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

The Meaning Behind 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they can no longer play their previously crucial role in building and sustaining reef ecosystems that host a variety of marine life.

Functional extinction is a phase before total extinction, a danger that now hangs for many coral species.

Scientists recently warned that a tipping point had been reached, meaning corals globally are set to be eradicated due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to slow ocean warming and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and worldwide."

Details of the New Research

The new research, featured in the journal Science, examined the outcome of staghorn and elkhorn corals off the Florida coast after a severe marine heatwave in 2023.

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

The two species are complex, reef-building corals and are named because they look like, in turn, the antlers of male deer and elks.

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 catastrophic, losses.

Regional Impact

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

Historical and Present Threats

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

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

The 2023 event caused the ninth occurrence 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 stay high, the corals die off entirely.

Global Implications

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

This poses 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 support fish that they can eat and gain an income from.

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

Conservation Efforts

In a desperate attempt to prevent a decline of endangered corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Attempts 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 past four decades.

But as global heating continues to escalate, there is little hope of continued existence of these species without major interventions, researchers warn.

Additional Researcher Insight

"Elkhorn species, in particular, are some of the key wave-breaking coral species in the area," said Andrew Baker, a ocean scientist at the Miami University.

"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 extraordinary measures to ensure we preserve these corals completely."