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Researchers have found that two of the primary coral species forming Florida's reef are now functionally extinct after a withering ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

Ecological extinction is a stage before global extinction, a threat that now hangs for many coral species.

Researchers recently alerted that a tipping point has been crossed, meaning corals globally are likely to be eradicated due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without swift, decisive measures to slow ocean warming and boost coral resilience, we risk the disappearance of even more corals from reefs in Florida and worldwide."

The New Research

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

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

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

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

Geographic Effects

• Along the Florida Keys, death rates reached 98% and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Historical and Present Threats

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

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

The 2023 heat event caused the ninth episode of 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 bleached white.

If temperatures remain elevated, the corals perish completely.

Worldwide Consequences

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

This poses a significant danger to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

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

Conservation Attempts

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

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Additional Expert Commentary

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

"They were once 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 extraordinary measures to ensure we don't lose these corals altogether."