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Scientists have discovered that two of the key coral species comprising Florida's reef have become ecologically extinct after a intense 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, indicates they are no longer able to play their once vital role in constructing and maintaining reef ecosystems that host a variety of marine life.

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

Scientists this month alerted that a tipping point had been reached, whereby corals globally are set to be wiped out due to global heating, which is raising ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent swift, decisive measures to reduce ocean heating and boost coral resilience, we risk the extinction 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 outcome of staghorn coral and elkhorn coral corals off the Florida coast after a severe marine heatwave in 2023.

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

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

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

Regional Impact

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

Past and Present Threats

The two Acropora species had already endured from many years of localized impacts in Florida, such as contaminated water from contaminants that run off the land, as well as illness.

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

The 2023 heat event caused the ninth occurrence of coral 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 stay high, the corals die off completely.

Global Consequences

Worldwide, 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 relies upon what are essentially the rainforests of the sea.
• Millions of people who depend upon corals to sustain fish that they can eat and gain an income from.

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

Preservation Efforts

In a desperate attempt to avert a death spiral of endangered corals, scientists have created repositories of Acropora in marine facilities and ocean-based nurseries.

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

But as climate change continues to intensify, there is little hope of long-term survival of these species absent major interventions, scientists caution.

Additional Expert Commentary

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

"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, its worth taking extraordinary measures to ensure we preserve these corals altogether."