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Researchers have found that two of the most important coral species comprising Florida's reef are now functionally extinct after a intense ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total 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 support a diversity of marine life.

Ecological extinction is a phase before total extinction, a threat that now looms for many coral species.

Scientists recently alerted that a critical threshold has been crossed, whereby corals globally are likely to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the extinction of additional coral species from reefs in Florida and around the world."

The Recent Study

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

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

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

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

Geographic Impact

• Along the Florida Keys, mortality rates hit 98% and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were lower, at about thirty-eight percent.

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 run off the land, as well as illness.

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

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

If temperatures remain elevated, the corals perish completely.

Global Implications

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

This presents a major threat to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Millions of people who depend upon corals to sustain fish that they can consume and gain an income 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 Efforts

In a desperate attempt to avert a death spiral of threatened corals, scientists have established collections of Acropora in marine facilities and offshore coral nurseries.

Attempts have been made 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 global heating continues to intensify, there is little hope of continued existence of these species without significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, in particular, are some of the key wave-dampening coral species in the area," noted a study co-author, a ocean scientist at the Miami University.

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."