The Seasonal and Spatial Patterns of Planktonic Bacterial and Fungal Community Structure and the Response to Environmental Factors in the Danjiangkou Reservoir, China

Planktonic microbial communities are essential for sustaining the cycling of materials and the flow of energy. However, little research has examined how planktonic bacteria and fungi in the Danjiangkou Reservoir (DJKR) are distributed and function across different seasons. The findings indicated that the DJKR maintained generally favourable water quality. Seasonal changes have a more pronounced effect on fungal diversity than on bacterial diversity, resulting in a significant decrease in fungal diversity. Among bacterioplankton, the dominant phyla were Proteobacteria, Actinobacteria and Bacteroidetes, while Basidiomycota, Ascomycota, Mucoromycota and Chytridiomycota accounted for 81.22% of the total fungi, being the dominant fungal groups. According to the KEGG annotation, the most active functions in bacteria and fungi were amino acid metabolism and translation, respectively. Seasonal shifts exerted a notable effect on the abundance of genes participating in nitrogen and phosphorus cycles. Total nitrogen (TN), pH, total phosphorus (TP) and water temperature (WT) were identified by redundancy analysis (RDA) as the key environmental factors influencing the community structure of bacteria and fungi. Stochastic processes exerted a predominant influence on the assembly dynamics of planktonic bacterial and fungal communities. This study offers a scientific foundation for protecting water resources at the DJKR.