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

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

Functional extinction is a stage preceding global extinction, a threat that now looms for many coral species.

Researchers recently warned that a tipping point had been reached, whereby corals around the world are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"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 immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and worldwide."

The Recent Study

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

This event raised 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 resemble, in turn, the antlers 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 devastating, losses.

Geographic Effects

• In the Florida Keys, mortality rates reached 98% and even 100%, showing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were reduced, at about 38%.

Past and Present Dangers

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

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

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

If temperatures remain elevated, the corals perish completely.

Global Implications

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

This poses a significant danger to:

• One-fourth 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 act as a protective barrier to safeguard our shorelines from intense hurricanes, which are themselves being intensified by increasing global heat.

Conservation Attempts

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

Attempts have been made to replant corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the last forty years.

But as climate change continues to intensify, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Further Researcher Insight

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

"They used to be common 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 don't lose these corals completely."