The Community Structure And Distribution Of Planktonic Microbes In The Main Stream Of The Yangtze River

Microorganisms play an important role in natural ecosystems.In water,microbes control the whereabouts of pollutants and have an important impact on Water environment health.As the largest river in China,the Yangtze River provides water for 400 million people along the Yangtze River.However,with the rapid development of cities,the upper,middle and lower reaches of the Yangtze River have been polluted to varying degrees.The original conditions of the water have been changed and water pollution has become increasingly serious.These seriously affect the daily life of the people in the basin.In order to provide scientific theoretical basis for the protection and restoration of the Yangtze River,this paper applies quantitative PCR and high-throughput sequencing technology based on 16S rRNA gene of bacterioplankton and planktonic archaea.Water samples were collected the mainstream of Yangtze River.The composition,spatial distribution and environmental factors of bacterioplanktonic and planktonic archaea communities in the mainstream of the Yangtze River were analyzed.The main conclusions are as follows:(1)By analyzing the physical and chemical properties of the three sections of the Yangtze River,it was found that the pH value and the concentration of DO and SS in the three-stage water body of the mainstream of the Yangtze River first decreases and then increased;the concentration of TN,NH4+-N and NO3--N increased first and then decreased;the concentration of TP and TOC continued to decrease along the water flow,while WT continued to rise.In addition,both the study area and the upper,middle and lower reaches of the three-stage water body,SS and TN showed a very significant correlation,and also showed correlation with TP in different areas,indicating that in theYangtze River,the nitrogen and phosphorus contaminants may be present in the water in the form of particle adsorption.At the same time,NH4+-N and TN had significant or extremely significant correlations in the basins other than the lower reaches,but NO3--N only showed a significant correlation with TN in the upper reaches,which indicated that the organic nitrogen conversion process was active in the water,nitrosation processes and nitrification processes may be inhibited by excessive concentrations of oxygen-consuming organics and toxic contaminants in the water.(2)In the analysis of the bacterioplankton samples in the upper and lower reaches of the Yangtze River,it was found that from the perspective of gene abundance,the gene abundance of the upper,middle and lower reaches of the bacterioplankton was not significantly different.At the same time,the inter-group difference test of a diversity in different water bodies showed that the Shannon diversity and Shannoneveness of bacterioplankton in the middle reaches were significantly lower than the lower reaches.In terms of community composition,the taxon with the highest relative abundance of bacterioplankton in the three waters was Proteobacteria at the phylum level.At the genus level,the dominant species in the upper reaches was Bacillus while in middle and lower reaches it is Comamonadaceae.Meanwhile,in lower reahces,the relative abundance of the functional microbe,Novosphingobium,which was closely related to the phosphorus content of the water,was also higher.In addition,the environmental factors affecting the composition of bacterioplankton in the three-stage water body were not identical.Bacterioplanktonic community of the upper reaches was significantly affected by the pH and SS.And the bacterioplanktonic communities in the middle and lower reaches are affected by DO,while that in the lower reahces waters was affected by WT and TP.(3)There was no significant difference in the gene abundance of planktonic archaea among three reaches of the Yangtze River In terms of alpha diversity,only the Shannoneveness of upper reaches was significantly higher than that in middle reaches.The planktonic archaea community was mainly composed of Crenarchaeota and Euryarchaeota at phylum level,and was composed mainly of two kinds of AOAs,Nitrosopumilus and Candidatus_Nitrososphaera at genus level.At the same time,there were higher abundance methanogens in the main stream,such as Methanosaeta,Methanosarcina and Methanobacterium.The analysis of environmental impact factors of planktonic archaeal community showed that the archaeal community in the upper reaches was mainly affected by DO,pH and SS,while the archaeal community in the middle and lower reaches was only affected by DO.