🔗 Share this article

Researchers have found that two of the most important coral species forming Florida's reef are now ecologically extinct following a intense ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

The near-total collapse of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that host a diversity of marine life.

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

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

Expert Perspective

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without immediate, ambitious actions to slow ocean warming and enhance coral survival, 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 journal Science, analyzed the fate of staghorn coral and elkhorn corals off the Florida coast following a severe marine heatwave in 2023.

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

The two species are intricate, reef-forming corals and are identified because they look like, in turn, the horns of male deer and elks.

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.

Regional Effects

• In the Florida Keys, death rates hit 98% and even one hundred percent, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Historical and Present Dangers

The two Acropora species had already endured from many years of localized impacts in Florida, such as poor water quality from contaminants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals perish completely.

Worldwide Consequences

Globally, coral reefs are among the ecosystems most at risk to the human-caused climate crisis.

This poses a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the rainforests of the sea.
• Millions of people who depend upon corals to support fish that they can eat and earn a livelihood from.

Corals also act as a protective barrier to protect our shorelines from powerful storms, which are themselves being worsened by increasing global heat.

Conservation Attempts

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

Efforts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover lost off the state in the past four decades.

But as climate change continues to intensify, there is slim chance of continued existence of these species absent significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the region," 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 flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."