Modélisation d’habitat des coraux d’eau froide dans le canyon de Lacaze-Duthiers, Golfe du Lion, Méditerranée occidentale

Submarine canyons are deep, sloping geological structures containing a variety of habitats such as boulders, vertical walls and sedimentary strata that support the development of cold-water corals, including the scleractinian Desmophyllum pertusum and Madrepora oculata, which can form impressive masses. These species are included on the IUCN Red List with the status "Endangered". It is therefore necessary to know their distribution in order to assess human impact and implement conservation and/or restoration actions. This study is based on videos recorded during 4 oceanographic campaigns (MEDSEACAN, MARUM, CALADU 2019 and CALADU 2021). Two methods (MaxEnt and GLM) were used to model and map the distribution of suitable habitats at different scales. The 10 m resolution was used to compare the distribution of corals (without distinction of species) predicted by the two methods on the overall canyon. The MaxEnt method predicted a slightly smaller surface area of suitable habitats (10.87 km²) than the GLM method (12.14 km²). These habitats are mainly located in the head and flanks of the canyon. Slope is the field variable with the highest contribution (around 70% with Maxent and 65% with GLM), followed by roughness and depth, with different contributions depending on the method, always below 20%. In addition, the 5 m resolution made it possible to characterize favorable habitats separately for each species. The habitat of D. pertusum extends to the lower flanks and south of the canyon, while that of M. oculata is restricted to the upper flanks in the north of the canyon. Explanatory variables also include slope, depth and roughness, as well as northern exposure, which is a proxy for major currents. Thus, the habitat predicted by the models for D. pertusum is on average less steep, less rough and deeper than that of M. oculata, but more dependent on orientation in relation to the prevailing currents.