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Scientists have discovered that two of the primary coral species forming Florida's reef have become functionally extinct after a intense ocean heatwave caused devastating losses.

The Meaning Behind 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the foundation 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.

Ecological extinction is a phase preceding total extinction, a danger that now looms for many coral species.

Researchers this month alerted that a tipping point has been crossed, meaning corals around the world are likely to be eradicated due to global heating, which is increasing ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," said Ross Cunning of the recent research. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and without immediate, ambitious actions to reduce ocean heating and boost coral resilience, we face the danger of the extinction of additional coral species from reefs in Florida and worldwide."

The Recent Study

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

This event elevated temperatures on Florida's fraying coral reefs to their highest levels in more than a century and a half.

The two species are intricate, reef-building corals and are identified because they resemble, respectively, the antlers 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 widespread, often devastating, losses.

Geographic Impact

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

Past and Present Threats

The two Acropora species had already suffered from decades of regional pressures in Florida, such as contaminated water from contaminants that wash off the land, as well as illness.

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

The 2023 event caused the ninth occurrence of bleaching on the Florida reef – a phenomenon whereby corals become thermally stressed and expel the algae partners living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals die off completely.

Worldwide Consequences

Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate emergency.

This poses a major threat to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Millions of people who rely on corals to sustain fish that they can consume and earn a livelihood from.

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

Conservation Attempts

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 escalate, there is slim chance of continued existence of these species without significant actions, researchers warn.

Further Researcher Insight

"Elkhorn species, in particular, are some of the most important wave-dampening coral species in the area," said a study co-author, a marine biologist at the University of Miami.

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