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Scientists have discovered that two of the key coral species comprising Florida's reef are now ecologically extinct following a withering ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Signifies

The near-total collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they are no longer able to play their once vital role in building and sustaining reef ecosystems that host a diversity of marine life.

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

Researchers recently warned that a tipping point has been crossed, meaning corals globally are likely to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"We're running out of time," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to slow ocean warming and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and worldwide."

The New Research

The new research, featured in the journal Science, analyzed the outcome of staghorn coral and elkhorn 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 more than a century and a half.

The two species are intricate, reef-building corals and are named because they look like, in turn, the horns of male deer and elk.

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

Regional Impact

• In the Florida Keys, mortality rates reached 98% and even 100%, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, death rates were reduced, 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 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 expel the algae partners living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals perish entirely.

Global Consequences

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

This poses a major threat to:

• One-fourth of all ocean life that depends on what are effectively the marine rainforests.
• Millions of people who depend upon corals to sustain fish that they can consume and earn a livelihood from.

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

Conservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have established repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to reseed corals on reefs in Florida, as well, in an effort to restore some of the ninety percent of coral cover lost off the state in the last forty years.

But as climate change continues to intensify, there is slim chance of continued existence 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," said Andrew Baker, a marine biologist 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 inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals completely."