Macroalgal- dominated coastal detritic communities from the Western Mediterranean and the Northeastern Atlantic

Abstract

This is a qualitative comparison of the distribution of macroalgal-dominated coastal detritic communities from the Western Mediterranean and the Northeastern Atlantic, based on our own data from the Balearic Islands (Western Mediterranean) and available data from the literature. The macroalgal-dominated coastal detritic bottoms in both regions can be distinguished by the presence of a high number of regional exclusive non-carbonated species, and the presence of a high number of maërl-forming species in the Mediterranean. Furthermore, regional differences in the distribution of some exclusive species allowed the distinction of three zones in the Northeastern Atlantic (United Kingdom, French Brittany and Galicia), while no differences were found in the Western Mediterranean. However, the algal communities considered in the selected literature could not be qualitatively distinguished, and all the samples should be considered as maërl beds. Lithothamnion corallioides and Phymatolithon calcareum were the most widespread maërl forming species in the two regions, while in the Western Mediterranean Spongites fruticulosus was also very frequent. According to the differences in the species composition of the basal and erect strata of these beds, and also in their species richness, five different morphologies of macroalgal-dominated detritic bottoms can be distinguished. Their main characteristic species and their biogeographic distribution are detailed.