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

The Meaning Behind 'Functional Extinction' Signifies

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

Functional extinction is a phase before global extinction, a danger that now hangs for many coral species.

Researchers recently alerted that a tipping point had been reached, whereby corals around the world are likely to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," stated the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without swift, decisive measures to reduce ocean heating and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and around the world."

The Recent Study

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

This event elevated 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-building corals and are named because they resemble, respectively, the horns of male deer and elks.

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

Geographic Effects

• Along the Florida Keys, mortality rates hit 98% and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Historical and Current Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

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

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

If temperatures remain elevated, the corals die off completely.

Worldwide Implications

Globally, coral reefs are among the ecosystems most at risk to the human-caused climate crisis.

This presents a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Millions of people who depend upon corals to sustain fish that they can eat and gain an income from.

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

Preservation Attempts

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

Efforts have been made to replant corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as global heating continues to escalate, there is little hope of continued existence of these species without significant actions, researchers warn.

Additional Expert Commentary

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

"They were once common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, its worth taking exceptional steps to ensure we preserve these corals completely."