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Researchers have found that two of the primary coral species forming Florida's reef are now ecologically extinct following a withering ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

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 fulfill their once vital role in constructing and maintaining reef ecosystems that host a variety of marine life.

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

Scientists this month warned that a tipping point has been crossed, whereby corals around the world are set to be wiped out due to climate change, 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 increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The Recent Study

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

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

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

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

Geographic Impact

• Along the Florida Keys, death rates reached 98% and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Historical and Present Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as poor water quality 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 event caused the ninth episode of bleaching on the Florida reef – a process whereby corals become thermally stressed and expel the algae partners living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals die off entirely.

Global Implications

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

This presents a significant danger to:

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

Corals also act as a barrier to protect our shorelines from intense hurricanes, which are themselves being worsened by rising global temperatures.

Preservation Attempts

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

Efforts have been made to reseed corals on reefs in Florida, as well, in an effort to restore some of the 90% of coral cover lost off the state in the past four decades.

But as global heating continues to intensify, there is little hope of long-term survival of these species without major interventions, scientists caution.

Additional Researcher Insight

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

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking exceptional steps to ensure we don't lose these corals altogether."