Two Crucial Florida Coral Species Deemed 'Functionally Extinct' After Severe Ocean Heatwave

Researchers have found that two of the most important coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, means they can no longer play their once vital role in constructing and maintaining reef ecosystems that support a diversity of marine life.

Functional extinction is a phase preceding total extinction, a threat that now hangs for many coral species.

Scientists this month alerted that a critical threshold has been crossed, meaning corals globally are set to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Perspective

"We're running out of time," said the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

The New Research

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

This event raised 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 male deer and elk.

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

Geographic Impact

• Along the Florida Keys, death rates hit ninety-eight percent and even one hundred percent, showing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were reduced, at about 38%.

Historical and Current Dangers

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

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

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

If temperatures stay high, the corals perish completely.

Global Implications

Worldwide, coral reefs are among the ecosystems most at risk to the anthropogenic climate emergency.

This poses a major threat 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 eat and earn a livelihood from.

Corals also act as a protective barrier to safeguard our shorelines from intense hurricanes, which are themselves being worsened by rising global temperatures.

Preservation Attempts

In a last-ditch effort to avert a death spiral of threatened corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to replant corals on reefs in Florida, too, in an effort to restore some of the 90% of coral cover disappeared off the state in the last forty years.

But as global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Further Expert Commentary

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

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."