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

What 'Functional Extinction' Signifies

The near-total collapse of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they are no longer able to fulfill their once vital role in building and sustaining reef ecosystems that support a diversity of marine life.

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

Scientists this month warned that a tipping point had been reached, whereby corals around the world are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," said Ross Cunning of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we face the danger of 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 journal Science, analyzed the fate of staghorn and elkhorn coral corals off the Florida coast after a severe marine heatwave in 2023.

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

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

However, researchers who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Impact

• In the Florida Keys, death rates hit ninety-eight percent and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about 38%.

Past and Present Dangers

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

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

The 2023 heat event caused the ninth occurrence of bleaching on the Florida reef – a phenomenon 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 perish entirely.

Worldwide Implications

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

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 rely on corals to sustain fish that they can eat and gain an income from.

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

Conservation Efforts

In a desperate attempt to avert a death spiral of threatened corals, scientists have created collections of Acropora in marine facilities and offshore coral nurseries.

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

But as global heating continues to escalate, there is little hope of long-term survival of these species without significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the region," said a study co-author, a marine biologist at the University of Miami.

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking exceptional steps to ensure we preserve these corals altogether."