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Scientists have discovered that two of the primary coral species comprising Florida's reef have become functionally extinct after a intense ocean heatwave led to devastating losses.

What 'Functional Extinction' Signifies

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 play their previously crucial role in building and sustaining reef ecosystems that host a diversity of marine life.

Ecological extinction is a stage preceding total extinction, a threat that now hangs for many coral species.

Researchers this month alerted that a tipping point has been crossed, meaning corals around the world are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Perspective

"Time is running out," said the lead author of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and worldwide."

The New Research

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

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

The two species are complex, reef-forming corals and are identified because they resemble, in turn, the antlers of male deer and elks.

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

Geographic Effects

• Along the Florida Keys, mortality rates reached ninety-eight percent and even 100%, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, death rates were lower, at about 38%.

Historical and Present Dangers

The two Acropora species had already endured from decades of regional pressures in Florida, such as poor water quality 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 heat event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the algae partners living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off entirely.

Global Consequences

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

This poses a major threat 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 sustain fish that they can consume and gain an income from.

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

Preservation Efforts

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

Attempts 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 last forty years.

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

Additional Expert Commentary

"Elkhorn corals, especially, are some of the most important wave-breaking coral species in the region," noted a study co-author, a ocean scientist at the University of Miami.

"They used to be abundant 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 completely."