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

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they are no longer able to play 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 looms for many coral species.

Scientists this month alerted that a tipping point had been reached, meaning corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we risk the extinction of even more corals from reefs in Florida and around the world."

The New Research

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

This event raised temperatures on Florida's deteriorating coral reefs to their highest levels in over 150 years.

The two species are intricate, reef-forming corals and are identified because they look like, in turn, the antlers of stags and elk.

However, researchers who performed underwater surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Geographic Impact

• In the Florida Keys, mortality rates reached ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been cooler, death rates were reduced, 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 contaminated water from contaminants that run off the land, as well as disease.

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

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

If temperatures remain elevated, the corals die off entirely.

Worldwide Consequences

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

This poses a significant danger to:

• One-fourth of all ocean life that relies upon what are essentially the rainforests of the sea.
• Millions of people who rely on corals to sustain 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 intensified by increasing global heat.

Preservation Attempts

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 undertaken to reseed corals on reefs in Florida, too, 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 without significant actions, researchers warn.

Additional Researcher Insight

"Elkhorn corals, especially, are some of the most important wave-dampening coral species in the region," noted a study co-author, a marine biologist at the Miami University.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals completely."