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Researchers have found that two of the most important coral species forming Florida's reef are now ecologically extinct after a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that host a variety of marine life.

Functional extinction is a phase preceding total extinction, a danger that now hangs for many coral species.

Scientists recently alerted that a tipping point has been crossed, whereby corals around the world are likely to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," said Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the extinction of additional coral species from reefs in Florida and around the world."

Details of the New Research

The recent study, published in the Science journal, analyzed the fate of staghorn 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 named because they resemble, respectively, the horns of stags and elks.

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 devastating, losses.

Regional Effects

• Along the Florida Keys, mortality rates hit 98% and even one hundred percent, showing 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 poor water quality from contaminants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals die off completely.

Worldwide Consequences

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

This presents a major threat to:

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

Corals also serve as a protective barrier to safeguard our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Preservation Efforts

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

Efforts have been undertaken 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 past four decades.

But as global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Further Expert Commentary

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

"They used to be 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 preserve these corals completely."