Response of river plankton and bacterial community distribution to environmental factors under the influence of water and sediment regulation of Xiaolangdi Reservoir, Yellow River

Zooplankton, phytoplankton, and bacteria constitute the basic ecological group of rivers, which not only plays an important role as primary producers, primary consumers and decomposers in the food chain, respectively, but also can respond quickly to the fluctuation in environmental conditions. In this research, the sampling was carried out at the pre-, inter- and post stage of the water and sediment regulation in 2018-2019, to clarify the effect of environmental factors on the distribution of plankton and bacterial communities in the downstream river. Through the quantitative monitoring of water environmental factors and plankton and bacterial communities, the variation of plankton and bacterial communities were analyzed. The structural equation model between plankton biomass and water environmental factors was established, and db-RDA analyzed the relationship between bacterial communities and environmental factors. The results showed that the process of water and sediment regulation had different impact patterns on phytoplankton, zooplankton and bacteria. Environmental factors such as dissolved oxygen(with the largest influence coefficient before water and sediment regulation, 0.86), Temperature(with the largest influence coefficient during water and sediment regulation, 0.76), and conductivity(with the largest influence coefficient after water and sediment regulation, 0.82) have the greatest impact on the biomass of plankton, while the total soluble solids, dissolved oxygen, conductivity and Chlorophyll-a has the greatest impact on the bacterial community. In the process of water and sediment regulation, the concentration of nutrients such as soluble silicate, total nitrogen and total phosphorus changes, which affects the biomass of plankton. At the same time, water and sediment regulation also weakened the predation of zooplankton on phytoplankton, which changed the relationship between plankton communities. The process of water and sediment regulation also increased the difference between the bacterial communities in the suspended and sedimentary state. This study clarified the response of plankton and bacterial communities to environmental factors at different stages of water and sediment regulation, and has certain theoretical significance for the ecological restoration of downstream rivers. © 2020, China Water Power Press. All right reserved.