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Researchers have found that two of the primary coral species comprising Florida's reef have become ecologically extinct following a withering ocean heatwave caused devastating losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they are no longer able to fulfill their previously crucial role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Ecological extinction is a phase before global extinction, a threat that now hangs for many coral species.

Scientists recently warned that a critical threshold has been crossed, whereby corals globally are likely to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," said the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and without swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The Recent Study

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 fraying 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 antlers of male deer and elks.

However, scientists who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Effects

• Along the Florida Keys, mortality rates hit ninety-eight percent and even 100%, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Historical and Present Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

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

The 2023 heat event caused the ninth episode of coral 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 remain elevated, the corals die off completely.

Worldwide Consequences

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

This poses a significant danger to:

• One-fourth of all ocean life that relies upon what are effectively the marine rainforests.
• Millions of people who rely on corals to support fish that they can eat and gain an income from.

Corals also act as a protective barrier to protect our shorelines from powerful storms, which are themselves being intensified by rising global temperatures.

Conservation Efforts

In a desperate attempt to avert a death spiral of endangered corals, scientists have created collections of Acropora in marine facilities 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 90% of coral cover lost off the state in the last forty years.

But as global heating continues to intensify, there is slim chance of continued existence of these species absent major interventions, researchers warn.

Further Researcher Insight

"Elkhorn corals, in particular, are some of the key wave-dampening coral species in the area," said a study co-author, a ocean scientist at the Miami University.

"They were once common on shallow reef tops 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 completely."