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Scientists have discovered that two of the key coral species comprising Florida's reef have become ecologically extinct after a withering ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

The near-total collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they are no longer able to play their previously crucial role in constructing and maintaining reef ecosystems that support a variety of marine life.

Ecological extinction is a stage before total extinction, a threat that now looms for many coral species.

Scientists recently alerted that a tipping point has been crossed, whereby corals globally are set to be eradicated 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 becoming more frequent and intense due to global warming, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we risk the disappearance of additional coral species from reefs in Florida and around the world."

Details of the New Research

The recent study, featured in the Science journal, examined the fate of staghorn and elkhorn coral corals off the Florida coast following a severe 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 named because they resemble, respectively, the horns of male deer and elks.

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Effects

• In the Florida Keys, mortality rates reached ninety-eight percent and even one hundred percent, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were lower, at about 38%.

Historical 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 run off the land, as well as illness.

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

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

If temperatures remain elevated, the corals die off completely.

Global Implications

Globally, coral reefs are among the ecosystems most at risk to the anthropogenic climate crisis.

This presents a significant danger to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to sustain 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 intensified by rising global temperatures.

Preservation Efforts

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

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover lost off the state in the past four decades.

But as climate change continues to escalate, there is little hope of long-term survival of these species without major interventions, researchers warn.

Further Researcher Insight

"Elkhorn species, especially, are some of the most important wave-dampening 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 continue protecting our coastlines from flooding during storms, its worth taking exceptional steps to ensure we don't lose these corals completely."