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

What 'Functional Extinction' Means

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

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

Scientists this month alerted that a tipping point has been crossed, meaning corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"Time is running out," stated the lead author of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, 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, analyzed the outcome of staghorn and elkhorn coral corals off the Florida coast after a intense marine heatwave in 2023.

This event raised temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are complex, reef-building corals and are identified because they resemble, respectively, the antlers of male deer and elk.

However, researchers who performed underwater surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Geographic Effects

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

Historical and Present Threats

The two Acropora species had already suffered from many years of regional pressures in Florida, such as contaminated water from contaminants that wash off the land, as well as disease.

But the 2023 heatwave has proved lethal for these temperature-sensitive species.

The 2023 event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the algae partners 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 significant danger to:

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

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

Conservation Efforts

In a last-ditch effort to avert a decline of threatened corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been undertaken 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 past four decades.

But as global heating continues to escalate, there is little hope of continued existence of these species absent significant actions, researchers warn.

Further Expert Commentary

"Elkhorn species, in particular, are some of the key wave-breaking coral species in the region," said a study co-author, a marine biologist at the University of Miami.

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