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

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they are no longer able to fulfill their once vital role in constructing and maintaining reef ecosystems that support a variety of marine life.

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

Researchers this month warned that a critical threshold has been crossed, meaning corals globally are likely to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Expert Insight

"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 climate change, and without swift, decisive measures to reduce ocean heating and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and around the world."

The Recent Study

The new research, published in the journal Science, examined the outcome of staghorn coral and elkhorn coral corals off the Florida coast after a intense marine heatwave in 2023.

This event elevated 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 named because they look like, in turn, the antlers of male deer and elks.

However, researchers who performed underwater 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 Impact

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

Historical and Present Threats

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

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

The 2023 heat event caused the ninth episode of coral 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 remain elevated, the corals die off completely.

Global Implications

Worldwide, 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 marine rainforests.
• Millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Conservation Efforts

In a last-ditch effort to avert a death spiral of threatened corals, scientists have created repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to restore some of the ninety percent of coral cover disappeared off the state in the past four decades.

But as climate change continues to intensify, there is slim chance of long-term survival of these species absent significant actions, researchers warn.

Additional Expert Commentary

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

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we don't lose these corals completely."