🔗 Share this article

Scientists have discovered that two of the primary coral species comprising Florida's reef have become functionally extinct after a intense ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they can no longer play their once vital role in building and sustaining reef ecosystems that host a diversity of marine life.

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

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

Researcher Perspective

"We're running out of time," stated the lead author of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

The Recent Study

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

This event elevated temperatures on Florida's fraying coral reefs to their peak temperatures in more than a century and a half.

The two species are complex, reef-forming corals and are identified because they look like, respectively, the horns of stags and elks.

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 Impact

• Along the Florida Keys, mortality rates reached ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were reduced, at about 38%.

Past and Current Threats

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from contaminants that run off the land, as well as illness.

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

The 2023 heat event caused the ninth episode of bleaching on the Florida reef – a process whereby corals become heat-stressed and eject the algae partners living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals perish completely.

Worldwide 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 relies upon what are effectively the marine rainforests.
• Millions of people who rely on corals to support fish that they can consume and gain an income from.

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

Preservation Efforts

In a desperate attempt to prevent a death spiral of threatened corals, scientists have established collections of Acropora in aquariums and offshore coral nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore 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 major interventions, researchers warn.

Further Researcher Insight

"Elkhorn species, in particular, are some of the key wave-dampening coral species in the area," said a study co-author, a ocean scientist at the University of Miami.

"They were once common 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 preserve these corals altogether."