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

The Meaning Behind 'Functional Extinction' Means

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 building and sustaining reef ecosystems that host a diversity of marine life.

Ecological extinction is a phase preceding total extinction, a threat that now looms for many coral species.

Researchers this month alerted that a tipping point has been crossed, whereby corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

"We're running out of time," said the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without swift, decisive measures to slow ocean warming and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

The New Research

The new research, featured in the journal Science, examined the outcome of staghorn and elkhorn corals off the Florida coast following a severe marine heatwave in 2023.

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

The two species are intricate, reef-forming corals and are named because they resemble, respectively, the horns of male deer 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 devastating, losses.

Regional Impact

• In the Florida Keys, death rates reached ninety-eight percent and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Historical and Current Threats

The two Acropora species had already endured from many years 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 proved fatal for these temperature-sensitive species.

The 2023 event caused the ninth occurrence of coral bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the algae partners 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 at risk to the anthropogenic climate crisis.

This poses a significant danger to:

• A quarter of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who rely on corals to support fish that they can consume and earn a livelihood from.

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

Conservation Efforts

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

Efforts have been undertaken to replant corals on reefs in Florida, as well, in an effort to restore some of the 90% of coral cover disappeared off the state in the past four decades.

But as global heating continues to intensify, there is slim chance of long-term survival of these species without major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn species, 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 used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals altogether."