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

The Meaning Behind 'Functional Extinction' Signifies

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

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

Scientists this month warned that a critical threshold had been reached, meaning corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

Details of the Recent Study

The recent study, featured in the journal Science, analyzed the fate of staghorn coral and elkhorn 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 more than a century and a half.

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

However, researchers who conducted diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Regional Impact

• Along the Florida Keys, death rates reached ninety-eight percent and even one hundred percent, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Past and Present Dangers

The two Acropora species had already suffered from decades of localized impacts in Florida, such as contaminated water from contaminants 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 episode of coral bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the algae partners living in their tissues, causing them to become ghostly white.

If temperatures remain elevated, the corals die off entirely.

Global Implications

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

This presents a major threat to:

• A quarter of all ocean life that depends on what are effectively the rainforests of the sea.
• Millions of people who rely on corals to support fish that they can eat and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have established repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover disappeared 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 absent significant actions, scientists caution.

Further Expert Commentary

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

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals completely."