Transition In Bacterial Communities Among Hydrological Changes And Different Regions In The Surface Water Of Poyang Lake

Poyang Lake is the largest freshwater lake in China both by area and volume. As a wetland of international importance, it provides habitats for a great variety of organisms and harbors ecologically significant functions. Bacteria, functioning as the dominant decomposer of organic matters, display a crucial role in biogeochemical processes in freshwater. So it is necessary to investigate the bacterial community and their corresponding geochemical functions simultaneously for a comprehensive understanding of the ecosystem. That's just what is currently lacking of in studies of Poyang Lake. The present study helps to fill in this blank.The surface water was collected from ten sampling sites in Lake Poyang in Apr. 2014, Jul. 2014, Oct. 2014 and Jan. 2015 respectively. Physicochemical parameters were measured, respectively. High-throughput sequencing technology were employed to analyze the composition and structure of bacterial community. Quantitative PCR and pyrosequencing of bacterial 16 S rRNA gene fragment were performed to analyze the bacterial abundance, composition and corresponding dominant biogeochemical processes in surface water from research region.Poyang Lake surface water in April 2014 to January 2015, excepts Baishazhou October samples, Nanjishan April, July, October, samples, Raohe in July and April samples, most of the surface water reached the eutrophication level. Poyang Lake water physicochemical properties exist significant differences in temporal and spatial, reflecting the significantly different from the other for the spring and summer seasons. Principal component analysis showed that the physical and chemical environment of Poyang Lake water quality changes in our study area and sampling period. Mainly variation factors were temperature, SD and EC. Water content of heavy metals although there are variations, but found no significant correlation between bacterial communities in the subsequent analysis is not included in the analysis.Poyang Lake water surface for bacterial abundance analysis shows that changes in the abundance of the surface waters of the bacterial community presented the law in time, between the different ecological zones, and no significant change in the law, or this is a big change the degree of change on the season overshadowed. The seasonal variation of the surface waters of Poyang Lake ecological regions most bacterial flora in spring and summer(April 2014, July) at a relatively low level, while in winter(October 2015) the highest level.Poyang Lake surface water bacterial community phylogenetic diversity was changed with the seasons change, showing the diversity of low winter and summer, spring and autumn high diversity. And between different ecological regions, diversity of bacteria in surface water has not changed significantly. In addition, Proteobacteria, Actinobacteria, Bacteroides, were dominant bacterial taxa in water of Poyang Lake; both physicochemical conditions and hydrological regime(water temperature) were statistically correlated with the bacterial abundance and compositions. Relationships of bacterial abundance and composition with water property parameters were explored using Pearson correlation analysis and canonical corresponding analysis(CCA) respectively. The results showed that the bacterial communities were variation among the seasons and the sites. It indicates that environmental factors spatial distribution inhomogeneity may be an important cause of differences in the composition of bacterial populations.