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Researchers have found that two of the most important coral species forming Florida's reef have become functionally extinct following a intense ocean heatwave caused devastating losses.

What 'Functional Extinction' Signifies

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

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

Scientists recently warned that a tipping point had been reached, whereby corals globally are likely to be wiped out due to global heating, which is increasing ocean temperatures to intolerable levels.

Expert Insight

"We're running out of time," stated the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and worldwide."

The New Research

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

This event raised 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-building corals and are identified because they resemble, in turn, the antlers 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 catastrophic, losses.

Geographic Effects

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

Past and Current Dangers

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

But the 2023 heatwave has been fatal for these heat-sensitive species.

The 2023 heat event caused the ninth episode of coral bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off entirely.

Worldwide Implications

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

This poses a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to avert a decline of endangered corals, scientists have established repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken to replant corals on reefs in Florida, too, in an effort to regain some of the 90% 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, scientists caution.

Further Expert Commentary

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

"They were once 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 completely."