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Scientists have discovered that two of the key coral species forming Florida's reef are now ecologically extinct following a withering ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that support a diversity of marine life.

Ecological extinction is a phase preceding global extinction, a danger that now hangs for many coral species.

Researchers this month warned that a tipping point has been crossed, whereby corals around the world are set to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

Details of the New Research

The new research, published in the journal Science, analyzed the outcome of staghorn coral and elkhorn coral corals off the Florida coast following a intense marine heatwave in 2023.

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are intricate, reef-forming corals and are named because they look like, respectively, the horns of male deer and elks.

However, scientists who performed underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often devastating, losses.

Regional Effects

• Along the Florida Keys, death rates hit ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Historical and Current Threats

The two Acropora species had already endured from many years of localized impacts in Florida, such as poor water quality from pollutants that wash off the land, as well as illness.

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

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

If temperatures remain elevated, the corals die off completely.

Global Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This poses a major threat to:

• A quarter of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to support fish that they can eat 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 increasing global heat.

Preservation Efforts

In a desperate attempt to avert a death spiral of threatened corals, scientists have created repositories 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 past four decades.

But as climate change continues to intensify, there is little hope of continued existence of these species without significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn species, especially, are some of the most important wave-breaking coral species in the region," noted Andrew Baker, a marine biologist at the Miami University.

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals completely."