Two Vital Florida Coral Species Declared 'Functionally Extinct' After Devastating Ocean Heatwave

Scientists have discovered that two of the primary coral species comprising Florida's reef are now functionally extinct after a intense ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they can no longer play their once vital role in building and sustaining reef ecosystems that support a diversity of marine life.

Functional extinction is a phase before total extinction, a threat that now looms for many coral species.

Scientists this month warned that a tipping point had been reached, whereby corals globally are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"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 enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

The New Research

The new research, featured in the Science journal, examined the outcome of staghorn coral 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 peak temperatures in more than a century and a half.

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

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

Regional Effects

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

Past and Current Threats

The two Acropora species had already endured from many years 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 heat event caused the ninth episode of coral bleaching on the Florida reef – a process whereby corals become thermally stressed and eject the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals perish entirely.

Global Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate emergency.

This poses a major threat to:

• One-fourth of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Conservation Efforts

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

Attempts have been undertaken to replant corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover lost off the state in the past four decades.

But as global heating continues to intensify, there is little hope of long-term survival of these species without major interventions, researchers warn.

Additional Expert Commentary

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

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."