The biogeography of ectotherm species in the Southern Ocean is partly determined by temperature, as seems to be indicated by species' spatial distribution with respect to the latitudinal heat gradient.

The REPCCOAI 2018 cruise proposed to (1) pursue continuous sampling of mesozooplankton with a Continuous Plankton Recorder and (2) sample mesozooplankton at a few stations using a WP2, and macrozooplankton (mainly Euphausiacea) and mesopelagic fish with an Isaacs Kidd Midwater Trawl.

This is the second of four cruises combined with OISO cruises for oceanographic surveys and THEMISTO cruises for acoustic surveys. It will study the spatial distribution of pelagic diversity from the subtropical zone to the Antarctic zone in the Indian part of the Southern Ocean.

Current models predict that subantarctic and subtropical zones will shift southward due to global warming, limiting the Antarctic zone to the South of the Antarctic Polar Front. These transition zones are where the strongest biogeographical gradients are observed as well as the abundance of plankton and mesopelagic fish which are prey for numerous bird and marine mammal species.

The related projects are Southern Ocean Continuous Plankton Recorder, CNRS's Zone atelier Antarctique and MESOPP (H2020).