Alice Della Penna (LOCEAN-IPSL, France); Cécile Bon (CEBC, France); Charles André Bost (CEBC, France); Christophe Guinet (CEBC, France); Philippe Koubbi (UPMC, France); Cedric Cotté (MNHN, France)

Ocean ecosystem services are under increasing pressure from fishing, traffic, pollution, mining and climate change. These threats are being addressed by policy makers with several initiatives (like the French "Plan for reconquering biodiversity") which aim at extending natural reserves to cover more than the current 3% of the ocean surface. This initiatives provides a valuable opportunity for satellite data analysis, and in particular for altimetry which can be used to identify the physical features like fronts, filaments and eddies that structure in space pelagic ecosystems. Focusing on the Crozet archipelago oceanic area (Indian Sector of the Southern Ocean), we have explored the role of altimetry for Marine Protected Areas by integrating telemetry data of marine predators with Lagrangian tools. Our analysis is based on a recent result, where we had showed that satellite-derived coherent structures of transport do not entrain only drifting organisms like phytoplankton and zooplankton, but also predators. By comparing animal trajectories to the coherent transport structures present in the region, we could identify a highly dynamical branch of the subantarctic front as an important foraging hotspot. By tracking this feature in historical altimetry data, the position of this foraging ground has been then extrapolated beyond the years in which animal tracking data is available, providing a map of its average density probability. This interannual analysis is also instrumental for testing how the position of the region is affected by regional modes of climatic variability and in turn by trends under plausible scenarios of climate change. Our results show how altimetry, and in particular high resolution data from future missions like SWOT, can respond to emerging societal needs like planning marine reserves in the open ocean.