Southern Ocean Trophic Changes from Phytoplankton to Upper Predator (SOTroC) – SOTroC

SOTroC investigate how atmospheric-oceanographic conditions influence the orientation of the southern ocean food webs. To do so, SOTroC will determine whether inter-annual variations in atmosphere-ocean forcing conditions translate into the emergence of contrasted food webs within the Southern Ocean (SO), cascading from phytoplankton to Mid Trophic Levels (MTL) composition and their consequences on foraging performances of an apex marine predator, the southern elephant seal (SES). SOTroC will address three main questions: 1) Are the winter-spring Mixed Layer Depth and stratification properties influence on the emergence of contrasted phytoplankton communities (WP1)? 2) Do the composition and biomass of MTL varies according to different phytoplankton communities (WP2)? 3) Do the foraging success of SES varies according to the composition and biomass of phytoplankton and MTL communities (WP3)? To achieve this we will take advantage of i) existing long-term in-situ physical, biogeochemical and biological data sets, mainly collected by seals as part of the SNO-MEMO, completed by those provided by oceanographic vessels, Argo floats and satellite. SOTroC will also benefit from Marion Dufresne i) echosounding data to assess MTL and ii) flux cytometer data provided by the for in-situ identification of phytoplankton species to validate satellite assessment of the composition of phytoplankton communities. In addition, a new breakthrough biologger designed to assess MTL abundance and composition deployed on SES. The originality and strength of the project relies on a trans- and multi-disciplinary approach associating researchers from four laboratories (LOG, LOCEAN, MIO, CEBC) studying the SO. With new-developed technological advances and numerous sampling platforms in a holistic and global approach, SOTroC will contribute to a better understanding of SO food web and ecosystems processes and therefore to the improvement of future projections in relation to climate change.