🔗 Share this article

Scientists have discovered that two of the most important coral species comprising Florida's reef are now functionally 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, means they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that host a diversity of marine life.

Ecological extinction is a phase before global extinction, a threat that now hangs for many coral species.

Researchers this month alerted that a critical threshold had been reached, whereby corals around the world are likely to be eradicated due to climate change, which is raising ocean temperatures to unbearable levels.

Researcher Perspective

"We're running out of time," said Ross Cunning of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent swift, decisive measures to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

Details of the New Research

The recent study, published in the Science journal, examined the fate of staghorn coral and elkhorn coral corals off the Florida coast after a severe 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-forming corals and are named because they look like, respectively, the antlers of stags and elks.

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

Regional Impact

• In the Florida Keys, death rates reached ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Historical and Current Threats

The two Acropora species had already suffered from many years of localized impacts in Florida, such as poor water quality from contaminants that wash off the land, as well as disease.

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

The 2023 event caused the ninth episode of coral bleaching on the Florida reef – a process 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 die off entirely.

Global Consequences

Worldwide, coral reefs are among the ecosystems most at risk to the human-caused climate crisis.

This presents a major threat to:

• One-fourth of all ocean life that relies upon what are effectively the marine rainforests.
• Millions of people who rely on corals to sustain fish that they can consume and gain an income from.

Corals also act as a barrier to safeguard our shorelines from intense hurricanes, which are themselves being worsened by rising global temperatures.

Preservation Attempts

In a last-ditch effort to avert a decline of threatened corals, scientists have established repositories of Acropora in marine facilities and ocean-based nurseries.

Attempts have been made to replant corals on reefs in Florida, too, 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 slim chance of continued existence of these species absent major interventions, scientists caution.

Additional Expert Commentary

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

"They used to be abundant on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, its worth taking exceptional steps to ensure we don't lose these corals completely."