Effects of different habitats on the bacterial community composition in the water and sediments of Lake Taihu, China.

Bacterial communities are sensitive to environmental fluctuations, and a better understanding of the relationships between bacterial community distribution and complex environmental conditions is important for the remediation of lake ecosystems. In this study, bacterial communities from 7 water and 7 sediment samples in 3 different regions (east, the hydrophyte-dominated region; north, the transitional region; west, the highly polluted region) of Lake Taihu were investigated via high-throughput sequencing. The physicochemical characterization showed that there were obvious differences in the trophic statuses of the three lake regions, which were mainly due to the differences in pollutant concentration and hydrophyte coverage. The Shannon and Simpson values indicated that the diversity of bacterial communities in water was the highest in the eastern region, followed by the northern and western regions, while there was no significant difference in the bacterial community characteristics in sediments among lake regions. We found that the western lake region had the highest Cyanobacteria concentration (34.71%), suggesting that Cyanobacteria may have competitive advantages over the other bacterioplankton in water columns without plants. The abundances of Chlorobi detected in the water samples in the east (2.69%) and north (6.66%) were higher than those in the west because the high turbidity in the western lake region was unsuitable for the growth of Chlorobi. Nitrospirae (average 6.36%) and Chloroflexi (average 11.62%) were more common in the sediments than in the water of Lake Taihu, suggesting that the nutrient level of Lake Taihu sediment was higher than that of water bodies. Welch's t test revealed that there were significant differences in species abundance (such as Microcystis, Synechococcus, Flavobacterium, and hgcI_clade) among the different regions, except that the east was relatively similar to the north. Canonical correspondence analysis demonstrated that TN, TP, and DO showed significant effects on the relative abundance of the dominant bacterial genera in water, while TOC, TP, and TN were positively correlated with TOC, TP and TN. This study provides useful information for understanding the variation in the diversity of bacterial communities in different habitats of Lake Taihu.