Contrasting Bacterial Dynamics in Subtropical Estuarine and Coastal Waters

Abstract

Seasonal succession and composition of both attached and free-living bacterial communities were studied in subtropical estuarine and coastal waters with contrasting hydrographic conditions. A higher abundance of attached bacteria was recovered in the estuarine waters containing high concentrations of dissolved organic carbon (DOC) resulting from the freshwater discharge in the adjacent Pearl River, and Proteobacteria, including α-, β-, and γ-groups, predominated the attached community at both stations. Free-living bacterial communities at both stations showed higher diversity and lower seasonality than their attached counterparts, and α-Proteobacteria accounted for the highest proportion at both stations. Redundancy analysis (RDA) demonstrated that, in addition to the obvious temperature effects, DOC and microphytoplankton (>20 μm Chl a) drive the temporal variation of attached bacteria at the estuarine and coastal stations, respectively. On the other hand, picophytoplankton ( 20 μm). These findings suggest that temperature and bottom–up effects play a more important role for the spatial–temporal variations of both attached and free-living bacterial communities in the subtropical estuarine and coastal waters.