Spatial and temporal changes in bacterial community structure in adjacent waters of Dagu River estuary of Jiaozhou Bay (China) revealed by high-throughput sequencing

Abstract

Dagu River, the largest sea-entering river in Jiaozhou Bay, middle of Yellow Sea (China) which has a significant impact on the waters adjacent to the estuary In this study, the bacterial abundance and community of seawater in adjacent waters of Dagu River estuary were investigated over four seasons using flow cytometry and high-throughput sequencing techniques. The bacterial abundance showed significant seasonal differences and the average abundance was highest in summer, followed by autumn, and lowest in spring, while the horizontal distribution in winter showed a higher bacterial abundance in nearshore waters. Temperature, phytoplankton abundance and virus abundance were the main factors influencing bacterial abundance. In addition, the dominant taxa of the bacterial community were the same among different seasons, but the relative abundance varied seasonally and there was no significant difference in the bacterial community structure among different stations. Proteobacteria and Bacteroides were the core groups in all seasons. Additionally, temperature and salinity were the major drivers of bacterial community. Moreover, the predicted bacterial functions in investigated waters were mainly focused on carbon and sulfur cycles, and there were seasonal differences in bacterial community function, but the spatial difference was not significant. These results indicated that the bacterial community structure in the waters adjacent to the Dagu River estuary was shaped more by seasonal variation than by spatial variation and provide the basic data and further understanding of characteristics of bacterial community structure in the semi-enclosed shallow bay.