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Scientists have discovered that two of the key coral species comprising Florida's reef have become ecologically extinct after a intense ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Signifies

The almost complete collapse of these corals, which once served as the backbone of reefs in Florida and the Caribbean, indicates they are no longer able to play their previously crucial role in constructing and maintaining reef ecosystems that host a variety of marine life.

Ecological extinction is a stage before global extinction, a danger that now hangs for many coral species.

Scientists this month alerted that a tipping point had been reached, whereby corals globally are set to be eradicated due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Insight

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to global warming, and absent immediate, ambitious actions to reduce ocean heating and enhance coral survival, we risk the extinction of even more corals from reefs in Florida and around the world."

Details of the Recent Study

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

This event elevated temperatures on Florida's deteriorating coral reefs to their highest levels in over 150 years.

The two species are complex, reef-forming corals and are named because they look like, in turn, the horns of male deer and elks.

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

Geographic Effects

• In the Florida Keys, death rates hit ninety-eight percent and even one hundred percent, showing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been lower, mortality rates were reduced, at about 38%.

Past and Current Threats

The two Acropora species had already suffered from decades of localized impacts in Florida, such as contaminated water from contaminants 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 occurrence 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 remain elevated, the corals perish entirely.

Worldwide Consequences

Globally, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This presents a significant danger to:

• One-fourth of all ocean life that relies upon what are essentially the marine rainforests.
• Millions of people who depend upon corals to support fish that they can eat and earn a livelihood from.

Corals also act as a protective barrier to safeguard our shorelines from powerful storms, 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 created repositories of Acropora in marine facilities and offshore coral nurseries.

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

But as global heating continues to intensify, there is slim chance of long-term survival of these species absent major interventions, scientists caution.

Further Researcher Insight

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

"They used to be common on shallow reef crests in the Caribbean, and if we want our reefs to continue protecting our coastlines from inundation during storms, it is worthwhile taking exceptional steps to ensure we preserve these corals altogether."