Charting the uncharted: Broad-scale benthic habitat distribution in the Brazilian continental margin

Abstract

Understanding the distribution of benthic habitats is of key relevance to inform management measures to protect this environment from ever growing human activities. Broad-scale habitat mapping has been developed under several initiatives around the world, mostly relying on the mapping environmental attributes that are vital to explain different benthic fauna composition. This approach usually depends on a habitat classification scheme that provides a common language and description of habitats. One of the most widely applied classification schemes is the European Union Nature Information System (EUNIS), which has been used under different broad- scale mapping projects. In this article, we applied the EUNIS approach to map the distribution of benthic habitats in the Brazilian margin, segmented on the three ecoregion provinces that occur within the country marine waters: North Brazil Shelf (NBS), Tropical Southwestern Atlantic (TSA) and Warm Temperate Southwestern Atlantic (WTSA). We compiled GIS layers of environmental parameters, including (i) bathymetry; (ii) substrate type; (iii) depth of euphotic zone; (iv) depth of wave base and; (v) geomorphic features. A map covering 5,800,000 km2 of the Brazilian margin was produced, most of which were classified as abyssal mud (34.03\%). Shelf habitats were mainly classified as offshore circalittoral mud (2.75\%), infralittoral sand (1.83\%) and circalittoral mud (1.77\%). Biogenic habitats are highly concentrated in the infralittoral zone (29,579 km2) compared to the area mapped in the circalittoral (415 km2) and offshore circalittoral (9840 km2). The results presented in this research are of major relevance for management purposes, especially for supporting the ongoing Marine Spatial Planning endeavor in Brazil. Understanding the broad distribution of benthic habitats is relevant for different information layers to be produced under this process, such as the identification of values for conservation, sensitivity to human pressures and provision of ecosystem services.