COMMUNITY COMPOSITION, DISTRIBUTION AND DIVERSITY OF INVERTEBRATES FROM DEEPSEA MEDITERRANEAN CANYONS AND ADJACENT SLOPES (FROM 850 TO 3000 M DEPTH). Ariadna Mecho 1*, Eva Ramirez-Llodra 1, Jacopo Aguzzi 1 and Joan Batista Company 1 1 Institut de Ciències del Mar (ICM-CSIC) -
[email protected] Abstract Information of bathyal and abyssal non-crustaceans invertebrates is scarce in the Mediterranean Sea, especially in submarine canyons. The present study presents an updated taxonomical classification for these groups and reports new data on their distribution and density in canyon areas and adjacent open sedimentary slopes. Samples were collected from 220 trawls and 36 ROV dives conducted in the Blanes, Palamós and Cap de Creus canyons and their adjacent slopes (north-western Mediterranean), between 850 and 3000 m depth. The most abundant Phylum was the Echinodermata, representing 52.9% of the total invertebrate density (calculated as ind.•km-²), and 48.6 % of the total invertebrate biomass (calculated as kg.•km-²). Five rare species for the Mediterranean were found: a sipunculid, 3 echinoderms and 1 carnivore ascidian. Keywords: Bathyal, Canyons, Zoobenthos, Systematics, North-Western Mediterranean
The western Mediterranean deep basin is composed by a complex collection of markedly different habitats, including sedimentary slopes, submarine canyons and seamounts. The specific geomorphologic characteristics of these habitats and associated abiotic processes result in large scale heterogeneity of the continental margin, allowing for the establishment and maintenance of diverse faunal communities [1]. In the deep Mediterranean Sea, these communities are mainly constituted by fishes and decapod crustaceans, which have been object of intensive taxonomical studies in comparison with other deep-sea fauna such as echinoderms, sipunculids or echiurans [2, 3]. Here, we present a complete taxonomical classification and we redefine the distribution, biomass and abundance of all non-crustacean invertebrates collected in our surveys in the NW Mediterranean since 2008. Samples were collected during 11 oceanographic cruises conducted in the Blanes, Palamós and Cap de Creus canyons and their adjacent slopes between 850 to 3000 m. A total of 220 benthic hauls were conducted and 36 ROV video transects were performed in the three canyons and adjacent area. Of those hauls, 121 samples were obtained by means of an otter-trawl Maireta system, other 43 hauls were conducted with an Agassiz dredge and finally, 56 samples were obtained with an epibenthic sledge. More than 4686 non-crustacean invertebrates belonging to 60 species were sampled. The most abundant Phylum was the Echinodermata representing 52.9% of the total non-crustacean invertebrate density, followed by the Phyla Brachiopoda (17.4%), Cnidaria (12.9%), Mollusca (10.4%), Echiura (2.7%) and Porifera (2.3%).The Sipuncula, Annelida, Bryozoa, Arthropoda and Chordata together represented 1.1% of the total density. Unidentified specimens represented only 0.3 % (Fig. 1a). In terms of biomass, the Phylum Echinodermata represented 48.6 % of the total non-crustacean invertebrate biomass, followed by the Phyla Cnidaria (22.5 %), Mollusca (19.9 %), and Brachiopoda (7.2 %). All remaining Phyla represented less than 1% each one (Fig. 1b). The most speciose Phyla were the Mollusca (with 23 species) and Echinodermata (with 11 species). From the 60 species identified, five were considered rare in the Mediterranean Sea. These species were the sipunculid Phascolosoma (Phascolosoma) turnerae Rice, 1985, three echinoderms Hedingia mediterranea (Bartolini Baldelli, 1914), Penilpidia ludwigi (von Marenzeller, 1893) and Gracilechinus alexandri (Danielssen & Koren, 1883), and the carnivore ascidian Dicopia antirrhinum C. Monniot, 1972. Additionally,10 from the 60 species identified were only reported inside canyon areas. The results are discussed in relation to the geomorphological and environmental characteristics of the different habitats sampled. Our study presents new information about taxonomical classification of Mediterranean Sea deep-sea non-crustacean invertebrates and increases the geographic and bathymetric distribution of some of these species. Additionally suggests that canyons could be an important habitat for specific species only present inside the canyons and for rare species.
Fig. 1. Non-crustacean community composition. a) Percentage of density (ind.•km-²) by Phylum. b) Percentage of biomass (kg.•km-²) by Phylum.
References 1 - Company J.B., et al., 2012. Submarine canyons in the Catalan Sea (NW Mediterranean): megafaunal biodiversity patterns and anthropogenic threats. In: Würtz M. (ed.), Mediterranean Submarine Canyons: Ecology and Governance. IUCN, Gland and Malaga, pp. 133–144. 2 - Ramirez-Llodra E., Ballesteros M., Company J.B., Dantart L., Sardà F. 2008. Spatio-temporal variations in the diversity, biomass and abundance of bathyal invertebrates in the Catalan Sea (Western Mediterranean). Marine Biology, 153, 297–309 3 - Mechó, A., Billett, D.S.M., Ramirez-Llodra, E., Aguzzi, J., Company, J.B. (submited). Rediscovered species and new bathymetric ranges of deep-sea echinoderms in the Mediterranean Sea (below 850 m depth). Deep Sea Res. Part I.
