In nearshore areas, only fossil biogenic formations or small coral assemblages on intertidal rock outcrops have been reported, which are usually referred to as sandstone reefs 20. The shallower sector of this continental shelf is subject to intense wind-driven longshore sediment drifts 16, and large biogenic reefs are absent 20. Historically, the continental shelf along the SAC is considered poor in terms of biogenic reef occurrence 17, 18, 19. This area extends for about 1000 km in the SE-NW direction, and has distinct environmental conditions, such as a large interannual variability in rainfall, a predominance of small rivers, and a strong influence of wind on coastal landscapes 16. Furthermore, the ARS may provide a bridge between the SW Atlantic and Caribbean, serving as an ecological corridor allowing the exchange of reef species between biogeographic provinces 7, 12, 13, 14.īetween the ARS and ERS (from coordinates 5° S 36° W to 2° S 44° W) is the Brazilian semi-arid coast (SAC) 16. In both cases, reefs are associated with other habitats, such as rhodolith beds, sponge bottoms and seagrass meadows, and the reef systems are more properly a mosaic of interconnected benthic habitats 8, 10, 11. Along the South Atlantic Ocean two main reef systems have been recognized to date: the Eastern Brazilian Reef System (ERS), which comprises shallow-water (< 30 m depth) and mesophotic (30–150 m) reefs along Brazil's eastern continental shelf 2, 3, 4 and the Amazon Reef System (ARS), encompassing mesophotic and rariphotic (30–220 m depth) ecosystems located on the Brazilian Equatorial Margin 5, 6, 7, 8, 9, 10 (Fig. Large clusters of interconnected reefs extending for hundreds to thousands of square kilometers-referred to as reef systems 1-are an important feature of tropical coasts.
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