Benthic diversity of the soft bottoms in a semi-enclosed basin of the Mediterranean Sea

The benthic diversity of the soft bottoms in the Taranto Seas (Mar Grande and Mar Piccolo) (eastern-central Mediterranean Sea) was studied during July 2002. Quantitative samples were taken using a Van Veen grab and granulometric analysis of the sediment was carried out. A total of 131 species were identified. Molluscs and annelids made up 77% of the species and 87% of the individual number. Data from these two groups were used for hierarchical clustering and multidimensional scaling. The diversity was calculated using the rarefaction method. Two main benthic species assemblages were identified. The first corresponded to the stations characterized by pelitic sediment and located in the Mar Piccolo, the second was made up by the stations with pelite with increasing percentages of sand and distributed in the Mar Grande. The first assemblage consisted of species that usually live on muddy bottoms rich in organic matter; the second consisted of a greater number of species, usually occurring on different types of bottoms. Diversity was found to be higher in the Mar Grande than in the Mar Piccolo, indicating that physico-chemical alterations of the environment probably play a leading role in controlling community structure.