Impacts of environmental factors on bacterial diversity of Xinkai river estuary in the coastal area of Qinhuangdao

Abstract:

[Objective] The goal of this study is to reveal the dynamics of bacterial communities and their relationship with environmental variables through analysis of 16S rRNA gene clone libraries derived from the three stations of Xinkai River estuary for better understanding the ecological functions of this region. [Methods] In August 2014, water samples were collected from 3 stations of Xinkai River estuary (XKH) area and its adjacent water in the coast of Qinhuangdao. Bacterial abundance was estimated using a fluorescence microscope and 16S rRNA gene clone libraries derived from the total bacterial DNA of the water samples. [Results] Total number of bacteria (2.62×106 cells/mL) and diversity of station W1 were higher than that of Xinkai River estuary XKH station (6.62×105 cells/mL) and the station W2 (2.02×106 cells/mL); 16S rRNA gene clone libraries of the stations XKH, W1, and W2 yielded 46, 51 and 56 OTUs, respectively. Those OTUs belonged to the members of 7 different bacterial phyla: Proteobacteria, Cyanobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Planctomycetes and Verrucomicrobia. Proteobacteria was the predominant taxa in the clone libraries of the stations XKH (50.9%) and W2 (75.9%). On the other hand, members of Cyanobacteria were the predominant taxa (38.2%) in the station W1. These dominant groups were closely related to availability of nitrogen and other nutrients of water column. The environmental factors, which affected the distribution of bacterial communities, were dissolved oxygen, pH and nitrogen nutrients. [Conclusion] Xinkai River estuary and its adjacent seawater contained rich bacterial diversity. Particularly, the water samples from the transition zone between the estuary and the sea harbored much higher bacterial diversity. Distribution of bacterial communities was largely regulated by nitrogen nutrients.