A Pair of Essential Florida Coral Species Declared 'Functionally Extinct' After Devastating Ocean Heatwave

Researchers have found that two of the most important coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave caused devastating losses.

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they are no longer able to fulfill their once vital role in constructing and maintaining reef ecosystems that support a diversity of marine life.

Functional extinction is a phase preceding total extinction, a threat that now hangs for many coral species.

Researchers this month alerted that a tipping point has been crossed, whereby corals globally are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"We're running out of time," said Ross Cunning of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the extinction of additional coral species from reefs in Florida and around the world."

Details of the New Research

The recent study, published in the journal Science, examined the outcome 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 highest levels in over 150 years.

The two species are intricate, reef-forming corals and are identified 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 nearly four hundred sites along Florida's coast, found widespread, often devastating, losses.

Regional Effects

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

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 marine heatwave has been lethal for these heat-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 symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals die off entirely.

Global Implications

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

This poses a major threat to:

• One-fourth of all ocean life that depends on what are effectively the marine rainforests.
• Millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

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

Preservation Efforts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have established 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 regain some of the ninety percent of coral cover disappeared off the state in the last forty years.

But as global heating continues to intensify, there is slim chance of long-term survival of these species without significant actions, scientists caution.

Further Expert Commentary

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

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals completely."