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

The Meaning Behind 'Functional Extinction' Means

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

Ecological extinction is a stage preceding global extinction, a threat that now looms for many coral species.

Scientists recently alerted that a critical threshold has been crossed, whereby corals around the world are likely to be eradicated due to climate change, which is increasing ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to global warming, and without swift, decisive measures to slow ocean warming and enhance coral survival, we risk the disappearance of additional coral species from reefs in Florida and around the world."

Details of the New Research

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

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

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

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often devastating, losses.

Geographic Effects

• In the Florida Keys, death rates hit 98% and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, mortality 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 wash off the land, as well as illness.

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

The 2023 event caused the ninth episode of coral 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 stay high, the corals die off completely.

Worldwide Consequences

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This presents a major threat to:

• A quarter of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can eat and earn a livelihood 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 death spiral of threatened corals, scientists have established collections of Acropora in marine facilities and offshore coral nurseries.

Attempts have been made to reseed corals on reefs in Florida, too, in an effort to regain some of the 90% of coral cover lost off the state in the past four decades.

But as global heating continues to intensify, there is little hope of continued existence of these species absent significant actions, researchers warn.

Additional Researcher Insight

"Elkhorn corals, especially, are some of the most important wave-dampening coral species in the area," noted a study co-author, a marine biologist at the University of Miami.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals completely."