Bacterial Community Structure In Different Eutrophic Areas Of Donghu Lake On High Throughput Sequencing

Bacteria is the main driving force of material circulation and energy flow in lake ecosystems,which is closely related to the eutrophication and algal bloom.In order to reveal the succession of bacterial diversity over time and the relationship with environmental factors in eutrophic areas of Donghu Lake,we collected the samples in two eutrophic areas(Guanqiao Lake and Sea World,referred to as H and L)from April 2016 to March 2017.The species,community structure and relative abundance of bacteria in water and sediment were studied by high-throughput sequencing.The main results are as follows:(1)There were 4368 and 4779 OTUs of water sample in H and L areas respectively,while the sediment samples were obtained 5181 and 5251 OTUs.That indicated there were abundant bacterial species in Donghu Lake,and the number of bacterial species in the sediment was higher than that of water.Compared with the H-area with higher eutrophication,the number of bacterial species in the water and sediment of the L-area with lower eutrophication was more.There was a significant difference in bacterial diversity of water and sediments between two areas.In the water,the bacterial diversity in the spring and summer of L-area was higher than that of H-area.However,in the autumn and winter it is the opposite.In the sediment,the bacterial diversity of L area is higher except for a few months.(2)The main bacterial phylum in H and L area were similar.Actinobacteria,Proteobacteria and Cyanobacteria were the main dominant bacteria in water,and in sediment,the major group was affiliated to Proteobacteria,followed by Chloroflexi and Nitrospirae.The relative bacterial abundance varied with time in both areas,in which the fluctuation of Actinobacteria,Bacteroidetes and Planctomycetes was more obvious in H area.In the sediment,the relative abundance of chloroflexi was higher in H area.On the contrary,that of Nitrospirae and Acidobacteria was higher in L area.This may be the response of bacterial community to eutrophication of Donghu Lake.(3)At the genus level,the bacterial communities of the Donghu Lake ecosystem were more dispersed and contained a large number of unclassified bacteria and uncultured bacteria.The composition and relative abundance dynamic change of the main bacteria groups in two areas were different.In the water,CL500-29 marine group,CL500-3,Microcystis and Synechococcus sp.PS717 were the most valuable species in the H-area.In the L-area,those species were CL500-3,CL500-29 marine group and Flavobacterium.In the sediments,Derocomonas,Desulfatiglans,Thiobacillus of H-area and nitrospira of L-area had significant differences.(4)The RDA analysis of bacteria and environmental factors showed that,temperature and chlorophyll-a were main factors affecting the bacterial community structure in water of both areas,and the NH4-N and pH were positively correlated with the bacterial communities in H-area and L-area respectively.In the sediment,the most important factors affecting the bacterial communities was NH4-N in H-area and OM in L-area.Moreover,pH had an important impact in both areas.In addition,there were other environmental factors which were selected in this study and had different correlations with the bacterial communities in two areas.