Unusual high coral cover in a Southwestern Atlantic subtropical reef

Abstract

Subtropical Brazilian reefs are commonly composed by rocky frameworks with low coral abundance. Contrarily to most tropical reefs, our knowledge on coral assemblages in subtropical reefs is still developing. Queimada Grande is a subtropical island in the Brazilian coast lying 35 km offshore from the state of São Paulo (24ºS). Despite the partial protection bestowed to this island, recreational fishing and scuba diving are considered important pressures on this ecosystem. We used photoquadrats to quantify the abundance of two dominant reef-building corals, Madracis decactis (Lyman, 1859) and the Brazilian endemic Mussismilia hispida (Verrill, 1902), on rocky reefs and in a previously unreported coral bank. The abundance of M. decactis and M. hispida accounted for 40-60% of the benthic cover, with the dominance of M. decactis in the coral bank and M. hispida in the rocky reefs. The coral cover at Queimada Grande Island is comparable to those in Brazilian tropical reefs and higher than those reported in corallith beds further south in Brazil, thus representing the southernmost reef with such high coral abundance in the Western Atlantic. Our study demonstrates the high tolerance of M. decactis and M. hispida and highlights this coral assemblage as a potential conservation hotspot. This is particularly important in the context of tropicalization, since subtropical areas might sustain great coralline communities in warmer scenarios driven by climate change.

Projected climate‐driven shifts in coral distribution indicate tropicalisation of Southwestern Atlantic reefs

“…decactis and Mu. hispida , increased their future occurrence probabilities at the subtropics, where they are already dominant (Capel et al., 2012; Grillo et al., 2021) and held the highest probabilities in current projections (see first column in Figures 3 and 4). For such well‐established species, we expect an increase in local abundances in subtropical reefs, which in association with the high algal dominance in the region (Aued et al., 2018) might intensify competition for space and hinder to some degree the settlement and growth of other coral species that could benefit from a range expansion into higher latitudes.…”

Low functional vulnerability of fish assemblages to coral loss in Southwestern Atlantic marginal reefs

“…Among them, Mussismilia hispida and Montastraea cavernosa were of high importance for fish. Mussismilia hispida is a widespread coral that forms extensive colonies, mainly in rocky reefs of southeastern Brazil 55 . Montastraea cavernosa is widespread in tropical reefs, and can form reef boulders with a disproportionately high cover below 20 m 56 .…”

Taxonomic and functional diversity of zooxanthellate corals and hydrocorals in Southwestern Atlantic reefs

“…The locality of Rio de Janeiro (RJ), the southern limit of most coral species, comprises rocky reefs near the beach to rocky islands (Oigman-Pszczol and Creed, 2004;Lima and Coutinho, 2016). The locality of São Paulo (SP) comprises rocky reefs from Ubatuba (23°30'S; up to 5m depth), to Queimada Grande Island (24°20'S, up to 20 m depth) where only two scleractinian corals occur, Madracis decactis and Mussismilia hispida (Pereira-Filho et al, 2019;Banha et al, 2020;Grillo et al, 2021;Pereira-Filho et al, 2021). The locality of Paraná(PR) comprises a few rocky reef islands where only Madracis decactis occurs.…”

“…Siderastrea stellata and Montastraea cavernosa, respectively). Nevertheless, the endemic brain coral Mussismilia hispida and the widespread Madracis decactis thrive, sometimes even in high abundances, in these cold and isolated reefs (Capel et al, 2012;Grillo et al, 2021). Southern coral assemblages share traits that were probably shaped by the interaction of colder waters, lower light incidence and biological resistance to larval settling.…”

“…Under warming scenarios, the probability of coral occurrence tends to increase towards southern regions (R7-R8) (Bleuel et al, 2021). Coral species such as Mussismilia hispida and Madracis decactis that already predominate in this region (Capel et al, 2012;Grillo et al, 2021) may have traits that facilitate their survival under severe conditions, such as greater dependence on heterotrophy or symbiont photosynthetic efficiency. This may partially explain the high resistance and resilience of Mu.…”