Bacterial community composition in aquatic and sediment samples with spatiotemporal dynamics in large, shallow, eutrophic Lake Chaohu, China

Lake Chaohu is a representative lake in China that suffers from severe eutrophication and algal blooms. In this study, the composition of bacterial communities in the water and sediment from one of the inlets and outlets of Lake Chaohu in response to spatiotemporal changes was analyzed by Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene. Substantially distinct bacterial community composition was observed between the water column and sediments in both the Zhaohe (the inlet, C1) and Yuxihe Rivers (the outlet, C2). The phyla of the water samples were Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes, whereas the sediment samples were dominated by Proteobacteria, Acidobacteria, Chloroflexi and Nitrospirae. The sediment exhibited higher diversity and richness than did the water column at the two sites, with the sediment samples from the Yuxihe River showing higher richness and lower diversity than those from the Zhaohe River. The pattern of spatiotemporal changes indicated the seasonal factor, rather than the region, to be the primary cause of the observed variation in the bacterial structure in Lake Chaohu. In water samples from the two study areas, unclassified genera of Cyanobacteria dominated in winter, with members of unclassified FamilyI and unclassified Cyanobacterium. Moreover, redundancy analysis indicated that water temperature (T), total phosphorus (TP), organic carbon (OC) and total nitrogen (TN) were all determined to be related to bacterial community structure. And T and TP were the main factors influencing the water bacterial structure and that OC and TN were the main indicators determining the sediment bacterial structure. The results of this study may be useful for indicating the tendency of bacteria to respond to environmental changes in Lake Chaohu.