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

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they can no longer fulfill their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase preceding total extinction, a threat that now hangs for many coral species.

Scientists this month warned that a critical threshold has been crossed, whereby corals around the world are set to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"We're running out of time," stated the lead author of the recent research. "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 face the danger of the extinction of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

The recent study, published in the Science journal, examined the fate of staghorn and elkhorn corals off the Florida coast following a severe marine heatwave in 2023.

This event raised temperatures on Florida's deteriorating coral reefs to their peak temperatures in more than a century and a half.

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

However, scientists who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Impact

• Along the Florida Keys, mortality rates reached ninety-eight percent and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about thirty-eight percent.

Past and Current Threats

The two Acropora species had already endured from many years of localized impacts in Florida, such as poor water quality from contaminants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals perish completely.

Global Implications

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

This presents a significant danger to:

• One-fourth of all ocean life that relies upon what are essentially the rainforests of the sea.
• Millions of people who rely on corals to sustain fish that they can eat and gain an income from.

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

Preservation Attempts

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

Attempts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore 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 continued existence of these species without major interventions, scientists caution.

Additional Researcher Insight

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

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."