TEMPORAL VARIATION IN PLANKTONIC PROTISTS AND ASSOCIATED BACTERIAL COMMUNITIES IN SCAPA FLOW, ORKNEY, U.K.. TEMPORAL VARIATION IN PLANKTONIC PROTISTS AND ASSOCIATED BACTERIAL COMMUNITIES IN SCAPA FLOW, ORKNEY, U.K.

Planktonic microbial eukaryotes and their associated bacterioplankton are highly important components of biogeochemical cycles. Complex associations and interactions exist between specific phytoplankton and bacterioplankton taxa that are essential for carbon cycling. We looked at composition and interactions in bacterioplankton and protist communities in the western North Sea around the Orkney Islands, Brings Deep, Scapa Flow, these islands and their surrounding waters are of both ecological and anthropogenic importance. Samples were collected monthly across Spring-Summer 2010 and Spring-Summer 2011. Using High-throughput sequencing we profiled the protist and associated bacterioplankton community. The study provides the first detailed assessment and site characterisation of microbial communities within the waters of Scapa Flow and shows that taxonomic composition of both phytoplankton and bacterioplankton are similar to those of the western English Channel and eastern North Sea. There were distinct transitions from spring to summer in phytoplankton associated bacterioplankton communities and a highly variable protist community from each sampling point both from month to month and between years. We found a diverse range of protist taxa dominated by diatoms and dinoflagellates and we were able to detect several harmful algal taxa which were also confirmed as present in cell counts. We then looked in detail at correlations between known phytoplankton associated bacteria orders: Alteromonadales, Flavobacteriales, Rhodobacterales and Verrucomicrobia and the dominant protist taxa, the diatoms and dinoflagellates. We were able to show correlations between many of the algal taxa and bacterioplankton from these orders, particularly the marine group Flavobacteriales and the Marine Roseobacter Clade with a range of diatom and dinoflagellate taxa. This provides further evidence that these groups are highly important, widespread, phytoplankton associates providing data on potential new relationships for hypothesis testing.