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

What 'Functional Extinction' Signifies

The near-total decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they can no longer play their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

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

Scientists this month alerted that a tipping point has been crossed, meaning corals globally are likely to be eradicated due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"We're running out of time," stated the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to global warming, and absent 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."

Details of the New Research

The new research, published in the journal Science, analyzed the outcome 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 peak temperatures in more than a century and a half.

The two species are intricate, reef-building corals and are named because they look like, respectively, the antlers of male deer and elk.

However, researchers who performed diver surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often devastating, losses.

Geographic Effects

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

Past and Present Dangers

The two Acropora species had already suffered from decades of localized impacts in Florida, such as contaminated water from pollutants that run off the land, as well as disease.

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

The 2023 event caused the ninth episode of bleaching on the Florida reef – a process whereby corals become heat-stressed and expel the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures stay high, the corals die off entirely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This poses a major threat to:

• A quarter of all ocean life that depends on what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and earn a livelihood from.

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

Conservation Efforts

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

Attempts have been made to replant 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 past four decades.

But as climate change continues to intensify, there is little hope of continued existence of these species absent significant actions, scientists caution.

Additional Expert Commentary

"Elkhorn corals, in particular, are some of the key wave-breaking coral species in the region," noted 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 extraordinary measures to ensure we don't lose these corals completely."