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Researchers have found that two of the key coral species forming Florida's reef have become ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

The near-total 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.

Functional extinction is a stage before global extinction, a threat that now looms for many coral species.

Scientists this month warned that a tipping point has been crossed, whereby corals globally are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

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 elevated temperatures on Florida's fraying coral reefs to their peak temperatures in over 150 years.

The two species are intricate, reef-forming corals and are named because they resemble, respectively, the horns of male deer and elk.

However, scientists who performed diver surveys of over fifty-two thousand 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 hit ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Current Threats

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

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

The 2023 event caused the ninth occurrence of coral 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 ghostly white.

If temperatures stay high, the corals perish completely.

Global Implications

Globally, coral reefs are among the ecosystems most at risk to the anthropogenic climate crisis.

This poses a significant danger to:

• A quarter of all ocean life that relies upon 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 powerful storms, which are themselves being intensified by rising global temperatures.

Conservation Efforts

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

Efforts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the last forty years.

But as global heating continues to escalate, there is slim chance of long-term survival of these species absent major interventions, scientists caution.

Further Researcher Insight

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the region," 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 keep safeguarding our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."