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Researchers have found that two of the primary coral species comprising Florida's reef have become functionally extinct following a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as 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 diversity of marine life.

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

Scientists recently alerted that a tipping point had been reached, whereby corals globally are set to be wiped out due to global heating, which is increasing ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," stated Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

Details of the New Research

The recent study, published in the journal Science, examined the fate of staghorn and elkhorn coral corals off the Florida coast after a intense marine heatwave in 2023.

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

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

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

Geographic Impact

• In the Florida Keys, mortality rates reached 98% and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Past and Current Threats

The two Acropora species had already suffered from many years of localized impacts in Florida, such as poor water quality from contaminants that wash off the land, as well as illness.

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

The 2023 event caused the ninth episode of coral bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and eject the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals perish entirely.

Worldwide Implications

Globally, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This presents a significant danger to:

• One-fourth of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can consume and gain an income from.

Corals also act as a protective barrier to protect our shorelines from powerful storms, which are themselves being worsened by increasing global heat.

Conservation Attempts

In a last-ditch effort to prevent a decline of endangered corals, scientists have established collections of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover lost 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 absent major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn corals, especially, are some of the key wave-breaking coral species in the area," noted Andrew Baker, a marine biologist at the University of Miami.

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."