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Researchers have found that two of the primary coral species forming Florida's reef are now functionally extinct following a intense ocean heatwave led to devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The near-total collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their once vital role in building and sustaining reef ecosystems that support a variety of marine life.

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

Researchers this month alerted that a critical threshold has been crossed, whereby corals around the world are likely to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Insight

"Time is running out," stated the lead author of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to slow ocean warming and boost coral resilience, we face the danger of the disappearance of additional coral species from reefs in Florida and worldwide."

The Recent Study

The recent study, featured in the Science journal, examined the fate of staghorn and elkhorn corals off the Florida coast after a intense 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 complex, reef-building corals and are identified because they resemble, respectively, the horns of stags and elk.

However, scientists who conducted underwater 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 Impact

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

Past and Current Dangers

The two Acropora species had already suffered from decades of regional pressures in Florida, such as poor water quality from pollutants that wash 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 coral bleaching on the Florida reef – a process whereby corals become thermally stressed and expel the algae partners living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish completely.

Worldwide Consequences

Globally, 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 relies upon what are effectively the marine rainforests.
• Hundreds of millions of people who depend upon corals to support fish that they can consume and earn a livelihood from.

Corals also act as a protective barrier to safeguard our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Preservation Efforts

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

Efforts have been made to reseed 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 global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the key wave-breaking coral species in the area," said Andrew Baker, a ocean scientist at the University of Miami.

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we don't lose these corals completely."