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Scientists have discovered that two of the primary coral species comprising Florida's reef have become ecologically extinct following a intense ocean heatwave caused devastating losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they are no longer able to fulfill their previously crucial role in building and sustaining reef ecosystems that support a diversity of marine life.

Functional extinction is a phase preceding total extinction, a danger that now hangs for many coral species.

Researchers recently alerted that a tipping point had been reached, meaning corals globally are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

Details of the New Research

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

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

The two species are complex, reef-building corals and are identified because they look like, respectively, the antlers of stags and elk.

However, scientists who conducted diver 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 hit ninety-eight percent and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Past and Current Dangers

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

But the 2023 marine heatwave has proved fatal for these heat-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 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 presents a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat 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 Efforts

In a last-ditch effort to prevent a decline of threatened corals, scientists have created repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken to replant corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as climate change continues to intensify, there is slim chance of continued existence of these species without major interventions, scientists caution.

Additional Researcher Insight

"Elkhorn corals, in particular, are some of the most important wave-dampening coral species in the area," noted Andrew Baker, 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, its worth taking exceptional steps to ensure we don't lose these corals completely."