Bacterial Diversity In Surface Water Of The Yellow Sea During And After A Green Alga Tide

From May to August2008, there was a gigantic green alga (Enteromorpha prolifera) tide in the centre of the Yellow Sea, China, which impacted the marine ecosystem and human activities. Based on the bacterial16S rRNA gene clone libraries, the influence of the green alga tide on the microbial community in surface seawater was estimated in four sites from July to August2008. We hope useful clues could be provided for further studies on the interactions and relationship between the green tide and the microbial community in surface seawater.The surface seawater samples used in this study were collected from four sites in the Yellow Sea, China by open-cruise R/V Beidou. Approximately200L of surface seawater from each site were collected in July (J1, J16, J20and J25) and August (A15, A23-2, A23and A13)2008, and the microbes were collected by cassette pressure filter through0.22μm membrane filters that were sealed and stored at-20℃until transport back to the laboratory stored at-80℃for later molecular analysis. Total DNA was extracted for PCR amplifications of the16S rRNA gene. A total of eight16S rRNA gene clone libraries were constructed. Clones with the correct-size fragment were further screened by RFLP, then clones with identical restriction patterns were selected for sequencing and further analysis.The228clones with unique pattern analyzed by RFLP were sequenced and fell into six bacterial phylums (Proteobacteria, Bacteroidetes, Cyanobacteria, Verrucomicrobia, Actinobacteria, Planctomycetes) taxonomically, domained by Alphaproteobacteria (33%), Gammaproteobacteria (25%), Bacteroidetes (23%) and Cyanobacteria (9%). Comparison between samples in July (J:during green alga tide) and August (A:after green alga tide) showed that the microbial community diversity of Alphaproteobacteria and Cyanobacteria rised after the tide but that of Gammaproteobacteria and Bacteroidetes decreased apparently. which indicated that the green alga tide did have influence on the microbial community in surface seawater.