小浪底水库下游浮游生物及细菌群落对水沙调控的响应规律

浮游动物、浮游植物和细菌群落广泛分布于河流生态系统,发挥着初级生产者、初级消费者和分解者的重要作用,对于环境条件的波动较为敏感。本文于2018—2019年黄河小浪底水库调水调沙前、中、后期对下游河流进行了调查采样,得出水环境因子、浮游生物与细菌群落的定量结果,以明确在不同调水调沙阶段下游河流水环境因子,浮游生物和细菌群落的演变规律及相互作用。通过结构方程模型(SEM)和基于距离的冗余分析(dbRDA)、分别明确了调水调沙影响下浮游生物以及细菌群落对水环境因子的响应规律。结果表明,调水调沙不同阶段下,浮游植物、浮游动物和细菌对于环境因子的响应方式具有较大的差异,溶解氧(在调水调沙前影响系数最大,为0.86)、温度(在调水调沙期间影响系数最大,为0.76),以及电导率(调水调沙后影响系数最大,为0.82)等环境因子对浮游生物的生物量影响最明显,而溶解氧(在调水调沙前)和叶绿素a(调水调沙期间至调水调沙后)对于细菌群落的影响最大。此外,调水调沙过程改变了浮游生物群落内部关系,削弱了浮游动物对浮游植物的捕食,同时也使得悬浮和沉积状态的细菌群落在样点之间的差异性增大。本研究明确了浮游生物及细菌群落在水沙调控不同阶段下对水环境因子的响应规律,对下游河流生态修复具有一定的理论意义。

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.