The Impact of Artificial Mixing and Oxygenation on bacteria in a Water Transfer Reservoir

Artificial Mixing and Oxygenation induced by Water-lifting aerations have the potential to enhance the water quality improvement in reservoirs. However, there is limited understanding of the bacterial community composition, assembly, and mechanisms behind water quality improvement under the WLA influence, especially in a water transfer reservoir. Here, the dynamics and relationship of water quality, bacterial diversity, and composition during pre-operation, in-operation, and post-operation of WLAs were analyzed using the high-throughput sequencing technology to explore the effects of artificially-regulated bacteria on water quality improvement. WLA operation led to the elimination of water stratification, significant bottom oxygenation and a reduction in nutrient concentrations. Also, WLA operation changed the bacterial community composition significantly, with the increase in richness, little difference in diversity, and significant increase in abundance of species with pollutant degradation functions, which resulted in the shift from stochastic processes to deterministic processes of the bacterial community assembly. As a result, the enhancement of the dominant bacteria responsible for organic matter degradation and denitrification and the suppression of the emergence of algae-related bacteria were observed during WLA operation, and the ecosystem stability were improved. The results of multiple analyses indicated a direct correlation between the artificial mixed oxygenation, changes in the bacterial community, and the reduction of nitrogen, phosphorus, and permanganate index in the water column. This study provides a novel insight into in-situ water quality enhancement and a valuable reference for understanding bacterial change patterns under artificially intervened conditions in water transfer reservoirs.