Effects of artificially induced early mixing of stratified reservoir waters on bacterial community structure and metabolic activity
In recent years, large and medium-sized reservoirs have become the primary source of drinking water for cities. Ensuring the safety of their water quality has become a global concern. In situ experiments have shown that water-lift aeration systems (WLAs) can disrupt the stratification of reservoir water bodies, inducing them to enter the natural mixing period 2.5 months earlier than those without human intervention. However, there is still a lack of in-depth research on the bioremediation mechanisms inherent in this period. Therefore, we systematically investigated spatial and temporal changes in water quality parameters, bacterial carbon metabolism activity, species composition, and microbial community symbiosis patterns in the Lijiahe Reservoir during the artificially induced natural mixing period. The natural mixing period initially had high water temperature and dissolved oxygen concentration. Microbial carbon metabolism activity and diversity were strong and did not significantly differ in the vertical direction. However, they decreased as mixing time prolonged. During the artificially induced natural mixing period, Actinobacteria and Proteobacteria were found to be the dominant species in the water body of Lijiahe Reservoir. The biodegradation of organic pollution was facilitated by the dominant genera CL500-29_marine_group (26.65%) and hgcI_clade (18.21%). Microbial communities were observed to interact more closely with each other at the beginning of natural mixing, as revealed by symbiotic network analysis. Redundancy analysis (RDA) revealed that water temperature, dissolved oxygen, and pollutants (total nitrogen and total phosphorus) co-regulated the microbial population structure in water bodies. The study's findings provide a scientific basis for in situ water quality bioremediation.