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Researchers have found that two of the most important coral species comprising Florida's reef are now functionally extinct after a intense ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

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

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

Scientists recently warned that a critical threshold had been reached, whereby corals globally are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," stated Ross Cunning of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and worldwide."

The New Research

The recent study, featured in the journal Science, examined the outcome of staghorn and elkhorn corals off the Florida coast following a intense marine heatwave in 2023.

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

The two species are intricate, reef-forming corals and are named because they resemble, in turn, the horns of stags and elk.

However, scientists who performed diver surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Geographic Impact

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

Historical and Present Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as poor water quality 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 episode of coral bleaching on the Florida reef – a process 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 die off entirely.

Global Consequences

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

This poses a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of millions of people who rely on corals to sustain fish that they can consume and earn a livelihood from.

Corals also act as a protective barrier to safeguard our shorelines from powerful storms, which are themselves being worsened by increasing global heat.

Conservation Efforts

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

Efforts have been undertaken to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover lost off the state in the last forty years.

But as climate change continues to intensify, there is little hope of continued existence of these species without significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, especially, are some of the key wave-breaking coral species in the region," said a study co-author, a ocean scientist at the Miami University.

"They were once 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 preserve these corals altogether."