Contribution to the knowledge of prosobranchs of Mauritanian deep-waters (Northwest Africa)
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1
Facultad de Ciencias del Mar, Universidad de Vigo, Spain
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2
Instituto Español de Oceanografía, Spain
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3
Institut Mauritanien de Recherches Océanographiques et des Pêches, Mauritania
Mauritanian waters harbour one of the most productive marine ecosystems of the world, due to the upwelling phenomena associated to the Canary current and the influence of trade winds (Pastor et al., 2008; Pellegri & Benazzouz, 2015). Mauritania represents the boundary between the temperate Lusitanian and the Tropical Eastern Atlantic Provinces (Briggs, 1995) and it is located within the northern alternance region of the tropical eastern Atlantic (Loeuff & von Cosel, 1997). The seasonal displacement of the thermal front along this area promotes faunistic exchanges and the Mauritanian fauna results a combination of both, temperate and tropical elements, that enhance its biodiversity (van Soest, 1993; Loeuff & von Cosel, 1997).
Nevertheless, and despite the interest of this area, only Duinevelt et al. (1993) and Michel et al. (2011) have studied the composition and assemblages of mollusks fauna of Mauritanian shelf; but their study area covered only the Banc d’Arguin (northern zone) to 370 m depth. In consequence, the current knowledge of the structure and composition of the gastropod communities off Mauritania is scarce, especially in deep waters.
This work is the result of the study of prosobranch collected along the Mauritanian coast during the four Spanish Maurit surveys and the two CCLME cruises carried out between 2007 and 2012, within the framework of EcoAfrik and CCLME-FAO projects.
The samples were mainly collected with a commercial trawl, but during the Maurit surveys a beam trawl and a rock dredge were also employed. Prosobranchs were on board sorted from the total catch to morphospecies level, and after counted and weighed. For each sample living specimens of the different morphospecies were photographed and a representative collection was preserved in 70% ethanol for further studies
A total of 7717 prosobranchs were captured in 113 of the 449 hauls carried out along Mauritanian shelf and continental slope, between 20 and 1867 m depth. We identified 68 species belonging to 24 families. The most specious families were Naticidae with 9 species, followed by Marginellidae (8 species) and Muricidae (7 species). The highest occurrence was recorded for Nassarius wolffi (63 stations, 14.0%), followed by Xenophora crispa (28 station, 6.2%), Afer pseudofusinus (28 stations, 6.2%) and Sveltia lyrata (19 stations, 4.23%). Fourteen species are by first time reported in Mauritanian waters, increasing our data the bathymetric ranges fifteen species.
A preliminary analysis of bathymetric distribution reveals a progressive decreasing of specific richness with increasing depth. Densities progressively decreases to 150 meters, in which it increases to 700 m, where decreases again; the increase in abundance between 150 and 700 m is due to the presence of Nassarius wolffi. Biomass decreases sharply to 50 m and remains more or less constant at deeper waters. Deeper than 1400 m prosobranchs were not collected.
References
Briggs, J.C. (1995) Global Biogeography. Developments in Palaeontology and Stratigraphy 14. Elsevier Science, Amsterdam.
Duineveld, G.C.A., Lavaleye, M.S.S., Noort,G.J. (1993). The trawlfauna of the Mauritanian shelf (Northwest Africa): density, species composition, and biomass. Hydrobiologia, 258: 65-173.
Le Loeuf, P., von Cosel, R. (1998). Biodiversity patterns of the marine benthic fauna on the Atlantic coast of tropical Africa in relation to hydroclimatic conditions and paleographic events. Acta Oecologica, 19(3): 309-321.
Michel, J., Westphal, H., von Cosel, R. (2011). The Mollusk fauna of soft sediments from the tropical, upwelling-influenced shelf of Mauritania (Northwestern Africa). Palaios, 26: 447-460.
Pastor V., Pelegrí J.L., Hernández-Guerra A., Font J., Salat J., Emelianov, M. (2008) Water and nutrient fluxes off Northwest Africa. Cont. Shelf. Res., 28: 915-936.
Pelegrí, J.L., Benazzouz, A. (2015) Coastal upwelling off North-West Africa. In: Valdés, L., Dénis-González (eds). Oceanographic and biological features in the Canary Current Large Marine Ecosystem. IOC Tech. Ser. 115. IOC-UNESCO, Paris, p 81-92.
Van Soest RWM (1993) Distribution of sponges on the Mauritanian continental shelf. In: Wolff WJ, Van der Land J, Nienhuis PH, Wilde PAW (eds). Ecological Studies in the Coastal Waters of Mauritania. Hydrobiologia 258:95–106.
Keywords:
Prosobranchia,
Biodiversity,
deep-sea,
Mauritania,
Northwest Africa
Conference:
XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.
Presentation Type:
Poster Presentation
Topic:
1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS
Citation:
Oñate
SC,
Ramil
F,
Mohamed
S and
Ramos
A
(2016). Contribution to the knowledge of prosobranchs of Mauritanian deep-waters (Northwest Africa).
Front. Mar. Sci.
Conference Abstract:
XIX Iberian Symposium on Marine Biology Studies.
doi: 10.3389/conf.FMARS.2016.05.00168
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Received:
03 May 2016;
Published Online:
03 Sep 2016.
*
Correspondence:
PhD. Sara C Oñate, Facultad de Ciencias del Mar, Universidad de Vigo, Vigo, PONTEVEDRA, Spain, saracastillo@uvigo.es