Mesophotic ecosystems: coral and fish assemblages in a tropical marginal reef (northeastern Brazil)

Mesophotic reefs (30-150m depths) have recently become recognized as species-rich marine ecosystems, even in areas showing suboptimal conditions, like turbid water with sediment resuspension. The present study reports a qualitative survey focused on scleractinian coral and fish assemblages in a marginal reef (northeastern Brazil, southwestern Atlantic) at lower mesophotic depth. Data collection was conducted in the summer of 2016 by scuba diving at 35-37m depths. The occurrence of scleractinian reef corals Siderastrea stellata and Montastraea cavernosa suggests that these two species can be important reef-builders in mesophotic ecosystems in northeastern Brazil. The fish assemblage was characterized by 33 observed species, representing a large variety of trophic categories. The compositions of coral and fish species showed similarities with those of shallow-water reefs in the area. This may become relevant in understanding the connectivity between shallow and deep populations in the light of mesophotic reefs serving as refugia.