46 - Habitat Mapping of a Cold-Water Coral Mound on Pen Duick Escarpment (Gulf of Cadiz)

Abstract

The Pen Duick Escarpment is a 6 km long, NW-SE oriented, 80–125 m high escarpment with a southwest-facing slope of 8–12°. It is located within the El Arraiche mud volcano field on the Moroccan continental margin (southern Gulf of Cadiz) in water depths of 550–650 m. This chapter provides acase study about habitat mapping of cold-water coral mound, Beta Mound, using a multibeam echosounder, ROV observations, and boxcore sampling. This habitat mapping revealed the presence of four different habitats: soft (bioturbated) sediment, soft sediment with patchy coral rubble, dense cold-water coral rubble fields, and rock slabs. All cold-water corals are dead except for one living Dendrophyllia cornigera. The coral rubble consists mainly of dead Dendrophyllia, Lophelia pertusa, and Madrepora oculata. On top of the coral rubble, numerous crinoids were observed, while the soft sediment is mostly colonized by several species of soft corals. Sponges, squat lobsters, echinoids, and holothurians were also observed. Cold-water corals provide hard-bottom substrate, refuge, and nursery for a large variety of species and are therefore considered important biodiversity hotspots. On Beta Mound, several invertebrate and fish species are living in the three-dimensional framework formed by the dead cold-water coral rubble. The megafauna of the coral rubble patches or fields is dominated by crinoids (Echinodermata, Crinoidea), which cover most of the surface of the rubble. Poriferans and crustaceans such as squat lobsters (Decapoda, Galatheidae) are also commonly found on the coral rubble areas. The fish Helicolenus dactylopterus was found in all the four habitats.