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Scientists have discovered that two of the most important coral species forming Florida's reef are now functionally extinct following a intense ocean heatwave led to catastrophic losses.

The Meaning Behind 'Functional Extinction' Means

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

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

Researchers this month alerted that a critical threshold had been reached, whereby corals globally are set to be eradicated due to global heating, which is raising ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," said the lead author of the new Florida study. "Extreme heatwaves are becoming more frequent and intense due to climate change, and absent swift, decisive measures to reduce ocean heating and enhance coral survival, we risk the extinction of additional coral species from reefs in Florida and worldwide."

The New Research

The recent study, published in the journal Science, examined the outcome of staghorn coral and elkhorn corals off the Florida coast after 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-forming corals and are named because they look like, in turn, the antlers of male deer and elks.

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 devastating, losses.

Geographic Impact

• In the Florida Keys, mortality rates reached 98% and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were lower, at about thirty-eight percent.

Historical and Current Threats

The two Acropora species had already endured from decades of localized impacts 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 heat-sensitive species.

The 2023 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 completely.

Global Implications

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

This presents a significant danger to:

• A quarter of all ocean life that depends on what are essentially the marine rainforests.
• Millions of people who rely on corals to sustain fish that they can eat and gain an income from.

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

Conservation Attempts

In a last-ditch effort to prevent a decline of endangered 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 restore some of the 90% of coral cover disappeared off the state in the past four decades.

But as climate change continues to escalate, there is little hope of long-term survival of these species absent significant actions, scientists caution.

Additional Researcher Insight

"Elkhorn corals, especially, are some of the key wave-breaking coral species in the area," said Andrew Baker, a marine biologist at the Miami University.

"They were once common on shallow reef tops 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 don't lose these corals altogether."