Diversity Of Planktonic And Sediment Bacterial Community In Chenghai, A Plateau Lake

Lake ecosystems play a vital role in expanding biodiversity.Normally,Bacteria play a key role in maintaining the diversity of the ecosystem by acting as both decomposers and consumer participants in the circulation and energy flow of matter in the lake.In order to know and explore the distribution,diversity and specific succession of bacteria in Chenghai Lake,a plateau lake,we used the 16S rRNA high-throughput sequencing method and real-time PCR to explore the diversity and composition of bacteria in the planktonic and surface sediments of Chenghai Lake,by sampling the lake water in four seasons and surface sediments in summer and winter.The results are shown below:?1?One year of water quality monitoring showed that the conductivity of Chenghai Lake peaked at 1314 S cm^-1,about 10 times that of 10 years ago.During the sampling period,the contents of chlorophyll-a and turbidity of water samples in spring and summer were significantly higher than those in autumn and winter,meaning spring and summer were the most suitable growing seasons for Chenghai algae,and the dominant growth of algae resulted in increased turbidity of water.During the sampling period,the total nitrogen concentration in Chenghai Lake was about 0.9mg L^-1,and the total nitrogen concentration was the lowest in summer.However,the total phosphorus concentration did not show significant seasonal changes,and its mean value was maintained at 0.06?0.1mg L^-1.The results of TSI_M show that Chenghai Lake has mild eutrophication during the sampling period,and reaches moderate eutrophication in spring and summer.?2?The dominant phytoplankton bacteria in June,September and December 2018and March 2019 were Actinomycetes,Verminobacteria and Cyanobacteria respectively.However,the Proteobacteria were the dominant bacterial in sediment samples taken from June and December 2018.The RDA?redundancy analysis?and network analysis shown that the seasonal differences of bacterial communities were correlated with environmental abiotic factors,and indicating that bacterial community changes were significantly correlated with species.?3?During the sampling period,the dominant cyanobacteria in March,June,September and December were Microcystis,Synechococcus,Unclassified Pseudanabaenaceae and Planktothrix respectively.RT-PCR of planktonic dominant algae showed that rpoC1 had the highest copied number in June,with an average of8.44×10⁴ copies L^-1,and the mean value was 4.32×10³ copies L^-1.But the copy number of sxtA gene has the lowest values in June,the mean value was 62 copies L^-1.But in December,the maximum value reached 2.88×10³ copies of L^-1.However,the genes copies number of rpoC1 and sxtA in December was significantly higher than that in June in the sediment composition?p<0.05?.?4?With the change of sampling season,the assembly process of planktonic bacteria community is dominated by randomization.However,the homogenization selection process affected the?-diversity among bacteria community.The linear fitting of non-weighted unifrac distance and?-nearest taxon index??NTI?indicates that water environmental factors affect the assembly process of planktonic bacteria in March and September.While Sediment environmental factors also affect the assembly process of benthic bacteria in June.