🔗 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 devastating losses.

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation 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 support a diversity of marine life.

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

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

Researcher Insight

"We're running out of time," said the lead author of the recent research. "Severe marine heatwaves are becoming more frequent and intense 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 worldwide."

Details of the Recent Study

The recent study, published in the Science journal, analyzed the outcome of staghorn and elkhorn coral corals off the Florida coast following a severe 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-forming corals and are named because they resemble, respectively, the horns of male deer and elk.

However, scientists 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.

Regional Effects

• In the Florida Keys, death rates hit ninety-eight percent 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 thirty-eight percent.

Historical and Present Dangers

The two Acropora species had already suffered from many years of regional pressures in Florida, such as poor water quality from contaminants that run off the land, as well as illness.

But the 2023 marine 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 heat-stressed and eject the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off completely.

Worldwide Implications

Globally, coral reefs are among the ecosystems most at risk to the anthropogenic climate crisis.

This presents a significant danger to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Conservation Attempts

In a desperate attempt to prevent a decline of endangered corals, scientists have created collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to reseed corals on reefs in Florida, as well, in an effort to restore some of the 90% of coral cover lost off the state in the past four decades.

But as global heating continues to escalate, there is little hope of long-term survival of these species absent significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, especially, are some of the most important wave-dampening coral species in the area," noted a study co-author, a ocean scientist 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 preserve these corals altogether."