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Scientists have discovered that two of the most important coral species comprising Florida's reef have become ecologically extinct following a intense ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Signifies

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

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

Researchers this month warned that a tipping point has been crossed, whereby corals globally are set to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without swift, decisive measures to slow ocean warming and enhance coral survival, 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 outcome of staghorn and elkhorn corals off the Florida coast after a severe marine heatwave in 2023.

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are complex, reef-forming corals and are named because they look like, in turn, the horns of male deer and elk.

However, scientists who performed diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Geographic Impact

• In the Florida Keys, death rates reached ninety-eight percent and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already endured from many years of regional pressures in Florida, such as poor water quality from contaminants that run off the land, as well as disease.

But the 2023 marine heatwave has proved lethal 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 eject the algae partners living in their tissues, causing them to become ghostly white.

If temperatures remain elevated, the corals die off completely.

Global Consequences

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

This presents a significant danger 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 sustain fish that they can consume and earn a livelihood from.

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

Conservation Attempts

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

Efforts have been undertaken to replant corals on reefs in Florida, too, 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 escalate, there is slim chance of continued existence of these species without major interventions, researchers warn.

Additional Researcher Insight

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

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals altogether."