Rhodolith Morphology and the Diversity of Polychaetes Off the Southeastern Brazilian Coast

Rhodoliths modify the physical characteristics of their environment, producing a habitat that can support diverse, associated fauna, where polychaetes often achieve high richness expressed in density and trophic diversity. Nevertheless, there are few studies that describe and identify the fauna associated with this habitat. In this research, specimens were collected from 6 to 18 m depth in Brazilian rhodolith beds: two off the southern coast of Espirito Santo, Brazil, and one in the Abrolhos bank, Brazil. The most common rhodoliths were Lithophyllum corallinae, Neogoniolithon sp., and Mesophylum erubescens. The rhodoliths ranged from large with short branches to small with long branches. Polychaetes at Espirito Santo, Brazil were predominately infaunal, whereas in Bahia, Brazil, they were mainly epifaunal living among finely branched structure. Twenty-six families were identified, four exclusive to Espirito Santo, Brazil, and nine in the Abrolhos, Brazil. The most common families registered different species composition in both rhodolith beds, except for Eunice multicylindris and Arabella mutans found in both regions. Syllidae was the most abundant and species-rich family in Abrolhos, Brazil. Rhodoliths off Espirito Santo, Brazil, hosted polychaetes dominated by burrowers, such as the Lumbrineridae, which were favored by their boxwork structure, built of invertebrates and inorganic material. Rhodoliths on the Abrolhos, Brazil, hosted polychaetes dominated by carnivorous or herbivores families, such as the Syllidae. There is a significant difference between Espirito Santo, Brazil, and the Abrolhos, as reflected by the polychaete taxocoenosis. This is demonstrated by a clear differentiation in species and family composition and also by feeding guilds, indicating how different rhodolith morphologies can affect community structure.