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Researchers have found that two of the most important coral species forming Florida's reef have become ecologically extinct following a intense ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they are no longer able to play their once vital role in constructing and maintaining reef ecosystems that host a variety of marine life.

Functional extinction is a stage preceding total extinction, a danger that now looms for many coral species.

Scientists recently warned that a critical threshold had been reached, meaning corals around the world are set to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

The Recent Study

The new research, featured in the Science journal, examined the outcome of staghorn coral and elkhorn corals off the Florida coast following a severe marine heatwave in 2023.

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

The two species are intricate, reef-forming corals and are identified because they resemble, in turn, the horns of male deer and elks.

However, researchers who conducted diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Regional Impact

• In the Florida Keys, death rates hit 98% and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were reduced, at about 38%.

Historical and Present Dangers

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

But the 2023 heatwave has been lethal for these temperature-sensitive species.

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

If temperatures stay high, the corals perish entirely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most at risk to the anthropogenic climate crisis.

This poses a major threat to:

• A quarter of all ocean life that relies upon what are effectively the marine rainforests.
• Hundreds of millions of people who depend upon corals to support fish that they can consume and gain an income from.

Corals also serve as a barrier to protect our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Preservation Attempts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have established repositories of Acropora in marine facilities and ocean-based nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to restore some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as climate change continues to escalate, there is slim chance of long-term survival of these species without significant actions, scientists caution.

Additional Expert Commentary

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

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals completely."