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

The Meaning Behind 'Functional Extinction' Means

The near-total decline of these corals, which once formed the foundation 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 support a variety of marine life.

Functional extinction is a stage before global extinction, a threat that now looms for many coral species.

Researchers recently alerted that a critical threshold has been crossed, whereby corals around the world are set to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"We're running out of time," said the lead author of the recent research. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we risk the disappearance of even more corals from reefs in Florida and around the world."

The New Research

The recent study, published in the journal Science, analyzed the outcome of staghorn coral and elkhorn corals off the Florida coast after a intense 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 intricate, reef-forming corals and are named because they resemble, respectively, the antlers of stags and elk.

However, researchers who performed diver 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, death rates hit 98% and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Historical and Current Dangers

The two Acropora species had already endured from many years of regional pressures in Florida, such as contaminated water from pollutants that wash off the land, as well as disease.

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

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

If temperatures remain elevated, the corals die off completely.

Global Consequences

Globally, coral reefs are among the ecosystems most vulnerable to the human-caused climate emergency.

This poses a significant danger to:

• A quarter of all ocean life that relies upon what are essentially the marine rainforests.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and earn a livelihood from.

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

Preservation Attempts

In a desperate attempt to prevent a decline of endangered corals, scientists have established collections of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to reseed 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 past four decades.

But as climate change continues to intensify, there is little hope of continued existence of these species absent major interventions, researchers warn.

Additional Expert Commentary

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," noted a study co-author, 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, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."