Equatorial Reefs May Act as Refugia for Corals During Marine Heatwaves
Florida Tech-Led Analysis Indicates Elevated Ocean Temps Weakened in the Equatorial Coral Triangle
A global analysis of coral bleaching across 81 countries reveals that reefs in the equatorial Coral Triangle region were exposed to the weakest marine heatwaves over the past two decades and may function as safe havens for corals even as global warming robs the planet of most of its other reefs.
Marine heatwaves, which are periods of elevated seawater temperatures that cause mass coral bleaching and mortality, are an existential threat to the survival of the world’s coral reefs. But a global network of marine-heatwave refugia – geographical areas that remain stable amid climate or environmental changes – may help sustain coral populations through heatwaves.
The 2.3-million-square-mile Coral Triangle is a wonderland of biodiversity spanning Indonesia, Malaysia, the Philippines, Papua New Guinea, Solomon Islands and Timor-Leste. Home to more than three-quarters of the world’s coral species, this marine region would be among the largest coral refugia on the planet.
“The severity of coral bleaching was reduced on any reefs, not just equatorial reefs, which were exposed to strong currents, high wave energy, frequent cloud coverage or turbidity. We suspect that marine-heatwave refugia for corals are concentrated near the Equator because cloud coverage is most frequent near the Equator,” said Zachary Ferris, a Ph.D. candidate in biological sciences at Florida Tech and first author on the paper. “Indeed, marine heatwaves and coral bleaching were least severe on reefs in the Coral Triangle region from 2002 to 2020, likely because frequent cloud coverage reduced solar radiation and heating during summers.”
“This work provides hope that there are locations worldwide where corals may survive marine heatwaves,” added Robert van Woesik, a professor and director of the Institute for Global Ecology at Florida Tech and co-author of the paper.
The team published, “Coral bleaching: the equatorial-refugia hypothesis” on Nov. 17 in the international journal Global Change Biology. Find the article at https://doi.org/10.1111/gcb.70594.
Ferris conducted the study with Andrew Walker, another Ph.D. candidate in biological sciences at Florida Tech, as well as Hävard Rue, a professor and chair of the statistics program at King Abdullah University of Science and Technology in Saudi Arabia, and van Woesik.
The study was funded by a National Science Foundation grant to van Woesik and a National Science Foundation Graduate Research Fellowship to Ferris.
