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Researchers have found that two of the primary coral species comprising Florida's reef are now functionally extinct after a intense ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The near-total 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 building and sustaining reef ecosystems that host a variety of marine life.

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

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

Expert Perspective

"We're running out of time," said 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 enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and worldwide."

Details of the New Research

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

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

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

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

Geographic Effects

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

Past and Current Dangers

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

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

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

If temperatures stay high, the corals perish entirely.

Worldwide Consequences

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

This presents a significant danger to:

• One-fourth of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and earn a livelihood from.

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

Preservation Efforts

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

Attempts have been undertaken to reseed corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover lost off the state in the past four decades.

But as climate change continues to escalate, there is little hope of long-term survival of these species without significant actions, scientists caution.

Further Researcher Insight

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

"They were once abundant on shallow reef tops 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."