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Researchers have found that two of the most important coral species forming Florida's reef have become functionally extinct after a intense ocean heatwave led to devastating losses.

What 'Functional Extinction' Means

The near-total decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a stage preceding total extinction, a danger that now looms for many coral species.

Scientists recently warned that a tipping point has been crossed, meaning corals globally are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

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

The Recent Study

The new research, featured in the journal Science, examined the fate 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 deteriorating coral reefs to their peak temperatures in over 150 years.

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

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

Regional Effects

• Along the Florida Keys, mortality rates hit 98% and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were reduced, at about 38%.

Historical and Present Threats

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from contaminants 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 bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish entirely.

Worldwide Consequences

Worldwide, 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 marine rainforests.
• Hundreds of millions of people who depend upon corals to support fish that they can consume and gain an income 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 death spiral of threatened corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been made 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 climate change continues to escalate, there is little hope of continued existence of these species without major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn corals, especially, are some of the key wave-dampening coral species in the area," noted Andrew Baker, a marine biologist at the Miami University.

"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, its worth taking extraordinary measures to ensure we preserve these corals completely."