Factors shaping viral abundance and community structure in the Southern Ocean

IX Simposio de Estudios Polares del Comité Español del Scientific Committee on Antarctic Research (SCAR), 5-7 September 2018, Madrid, España.-- 1 page

Marine viruses are the most abundant biological entities in marine ecosystems, and due to their life cycle’ they have an impact on biogeochemical cycles, contributing in making life possible in the oceans. These days, there is a large and well-established knowledge on what regards to viruses’ role in the marine ecosystems. They influence the particle size distribution, particle sinking rates, bacterial and algal biodiversity, and the release of organic compounds derived from biological metabolism. However, little is known about the influence that the interaction between environmental and biological factors may have on marine viruses’ communities. In Antarctic and the sub-Antarctic waters, phytoplankton blooms occur during the Austral summer, and is then when viruses and bacteria can reach their greatest abundance and activity rates. These algal blooms are usually dominated by different taxonomic groups: diatoms, dinoflagellates, haptophytes, cryptomones, etc. Besides, phytoplankton communities are accompanied by bacterial communities, and they are influenced by environmental conditions. Then, all these interactions may have a role in the function and structure of marine viruses. To test which are the main drivers contributing to shape viral community distribution and structure, four environmentally contrasting locations were sampled during the Austral summer-2015. Three locations were near Orkney and Anvers Islands close to the Antarctic Peninsula, and one in the South Georgia Islands in the sub-Antarctic Ocean. These locations presented different physicochemical and biological conditions (e.g. temperature, salinity, viral and bacterial abundance, phytoplankton taxa...). We characterized the physicochemical conditions and the phytoplankton community of these locations, and we studied the marine viral community structure by using the fingerprint technique: Randomly amplified polymorphic DNA-PCR (RAPD) that allowed to group similar viral communities. Indeed, the four zones showed dissimilar water column structures due to different temperature and salinity vertical distribution patterns. Through Redundancy analyses (RDA) we observed that temperature and salinity were significantly (p<0.0002) correlated with viral community structure. In general, biological factors (i.e. viral and bacterial abundance, bacterial productivity, and chlorophyll a concentration) were different among zones, meaning different conditions for the development of marine life. South Georgia (sub-Antarctic waters) standed out from the rest of the areas, due to its high biological productivity. The application of RAPD-PCR revealed a grouping behavior of viral communities, that is viral communities within each sampling site were rather similar than among sites. Finally, from the outcome of the above-mentioned RDA analyses, showed that bacterial production, chlorophyll a and inorganic nutrients (p<0.0002) should be qualitatively and quantitatively considered as important variables shaping viral distribution and community structure in the studied Antarctic waters

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