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Researchers have found that two of the most important coral species forming Florida's reef are now functionally extinct following a withering ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill their once vital role in building and sustaining reef ecosystems that support a variety of marine life.

Ecological extinction is a phase before global extinction, a danger that now looms for many coral species.

Scientists recently alerted that a critical threshold has been crossed, meaning corals around the world are set to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," stated the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and absent swift, decisive measures to reduce ocean heating and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and worldwide."

The Recent Study

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

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

The two species are complex, reef-building corals and are identified because they resemble, in turn, the horns of stags and elks.

However, scientists 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

• In the Florida Keys, mortality rates hit 98% and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Historical and Current Dangers

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

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

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

If temperatures stay high, the corals die off entirely.

Global 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 rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Conservation Attempts

In a desperate attempt to avert a death spiral of endangered corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover lost off the state in the past four decades.

But as climate change continues to escalate, there is little hope of continued existence of these species without major interventions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the key wave-dampening coral species in the region," said Andrew Baker, a ocean scientist 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, its worth taking exceptional steps to ensure we preserve these corals altogether."