Objectives

          To achieve this objective, the diversity of procaryotes has been investigated all over the water column from surface to the mesopelagic realm. Diatoms are classically mentioned as the major primary producers in the SO and their diversity was described in detail in previous studies. By contrast, other phytoplankton groups such as haptophytes and dinoflagellates were far less studied, and MOBYDICK payed special attention to these organisms as recent findings suggest their importance for vertical C export efficiency even in the Southern Ocean. Focus has also been put on potential parasites, organic matter decomposers and endosymbionts that represent other functional groups that were missed by classical approaches. Within micro– (20–200 μm) and mesozooplankton (200 μm–2 cm), organisms such as pteropods have also been overlooked although evidence from zooplankton community studies indicates that they are consistent, and sometimes dominant components of the Southern Ocean zooplankton. Heterotrophic dinoflagellates have previously been identified as the most important group of phytoplankton grazers in the Kerguelen region, shedding new light on the roles of dinoflagellates and ciliates in the transfer of C to mesozooplankton. Within macrozooplankton / micronekton (2–20 cm), copepods and krill were intensively studied. By contrast, our knowledge on other macrozooplankton remains limited, and of particular interest in the SO are gelatinous zooplankton including salps and ctenophores. Finally, the lack of consideration for myctophids (lanternfishes) and other nektonic organisms such as squids, whereas they form a major component of fish biomass , has led to a simplistic vision of a general central role of the krill Euphausia superba in food webs of the Southern Ocean. MOBYDICK fills this gap by providing a detailed description of of the biological diversity associated to these groups.