Spatial Variability of Microbial Communities in the Ross Sea, Antarctica

Antarctic microbial communities play a vital role in many of the major biogeochemical cycles that occur throughout regions of the Southern Ocean. In late austral spring to summer, openings in sea ice, known as polynyas, are hotspots for biological production. Polynya-associated phytoplankton blooms are typically dominated by specific eukaryotic taxa, Phaeocystishave been reported to occur mainly in the austral spring and early summer, while diatoms are more common towards the end of the summer. It has been proposed that recent temporal differences in the dominant phytoplankton species may be associated with warming temperatures and phytoplankton blooms have been associated with subsequent changes in the prokaryotic community. Interactions between phytoplankton blooms, the microbial community, and nutrient-flux in Antarctic marine systems are still not fully understood. We utilized next-generation Illumina Miseq sequencing to investigate the community structure of both prokaryotes and eukaryotes collected from depth profiles at eleven sites from the Ross Sea polynya from December 2004 to January 2005. Chloroplast/mitochondrial 16S rRNA sequences indicated that the phytoplankton bloom was dominated by the diatom genus Pseudo-nitzchia and that Syndiniales was the dominant eukaryotic taxa based on 18S rRNA gene sequencing. The prokaryotic 16S rRNA gene sequences were dominated by SAR 11, Oceanospirilalles, and Flavobacteriales. Both prokaryotic and eukaryotic communities in surface waters (0-30 m) were similar across all stations. Greater horizontal and vertical variability was seen below 30 m. Further analyses will investigate the relationships between community composition, microbial production, and biogeochemical parameters.