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Researchers have found that two of the key coral species forming Florida's reef have become functionally extinct following a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, indicates they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Functional extinction is a stage before total extinction, a danger that now hangs for many coral species.

Scientists recently warned that a tipping point has been crossed, meaning corals globally are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"Time is running out," stated Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to global warming, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

Details of the Recent Study

The recent study, published in the Science journal, analyzed the outcome of staghorn coral and elkhorn coral corals off the Florida coast following a severe marine heatwave in 2023.

This event raised temperatures on Florida's deteriorating coral reefs to their peak temperatures in more than a century and a half.

The two species are complex, reef-forming corals and are named because they resemble, respectively, the antlers of male deer and elks.

However, scientists who performed underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Effects

• In the Florida Keys, death rates reached 98% and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were reduced, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already suffered from decades of regional pressures in Florida, such as poor water quality from contaminants that run off the land, as well as illness.

But the 2023 marine heatwave has proved lethal for these heat-sensitive species.

The 2023 heat event caused the ninth occurrence of coral bleaching on the Florida reef – a process whereby corals become thermally stressed and expel the algae partners living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals perish completely.

Worldwide Consequences

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate emergency.

This poses a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who rely on corals to sustain fish that they can consume and gain an income from.

Corals also serve as a barrier to safeguard our shorelines from intense hurricanes, which are themselves being worsened by increasing global heat.

Preservation Efforts

In a last-ditch effort to avert a decline of threatened corals, scientists have established repositories of Acropora in aquariums and ocean-based nurseries.

Attempts have been made to replant corals on reefs in Florida, too, in an effort to regain some of the 90% of coral cover lost off the state in the last forty years.

But as global heating continues to escalate, there is slim chance of long-term survival of these species without significant actions, researchers warn.

Further Researcher Insight

"Elkhorn corals, especially, are some of the key wave-dampening coral species in the area," said a study co-author, a marine biologist at the University of Miami.

"They were once common on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals completely."