Two Crucial Florida Coral Species Deemed 'Functionally Extinct' Following Devastating Ocean Heatwave

Scientists have discovered that two of the key coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave led to devastating 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 previously crucial role in building and sustaining reef ecosystems that host a variety of marine life.

Ecological extinction is a stage preceding global extinction, a danger that now looms for many coral species.

Scientists this month alerted that a critical threshold has been crossed, meaning corals around the world are set to be eradicated due to climate change, which is raising ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the disappearance of additional coral species from reefs in Florida and worldwide."

Details of the Recent Study

The new research, featured in the Science journal, examined the outcome of staghorn 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 look like, in turn, the antlers of stags and elks.

However, researchers who performed underwater 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

• In the Florida Keys, mortality rates hit 98% and even 100%, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Past and Present Threats

The two Acropora species had already endured from many years of localized impacts 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 heat event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and expel the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish completely.

Global Consequences

Worldwide, coral reefs are among the ecosystems most at risk to the anthropogenic climate emergency.

This presents 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 rely on corals to support fish that they can consume and earn a livelihood from.

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

Preservation Attempts

In a last-ditch effort to prevent a death spiral of endangered corals, scientists have created repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been made to reseed corals on reefs in Florida, too, in an effort to regain some of the ninety percent of coral cover lost off the state in the last forty years.

But as global heating continues to intensify, there is little hope of continued existence of these species without significant actions, scientists caution.

Additional Expert Commentary

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

"They were once abundant 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 completely."