🔗 Share this article

Researchers have found that two of the key coral species comprising Florida's reef are now ecologically extinct following a withering ocean heatwave caused devastating losses.

What 'Functional Extinction' Means

The almost complete decline of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they can no longer fulfill their once vital role in constructing and maintaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase before global extinction, a danger that now looms for many coral species.

Researchers this month alerted that a tipping point has been crossed, whereby corals around the world 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 new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to global warming, and absent immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the extinction of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

The recent study, published in the journal Science, analyzed the outcome of staghorn coral 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 peak temperatures in more than a century and a half.

The two species are complex, reef-forming corals and are identified because they look like, respectively, the antlers of stags and elks.

However, scientists 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.

Geographic Effects

• Along the Florida Keys, mortality rates reached ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been cooler, mortality rates were lower, at about 38%.

Past and Current Threats

The two Acropora species had already endured from decades of localized impacts in Florida, such as contaminated water from pollutants that wash off the land, as well as disease.

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

The 2023 heat event caused the ninth episode of 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 remain elevated, the corals die off entirely.

Worldwide Consequences

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

This poses a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to support fish that they can eat and gain an income from.

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

Conservation Efforts

In a last-ditch effort to prevent a decline of threatened 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, too, in an effort to regain some of the 90% of coral cover disappeared off the state in the last forty years.

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

Additional Expert Commentary

"Elkhorn corals, especially, are some of the key wave-dampening coral species in the area," said a study co-author, a ocean scientist at the Miami University.

"They were once common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, it is worthwhile taking extraordinary measures to ensure we preserve these corals altogether."