First assessment on Southwestern Atlantic equatorial deep-sea coral communities

Abstract

Deep-sea coral communities are poorly known in the Southwestern Atlantic (SWA), particularly in the equatorial/subequatorial latitudes embraced by the northeastern Brazilian Exclusive Economic Zone (EEZ). Such knowledge gap has lead to the idea that the latter has low species richness when compared to southern Brazilian regions. Recent studies, however, indicate the northeastern slope as highly suitable for deep-sea coral habitats. Herein, based on recent sampling efforts, we confirm that deep-sea coral richness in that region is higher than previously thought. Trawl surveys carried out in 2011 at the Potiguar Basin, Rio Grande do Norte State, yielded the identification of at least 51 coral species, including 28 octocorals, 16 scleractinians, and seven antipatharians, including five new records for the South Atlantic and 11 new occurrences for the northeastern Brazilian waters. Comprising 29 species, the upper slope communities (102–200 m) showed the highest richness. Species richness between northeastern and southern Brazil is briefly compared, indicating a decrease of species richness southwards. Since most of the studied area is under influence of the same water masses, proximity to the Caribbean fauna may explain the species richness found in the northern Brazilian external shelf and slope. Finally, we suggest that biogeographic units within the Brazilian upper and middle slope are closer to shallow-water provinces than to deep-sea ones.