Abstract
Mass coral bleaching has increased in intensity and frequency and has severely impacted shallow tropical reefs worldwide. Although extensive investigation has been conducted on the resistance and resilience of coral reefs in the Indo-Pacific and Caribbean, the unique reefs of the South Atlantic remain largely unassessed. Here we compiled primary and literature data for reefs from three biogeographical regions: Indo-Pacific, Caribbean and South Atlantic and performed comparative analyses to investigate whether the latter may be more resistant to bleaching. Our findings show that South Atlantic corals display critical features that make them less susceptible to mass coral bleaching: (i) deeper bathymetric distribution, as species have a mean maximum depth of occurrence of 70 m; (ii) higher tolerance to turbidity, as nearly 60% of species are found in turbid conditions; (iii) higher tolerance to nutrient enrichment, as nitrate concentration in the South Atlantic is naturally elevated; (iv) higher morphological resistance, as massive growth forms are dominant and comprise two thirds of species; and (v) more flexible symbiotic associations, as 75% of corals and 60% of symbiont phylotypes are generalists. Such features were associated with occurrence of fewer bleaching episodes with coral mortality in the South Atlantic, approximately 60% less than the Indo-Pacific and 50% less than the Caribbean. In addition, no mass coral mortality episodes associated with the three global mass bleaching events have been reported for the South Atlantic, which suffered considerably less bleaching. These results show that South Atlantic reefs display several remarkable features for withstanding thermal stress. Together with a historic experience of lower heat stress, our findings may explain why climate change impacts in this region have been less intense. Given the large extension and latitudinal distribution of South Atlantic coral reefs and communities, the region may be recognized as a major refugium and likely to resist climate change impacts more effectively than Indo-Pacific and Caribbean reefs.
Highlights
Coral reefs are diverse marine ecosystems that harbor approximately 25% of marine eukaryotic and prokaryotic species in less than 1% of the ocean surface area (Spalding et al, 2001; Knowlton et al, 2010; Sheppard et al, 2018)
To address the six hypotheses, data were compiled for four specific coral traits, as well as for reef nutrient concentration and the frequency of coral mortality associated with bleaching episodes
Several species shared between the Caribbean and South Atlantic have been reported deeper than 100 m, such as Agaricia fragilis, Montastraea cavernosa, Madracis decactis, Meandrina brasiliensis, and Scolymia wellsii (Supplementary Table S1)
Summary
Coral reefs are diverse marine ecosystems that harbor approximately 25% of marine eukaryotic and prokaryotic species in less than 1% of the ocean surface area (Spalding et al, 2001; Knowlton et al, 2010; Sheppard et al, 2018). Marine heat waves in combination with background warming and consequential elevated sea surface temperatures are responsible for the bleaching phenomenon, in which the key symbiotic relationship between reef-building corals and photosynthetic Symbiodiniaceae dinoflagellates is disrupted (Glynn, 1993, 1996; Fitt et al, 2001). Because the symbiotic relationship is obligate for most shallow-water reef-building corals, bleaching frequently leads to coral mortality (Glynn, 1993; Brown, 1997; Hoegh-Guldberg, 1999). The loss of structural complexity reduces the ability of shallow reefs to absorb wave energy and protect coastal communities from storms and erosion (Sheppard et al, 2005)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call