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Scientists have discovered that two of the primary coral species forming Florida's reef have become ecologically extinct following a intense ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates 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 phase preceding global extinction, a danger that now looms for many coral species.

Scientists recently alerted that a tipping point has been crossed, meaning corals around the world are likely to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

"We're running out of time," said the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

Details of the Recent Study

The recent study, featured in the Science journal, analyzed the fate of staghorn coral and elkhorn coral corals off the Florida coast after a severe marine heatwave in 2023.

This event raised temperatures on Florida's fraying 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, in turn, the horns of male deer and elk.

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

Geographic Impact

• In the Florida Keys, mortality 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 thirty-eight percent.

Past and Current Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as poor water quality from pollutants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals perish entirely.

Global Implications

Worldwide, 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 depend upon corals to support fish that they can eat and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have created repositories 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 ninety percent of coral cover disappeared off the state in the last forty years.

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

Further Researcher Insight

"Elkhorn species, especially, are some of the most important wave-breaking coral species in the area," 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, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."