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Scientists have discovered that two of the most important coral species comprising Florida's reef have become functionally extinct following a intense ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

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

Researchers recently alerted that a critical threshold had been reached, whereby corals globally are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

Details of the New Research

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

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

The two species are intricate, reef-building corals and are named because they look like, respectively, the horns of male deer and elk.

However, researchers who performed underwater surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found extensive, often devastating, losses.

Geographic Effects

• Along the Florida Keys, death rates hit 98% and even 100%, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Current Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from pollutants that wash off the land, as well as illness.

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

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

If temperatures stay high, the corals perish completely.

Global Consequences

Worldwide, coral reefs are among the ecosystems most at risk to the human-caused climate emergency.

This presents a major threat to:

• A quarter 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 eat and earn a livelihood from.

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

Conservation Efforts

In a desperate attempt to prevent a death spiral of endangered corals, scientists have established 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 ninety percent of coral cover disappeared off the state in the last forty years.

But as global heating continues to intensify, there is little hope of long-term survival of these species without major interventions, scientists caution.

Additional Researcher Insight

"Elkhorn species, especially, are some of the key wave-breaking coral species in the region," noted a study co-author, a ocean scientist at the University of Miami.

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking exceptional steps to ensure we don't lose these corals completely."