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Scientists have discovered that two of the key coral species forming Florida's reef are now functionally extinct after a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

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 diversity of marine life.

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

Researchers recently warned that a critical threshold has been crossed, whereby corals around the world are set to be eradicated due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," said 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 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 Recent Study

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

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures 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 male deer and elk.

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Geographic Impact

• In the Florida Keys, death rates reached ninety-eight percent and even 100%, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Historical and Present Dangers

The two Acropora species had already endured from many years of regional pressures in Florida, such as poor water quality from pollutants that run off the land, as well as illness.

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

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

If temperatures stay high, the corals perish entirely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused 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.
• Millions of people who depend upon corals to sustain fish that they can eat and earn a livelihood from.

Corals also serve as a barrier to safeguard our shorelines from powerful storms, which are themselves being intensified by increasing global heat.

Conservation Attempts

In a desperate attempt to prevent a decline of endangered corals, scientists have created collections of Acropora in aquariums and ocean-based nurseries.

Efforts 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 long-term survival of these species absent major interventions, researchers warn.

Further 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 were once common 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 don't lose these corals completely."