Marine unicellular eukaryote succession Targeted Locus (Loci)
Diversity and succession of unicellular eukaryotes based on TAG-pysosequencing were studied in the Eastern English Channel (EEC) during the 2009 winter to summer succession. We expected that pyrosequencing would allow to expand the breadth the known planktonic diversity and include novel and overlooked organisms in the planktonic succession pattern. A tentative phylogenetic tree analysis, showed that the 72 most abundant unique OTUs belonged to 15 known major taxa and three unaffiliated clades. Three of the five most abundant OTUs belonged to overlooked groups (Cercozoa, Ascomycota, and an unaffiliated eukaryote). Numerous, overlooked higher taxa such as Cercozoa, Eustigmatophyceae, Labyrithulomycetes, Telonemia, Ichtyosporea, Picobiliphyta were included in the data set. Network analysis between dates clearly showed the plankton community succession defining the pivotal dates between the winter conditions, the extensive spring bloom and the separation of the early summer diatom communities from the previous ones. The OTUs-based network revealed that Fungi were connected with all major taxonomic groups except Haptophyceae and Dinophyceae. The Cercozoa were mostly connected with the Fungi, the Bacillariophyceae and several of the miscellanea OTUs. Overall, pyrosequencing allowed to complement the succession pattern increasing the depth taxonomic resolution in the different groups. Additionally, data analysis implied that the food web model based on predator-prey (e.g. phytoplankton -grazers) relationships is just a part of the ecological picture and that overlooked organisms exploiting a variety of neglected trophic strategies, such as saprotrophy and parasitism are persistent and abundant members of the community.