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Scientists have discovered that two of the most important coral species comprising Florida's reef have become ecologically extinct following a intense ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The near-total collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their previously crucial role in building and sustaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase before global extinction, a danger that now hangs for many coral species.

Scientists recently warned that a critical threshold had been reached, whereby corals globally are likely to be eradicated due to climate change, which is raising ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," said Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and without immediate, ambitious actions to slow ocean warming and boost coral resilience, we risk the disappearance of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

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

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

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

However, researchers who performed underwater surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Geographic Effects

• Along the Florida Keys, death rates hit ninety-eight percent and even 100%, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about thirty-eight percent.

Historical and Present 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 disease.

But the 2023 marine 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 thermally stressed and eject the algae partners living in their tissues, causing them to become ghostly white.

If temperatures remain elevated, the corals perish entirely.

Worldwide Consequences

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

This poses a significant danger to:

• One-fourth of all ocean life that depends on what are essentially the rainforests of the sea.
• Millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

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

Preservation Efforts

In a last-ditch effort to prevent a death spiral of threatened corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Efforts have been made to reseed corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover disappeared off the state in the past four decades.

But as climate change continues to escalate, there is slim chance of continued existence of these species without significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn corals, especially, are some of the most important wave-breaking coral species in the region," said a study co-author, a marine biologist at the Miami University.

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking exceptional steps to ensure we preserve these corals altogether."