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Researchers have found that two of the most important coral species forming Florida's reef have become ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Means

The near-total collapse 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 building and sustaining reef ecosystems that support a diversity of marine life.

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

Researchers recently 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 unbearable levels.

Expert Insight

"Time is running out," said Ross Cunning of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

The New Research

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

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

The two species are intricate, reef-forming corals and are named because they look like, in turn, the antlers 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 devastating, losses.

Geographic Impact

• Along the Florida Keys, death rates hit 98% and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Current Dangers

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 lethal for these heat-sensitive species.

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

If temperatures stay high, the corals die off completely.

Worldwide Implications

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

This poses a significant danger to:

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

Corals also act as a barrier to protect our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Preservation Efforts

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

Efforts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover lost off the state in the last forty years.

But as global heating continues to intensify, there is slim chance of continued existence of these species without significant actions, researchers warn.

Additional Expert Commentary

"Elkhorn corals, especially, are some of the key wave-breaking coral species in the region," noted Andrew Baker, a marine biologist 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, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."