Ecological succession of pico- and nanophytoplankton in a coastal bay of NW Mediterranean sea

The long-term evolution of pico-and nanophytoplanktonic communities in two coastal contrasting sites from the bay of Toulon was studied using monthly flow cytometry analyses during a seven-year period. Results high-lighted higher abundance of both pico-and nanophytoplanktonic communities in the more eutrophic site (i. e. the Little Bay). Moreover, even if both sites were widely dominated by Synechococcus spp. population, it rep-resented more than 90% of the population during summer in the Large Bay. Using diversity indices and rank frequency diagrams to study ecological successions in both sites, communities from the Little Bay (the most polluted site) appeared, paradoxically, as more diversified and more mature than that from the Large Bay. Communities from the Large Bay appeared as less diversified and juvenile linked to the dominance of Syn-echococcus spp. The complementarity of diversity indices and rank frequency diagram was revealed in this present work.

Automated summary

The long-term evolution of pico-and nanophytoplanktonic communities was studied in two contrasting coastal sites from the bay of Toulon using monthly flow cytometry analyses over a seven-year period. The more eutrophic site showed higher abundance of both pico-and nanophytoplanktonic communities. Despite the dominance of Synechococcus spp. population in both sites, it accounted for over 90% of the population during summer in the Large Bay. The use of diversity indices and rank frequency diagrams revealed that the more polluted site had a paradoxically more diversified and mature community compared to the less diversified and juvenile community in the Large Bay, which was attributed to the dominance of Synechococcus spp.