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Scientists have discovered that two of the primary coral species forming Florida's reef have become ecologically extinct following a intense ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

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

Ecological extinction is a stage before global extinction, a danger that now looms for many coral species.

Scientists recently warned that a tipping point has been crossed, meaning corals globally are set to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," stated Ross Cunning of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and worldwide."

Details of the New Research

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

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

The two species are complex, reef-forming corals and are named because they look like, in turn, the antlers 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 extensive, often devastating, losses.

Regional Impact

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

Past 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 marine heatwave has been lethal for these temperature-sensitive species.

The 2023 heat event caused the ninth episode of coral bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals die off entirely.

Global Implications

Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate emergency.

This presents a major threat to:

• One-fourth of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and gain an income from.

Corals also act as a protective barrier to protect our shorelines from powerful storms, which are themselves being worsened by increasing global heat.

Preservation Attempts

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 undertaken to reseed corals on reefs in Florida, too, in an effort to restore some of the ninety percent of coral cover lost off the state in the last forty years.

But as climate change continues to escalate, there is little hope of long-term survival of these species absent major interventions, scientists caution.

Additional Expert Commentary

"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 University of Miami.

"They used to be abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals completely."