Vertical Changes of Planktonic Bacteria Community and Predictive Functional Analysis in Summer Dali-Nor Lake

Planktonic bacteria is the key component of water ecosystem, playing an important role in processes of materials and energy cycle. In this study, we have collected 43 water samples from the surface water, middle water and bottom water in the summer Dali-nor lake, an inland closed lake in the Inner Mongolia Plateau. Based on 16S rRNA gene-based high throughput sequencing technology, the vertical variation characteristics and ecological function of planktonic bacterial community have been analyzed in detail. The results show that: in summer, the diversity of phytoplankton community in Dali lake is the highest in surface water, the lowest in middle water, and the richness is the highest in bottom water, and the lowest in middle water. In addition, the Actinobacteria is the most dominant class, which is 24.70% in the surface water, 21.06% in the middle water, and 24.77% in the bottom water respectively. Redundancy analysis results show that the dominant microbial acceptance indicators in different depths of water have different effects. The dominant microflora in surface water of Dali-nor lake is most affected by TDS and EC, which represent exogenous input. The dominant microflora in middle water is mainly affected by different forms of nutrient elements. In bottom water, the dominant microflora is most obviously affected by Chla and COD. And the change of water depth is also one of the key factors affecting the structure of dominant flora in middle and bottom water. On the whole, the vertical difference of the physical and chemical proxies caused by the change of water depth, has become one of the key factors affecting the structural characteristics of planktonic bacteria in summer Dali-nor lake.