DIVERSITY AND COMMUNITY COMPOSITION OF BACTERIOPLANKTON IN THE BERING SEA DURING SUMMER 2010

Marine bacterioplankton play a key biogeochemical role in the marine ecosystem.To investigate the diversity and community composition of bacterioplankton in the Bering Sea(Arctic Ocean),we collected samples from different depths during the Fourth Chinese National Arctic Research Expedition(2010 summer).Samples were analyzed using DGGE and clone libraries were constructed.In the basin area of the Bering Sea,the Shannon diversity index of bacterioplankton was highest(2.61) from B07-50 m,and lowest(1.99) from B07-3 m.There was greater variability in bacterial diversity within the basin than on the shelf of the Bering Sea,possibly related to complex changes in the marine environment.Through cloning and sequencing,the bacterioplankton was divided into four main phylogenetic groups: Alphaproteobacteria,Betaproteobacteria,Gammaproteobacteria and Bacteroidetes.Gammaproteobacteria dominated the samples,accounting for 53% of all bacteria,with another 37% identified as Bacteroides.The four groups varied in their spatial distribution,Gammaproteobacteria and Bacteroidetes were found at three sites(B07,B13 and B15),Alphaproteobacteria only existed in samples from 50 m and 100 m at B07,and Betaproteobacteria was found in all three sites,except for surface waters of B13.Temperature decreased and salinity increased with depth at the three stations in the B section of the Bering Sea.Generally,nitrate,phosphate and silicate concentrations were greater in the basin area(B07 station) than in the shelf area(B15 and B13 station).Conversely,ammonia concentration was greater in the shelf area than in the basin.