Two Vital Florida Coral Species Declared 'Functionally Extinct' After Devastating Ocean Heatwave

Researchers have found that two of the key coral species forming Florida's reef have become functionally extinct after a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

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

Functional extinction is a phase before total extinction, a threat that now looms for many coral species.

Scientists recently alerted that a tipping point had been reached, whereby corals around the world are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

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

The Recent Study

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

This event elevated 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-forming corals and are named because they resemble, in turn, the horns of male deer and elk.

However, scientists who performed diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Impact

• In the Florida Keys, mortality rates hit 98% 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 Present Dangers

The two Acropora species had already endured from many years of localized impacts in Florida, such as poor water quality from pollutants that run off the land, as well as illness.

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

The 2023 heat event caused the ninth episode of 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 bleached white.

If temperatures remain elevated, the corals perish entirely.

Global Implications

Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate crisis.

This presents a major threat to:

• A quarter of all ocean life that relies upon what are essentially the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can consume and gain an income from.

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

Conservation Attempts

In a last-ditch effort to avert a decline of endangered corals, scientists have created repositories of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover lost off the state in the last forty years.

But as global heating continues to escalate, there is slim chance of continued existence of these species without major interventions, researchers warn.

Additional Researcher Insight

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

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