Two Crucial Florida Coral Species Declared 'Functionally Extinct' After Severe Ocean Heatwave

Scientists have discovered that two of the key coral species comprising Florida's reef have become ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Means

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 previously crucial role in constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a phase before global extinction, a danger that now looms for many coral species.

Scientists this month warned that a critical threshold has been crossed, whereby corals globally are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Insight

"We're running out of time," said the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the extinction 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 outcome of staghorn and elkhorn coral corals off the Florida coast following a severe marine heatwave in 2023.

This event elevated temperatures on Florida's deteriorating coral reefs to their highest levels 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 horns of stags and elk.

However, scientists who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found extensive, often devastating, losses.

Geographic Impact

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

Historical and Current Threats

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

But the 2023 marine heatwave has been 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.

Worldwide Consequences

Globally, coral reefs are among the ecosystems most vulnerable 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 rely on corals to sustain fish that they can eat and earn a livelihood from.

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

Conservation Attempts

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

Efforts have been made to reseed 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 intensify, there is little hope of continued existence of these species absent major interventions, scientists caution.

Additional Expert Commentary

"Elkhorn species, 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 abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we don't lose these corals completely."