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Scientists have discovered that two of the primary coral species comprising Florida's reef have become functionally extinct after a intense ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, indicates they can no longer play their previously crucial role in building and sustaining reef ecosystems that support a diversity of marine life.

Functional extinction is a phase preceding global extinction, a danger that now looms for many coral species.

Scientists this month warned 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.

Researcher Perspective

"Time is running out," said the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to reduce ocean heating and boost coral resilience, we risk the disappearance of even more corals from reefs in Florida and around the world."

The New Research

The new research, published in the journal Science, analyzed the fate of staghorn coral 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 highest levels in more than a century and a half.

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

However, scientists 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.

Regional Impact

• Along 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 lower, mortality rates were lower, at about 38%.

Past and Present Threats

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

But the 2023 marine heatwave has been fatal for these heat-sensitive species.

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

If temperatures stay high, the corals perish completely.

Global Consequences

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

This presents a significant danger to:

• One-fourth of all ocean life that depends on what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and earn a livelihood from.

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

Preservation Attempts

In a desperate attempt to avert a decline of threatened corals, scientists have established collections of Acropora in aquariums 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 ninety percent of coral cover lost off the state in the last forty years.

But as climate change continues to intensify, there is little hope of continued existence of these species absent major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn species, especially, are some of the most important wave-breaking coral species in the area," said a study co-author, a marine biologist 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 inundation during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."