Reefs distribution and inter reef sedimentation on Tamandaré continental shelf, Northeast Brazil

Abstract The Tamandare–PE continental shelf, on the eastern Brazilian coast is narrow (35 km), shallow with a shelf break at 90 m water depth, has mixed carbonate and siliciclastic sedimentation, and widespread occurrences of ridges and patch reefs. Habitat mapping was carried out using an interferometric swath system (EdgeTech 4600), digital processing of Landsat 8 image, surficial sediment sampling, and underwater video surveys to identify sediment-covered zones and coral reefs. Seven acoustic backscatter patterns were defined, three of which represent hard-substrate habitats and associated biogenic reefs and four represent soft sediment habitats where muddy to gravelly substrates have developed. Reefs attached to the Tamandare Bay and coast have a more complex relief, with caves and steep flanks averaging 4 m in height but reaching 10 m height on the seaward flanks. A second reef field, the Crapitanga Reef, has lower relief with an average height of 2 m, but with knolls up to 6 m high, attributed to an advanced bioerosion stage. A muddy sediment body occurs inbetween reef fields and extends into paleochannels, where there are extensive shrimp fishing activities.