Marine Habitats in Conservation Units on the Southeast Coast of Brazil

Abstract

Continental shelves with diversified physiography, geomorphology marked by rocky reefs, channels, and marginal terraces, besides several terrestrial and marine sediments, have a rich mosaic of habitats ideal for the conservation and reproduction of marine life. This work, as part of the research project Detailed Study of the Ocean Bed inside the Santa Cruz WLR, Costa das Algas EPA and 2000m Immediate Environment, aims at mapping the marine habitats located in two Conservation Units, Costa das Algas EPA (Environmental Protection Area) and Santa Cruz WLR (Wildlife Refuge), located south of the Doce River mouth, on the southeast coast of Brazil. For this purpose, data on the type, distribution, and composition of seabed sediments, as well as information on the seabed geomorphology using bathymetric data, seabed records by ROV imaging, and benthic fauna at the phylum taxonomic level were determined in the studied areas. The results indicated the presence of five sedimentary facies defined by the terrigenous and marine sedimentation regimes, separated in the vicinity of the -35 m isobath. The sandy-clayey sediments deposited by the fluvial discharges from the region rivers predominate in the first case. On the other hand, the marine sedimentation consists of biolitoclastic and bioclastic sediments, with rhodolith pebbles as well. In addition, three hydrodynamic zones/regions were defined, according to the presence and type of seabed ripples formed by near-bottom waves. The bathymetric data revealed seabed features such as reef structures, or rocky reefs, as well as submerged channels originated by marine regression. This set of characteristics defined eleven marine habitats, and among them, those consisting of biolitoclastic, bioclastic and rhodolith sediments, as well as rocky reefs and submerged channels, which had the greatest abundance of marine fauna and flora organisms. On the other hand, the habitats defined by the terrigenous sedimentation had a lower abundance of organisms. This finding indicates that the marine sedimentation regime predominated over the terrigenous, especially in the Costa das Algas EPA, which generally represents an area with high potential for proliferation and preservation of marine benthic and demersal fauna and flora. In view of this, the mapping of the Conservation Units presented here for the first time on a detailed scale can help to understand the importance of these areas for the preservation and maintenance of marine life.