A Pair of Vital Florida Coral Species Deemed 'Functionally Extinct' Following Severe Ocean Heatwave

Scientists have discovered that two of the most important coral species comprising Florida's reef have become ecologically extinct after a withering ocean heatwave caused catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

The almost complete decline 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 previously crucial role in building and sustaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase preceding global extinction, a danger that now hangs for many coral species.

Scientists this month alerted that a tipping point had been reached, meaning corals around the world are likely to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"We're running out of time," said the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to slow ocean warming and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

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

This event raised temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.

The two species are complex, reef-forming corals and are named because they resemble, respectively, the horns of stags and elks.

However, researchers who conducted underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Impact

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

Historical and Present Threats

The two Acropora species had already endured from decades of regional pressures in Florida, such as contaminated water from pollutants that wash off the land, as well as disease.

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

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

This poses a major threat to:

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

Corals also serve as a barrier to protect our shorelines from intense hurricanes, which are themselves being worsened by increasing global heat.

Preservation Efforts

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

Attempts have been made 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 intensify, there is little hope of continued existence of these species without significant actions, scientists caution.

Further Expert Commentary

"Elkhorn corals, in particular, are some of the most important wave-breaking coral species in the region," said a study co-author, a marine biologist at the Miami University.

"They used to be abundant on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking exceptional steps to ensure we preserve these corals altogether."