Patterns of diversity in rocky subtidal macroalgal assemblages in relation to depth

Abstract

Abstract One of the peculiarities of subtidal rocky assemblages of the Mediterranean Sea in comparison to other geographical regions is the development of important biogenic structures in deeper habitat that can influence coastal diversity. We compared species composition, alpha diversity, functional diversity and patterns of spatial variability between shallow and deep subtidal macroalgal assemblages of the Mediterranean Sea. Shallow and deep assemblages differed greatly both in species composition and abundance of morphological groups, leading to high between-habitat (beta) diversity related to a depth gradient. Moreover, patterns of spatial variability changed between habitats, resulting in greater large-scale variability in shallow habitat and greater small-scale variability in deep habitat. Finally, deep assemblages had a greater number of species than shallow assemblages. These findings have important implications for the management of Mediterranean coastal systems.