Two Crucial Florida Coral Species Declared 'Functionally Extinct' After Devastating Ocean Heatwave

Researchers have found that two of the most important coral species forming Florida's reef have become ecologically extinct after a intense ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Means

The almost complete collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, indicates they can no longer play their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

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

Researchers recently alerted that a critical threshold had been reached, whereby corals around the world are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"We're running out of time," said the lead author of the new Florida study. "Severe marine 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 risk the disappearance of even more corals from reefs in Florida and worldwide."

The New Research

The recent study, featured in the journal Science, examined the outcome of staghorn coral and elkhorn 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 named because they resemble, in turn, the antlers of male deer and elk.

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

Regional Effects

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

Past and Present Dangers

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

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

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

If temperatures stay high, the corals die off completely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate crisis.

This presents a major threat to:

• A quarter of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of 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 worsened by increasing global heat.

Conservation Efforts

In a last-ditch effort to avert a death spiral of threatened corals, scientists have established repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken 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 last forty years.

But as global heating continues to escalate, there is little hope of long-term survival of these species without major interventions, researchers warn.

Further Expert Commentary

"Elkhorn corals, in particular, are some of the most important wave-breaking coral species in the region," said Andrew Baker, a marine biologist at the University of Miami.

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."