[Community Structure of Microorganisms and Its Seasonal Variation in Beihai Lake]

Water samples were collected in summer, autumn, winter, and spring in Beihai Lake for the analysis of water quality and microbial community structure. It was found that the water quality in summer and autumn was worse than in winter and spring, and TN and TP were the most important factors affecting the water quality. The microbial community structure was investigated using MiSeq high-throughput sequencing. It was found that the phyla Cyanobacteria, Proteobacteria, Actinobacteria, and Bacteroidetes were abundant in all the samples, whereas their relative abundances differed among the four seasons. In summer and autumn, the microbial diversities were higher, and the phylum Cyanobacteria was most abundant, with the genus Synechococcus dominant. In winter, the phylum Proteobacteria was dominant. In spring, Actinobacteria and Bacteroidetes were abundant, accounting for 51.5%-64.3% of the bacterial community. The redundancy analysis (RDA) results showed that the microbial communities were mostly affected by water temperature in Beihai Lake. Overall, the water quality of Beihai Lake was qualified for the use of landscape water. However, the abundance of Synechococcus in summer may lead to algal blooms. Thus, it is necessary to strengthen the monitoring and estimation of water quality in Beihai Lake.