Diversity, community structure and habitat use of molluscs in marinas from the Iberian Peninsula and Northern Africa

Although the number of marinas along shorelines has significantly increased during the last years, there is a lack of studies on mobile epifauna associated to floating pontoons or infauna inhabiting soft bottoms of marinas. Artificial hard substrate (lateral surface of pontoons) and soft substrate (sediment) were sampled in 42 marinas along the Iberian Peninsula and Northern Africa and 48 different species of molluscs were found. Species richness and Shannon diversity values were higher in sediments than in hard substrates; multivariate analyses also revealed differences in species composition and trophic guilds between these two habitats. The most abundant species on the hard substrate were Mytilus galloprovincialis and Musculus subpictus, and Corbula gibba and Parvicardium exiguum in sediments. Although filter feeders were dominant in both habitats, herbivorous species were only found on the hard substrate while deposit feeders were restricted to sediments. As diversity, abundance and trophic patterns were not always consistent for all localities, a local scale effect must be considered in environmental programs for marinas. None exotic mollusc was detected, so this study provides baseline information necessary as a first step in monitoring programmes for early detection of new incoming exotic species. Faunistic knowledge is mandatory to provide local governments, policy makers and authorities with readily accessible species datasets and ecological information. This should be a priority to address an integrated and sustainable management of marinas.