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Scientists have discovered that two of the key coral species forming Florida's reef are now functionally extinct following a withering ocean heatwave caused 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, means they can no longer fulfill their once vital role in building and sustaining reef ecosystems that support a diversity of marine life.

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

Researchers recently warned that a critical threshold has been crossed, whereby corals around the world are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"Time is running out," stated the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to slow ocean warming and enhance coral survival, we risk the disappearance of additional coral species from reefs in Florida and worldwide."

The New Research

The recent study, published in the journal Science, analyzed the fate 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 deteriorating coral reefs to their highest levels in more than a century and a half.

The two species are intricate, reef-forming corals and are identified because they look like, in turn, the antlers of stags 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

• Along the Florida Keys, mortality rates hit 98% and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Historical and Present 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 illness.

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

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

If temperatures stay high, the corals perish completely.

Worldwide Implications

Globally, coral reefs are among the ecosystems most vulnerable to the human-caused climate emergency.

This poses a significant danger to:

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

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

Conservation Attempts

In a desperate attempt to prevent a decline of threatened corals, scientists have established repositories of Acropora in marine facilities and offshore coral nurseries.

Efforts have been undertaken to replant 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 global heating continues to escalate, there is slim chance of continued existence of these species absent major interventions, scientists caution.

Further Expert Commentary

"Elkhorn corals, especially, are some of the key wave-dampening coral species in the region," said a study co-author, a ocean scientist at the Miami University.

"They used to be abundant 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 preserve these corals altogether."