Spatial distribution of bacterial community in river-lake ecotone of Poyang lake during dry season

Abstract:

[Background] The microbial community composition at the interface has become one of the research hotspots in the field of microecosystem. [Objective] The objective of the study is to explore the spatial distribution of bacterial community river-lake ecotone of Poyang lake during dry season. [Methods] Eleven typical sampling points in the Poyang lake river-lake ecotone were selected to collect water samples for analyzing physical and chemical indicators. The 16S rRNA gene sequence data of the above samples were obtained by PCR. The diversity and richness of microbial communities were calculated and compared of 11 sampling sites. According to the Beta diversity distance matrix, the similarity tree diagram was used to cluster the samples to explore the microbial distribution in the Poyang lake river-lake ecotone. The relationship between physical and chemical factors and microbial community distribution was studied based on redundancy analysis (RDA). [Results] The Poyang lake river-lake ecotone water was slightly acidic, and TN content exceeded standard V, and the content of TP fluctuated between the standards of II, III and IV. The composition of dominant species of bacteria in the interlaced zone of Poyang lake is roughly similar except the difference of relative abundance. Microbial community structure at phylum level was Proteobacteria (36.18%), Firmicutes (22.18%), Bacteroidetes (17.06%) and Actinobacteria (8.87%). The proteobacteria in the water was dominated by γ-proteobacteria, and the β-proteobacteria was the sub-dominant flora. At the genus level, other geniuses of Actinobacteria had the highest relative abundance (11.4%). The microbial diversity index (Ace, Chao1, Shannon and Simpson) of Le?an River (R9) and confluence zone of Poyang lake and Yangtze river (H11) was higher than others, Wanjia bridge (N2), confluence zone of Poyang lake and Ganjiang (W6) and Yaohu lake (Y10) microorganisms has the lowest diversity index. The composition of microbial community was divided into two categories. The composition of Poyang lake Dahuchi reserve (W7), Le?an river (R9) and confluence zone of Poyang lake and Yangtze river (H11) were similar, and the composition of the other 8 samples was similar. The main environmental factors affecting the distribution of microbial communities were pH (P=0.735 2), TN (P=0.761 4) and TP (P=0.612 8). [Conclusion] The spatial distribution of bacterial communities in the river-lake ecotone of Poyang Lake in the dry season was obviously different. The spatial and geographical differences superimposed on the disturbance of human activities affected vegetation, hydrology, eutrophication degree, etc., thus causing differences in physical and chemical indicators of water, and then affecting the composition of bacterial communities, the composition of bacterial community was similar in areas with similar physical and chemical indexes. The bacterial diversity was low in the area with serious eutrophication. The study is helpful to understand the structure and function of Poyang lake ecosystem, provide technical support for water environment management and ecological protection of Poyang lake, and of great significance to maintain the ecological balance of Poyang lake.