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Scientists have discovered that two of the key coral species forming Florida's reef are now functionally extinct following a withering ocean heatwave caused devastating 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 play their once vital 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 hangs for many coral species.

Researchers recently warned that a tipping point had been reached, meaning corals globally are likely to be eradicated due to global heating, which is increasing ocean temperatures to intolerable levels.

Expert Perspective

"We're running out of time," stated Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent swift, decisive measures to reduce ocean heating and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and around the world."

The New Research

The new research, featured in the journal Science, examined the fate of staghorn and elkhorn corals off the Florida coast following a intense marine heatwave in 2023.

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

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

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

Regional Impact

• Along the Florida Keys, mortality rates hit ninety-eight percent and even 100%, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Past and Present Dangers

The two Acropora species had already endured from many years 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 been fatal for these temperature-sensitive species.

The 2023 event caused the ninth episode of coral bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish entirely.

Global Consequences

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

This poses a major threat to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Hundreds of millions of people who rely on corals to support fish that they can consume and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to avert a death spiral of endangered corals, scientists have created repositories of Acropora in aquariums and offshore coral nurseries.

Efforts 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 last forty years.

But as global heating continues to escalate, there is slim chance of continued existence of these species without significant actions, researchers warn.

Further Researcher Insight

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," noted Andrew Baker, 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 inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."