🔗 Share this article

Scientists have discovered that two of the most important coral species forming Florida's reef are now ecologically extinct following a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

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

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

Scientists recently alerted that a critical threshold had been reached, whereby corals globally are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

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

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

The two species are complex, reef-building corals and are named because they look like, in turn, the horns of stags and elk.

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 catastrophic, losses.

Regional Impact

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

Historical and Present Dangers

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from contaminants that wash off the land, as well as disease.

But the 2023 marine heatwave has proved fatal for these heat-sensitive species.

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

If temperatures stay high, the corals perish completely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the anthropogenic 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 support fish that they can eat and gain an income from.

Corals also act as a protective barrier to safeguard our shorelines from powerful storms, which are themselves being intensified by increasing global heat.

Preservation Attempts

In a last-ditch effort to avert a death spiral of endangered corals, scientists have created collections of Acropora in aquariums and ocean-based nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, too, 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 major interventions, researchers warn.

Further Researcher Insight

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

"They were once common 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 extraordinary measures to ensure we don't lose these corals altogether."