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

What 'Functional Extinction' Signifies

The near-total decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, indicates they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that support a diversity of marine life.

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

Scientists recently alerted that a tipping point had been reached, whereby corals around the world are set to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, 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."

Details of the Recent Study

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

This event elevated temperatures on Florida's fraying coral reefs to their highest levels in more than a century and a half.

The two species are intricate, reef-building corals and are identified because they look like, respectively, the antlers of male deer and elk.

However, researchers who performed underwater surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often devastating, losses.

Regional Effects

• Along 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 lower, at about thirty-eight percent.

Historical and Current Dangers

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

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

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

If temperatures stay high, the corals die off completely.

Worldwide Consequences

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

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 depend upon corals to support fish that they can consume and earn a livelihood from.

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

Conservation Attempts

In a desperate attempt to avert a death spiral of endangered corals, scientists have created repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover lost off the state in the past four decades.

But as global heating continues to intensify, there is little hope of continued existence of these species absent significant actions, researchers warn.

Additional Researcher Insight

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

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals altogether."