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

Abstract

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 majorMEs 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. K E Y W O R D S climate change, coral reef, deep-sea refugia, marine biogeography, marine conservation, rhodolith bed 1 | INTRODUC TI ON Developments in the marine sciences, especially in terms of methodology and equipment, have allowed the exploration of progressively deeper oceanic zones, providing a more detailed picture of the hidden biodiversity in mesophotic ecosystems (MEs; Loya, Eyal, Treibitz, Lesser, & Appeldoorn, 2016). These ecosystems are characterized by the presence of light-dependent corals and associated species (e.g.,

South Atlantic Coral Reefs Are Major Global Warming Refugia and Less Susceptible to Bleaching

“…Our results show that South Atlantic corals occupy greater depth zones, are tolerant to higher turbidity and nutrification, are morphologically resistant, engaged in flexible symbiotic associations, and most importantly, are less affected by bleaching ( Figures 4A,B). In addition, they harbor numerous mesophotic reefs, possibly more than anywhere else in the world, that may serve as additional refugia (Soares et al, 2019). This qualifies South Atlantic reefs, especially its largest reefs in the Abrolhos Bank, as bioclimatic units (BCUs).…”

“…South Atlantic reefs are also distinctive because they are mostly coastal as atolls and oceanic archipelagos are very few (Leão et al, 2016). In addition, they encompass extensive mesophotic reefs (Meirelles et al, 2015;Francini-Filho et al, 2019;Soares et al, 2019) the largest rhodolith beds in the world (Pereira-Filho et al, 2011;Amado-Filho et al, 2012;Moura et al, 2016) and are significantly influenced by river discharge (Leão et al, 2003(Leão et al, , 2016Moura et al, 2016). Therefore, South Atlantic reefs display several features that are unique to them and not typically found in the more studied reef habitats of the Indo-Pacific and Caribbean.…”

Why do mesophotic coral ecosystems have to be protected?

“…In temperate regions, TMEs (temperate mesophotic ecosystems) are also defined as light-dependent communities located at~30-150 m depth (Turner et al, 2019). Boavida et al, 2016aBoavida et al, , 2016b, whereas in tropical MCEs, rhodoliths, sponges, black corals, gorgonians, and massive corals dominate Soares et al, 2019). Similar to shallow-water coral reefs, MCEs provide ecosystem goods and services (EGS) (Baker et al, 2016).…”

Unexplored diversity of the mesophotic echinoderm fauna of the Easter Island ecoregion

“…Mesophotic ecosystems could act as potential biodiversity reservoirs with higher rates of endemism and coral coverage and may be able to maintain a healthier status than their shallower counterparts (Soares et al 2018).…”