Deep-sea coral habitats off the north atlantic Morocco: Distribution and associated communities.

Abstract

The recent decline in the health status of deep-sea habitats around the world has pushed the need to document and map their distribution to preserve them in their marine ecosystems. This work describes deep-water coral habitats (133-729 m) and their associated communities, based on nine ROV video transects. These transects cover a 171 km sub-seafloor profile within a predefined 5560 km² area along the North Atlantic coast of Morocco, surveyed in 2020 as part of a coral habitat mapping study under the FAO-NANSEN programme. The nine sites were initially explored using multibeam echosounder, to generate a detailed bathymetry map allowing for the positioning of video transects. Megafauna and sediment composition was recorded along transects, and in total 1854 individuals were annotated, and 59 taxa were identified. To identify coral communities and related species assemblages, we used a cluster analysis for classification and the ordination analysis Detrended Correspondence Analysis (DCA) to identify the environmental drivers behind the community patterns. Eight environmental variables were compared with the DCA ordination results, and the important variables were bedrock, mud and depth. The results revealed six megabenthic communities. Three groups were associated with soft sediments, mainly mud. Group I, at depths of 605-726 m, was characterized by Ceriantharia and Synaphobranchus kaupii. Group V, at 133 m depth, was dominated by Ceriantharia. Group VI, consisting of Centrostephanus sp. and a fish community (Scorpaenidae, Capros aper, and Macroramphosus sp.), was found at 201 m depth. In mixed bottoms, where mud is the dominant substrate, Group II was characterized by Crinoidea and sea pens (Funiculina quadrangularis and Virgularia mirabilis) at a depth range of 207-369 m, while Group III, found at depths of 465-602 m, was characterized by sea pens (Pennatula phosphorea and Funiculina quadrangularis), Crinoidea, and the key species Isidella elongata. Group IV, at 207 m depth, was represented by Sertularella sp. and Ellisella paraplexauroides as the dominant species. This first study about mapping deep sea coral habitats in the North Atlantic coast of Morocco reveals the identification of different habitats and new species. It contributes to Strengthen Science for Conservation and Sustainable Management of Deep-Water Corals in Morocco.