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Researchers have found that two of the most important coral species forming Florida's reef are now functionally extinct after a intense ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer play their once vital role in constructing and maintaining reef ecosystems that support a variety of marine life.

Ecological extinction is a phase preceding global extinction, a threat that now looms for many coral species.

Researchers recently warned 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

"We're running out of time," said Ross Cunning of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to slow ocean warming and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and around the world."

Details of the Recent Study

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

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

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

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

Regional Impact

• Along the Florida Keys, mortality rates hit ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Historical and Current Dangers

The two Acropora species had already endured from many years of localized impacts in Florida, such as contaminated water from contaminants that wash off the land, as well as illness.

But the 2023 heatwave has been fatal for these temperature-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 stay high, the corals die off entirely.

Global Implications

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

This presents a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the marine rainforests.
• 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 powerful storms, which are themselves being worsened by rising global temperatures.

Conservation Efforts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have established collections of Acropora in marine facilities and ocean-based nurseries.

Attempts have been made 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 global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Further Expert Commentary

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

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking exceptional steps to ensure we preserve these corals altogether."