A Pair of Vital Florida Coral Species Declared 'Functionally Extinct' After Devastating Ocean Heatwave

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

What 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, means they are no longer able to fulfill their once vital role in building and sustaining reef ecosystems that host a diversity of marine life.

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

Researchers this month warned that a tipping point had been reached, meaning corals globally are set to be eradicated due to climate change, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," said the lead author of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and worldwide."

Details of the New Research

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

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

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

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

Regional Effects

• Along the Florida Keys, mortality rates hit 98% and even one hundred percent, showing a total eradication of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Historical and Current Threats

The two Acropora species had already suffered 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 marine heatwave has been fatal for these heat-sensitive species.

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

If temperatures stay high, the corals perish entirely.

Worldwide Implications

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

This presents a major threat to:

• One-fourth of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who rely on corals to sustain fish that they can eat and earn a livelihood from.

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

Conservation Attempts

In a last-ditch effort to avert a decline of endangered corals, scientists have established collections of Acropora in marine facilities and offshore coral nurseries.

Efforts have been undertaken to reseed corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover disappeared off the state in the last forty years.

But as climate change continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn corals, especially, are some of the key wave-breaking coral species in the area," said Andrew Baker, a marine biologist at the University of Miami.

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."