Diversity and distribution of bacterioplankton in the coastal upwelling waters off Hainan Island, China

The diversity, community composition and 16S rRNA gene abundance of bacterioplankton along a transect across an upwelling area off the eastern coast of Hainan Island (the Qiongdong upwelling) were investigated in August of 2016 using high throughput sequencing and quantitative PCR assay of 16S rRNA genes. Compared with the offshore stations, the inner-shelf stations had higher bacterial gene abundance (up to 3 fold) and operational taxonomic unit richness, a result of the influence of upwelled and fresher waters. Overall, a majority of the reads were affiliated with Gammaproteobacteria (11%–74%) and Alphaproteobacteria (14%–43%). The structure of the bacterial community was significantly affected by salinity, dissolved oxygen, NO 3 − and NH 4 + , which also defined the physicochemical features of the upwelled waters. Horizontally, the relative abundances and gene abundances of Rhodobacteraceae , SAR86, Cyanobacteria and Bacteroidetes in eutrophic zone decreased from the inner to outer shelves and slope, whereas Alteromonas, Vibrio and Oceanospirillaceae exhibited an opposite trend. This study stresses the riverine influence on the oceanographic condition and spatial variability of bacterioplankton diversity and distribution in the Qiongdong upwelling.