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

What 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer play their previously crucial role in building and sustaining reef ecosystems that support a diversity of marine life.

Functional extinction is a stage preceding total extinction, a danger that now looms for many coral species.

Scientists this month alerted that a tipping point has been crossed, whereby corals globally are set to be wiped out due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to slow ocean warming and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The Recent Study

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

This event elevated temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.

The two species are complex, reef-building corals and are named because they look like, respectively, the antlers of stags and elk.

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 widespread, often devastating, losses.

Geographic Impact

• Along the Florida Keys, death rates hit 98% and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Historical and Present Dangers

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from pollutants that run off the land, as well as illness.

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

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

If temperatures stay high, the corals perish entirely.

Global Implications

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

This poses a major threat to:

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

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

Conservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have created collections of Acropora in aquariums and ocean-based nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as climate change continues to escalate, there is slim chance of continued existence of these species without significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the region," noted Andrew Baker, a marine biologist at the Miami University.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking exceptional steps to ensure we don't lose these corals altogether."