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

The Meaning Behind 'Functional Extinction' Means

The near-total collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they can no longer play their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase before global extinction, a danger that now hangs for many coral species.

Scientists this month warned that a tipping point had been reached, whereby corals globally are likely to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Expert Insight

"Time is running out," stated the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without swift, decisive measures to reduce ocean heating and boost coral resilience, we face the danger of the extinction of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

The new research, published in the journal Science, examined the outcome of staghorn coral and elkhorn coral corals off the Florida coast following a severe marine heatwave in 2023.

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

The two species are complex, reef-building corals and are identified because they resemble, respectively, the antlers of stags and elks.

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

Regional Impact

• In the Florida Keys, mortality rates hit ninety-eight percent and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Historical and Present Threats

The two Acropora species had already suffered from decades 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 fatal for these temperature-sensitive species.

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

If temperatures remain elevated, the corals perish completely.

Worldwide Implications

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

This presents a major threat to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and gain an income from.

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

Conservation Efforts

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

Attempts have been undertaken to replant 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 intensify, there is little hope of long-term survival of these species absent major interventions, scientists caution.

Additional Expert Commentary

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

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."