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Scientists have discovered that two of the most important coral species comprising Florida's reef have become ecologically extinct following a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone 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 preceding global extinction, a threat that now hangs for many coral species.

Scientists recently warned that a tipping point has been crossed, whereby corals globally are set to be eradicated due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

Details of the New Research

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

This event raised 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-forming corals and are named because they resemble, respectively, the horns of male deer and elks.

However, researchers 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

• In the Florida Keys, mortality rates reached 98% and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were reduced, at about 38%.

Historical and Current Threats

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

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

The 2023 heat event caused the ninth occurrence of 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.

Global Consequences

Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate emergency.

This presents a major threat 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 serve as a barrier to protect our shorelines from powerful storms, which are themselves being intensified by rising global temperatures.

Preservation Attempts

In a desperate attempt to avert a death spiral of threatened corals, scientists have created collections of Acropora in aquariums and ocean-based nurseries.

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to regain some of the 90% of coral cover lost off the state in the last forty years.

But as global heating continues to escalate, there is little hope of continued existence of these species without significant actions, researchers warn.

Additional Expert Commentary

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

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."