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Researchers have found that two of the primary coral species comprising Florida's reef are now ecologically extinct following a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they are no longer able to play their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

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

Researchers this month warned that a critical threshold has been crossed, whereby corals around the world are set to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and worldwide."

The Recent Study

The new research, published in the Science journal, examined the outcome of staghorn and elkhorn corals off the Florida coast following a severe 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 complex, reef-forming corals and are identified because they look like, respectively, the antlers of stags 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 widespread, often catastrophic, losses.

Geographic Impact

• Along the Florida Keys, mortality rates reached 98% and even 100%, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Past 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 wash 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 occurrence 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 bleached white.

If temperatures remain elevated, the corals die off entirely.

Worldwide Consequences

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate emergency.

This poses a major threat to:

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

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

Preservation Attempts

In a last-ditch effort to prevent a death spiral of threatened corals, scientists have created collections of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to restore some of the ninety percent 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 significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn species, in particular, are some of the key wave-breaking coral species in the area," said Andrew Baker, a marine biologist at the University of Miami.

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