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Researchers have found that two of the most important coral species comprising Florida's reef are now ecologically extinct after a withering ocean heatwave led to devastating losses.

What 'Functional Extinction' Means

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

Functional extinction is a phase before total extinction, a threat that now looms for many coral species.

Scientists this month warned that a tipping point had been reached, whereby corals globally are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to slow ocean warming and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and worldwide."

The Recent Study

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

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are intricate, reef-building corals and are identified because they resemble, respectively, the horns of male deer and elks.

However, scientists who conducted diver 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

• Along the Florida Keys, death rates reached 98% and even one hundred percent, showing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about 38%.

Past and Current Threats

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 heatwave has proved lethal for these temperature-sensitive species.

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

If temperatures stay high, the corals perish entirely.

Worldwide Implications

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

This presents a significant danger to:

• One-fourth of all ocean life that relies upon what are effectively the marine rainforests.
• 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 powerful storms, which are themselves being intensified by increasing global heat.

Conservation Efforts

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

Efforts have been undertaken to replant 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 escalate, there is little hope of continued existence of these species without significant actions, researchers warn.

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 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 exceptional steps to ensure we don't lose these corals altogether."