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Scientists have discovered that two of the primary coral species forming Florida's reef are now functionally extinct after a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

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

Researchers this month alerted that a critical threshold had been reached, whereby corals around the world are set to be wiped out due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Insight

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and without swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The New Research

The recent study, featured in the journal Science, examined the outcome of staghorn and elkhorn coral corals off the Florida coast after a intense marine heatwave in 2023.

This event elevated 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 resemble, respectively, the antlers of stags and elk.

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

Regional Impact

• Along the Florida Keys, death rates hit 98% and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about 38%.

Past and Present Dangers

The two Acropora species had already endured from decades 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 event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and eject the algae partners living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish completely.

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 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 act as a protective barrier to safeguard our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Conservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have created collections of Acropora in marine facilities and ocean-based nurseries.

Attempts have been undertaken to replant corals on reefs in Florida, as well, in an effort to restore some of the 90% of coral cover disappeared off the state in the past four decades.

But as climate change continues to intensify, there is slim chance of long-term survival of these species without major interventions, researchers warn.

Additional Researcher Insight

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

"They used to be abundant 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 exceptional steps to ensure we don't lose these corals altogether."