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

What 'Functional Extinction' Means

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

Ecological extinction is a phase preceding global extinction, a threat that now hangs for many coral species.

Researchers recently alerted that a tipping point has been crossed, whereby corals globally are set to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Expert Insight

"We're running out of time," stated Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to global warming, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and around the world."

The Recent Study

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

This event raised temperatures on Florida's fraying 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 stags and elks.

However, researchers who performed diver surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often devastating, losses.

Regional Effects

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

Past and Current Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

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

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

If temperatures stay high, the corals die off entirely.

Global Implications

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

This presents a major threat 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 gain an income from.

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

Conservation Efforts

In a last-ditch effort to avert a death spiral of threatened corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Efforts 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 last forty years.

But as climate change continues to escalate, there is little hope of continued existence of these species without major interventions, researchers warn.

Additional Researcher Insight

"Elkhorn corals, in particular, are some of the key wave-dampening coral species in the region," said a study co-author, a marine biologist at the University of Miami.

"They used to be abundant on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, its worth taking exceptional steps to ensure we don't lose these corals completely."