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

What 'Functional Extinction' Means

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

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

Researchers recently alerted that a tipping point has been crossed, meaning corals globally are likely to be wiped out due to climate change, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"We're running out of time," stated the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we face the danger of the disappearance of even more corals from reefs in Florida and around the world."

The New Research

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

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

The two species are intricate, reef-building corals and are identified because they resemble, respectively, the antlers of stags and elk.

However, researchers who conducted underwater surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Geographic Impact

• In the Florida Keys, mortality rates hit 98% and even one hundred percent, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Historical and Current Threats

The two Acropora species had already suffered from decades of localized impacts in Florida, such as poor water quality from pollutants that wash off the land, as well as illness.

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

The 2023 heat event caused the ninth occurrence of coral bleaching on the Florida reef – a process whereby corals become thermally 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 Consequences

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

This presents a significant danger to:

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

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

Preservation Attempts

In a desperate attempt to avert a decline of threatened corals, scientists have created repositories of Acropora in aquariums and offshore coral nurseries.

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

But as climate change continues to escalate, there is slim chance of continued existence of these species absent major interventions, researchers warn.

Further Researcher Insight

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

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."