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Scientists have discovered that two of the primary coral species forming Florida's reef are now functionally extinct after a withering ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a stage preceding total extinction, a threat that now looms for many coral species.

Scientists recently warned that a critical threshold has been crossed, whereby corals globally are set to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"Time is running out," said Ross Cunning of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

The Recent Study

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

This event raised temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.

The two species are complex, reef-building corals and are identified because they resemble, respectively, the antlers 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 devastating, losses.

Geographic Impact

• In the Florida Keys, death rates hit ninety-eight percent and even one hundred percent, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Past and Current Dangers

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

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

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

If temperatures remain elevated, the corals die off completely.

Global Consequences

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

This poses a significant danger to:

• One-fourth of all ocean life that relies upon 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 gain an income from.

Corals also serve as a protective barrier to protect our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Preservation Efforts

In a last-ditch effort to avert a death spiral of endangered corals, scientists have established repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been undertaken 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 escalate, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Further Researcher Insight

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

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals completely."