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

What 'Functional Extinction' Means

The near-total decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that host a diversity of marine life.

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

Researchers this month warned that a critical threshold had been reached, meaning corals globally are likely to be wiped out due to climate change, which is raising ocean temperatures to unbearable 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 global warming, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

The Recent Study

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

This event raised temperatures on Florida's fraying coral reefs to their highest levels in more than a century and a half.

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

However, researchers who conducted underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Effects

• Along the Florida Keys, death rates reached 98% and even 100%, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Historical and Current Threats

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from pollutants that wash off the land, as well as illness.

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

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

If temperatures stay high, the corals die off entirely.

Global Implications

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

This poses a major threat to:

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

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

Preservation Efforts

In a last-ditch effort to avert a death spiral of threatened corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been undertaken to replant 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 past four decades.

But as climate change continues to intensify, there is slim chance of long-term survival of these species without significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," noted Andrew Baker, a ocean scientist at the Miami University.

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals completely."