🔗 Share this article

Researchers have found that two of the key coral species comprising Florida's reef have become functionally extinct following a withering ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the backbone 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 diversity of marine life.

Functional extinction is a phase before total extinction, a danger that now looms for many coral species.

Researchers this month warned that a critical threshold had been reached, meaning corals around the world are likely to be eradicated due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and worldwide."

The New Research

The new research, featured in the Science journal, analyzed 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 peak temperatures in more than a century and a half.

The two species are complex, reef-building corals and are identified because they look like, in turn, the antlers of stags and elks.

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

Regional Impact

• Along the Florida Keys, mortality rates hit 98% and even one hundred percent, showing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Past and Current Threats

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

But the 2023 heatwave has proved lethal for these temperature-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 ghostly white.

If temperatures remain elevated, the corals perish entirely.

Worldwide Implications

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

This poses a major threat to:

• One-fourth of all ocean life that depends on what are essentially the marine rainforests.
• Millions of people who depend upon corals to sustain fish that they can consume and earn a livelihood from.

Corals also serve as a protective barrier to safeguard our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Conservation Efforts

In a desperate attempt to avert a decline of threatened corals, scientists have created repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to regain 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 long-term survival of these species without significant actions, scientists caution.

Additional Expert Commentary

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

"They used to be common 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 exceptional steps to ensure we don't lose these corals completely."