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Researchers have found that two of the key coral species forming Florida's reef have become functionally extinct following a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that host a diversity of marine life.

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

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

Expert Insight

"Time is running out," said the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and around the world."

Details of the New Research

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

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

The two species are complex, reef-forming corals and are identified because they resemble, respectively, the horns of male deer and elk.

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

Regional Effects

• Along the Florida Keys, death rates hit ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Past and Current Threats

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 lethal for these temperature-sensitive species.

The 2023 heat event caused the ninth episode of 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 entirely.

Global Implications

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

This presents a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of millions of people who rely on corals to sustain fish that they can consume and earn a livelihood from.

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

Conservation Efforts

In a desperate attempt to avert a death spiral of endangered corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Efforts have been undertaken 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 past four decades.

But as global heating continues to escalate, there is slim chance of long-term survival of these species without major interventions, researchers warn.

Further Researcher Insight

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the region," said Andrew Baker, a ocean scientist at the Miami University.

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals altogether."