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Scientists have discovered that two of the primary coral species forming Florida's reef have become ecologically extinct after a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The near-total decline of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means 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 stage before total extinction, a danger that now looms for many coral species.

Scientists recently warned that a critical threshold had been reached, meaning corals around the world are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," stated Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and without swift, decisive measures to slow ocean warming and boost coral resilience, we face the danger of the extinction of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

The new research, published in the Science journal, 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 over 150 years.

The two species are complex, reef-building corals and are identified because they look like, in turn, the antlers of stags and elk.

However, researchers who performed underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Effects

• Along the Florida Keys, death rates reached ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Historical and Present Dangers

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

But the 2023 heatwave has been lethal 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 heat-stressed and eject the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off completely.

Worldwide Implications

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

This poses a significant danger to:

• A quarter of all ocean life that depends on what are effectively the marine rainforests.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and gain an income from.

Corals also serve 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 decline of threatened corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Efforts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover disappeared off the state in the last forty years.

But as global heating continues to intensify, there is little hope of long-term survival of these species absent significant actions, researchers warn.

Further Expert Commentary

"Elkhorn species, in particular, are some of the key wave-breaking coral species in the region," noted a study co-author, a ocean scientist at the University of Miami.

"They used to be common on shallow reef tops 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 preserve these corals completely."