Diversity and distribution of nano- and picoeukaryotes in the Southern Ocean as revealed by 454-pyrosequencing, clone libraries and microscopy

Summary

In this study we explored the diversity and distribution of planktonic nano- and picoeukaryotes in Antarctic waters by combining 454-pyrosequencing, clone libraries and electron microscopy. Water samples were collected and physico-chemical parameters measured during summer 2008 with the Norwegian R/V G.O. Sars in the Atlantic sector of the Southern Ocean, at stations along a transect (15°E) between 45-67o S. Ribosomal DNA of plankton in the size range 0.8-35µm was amplified with universal eukaryotic and haptophyte specific primers followed by pyro- and Sanger sequencing. Most rDNA sequences could not be assigned to a cultured and sequenced species (at ≥99,3% identity level) indicating that a large fraction of the plankton community remains to be genetically characterized. Electron microscopy revealed some of this diversity, but more cultured strains are needed as reference for a precise identification. The taxonomic groups represented with highest number of clones/reads were dinoflagellates, stramenopiles and haptophytes. The species composition was significantly different at the northernmost station compared to further south, suggesting that nano- and picoeukaryote species composition and distribution may serve as indicators of climate change in polar waters.