Two Crucial Florida Coral Species Declared 'Functionally Extinct' Following Severe Ocean Heatwave

Scientists have discovered that two of the most important coral species comprising Florida's reef are now ecologically extinct following a withering ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that support a variety of marine life.

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

Researchers this month warned that a tipping point had been reached, whereby corals globally are set to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and worldwide."

The New Research

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

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

The two species are intricate, reef-forming corals and are named because they look like, respectively, the antlers of stags and elk.

However, researchers who conducted diver surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Impact

• Along the Florida Keys, death rates hit ninety-eight percent and even 100%, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Past and Current Dangers

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

But the 2023 marine heatwave has been fatal for these heat-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 symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off entirely.

Global Consequences

Worldwide, coral reefs are among the ecosystems most vulnerable to the anthropogenic 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 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 increasing global heat.

Conservation Efforts

In a desperate attempt to prevent a decline of threatened corals, scientists have created repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been undertaken to replant 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 last forty years.

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

Additional Researcher Insight

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

"They were once abundant on shallow reef crests 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 altogether."