Filling a knowledge gap on the biodiversity of rhodolith-associated Echinodermata from northeastern Brazil

Rhodolith beds formed by non-articulated calcareous algae have been recognized as important habitats for a range of organisms. The Brazilian coast is home to one of the largest beds of the Southwestern Atlantic, but the lack of faunal studies in these habitats represents one of our major gaps in the knowledge of Brazilian biodiversity. This study compares the composition, abundance and diversity of echinoderm species associated with rhodoliths in three different isobaths (10, 15 and 20 m) along the coast of the State of Paraiba, Northeastern Brazil. These rhodolith beds provided 2,855 specimens, representing 32 species from four Classes, of which Ophiuroidea was the most numerous. The echinoderm community was significantly different considering the abundance of individuals (F=452.86, p=0.001) and the number of species (F=45.14, p=0.006) among the three depths analyzed. Abundance and species numbers decrease with increasing depth. Rhodolith beds in the State of Paraiba are an important habitat for echinoderms, harboring a high diversity and abundance of associated species. Richness and diversity records exceed those found in other coastal areas around the world, indicating that these banks are of special relevance for the conservation of echinoderms in Brazil.