| Summary: | Mauritanian slope is one of the most interesting marine regions in the East Atlantic, both at geomorphologic and hydrological levels, characterized by enormous mud-slides, wide and deep canyons and a giant cold-water coral reef, as well as sedimentary features influenced by the Saharan dust, Canary Current and upwelling system. Little was known on the biodiversity and composition of the deep benthic ecosystems in Northwest Africa until the onset of the Spanish multidisciplinary research program (Maurit surveys). The four Spanish cruises carried out annually between 2007 and 2010, covered with multibeam echosounder the totality of the area, performing a lot of oceanographic and biological stations using different sampler gears. It has allowed a detailed cartography of the upper and middle slope, the characterization of the main vulnerable habitats and a first overview of the epibenthos biodiversity. Obvious differences in diversity and composition between soft and hard bottoms assemblages exists. In sandy and muddy bottoms (approximately the 95% of slope between 120 and 2000-m depth) epibenthos diversity only reached mean values of 22 species by station (γ diversity > 700 species, in 283 trawling stations). Biomass and abundances are dominated by detritovore holothuroids and scavenger decapods, specially the holothuroids Enypniastes eximia, Bentothuria funebris and Paelopatides grisea, which account for more than 80% of the total biomass. Hard bottoms, such as the living coral-reef areas (southern Mauritania), Arguin and Timiris canyons, and the small seamount discovered during the Maurit surveys, exhibited diversity values comprised between 50 and 80 species. In this case, benthic assemblages are dominated by suspension-feeders in a proportion of 75–80%. The most representative species are Lophelia pertusa, Geodidae and other Demospongiae, the bivalves Acesta excavata and Neopycnodonte zibrowii, and the ophiuroid Ophiothrix maculata. Despite the existence of important suspension-feeder communities along the ...
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