Effects Of River Backflow On Microbial Community Structure In Upstream

Nanming River is an important river of the Wujiang River system in the upper reaches of Yangtze River,and Pudu River is a tributary of Nanming River,both of which are important rivers in Guiyang City.As a result of the construction of the Yuefeng Hydropower Station downstream of the Nanming River,the reservoir storage has raised the water level of the river,resulting in the backflow of water from the Nanming River into the Pudu River,a tributary of the upper reaches of the river,resulting in a serious impact on the water quality of the river.In this paper,by studying the diversity of microbial communities and the distribution structure of phytoplankton in Pudu River and Nanming River,the effects of different seasons and river backflow on the two rivers are explored,and the main conclusions are as follows.(1)The overall environmental factors of Pudu River and Nanming River were examined,and the results showed that temperature was the most influential factor in terms of seasonal changes;in terms of point distribution,the upper reaches of Pudu River had better water quality and was less polluted,while the water quality gradually deteriorated in the backflow area and reached the worst in the water bodies at the confluence of the two rivers and after the confluence;the points in the upper reaches of Pudu River and the confluence of the two rivers,and the points in Nanming River had the highest TN,TP,and NH4⁺-N content showed a significant decrease,indicating that the environmental factors were more influenced by the Nanming River when the main stream Nanming River backed up into the tributary Pudu River.The principal component analysis shows that TN,TP,NH4⁺-N,BOD5 and COD have more influence on the whole environmental factors of the river water,and the influence of chromaticity on the whole environmental factors is smaller.(2)The diversity of microbial communities in Pudu River and Nanming River was analyzed and tested for differences between groups.clustered separately,and the results indicated that the mainstream had a significant influence on the tributary backflow,and the microbial diversity at the confluence was similar to that of the Nanming River.(3)The community structure of microorganisms at the phylum level was the first dominant species of Proteobacteria in all seasons;while in the genus,the dominant genus was Acidovorax in both spring and summer,Lactobacillus in autumn,and unidentified?Chloroplast in winter.river water Temperature significantly influenced the structure of the microbial community in the river,with the number of microbial populations OUTs coexisting in all seasons was 1449,and the number possessed in autumn far exceeded that in spring,summer and winter.The number of OTUs of coexisting microbial populations in the two river sections was 1,361,while the number of sampling sites did not differ significantly.The composition of the microbial community in the river water was affected by the location of different river sections by river backflow,but the number of OTUs of specific microbial populations in each location section was limited and there was no particularly significant difference.(4)A total of 167 species of phytoplankton and 189 species of zooplankton were found in the two river sections,and both showed a significantly higher number of species in summer than in winter,and a clear seasonal turnover phenomenon;the upstream flowing river section of the Pudu River had lower primary force,better water quality,lower species richness and perfect aquatic ecosystem,while the zooplankton density and biomass in the river backflow area were significantly higher,which also indicated that the water body in the backflow area had higher primary The high productivity,high nutrient elements in the water column and poor water quality in the backed-up area.