Coral reefs face existential threats from climate change and water pollution, among other environmental stresses. However, some of these reefs may well have a chance to survive for decades to come.
So say scientists at the Rosenstiel School of Marine, Atmospheric and Earth Sciences at the University of Miami, who found that some reefs in the tropical Pacific Ocean could maintain high coral cover well into this century, mixing the symbiotic algae they shelter.
These findings, they say, “offer a glimmer of hope in an often bleak picture of the future of coral reefs“.
Some corals are combating rising water temperatures by increasing their heat tolerance, switching the symbiotic algal communities they host to provide energy through photosynthesis.
“Our results suggest that some reefs in the eastern tropical Pacific, which includes the Pacific coasts of Panama, Costa Rica, Mexico and Colombia, could maintain high coral cover well into the 2060s.“, explains coral biologist Ana Palacio-Castro, who was the main author of a study on discoveries .
“However, while this could be seen as good news for these reefs, their survival may not continue beyond that date unless we reduce global greenhouse gas emissions and reduce global warming on a larger scale.”, warns Palácio-Castro.
Coral reefs and symbiotic algae
Coral reefs living in shallow waters in the eastern tropical Pacific Ocean predominantly comprise branching corals of the genus pocillopora which harbor microscopic algae in their tissues to provide energy from sunlight.
When corals lose these symbiotic algae, they turn white in a phenomenon known as bleaching, which is often fatal to corals. Heat stress can cause these algae to die, and the researchers wanted to examine how corals can increase their heat tolerance.
They did this by sifting through more than four decades of coral reef monitoring data in one of the world’s longest datasets in Panama. They analyzed data on temperature, coral cover, bleaching and mortality during three oceanic heat waves (1982-1983, 1997-1998 and 2015-2016), as well as data on symbiotic algal communities.
historic heat waves
“The 1982-83 heat wave significantly reduced coral cover on the reef, but the effects of the 1997-98 and 2015-16 El Niño were milder, especially for corals in the genus Pocillopora, sometimes known as cauliflower coral. flower, the predominant coral reef. – coral building in the eastern tropical Pacific”, say scientists.
“During strong oceanic heat waves, the heat-resistant alga Durusdinium glynnii becomes increasingly common in this particular lineage of corals, allowing them to better withstand periods of high temperatures.”, continue to explain.
“When combined with future climate projections of thermal stress, reefs that were predominantly composed of Pocillopora corals and that harbored this heat-tolerant alga were shown to be better equipped to survive and maintain high levels of coral cover during the night. , indicating that some reef systems may be more resistant to warming than previously thought”, they add.
Study results on coral reefs
The results indicate that some reefs can survive for several decades thanks to their ability to mix symbionts, according to Andrew Baker, professor of marine biology and ecology at the Rosenstiel School and lead author of the study.
“While we don’t believe most reefs can survive this way, it does suggest that remnants of our current reefs may persist longer than previously thought, albeit potentially with far fewer species,” says Baker.
“Coral reefs are incredibly valuable natural resources, providing coastal protection and fisheries benefits, as well as supporting many local communities. We can still make a difference by protecting them,” he emphasizes.
