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

What '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 constructing and maintaining reef ecosystems that support a diversity of marine life.

Functional extinction is a stage before global extinction, a threat that now hangs 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 increasing ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," said the lead author of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and absent immediate, ambitious actions to slow ocean warming 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 new research, featured in the Science journal, examined the fate of staghorn and elkhorn coral corals off the Florida coast after a intense marine heatwave in 2023.

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

The two species are intricate, reef-building corals and are named because they look like, in turn, the horns of stags and elks.

However, scientists 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.

Geographic Effects

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

Historical and Present Threats

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

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

The 2023 heat event caused the ninth occurrence of coral bleaching on the Florida reef – a process whereby corals become thermally 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

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

This presents a major threat to:

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

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

Conservation Attempts

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

Attempts have been made to replant 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 major interventions, scientists caution.

Additional Researcher Insight

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

"They were once common on shallow reef tops 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 don't lose these corals altogether."