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Researchers have found that two of the key coral species forming Florida's reef have become functionally extinct following a withering ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete 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 support a diversity of marine life.

Ecological extinction is a stage preceding total extinction, a danger that now hangs for many coral species.

Researchers this month warned that a critical threshold had been reached, whereby corals globally are likely to be wiped out due to global heating, which is increasing ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and around the world."

Details of the Recent Study

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

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

The two species are complex, reef-forming corals and are identified because they look like, respectively, the horns 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 catastrophic, losses.

Regional Effects

• In the Florida Keys, mortality rates reached ninety-eight percent and even one hundred percent, 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 Present Dangers

The two Acropora species had already suffered from many years of regional pressures in Florida, such as contaminated water from contaminants that run off the land, as well as illness.

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

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

If temperatures stay high, the corals die off entirely.

Worldwide Consequences

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

This poses a major threat 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 intense hurricanes, which are themselves being worsened by rising global temperatures.

Preservation Attempts

In a desperate attempt to avert a decline of endangered corals, scientists have established repositories of Acropora in aquariums and ocean-based nurseries.

Efforts have been undertaken to replant corals on reefs in Florida, as well, 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 intensify, there is slim chance of continued existence of these species absent significant actions, researchers warn.

Further Researcher Insight

"Elkhorn species, especially, are some of the most important wave-breaking coral species in the area," noted a study co-author, a marine biologist at the Miami University.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."