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

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the backbone 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 total extinction, a threat that now looms for many coral species.

Researchers recently warned that a critical threshold had been reached, meaning corals around the world are likely to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"Time is running out," said Ross Cunning of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

Details of the New Research

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

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

The two species are intricate, reef-forming corals and are identified because they resemble, respectively, the horns of male deer and elks.

However, researchers who performed diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often devastating, losses.

Regional Impact

• In the Florida Keys, mortality rates hit 98% and even one hundred percent, showing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already endured from many years of regional pressures in Florida, such as poor water quality from pollutants that wash off the land, as well as disease.

But the 2023 marine heatwave has proved 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 heat-stressed and eject the algae partners living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals perish completely.

Worldwide Implications

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

This presents a significant danger to:

• One-fourth of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can eat and earn a livelihood from.

Corals also serve as a 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 threatened corals, scientists have established collections of Acropora in aquariums and offshore coral nurseries.

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

But as climate change continues to escalate, there is slim chance of continued existence of these species absent major interventions, researchers warn.

Further Expert Commentary

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

"They were once abundant 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."