoir in North China, the Miyun Reservoir is the most important surface drinking water source in Beijing. Bacteria are key regulators of reservoir ecosystem structure and function, and exploring the community distribution characteristics of bacteria is important for maintaining water quality safety in reservoirs. The spatiotemporal distribution and environmental factors of bacterial communities in the water and sediment of the Miyun Reservoir were explored using the high-throughput sequencing method. The results showed a higher α-diversity and non-significant seasonal variation of the bacterial community in the sediment, and the abundant sedimental species were affiliated with Proteobacteria. For planktonic bacteria, Actinobacteriota was the dominant phylum, and the seasonal variance was represented by CL500-29_marine_group and hgcI_clade in the wet season and Cyanobium_PCC-6307 in the dry season. Additionally, obvious differences in key species were also found in water and sediment, and more indicator species were obtained in sedimental bacteria. Further, a more complex co-existence network was identified in water compared to that in sediment, indicating the strong ability of planktonic bacteria to resist environmental changes. Environmental factors had a significantly higher effect on the bacterial community of the water column than that of the sediment. Furthermore, SO^2-₄ and TN were the main factors affecting planktonic bacteria and sedimental bacteria, respectively. These findings revealed the distribution patterns and driving forces of the bacterial community in the Miyun Reservoir, which will provide important guidance for reservoir management and water-quality assurance.