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Scientists have discovered that two of the most important coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The near-total decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill their once vital role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Functional extinction is a stage before total extinction, a danger that now hangs for many coral species.

Researchers recently alerted that a tipping point had been reached, whereby corals globally are set to be eradicated due to climate change, which is increasing ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," stated Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and around the world."

The New Research

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

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

The two species are intricate, reef-building corals and are identified because they look like, in turn, the horns of male deer and elks.

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often devastating, losses.

Geographic Impact

• Along the Florida Keys, death rates reached 98% and even 100%, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Present Dangers

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

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

The 2023 event caused the ninth episode of 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 ghostly white.

If temperatures stay high, the corals perish completely.

Global Implications

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

This poses a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• 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 protect our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Conservation Attempts

In a last-ditch effort to prevent a decline of endangered corals, scientists have created repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to reseed corals on reefs in Florida, as well, 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 escalate, there is little hope of continued existence of these species absent major interventions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the most important wave-dampening coral species in the area," said Andrew Baker, a marine biologist at the Miami University.

"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, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."