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

The Meaning Behind '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 previously crucial role in building and sustaining reef ecosystems that host a diversity of marine life.

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

Researchers this month alerted that a critical threshold had been reached, whereby corals globally are set to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," stated the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures 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 New Research

The recent study, featured in the Science journal, analyzed the outcome of staghorn coral and elkhorn 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-forming corals and are identified because they resemble, respectively, the antlers of male deer and elk.

However, scientists who conducted diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often catastrophic, losses.

Geographic Impact

• In the Florida Keys, death rates hit 98% and even 100%, showing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Past and Current Threats

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

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

The 2023 event caused the ninth occurrence of coral 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 ghostly white.

If temperatures remain elevated, the corals perish completely.

Global Implications

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

This poses a significant danger 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 gain an income from.

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

Conservation Attempts

In a last-ditch effort to prevent a decline of threatened corals, scientists have created collections of Acropora in marine facilities 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 90% of coral cover disappeared off the state in the past four decades.

But as climate change continues to intensify, there is little hope of long-term survival of these species without major interventions, researchers warn.

Additional Researcher Insight

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

"They were once common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking extraordinary measures to ensure we preserve these corals altogether."