Mesophotic ecosystems : distribution, impacts and conservation in the South Atlantic

Abstract

Unidad de excelencia María de Maeztu MdM-2015-0552

Aim: this study reviews recent research on the South Atlantic Mesophotic ecosystems (MEs) and the pressures threatening them, and offers suggestions for their management and conservation. - Location: the South Atlantic Ocean. - Methods: a comprehensive compilation of the scientific literature was performed to examine the distribution, human impacts and conservation status of the South Atlantic MEs. - Results: our review indicated that the South Atlantic Ocean (SAO) is one of the major MEs areas in the world's oceans. The South Atlantic MEs are composed of a mosaic of distinct seascapes, mainly rhodolith beds, mesophotic reefs (i.e., rocky and biogenic) and marine animal forests (e.g., sponge aggregations, octocoral and black coral forests) that occur along the East South American and West African coasts, seamounts and oceanic islands. Throughout the SAO, the distinct seascapes of MEs are usually formed on the middle and outer continental shelves, shelf-edge, seamounts, submarine canyons, incised valleys and paleochannels, reef structures and insular shelves. We highlighted sea temperature anomalies, ocean acidification, extreme floods and droughts, fisheries, invasive species, marine debris, mining, and oil and gas exploitation as major threats to these ecosystems. - Main conclusions: given the threats to the South Atlantic MEs, growing human pressures may degrade these ecosystems in the next years and undermine their unique biodiversity as well as their potential to provide connectivity between regions and depths. Our review revealed the existence of some extensive and unprotected formations, which urgently demand in-depth investigations and conservation action.