Spatial Distribution Charateristics And Driving Factors Of Bacterial Communities In Lancang River Cascade Reserviors

The cascade development of rivers,as the main form of exploitation and utilization of hydro power resources,has a serious impact on river ecosystem while promoting regional economic development The "reservoir continuum" formed by the construction of cascade dams disturbs the hydro logical rhythm of rivers,changes the physical and chemical properties of water bodies,and may also lead to corresponding changes in the structure and functional characteristics of biological communities.As an important pare of reservoir ecosystem.microorganism is an importam index to evaluate the state of water ecosystem,which affects the biogeochemical cycle of nutrient.However.limited to the complexity of cascade development,current microbial communities in river cascade reservoirs.The study on the spatial and temporal distribution and population characteristics of fall is still relatively lacking.Based on this,this study took the cascade hydro power stations(Miaowei.Gongguoqiao,Xiaowan,Manwan.Dachaoshan,Nuozhadu and Jinghong)in Lancang River basin as the research object,and used Illumina MiSeq high-throughput sequencing technology to identify the spatiotemporal variation characteristics of bacterial diversity and composition structure in the water body of the cascade reservoir in Lancang River,and to explore the key driving factors affecting the change of flora,The main achievements of this thesis are as follows:(1)The physical and chemical indexes of the reservoirs are mainly seasonal,the dissolved oxygen(DO)content is higher in winter than in summer,but the overall spatial variation fluctuation is small;The electrical conductivity(EC)is obviously higher in winter,the spatial variation is not obvious;the water body is alkaline in summer and winter,the spatial distribution is not different,the seasonal difference is significant,the pH value of summer water body is higher;redox potential(ORP)increased significantly in winter,and the upper middle reaches meservoir was higher than the downstream reservoin,The change trend of chemical oxygen demand(COD)in summer and winter is basically the same.the COD content in winter has a certain incrase,and the downstream reservoir has an upward trend:the total nitrogen(TN)content has increased in wiater compared with summer,and the spatial distribution has a gradual upward trend;there is no significant difference in the spatial and seasonal changes of total phosphorus(TP),and there is no significant fluctuation change.The total nitrogen(TN)concentration of the entire reservoir section meets the surface water class ? standard.and the total phosphorus(TP)meets the surface water class ? water standard.The reservoir water body appears to be more affected by nitrogen than phosphorus.(2)The ACE index and Chaol index of the seven reservoirs have the same trena.In general,the correlation between baclcrial community and season is very high,and the diversity of flora of most reservoirs is increased in winter.The investigation of natural channel diversity index shows that cascade reservoir construction significantly reduces the diversity of flora;PCA and clustelr analysis show that there are some differences in the structure of flora among different reservoirs,the overall performance is the significant seasonal difference;Proteobacteria and Actinobacteria accounted for the highest proportion in the seven reservoirs,occupying a dominant position in each reservoir,indicating that the dominant bacteria species of the reservoir did not change significantly,but there was a significant difference in the relative abundance of Cyanobacteria Firmicutes,etc.The door is more demanding on environmental conditions and maybe a unique dominant bacteria door at some points.Acinetobacter is the genus with the highest average relative abundance,followed by CL500-29_marine_group of Acidimicrobiaceae,and the third and fourth are Arthrobacter and hgcl-clade,which belong to Actinobacteria,It can be seen from the review of the natural river section gate and the distribution of horizontal bacterial flora that the distribution of cascade reservoirs has significantly changed the distribution of bacterial communities.The blue bacteria gate is a unique dominant bacteria gate in the reservoir section,indicating that the construction of cascade reservoirs leads to eutrophication danger.(3)The correlation analysis of the bacterial community of the reservoir water and environmental factors can find that the key water environmental factors that affect the diversity of the flora are various forms of nitrogen,total phosphorus,and DO in the water body.The presence of dominant colonies appears to be related to the existence of various forms of nitrogen.RDA analysis shows that TN,NH4+-N,EC are the most important driving factors for the change of the microbial flora structure in cascade reservoirs.This analysis shows that the influence of nitrogen is the most important cause of all environmental factors,although the water body is not completely Destruction,but the effect of increasing nitrogen pollution caused by cascade reservoir construction is worthy of our attention.