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Scientists have discovered that two of the most important coral species forming Florida's reef have become ecologically extinct after a intense ocean heatwave led to 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, indicates they are no longer able to play their once vital role in constructing and maintaining reef ecosystems that support a diversity of marine life.

Ecological extinction is a phase preceding global extinction, a threat that now looms for many coral species.

Researchers this month alerted that a tipping point has been crossed, whereby corals globally are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

"We're running out of time," said the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we risk the disappearance of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

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

This event raised 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 resemble, in turn, the antlers of stags and elks.

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Geographic Effects

• Along the Florida Keys, mortality rates reached 98% and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Historical and Current Dangers

The two Acropora species had already suffered from decades of regional pressures in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

But the 2023 marine heatwave has been fatal for these heat-sensitive species.

The 2023 heat event caused the ninth episode of bleaching on the Florida reef – a process 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 die off entirely.

Worldwide Implications

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

This presents a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Preservation Attempts

In a desperate attempt to avert a death spiral of threatened corals, scientists have established 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 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 little hope of continued existence of these species absent significant actions, researchers warn.

Additional Researcher Insight

"Elkhorn species, 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 Miami University.

"They used to be 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 extraordinary measures to ensure we preserve these corals completely."