Vertical Stratification of Bacterial Diversity in the Ross Sea, Antarctica revealed by 16S rDNA pyrosequencing

Abstract

Marine microorganisms play significant roles in the biogeochemical cycles. In this study, the prokaryotic diversity in the water column from Ross Sea was analyzed by pyrosequencing method. Seawater samples were collected from ten stations using CTD during the expedition of ice breaker ARAON in 2011. We found there was no significant difference in the bacterial communities and environmental factors among sampling sites. In all stations, phylotypes included in three phyla Bacteroidetes, Alphaproteobacteria, and Gammaprotoeobacteria were predominant composing 62% to 99% at all depths and the vertical stratification of bacterial communities in the water column was remarkable. As the sampling depth extended, the proportion of Bacteroidetes decreased while that of Gammaproteobacteria increased. The proportion of Alphaproteobacteria was relatively consistent along a vertical profile. Also as the sampling depth extended, relative abundance of phylotypes included in phyla or candidate phyla such as Deltaproteobacteria, SAR406, and Verrucomicrobia that were not found at all or very few were found in the surface community were increased.ns using CTD during the expedition of ice breaker ARAON in 2011. We found there was no significant difference in the bacterial communities and environmental factors among sampling sites. In all stations, phylotypes included in three phyla Bacteroidetes, Alphaproteobacteria, and Gammaprotoeobacteria were predominant composing 62% to 99% at all depths and the vertical stratification of bacterial communities in the water column was remarkable. As the sampling depth extended, the proportion of Bacteroidetes decreased while that of Gammaproteobacteria increased. The proportion of Alphaproteobacteria was relatively consistent along a vertical profile. Also as the sampling depth extended, relative abundance of phylotypes included in phyla or candidate phyla such as Deltaproteobacteria, SAR406, and Verrucomicrobia