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

The Meaning Behind 'Functional Extinction' Means

The near-total collapse of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they can no longer play their once vital role in building and sustaining reef ecosystems that support a variety 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 has been crossed, whereby corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"Time is running out," stated the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to slow ocean warming and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

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

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

The two species are intricate, reef-forming corals and are identified because they resemble, in turn, the horns of male deer and elks.

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

Regional Impact

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

Past and Present Dangers

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

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

The 2023 heat event caused the ninth occurrence 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 ghostly white.

If temperatures stay high, the corals perish entirely.

Worldwide Consequences

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

This poses a significant danger to:

• One-fourth of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and earn a livelihood from.

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

Preservation Attempts

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

Efforts have been made to replant corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover lost off the state in the past four decades.

But as climate change continues to intensify, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Additional Expert Commentary

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

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals altogether."