Species composition and patterns of diversity of macroalgal coralligenous assemblages in the north-western Mediterranean Sea

This paper contributes to the knowledge of macroalgal coralligenous systems. The species composition of coralligenous assemblages of Tuscany's coasts and islands (north-western Mediterranean Sea) was examined and different aspects of alpha and beta diversity were evaluated. The encrusting layer of coralligenous habitat in the study areas mostly comprised the Corallinales Mesophyllum alternans. A total of 187 epiphytic macroalgal species was observed, among them 29 Ochrophyta, 14 Chlorophyta and 144 Rhodophyta. In the studied area, coralligenous assemblages show a similar structure across large scales, as 41 species were common to all the studied locations. Multivariate analysis showed that locations along continental coasts were distinct from islands. Vertical and horizontal substrata were distinct on islands, but not in coastal locations. The studied assemblages showed a high diversity, especially in relation to the smaller spatial scales examined.