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Scientists have discovered that two of the primary coral species forming Florida's reef have become ecologically extinct after a intense ocean heatwave led to catastrophic losses.

The Meaning Behind '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 constructing and maintaining reef ecosystems that support a variety of marine life.

Ecological extinction is a stage preceding total extinction, a threat that now hangs for many coral species.

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

Researcher Insight

"Time is running out," said the lead author of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to slow ocean warming and enhance coral survival, we risk the extinction of additional coral species from reefs in Florida and around the world."

Details of the New Research

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

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

The two species are complex, reef-building corals and are identified because they look like, respectively, the horns of male deer and elk.

However, scientists who conducted diver surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Regional Impact

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

Historical and Current Dangers

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

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

The 2023 event caused the ninth episode 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 perish completely.

Worldwide Implications

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

This poses a major threat to:

• One-fourth of all ocean life that depends on what are essentially the rainforests of the sea.
• 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 safeguard our shorelines from powerful storms, which are themselves being worsened by increasing global heat.

Conservation Attempts

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

Attempts have been made to reseed corals on reefs in Florida, too, in an effort to regain some of the 90% 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 absent significant actions, researchers warn.

Additional Researcher Insight

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

"They used to be 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."