Molluscan assemblages in littoral soft bottoms of the Alboran Sea (Western Mediterranean Sea)

Abstract

The structure of the molluscan assemblages inhabiting the subtidal bottoms off the west coast of Malaga province (southern Spain) and their relation to sediment characteristics were analysed with both univariate and multivariate parameters. Five significantly different molluscan assemblages were identified and assigned to ‘sables fins bien calibrés’ (SFBC, well sorted fine sands); ‘détritique côtier’ (DC, coastal bioclastic sands); ‘détritique envasé’ (DE, muddy bioclastic sands); and ‘coralligène’ (CO, coralligenous) biocoenoses of Pérès and Picard classification. A total of 234 molluscan species were identified, with gastropods as the dominant group (135 species). An increase of diversity and evenness with depth has been observed, with the highest values for both indexes on a rocky outcrop, and the lowest in the shallower fine sand assemblage dominated by few species. The different molluscan assemblages inhabiting these sublittoral bottoms were conditioned by depth, percentage of gravel and percentage of clay. A large proportion of tropical West African species is found in the area, some of them reaching their distributional limit towards the Mediterranean Sea. The southern Iberian coasts, in the confluence of Atlantic and Mediterranean waters and between Africa and Europe, are therefore highlighted as one of the areas with highest molluscan species richness in Europe, and require a conservation policy in order to preserve this unique European biodiversity heritage.

Keywords:

• Alboran Sea
• assemblages
• bivalve
• gastropod
• soft bottoms
• species richness

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We would like to express our sincere gratitude to Dr Carmen Salas (Universidad de Málaga) for her comments on this manuscript and her valuable help during the sampling surveys and the identification of bivalve specimens. We would also like to thank José S. Guirado, Fernando Ortega and Rafael Barba (Dirección General de Gestión del Medio Natural) for their help and continuous interest; to the captain and crew of the ship AMA 8 for their cooperation during the sampling campaign; to the colleagues of our department, mainly to Dr J. Enrique García Raso and J. Enrique García Muñoz (members of this Project) for their help and interesting suggestions. We also thank CEMOSA for its collaboration in granulometric analyses and the Department of Ecology and Geology (UMA) for their help in the analysis of organic matter content. This Project has been supported by the ‘Consejería de Medio Ambiente de la Junta de Andalucía’ (contract with the University of Malaga; reference 807/46.2284).

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark