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Researchers have found that two of the primary coral species comprising Florida's reef are now ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

The near-total decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill 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 danger that now hangs for many coral species.

Scientists this month warned that a tipping point had been reached, meaning corals globally are likely to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we risk the extinction of additional coral species from reefs in Florida and worldwide."

Details of the Recent Study

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

This event elevated temperatures on Florida's deteriorating 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 antlers of male deer and elk.

However, researchers who conducted underwater surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often catastrophic, losses.

Geographic Effects

• Along the Florida Keys, mortality rates reached 98% and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already suffered from decades of regional pressures in Florida, such as poor water quality from contaminants that wash off the land, as well as illness.

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

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

If temperatures remain elevated, the corals perish completely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most at risk to the human-caused climate emergency.

This presents a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Millions of people who rely on corals to sustain fish that they can consume 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 rising global temperatures.

Conservation Attempts

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

Efforts have been made to reseed corals on reefs in Florida, as well, in an effort to restore 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 significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," said Andrew Baker, 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 keep safeguarding our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."