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Scientists have discovered that two of the key coral species forming Florida's reef are now ecologically extinct following a withering ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their once vital role in building and sustaining reef ecosystems that host a diversity of marine life.

Ecological extinction is a phase preceding global extinction, a threat that now looms for many coral species.

Researchers this month warned that a tipping point had been reached, whereby corals around the world are set to be eradicated due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without 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."

The New Research

The recent study, published in the journal Science, examined the outcome of staghorn and elkhorn corals off the Florida coast after a severe marine heatwave in 2023.

This event raised temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are complex, reef-building corals and are named because they look like, in turn, the antlers of male deer and elk.

However, researchers 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, mortality rates reached 98% and even 100%, showing 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 decades of regional pressures in Florida, such as contaminated water from contaminants that wash off the land, as well as disease.

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

The 2023 event caused the ninth episode 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 remain elevated, the corals perish completely.

Worldwide Consequences

Globally, 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 relies upon what are effectively the rainforests of the sea.
• Millions of people who rely on corals to sustain fish that they can consume and earn a livelihood 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 prevent a decline of threatened corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Efforts have been made to replant 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 climate change continues to escalate, there is little hope of continued existence of these species without significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," said 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."