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

What 'Functional Extinction' Signifies

The near-total decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their previously crucial role in building and sustaining reef ecosystems that support a diversity of marine life.

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

Scientists recently alerted that a tipping point has been crossed, meaning corals around the world are likely to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Insight

"We're running out of time," stated Ross Cunning of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and worldwide."

The Recent Study

The recent study, published in the journal Science, examined the fate of staghorn and elkhorn corals off the Florida coast following a intense marine heatwave in 2023.

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

The two species are intricate, reef-building corals and are named because they look like, respectively, the antlers of stags and elk.

However, researchers who performed underwater surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Effects

• Along the Florida Keys, death rates hit 98% and even one hundred percent, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, death rates were lower, at about thirty-eight percent.

Past and Current Threats

The two Acropora species had already endured from decades of localized impacts in Florida, such as contaminated water from contaminants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals perish completely.

Global Implications

Globally, coral reefs are among the ecosystems most at risk to the anthropogenic climate crisis.

This presents a major threat to:

• A quarter of all ocean life that depends on what are effectively the rainforests of the sea.
• Millions of people who rely on corals to support fish that they can eat and earn a livelihood from.

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

Preservation Efforts

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

Attempts have been made to replant corals on reefs in Florida, too, in an effort to restore 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 absent major interventions, scientists caution.

Further Researcher Insight

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

"They were once common 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."