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Scientists have discovered that two of the most important coral species comprising Florida's reef are now ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

Functional extinction is a stage before total extinction, a threat that now hangs for many coral species.

Researchers this month 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 new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The New Research

The recent study, published in the Science journal, examined the fate of staghorn and elkhorn coral corals off the Florida coast following a severe 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 complex, reef-forming corals and are named because they look like, respectively, the horns of male deer and elk.

However, scientists who performed diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often devastating, losses.

Regional Effects

• Along the Florida Keys, mortality rates reached ninety-eight percent and even one hundred percent, revealing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about 38%.

Past and Present Dangers

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

But the 2023 heatwave has been lethal for these heat-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 ghostly white.

If temperatures remain elevated, the corals perish completely.

Worldwide Implications

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

This poses a significant danger to:

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

Corals also act as a 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 endangered corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover lost off the state in the last forty years.

But as climate change continues to intensify, there is slim chance of continued existence of these species without significant actions, researchers warn.

Further Expert Commentary

"Elkhorn corals, especially, are some of the key wave-dampening coral species in the area," said Andrew Baker, 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 continue protecting our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we don't lose these corals altogether."