Temporal-spatial Variability Of Bacterial Community Structure In The Surface Water From Poyang Lake, China

The surface water was collected from ten sampling sites in Lake Poyang in Oct. 2010 and May 2011 respectively. Physicochemical parameters were measured, respectively.DGGE (denaturing gradient gel electrophoresis) and high-throughput sequencing technology were employed to analyze the composition and structure of bacterial community, and canonical correspondence analysis (CCA) was utilized to investigate the relationships between bacterial community and physicochemical parameters.The results are as follows:a. The results indicated that the contents of COD, TN and TP in Lake Poyang have been subjected to the eutrophication status. The COD content reached the level of extreme eutrophication in some of the sites in May 2011. There were significant differences among physicochemical parameters temporally and spatially.The contents of COD, TN, NH4+-N, NO3--N and TN/TP in Oct.2010 were significantly lower than those in May 2011. In contrast, the contents of TP and Chl-a were significantly higher in Oct.2010 than May 2011. For the spatial aspect, the highest concentrations of TN and TP were in Rao River Estuary while the lowest were in Nanjishan Region and the northern Estuary of Ganjiang River in Oct.2010. The highest concentrations of COD and TN were in Hukou, and the lowest concentrations of TN and TP was in Xiu River Estuary in May 2011.The content of Chl-a in Nanjishan Region was significantly higher than other sampling sites in both seasons. Principal component analysis showed that the water quality of Lake Poyang was mainly affected by DO, SD, EC.b. The contents of heavy metals Cu, Zn, Pb and Cd was significantly different between different seasons in Lake Poyang. Contents of Pb and Cd were significantly different among sites within the same season, while the contents of Cu and Zn were not. The contents of Cu and Zn in Oct.2010 were significantly higher than those in May 2011, but the content of Pb was lower than those in May 2011. The highest concentration of Cu was in Xiu River Estuary and Rao River Estuary. The highest concentration of Pb was observed in the main regions of the Southern and northern lake, while the lower in Xin River Estuary. The highest concentration of Cd was in Xin River Estuary and Rao River Estuary while the lower in Nanjishan Region. The highest concentration of Zn was in Xiu River Estuary, and it was lower in Houkou. But it showed the opposite trend in May 2011.The average heavy metal content in the whole lake conformed the water quality standards of the national fisheries in addition to the content of Pb in May 2011. Correlation analysis showed that there were strong correlation between Cu and Zn in both seasons. The accumulation of heavy metals was less affected by the Physicochemical parameters.c. The richness and diversity of bacterial community in surface water of Lake Poyang were highe but different in the two seasons. The bacterial richness, evenness and diversity were higher in Fu River Estuary and Nanjishan Region while lower in Hukou and the main regions of the northern and southern Lake in Oct.2010. The highest bacterial richness, evenness and diversity were in the northern Esturay of Ganjiang River,orderly followed by Houkou, the main regions of the northern and southern Lake and Fu River Estuary,while it was lower in Xiu River Estuary and Sanjiangkou in May 2011.Compared with October 2010, the whole lake bacterial community richness were reduced with the exception of Huko、northern Estuary of Ganjiang River and the main regions of the northern and southern Lake. Bacterial diversity were increased greatly except Nanjishan Region, Fu River Estuary and Xin River Estuary.d. According to the analysis of DGGE fingerprint,the bacterial community structures were different among sampling sites.Cluster analysis of bacterial community based on DGGE showed that the sites clustering was mainly affected by their spatial distribution and nutrient contents. High similarity was found between bacterial communities from Hukou site^ the main regions of the northern and southern Lake and northern estuary of Ganjiang River. Moreover, bacterial communities in Sanjiangkou Region and Xin River Estuary also presented high similarity. Further PCA results showed that bacterial communities in surface water of Lake Poyang is mainly affected by nitrogen nutrients, COD, EC, and Pb, in which EC and Pb were more significant factors.e. The bacterial communities of Poyang Lake were subjected to the following 19 phylum:Proteobacteria,Actinobacteria, Bacteroides, cyanobacteria, Verrucomicrobia, Deinococcus-Thermus,Firmicutes,Gemmatimonadetes,Planctomycetes,Acidobacteria, Nitrospira, TM7, Chloroflexi,Armatimonadetes, chlamydia, Fusobacteria, Spirochaetes, WS3, Synergistetes.The dominant bacteria in the two seasons (content>1%)were Actinobacteria, Bacteroidete, Cyanobacteria, Verrucomicrobia and β-Proteobacteria, γ-Proteobacteria, a-Proteobacteria. WS3 is unique in Hukou site in October 2010; the Firmicutes, Armatimonadetes, Synergistetes, Fusobacteria and Spirochaetes, among which the Synergistetes was unique in the Xingzi Region, were unique in May 2011.f. Proteobacteria showed the highest content in bacteria, followed by Actinobacteria and Bacteroides. In the same season, the content of Proteobacteria presented a regularity according to the geographical distribution of the sampling sites: From the North (Hukou) to south (Rao River Estuary) gradually increased, while it was opposite for actinomycetes. Compared with October 2010,the content of the species in the lake have risen expect TM7, Chloroflexi, Firmicutes and γ-Proteobacteria. The nutrient effect on the composition of bacterial species:the content ofa-Proteobacteria, γ-Proteobacteria were lower in sites with lower nutrient contents where 8-Proteobacteria and cyanobacteria content was highe, β-Proteobacteria showed no obvious regularity with nutrient contents.g. There was high similarity between Acidobacteria, Planctomycetes, Nitrospira, Chlamydiae, Verrucomicrobia, α-Proteobacteria and 8-Proteobacteria, These bacteria were negatively correlated with TOC, but less influenced by nutrients; the content of Cyanobacteria was negatively correlation with TP. Overall, the measured environmental parameters relatively impacted the distribution of bacterial communities.