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

What 'Functional Extinction' Signifies

The almost complete decline 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 constructing and maintaining reef ecosystems that host a variety of marine life.

Ecological extinction is a stage before total extinction, a danger that now looms for many coral species.

Researchers this month warned that a tipping point had been reached, meaning corals around the world are set to be wiped out due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," stated Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and worldwide."

The New Research

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

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

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

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

Geographic Effects

• In the Florida Keys, death rates reached 98% and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Historical and Present Threats

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

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

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

If temperatures stay high, the corals perish entirely.

Global Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This presents a significant danger to:

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

Corals also serve as a barrier to safeguard 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 endangered corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover disappeared off the state in the past four decades.

But as global heating continues to escalate, there is little hope of continued existence of these species absent significant actions, researchers warn.

Additional Researcher Insight

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

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