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Scientists have discovered that two of the most important coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as 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 support a variety of marine life.

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

Researchers recently warned that a tipping point has been crossed, meaning corals globally are set to be eradicated due to global heating, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," said the lead author of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to slow ocean warming and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and around the world."

Details of the New Research

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

This event raised temperatures on Florida's fraying 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 horns of male deer and elks.

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

Geographic Effects

• Along the Florida Keys, death rates reached 98% and even 100%, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Current Dangers

The two Acropora species had already suffered from many years of regional pressures in Florida, such as contaminated water from contaminants that run off the land, as well as disease.

But the 2023 marine heatwave has been fatal 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 eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals perish completely.

Global Implications

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

This presents a significant danger to:

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

Corals also serve as a barrier to safeguard our shorelines from powerful storms, which are themselves being intensified by rising global temperatures.

Preservation Efforts

In a desperate attempt to avert a decline of endangered corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, too, 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 slim chance of continued existence of these species absent significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn species, especially, are some of the key wave-breaking coral species in the region," said a study co-author, a marine biologist at the University of Miami.

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."