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Researchers have found that two of the key coral species comprising Florida's reef are now ecologically extinct after a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

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

Functional extinction is a stage preceding global extinction, a threat that now hangs for many coral species.

Researchers recently warned that a critical threshold had been reached, meaning corals globally are set to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"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 without immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the extinction of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

The new research, featured in the Science journal, examined the fate of staghorn and elkhorn corals off the Florida coast following 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 intricate, reef-building corals and are identified because they look like, respectively, the antlers 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 catastrophic, losses.

Regional Effects

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

Historical and Current Dangers

The two Acropora species had already endured 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 fatal for these temperature-sensitive species.

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

If temperatures stay high, the corals perish entirely.

Worldwide Consequences

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

This poses a significant danger to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Millions of people who depend upon corals to sustain fish that they can eat and gain an income from.

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

Conservation Efforts

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

Efforts have been made to reseed corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover disappeared off the state in the past four decades.

But as global heating continues to intensify, there is little hope of continued existence of these species absent significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the key wave-dampening coral species in the area," 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 keep safeguarding our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."