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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.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Functional extinction is a stage preceding total extinction, a danger that now hangs for many coral species.

Researchers this month alerted that a tipping point had been reached, whereby corals around the world are likely to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," stated Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without immediate, ambitious actions to slow ocean warming and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and worldwide."

The New Research

The recent study, featured in the Science journal, analyzed the fate of staghorn and elkhorn corals off the Florida coast following a severe marine heatwave in 2023.

This event raised temperatures on Florida's deteriorating coral reefs to their peak temperatures in more than a century and a half.

The two species are complex, reef-forming corals and are identified because they look like, in turn, the horns of male deer and elk.

However, researchers who conducted underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Impact

• In the Florida Keys, death rates hit 98% and even 100%, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about thirty-eight percent.

Past and Current Threats

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

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

The 2023 event caused the ninth occurrence of coral 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.

Worldwide Consequences

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

This presents 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 rely on corals to sustain fish that they can eat and gain an income from.

Corals also act 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 prevent a death spiral of endangered corals, scientists have created repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been undertaken to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover lost off the state in the past four decades.

But as climate change continues to escalate, there is slim chance of long-term survival of these species without major interventions, scientists caution.

Additional Researcher Insight

"Elkhorn species, especially, are some of the key wave-breaking coral species in the area," said Andrew Baker, a marine biologist at the University of Miami.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals completely."