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Researchers have found that two of the key coral species comprising Florida's reef are now ecologically extinct following a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their previously crucial role in constructing and maintaining reef ecosystems that host a diversity of marine life.

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

Scientists recently warned that a critical threshold had been reached, meaning corals around the world are likely to be wiped out due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"We're running out of time," stated Ross Cunning of the recent research. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and around the world."

Details of the New Research

The new research, published in the Science journal, analyzed the fate of staghorn coral and elkhorn coral corals off the Florida coast following a severe 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 complex, reef-building corals and are identified because they resemble, respectively, the antlers of stags and elks.

However, researchers 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 devastating, losses.

Regional Impact

• In the Florida Keys, mortality rates reached 98% and even one hundred percent, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were reduced, at about thirty-eight percent.

Past and Current Threats

The two Acropora species had already endured from decades 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 been fatal for these temperature-sensitive species.

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

Global Implications

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

This presents a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the marine rainforests.
• Hundreds of millions of people who rely on corals to sustain fish that they can eat and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to prevent a death spiral of threatened corals, scientists have established repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been undertaken 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 last forty years.

But as climate change continues to escalate, there is slim chance of long-term survival of these species without significant actions, researchers warn.

Additional Researcher Insight

"Elkhorn species, especially, are some of the key wave-breaking coral species in the area," said Andrew Baker, a marine biologist at the Miami University.

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."