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Researchers have found that two of the key coral species comprising Florida's reef are now ecologically extinct after a intense ocean heatwave led to devastating losses.

What 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that support a variety of marine life.

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

Scientists this month alerted that a tipping point has been crossed, meaning corals around the world are likely to be eradicated due to global heating, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," said the lead author of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the disappearance of additional coral species from reefs in Florida and worldwide."

The Recent Study

The recent study, published in the Science journal, examined the fate of staghorn and elkhorn coral corals off the Florida coast following 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 intricate, reef-building corals and are identified because they look like, respectively, the horns of stags and elk.

However, researchers who conducted underwater surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Regional Impact

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

Historical and Current Threats

The two Acropora species had already suffered from decades of regional pressures in Florida, such as poor water quality from pollutants that wash off the land, as well as disease.

But the 2023 marine heatwave has been 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 heat-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 Consequences

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

This poses a significant danger to:

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

Corals also serve as a protective barrier to safeguard our shorelines from powerful storms, which are themselves being intensified by increasing global heat.

Preservation Efforts

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

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

But as climate change continues to escalate, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Further Researcher Insight

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the region," noted Andrew Baker, a marine biologist at the University of Miami.

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