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Researchers have found that two of the key coral species forming Florida's reef are now functionally extinct following a intense ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill their once vital role in constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a phase preceding total extinction, a threat that now looms for many coral species.

Scientists this month alerted that a tipping point had been reached, meaning corals around the world are set to be eradicated due to climate change, which is raising ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," said the lead author of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to climate change, 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 around the world."

The Recent Study

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

This event raised temperatures on Florida's deteriorating coral reefs to their highest levels in more than a century and a half.

The two species are complex, reef-building corals and are named because they resemble, in turn, the horns of male deer and elks.

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

Geographic Impact

• Along the Florida Keys, death rates reached 98% and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were lower, at about 38%.

Historical and Present Dangers

The two Acropora species had already suffered from decades of localized impacts in Florida, such as poor water quality from contaminants that run off the land, as well as illness.

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

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

If temperatures remain elevated, the corals perish completely.

Worldwide Implications

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

This presents a significant danger to:

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

Corals also act as a protective barrier to safeguard our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Preservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have created repositories of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to reseed corals on reefs in Florida, as well, in an effort to regain 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 long-term survival of these species absent significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the most important wave-dampening coral species in the region," noted a study co-author, a marine biologist at the University of Miami.

"They were once common 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 exceptional steps to ensure we preserve these corals completely."