Associated fauna in a mesophotic rhodolith bed in the Campos Basin, Brazil, southwestern Atlantic

Rhodolith beds are predominantly formed by calcareous red algae with a rich benthic fauna. Nonetheless, little is known about the biota relationships with their structural variability. Rhodolith shape, size and vitality were examined from 22 sampling stations in dense and sparse areas of a mesophotic rhodolith bed in the Campos Basin, Brazil located within a major oil production area. Nine taxonomic benthic faunal groups were identified: Mollusca (58 taxa), Polychaeta (51), Echinodermata (27), Crustacea (24), Bryozoa (20), Porifera (19), Cnidaria (6), Ascidiacea (2) and Brachiopoda (1). Cnidaria, Mollusca, Bryozoa and Brachiopoda were abundant in areas with gravelly/rhodolith bottoms, while Polychaeta were associated with sandy/muddy bottoms. The faunal composition in the Peregrino oil field showed greater species richness than observed in other rhodolith beds worldwide. The present study contributes to the knowledge of the structural, taxonomical and functional characteristics of a rhodolith bed present along the Brazilian continental shelf.