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

The Meaning Behind 'Functional Extinction' Signifies

The near-total decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, means they can no longer play their previously crucial role in building and sustaining reef ecosystems that host a variety of marine life.

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

Scientists recently warned that a tipping point had been reached, whereby corals globally are set to be wiped out due to climate change, which is raising ocean temperatures to unbearable levels.

Expert Perspective

"Time is running out," stated Ross Cunning of the recent research. "Extreme 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 face the danger of the extinction of even more corals from reefs in Florida and around the world."

The Recent Study

The new research, published in the Science journal, analyzed the outcome of staghorn coral and elkhorn corals off the Florida coast following 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 intricate, reef-building corals and are identified because they look like, respectively, the horns of male deer and elk.

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

Regional Effects

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

Past and Present Dangers

The two Acropora species had already suffered from many years of regional pressures in Florida, such as poor water quality from pollutants that run off the land, as well as illness.

But the 2023 heatwave has proved fatal 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 algae partners living in their tissues, causing them to become bleached white.

If temperatures remain elevated, the corals die off entirely.

Global Implications

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 relies upon what are effectively the marine rainforests.
• Millions of people who rely on corals to support fish that they can consume and gain an income from.

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

Conservation Attempts

In a desperate attempt to avert a decline of threatened corals, scientists have established repositories of Acropora in aquariums and ocean-based nurseries.

Efforts have been made to reseed corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover lost off the state in the past four decades.

But as climate change continues to intensify, there is little hope of continued existence of these species absent significant actions, researchers warn.

Further Researcher Insight

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

"They were once abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals completely."