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Researchers have found that two of the most important coral species forming Florida's reef are now functionally extinct following a intense ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Signifies

The near-total collapse of these corals, which once served as the foundation of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill their previously crucial role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Functional extinction is a stage before total extinction, a threat that now hangs for many coral species.

Scientists recently alerted that a tipping point has been crossed, whereby corals globally are likely to be wiped out due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"We're running out of time," stated the lead author of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of additional coral species from reefs in Florida and worldwide."

Details of the Recent Study

The new research, published in the Science journal, examined the outcome of staghorn and elkhorn corals off the Florida coast after a severe marine heatwave in 2023.

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

The two species are complex, reef-building corals and are identified because they resemble, in turn, the horns of male deer and elk.

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

Regional Effects

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

Historical and Present Dangers

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 disease.

But the 2023 marine heatwave has been lethal 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 eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals die off completely.

Global Implications

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

This poses a major threat to:

• One-fourth of all ocean life that relies upon 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 protective barrier to safeguard our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Preservation Efforts

In a desperate attempt to prevent a decline of threatened corals, scientists have established repositories of Acropora in aquariums and ocean-based 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 lost off the state in the past four decades.

But as global heating continues to escalate, there is slim chance of long-term survival of these species without significant actions, scientists caution.

Further Researcher Insight

"Elkhorn species, in particular, are some of the most important wave-breaking coral species in the area," noted a study co-author, a ocean scientist at the University of Miami.

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals altogether."