A Pair of Essential Florida Coral Species Declared 'Functionally Extinct' After Severe Ocean Heatwave

Researchers have found that two of the key coral species comprising Florida's reef are now functionally extinct following a intense ocean heatwave caused catastrophic losses.

The Meaning Behind '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 constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a stage before total extinction, a threat that now looms for many coral species.

Researchers recently alerted that a critical threshold had been reached, whereby corals around the world are set to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," said the lead author of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and around the world."

The New Research

The recent study, published in the Science journal, analyzed the outcome of staghorn coral 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 complex, reef-forming corals and are identified because they resemble, respectively, the horns of male deer and elk.

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

Regional Impact

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

Historical and Current Threats

The two Acropora species had already endured from decades of regional pressures in Florida, such as poor water quality from pollutants that wash off the land, as well as disease.

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

The 2023 heat event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and expel the algae partners 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 crisis.

This poses a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the rainforests of the sea.
• Millions of people who rely on corals to support fish that they can consume and gain an income from.

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

Preservation Efforts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have created collections 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 lost off the state in the last forty years.

But as climate change continues to intensify, there is little hope of long-term survival of these species absent major interventions, researchers warn.

Further Researcher Insight

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

"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 extraordinary measures to ensure we preserve these corals completely."