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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 caused catastrophic losses.

What 'Functional Extinction' Signifies

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

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

Scientists this month warned that a critical threshold had been reached, whereby corals globally are set to be eradicated due to global heating, which is raising ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent swift, decisive measures to reduce ocean heating and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

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

This event raised temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.

The two species are intricate, reef-building corals and are identified because they resemble, respectively, the horns of stags and elks.

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

Regional Impact

• In 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 lower, death rates were lower, at about 38%.

Historical and Present Dangers

The two Acropora species had already suffered from many years of regional pressures 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 temperature-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 ghostly white.

If temperatures stay high, the corals die off completely.

Global Implications

Globally, 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 effectively the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can consume and gain an income from.

Corals also serve as a protective barrier to protect our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Preservation Efforts

In a last-ditch effort to prevent a decline of endangered corals, scientists have created repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been made 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 past four decades.

But as climate change continues to escalate, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn species, especially, are some of the key wave-breaking coral species in the region," said a study co-author, 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 keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals altogether."