Preliminary characterization of Vulnerable Marine Ecosystems and associated communities of Chella Bank (Alboran Sea, W Mediterranean)

Poster presentation at ATLAS 3rd General Assembly.

Seamounts may promote the presence of vulnerable marine ecosystems (VMEs) worldwide. In the Alboran Sea (W Mediterranean Sea), the Chella Bank (locally known as “Seco de los Olivos”) is a seamount that covers ca. 100 km² and is under the influence of different water masses in this important Atlanto-Mediterranean biogeographical transition zone. During the MEDWAVES expedition (September-October 2016) within the frame of the H2020 ATLAS project, biological and sediment samples collected with Van Veen dredge and ROV underwater videos were obtained in sedimentary and coral rubble bottoms of Chella Bank. The analyses have revealed a diverse invertebrate community associated with these bottoms containing abundant cold-water coral (CWC) remains (mainly Madrepora oculata and Lophelia pertusa), which provide complex heterogeneous microhabitats to many different taxa. The community associated with the coral rubble bottoms is mainly composed of different genera of bivalves (Mendicula, Limopsis, Asperarca), gastropods (Gibberula, Epitonium), small crustaceans (class Malacostraca), polychaetes (Eunice), ophiuroideans (Ophiothrix), bryozoans (order Cyclostomata), hydrozoans (Cryptolaria), poriferans (Terpios, Haliclona) and brachiopods (Megathiris, Megerlia), among other taxa. Furthermore, the megafauna include cnidarians (Bebryce, Acanthogorgia, Dendrophyllia), sponges (Pachastrella) and dense shoals of the carangid fish Caranx rhonchus. Unlike coral rubble bottoms, macro- and micro-fauna inhabiting close sandy, muddy or hemipelagic muddy habitats seems less diverse (up to four times in terms of abundance and species richness). These communities are mainly composed of polychaetes, small crustaceans and bivalves (Abra, Ennucula, Yoldiella), together with shoals of the ammodytid fish Gymnammodytes cicerelus. Coral rubble bottoms of Chella Bank may therefore represent an interesting habitat for conservation, harboring a good representation of the biodiversity linked to CWC communities. This study increases the scarce information on biodiversity and biogeography (WP3) for this area that probably favors the connectivity of CWC associated fauna (WP4) between the Atlantic and Mediterranean basins.