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Scientists have discovered that two of the key coral species comprising Florida's reef are now ecologically extinct following a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they are no longer able to play their once vital role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Functional extinction is a phase before total extinction, a danger that now hangs for many coral species.

Scientists recently warned that a critical threshold has been crossed, meaning corals globally are likely to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Perspective

"We're running out of time," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

The new research, published in the Science journal, examined 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 fraying coral reefs to their peak temperatures in over 150 years.

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

However, researchers who conducted underwater 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, death rates hit 98% and even one hundred percent, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Past and Present Threats

The two Acropora species had already suffered from many years of localized impacts 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 event caused the ninth episode of coral bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and expel 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 at risk to the human-caused climate crisis.

This presents a major threat to:

• One-fourth of all ocean life that relies upon what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

Corals also act as a barrier to safeguard our shorelines from intense hurricanes, which are themselves being worsened by rising global temperatures.

Conservation Attempts

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

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to restore some of the ninety percent of coral cover lost off the state in the past four decades.

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

Additional 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 Miami University.

"They used to be 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 preserve these corals completely."