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

The Meaning Behind 'Functional Extinction' Means

The almost complete collapse of these corals, which once served as the foundation 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 support a diversity of marine life.

Ecological extinction is a phase before global extinction, a threat that now looms for many coral species.

Scientists recently warned that a tipping point had been reached, meaning corals globally are likely to be wiped out due to global heating, which is increasing ocean temperatures to intolerable levels.

Researcher Insight

"We're running out of time," said the lead author of the recent research. "Extreme heatwaves are increasing in frequency and severity due to climate change, and without immediate, ambitious actions to slow ocean warming and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and around the world."

Details of the Recent Study

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

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

The two species are complex, reef-building corals and are named because they resemble, in turn, the antlers of male deer and elks.

However, scientists who conducted underwater surveys of over fifty-two thousand colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, 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 lower, death rates were reduced, at about 38%.

Historical and Present Threats

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

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

The 2023 heat event caused the ninth episode of bleaching on the Florida reef – a phenomenon whereby corals become heat-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 Consequences

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

This presents a significant danger to:

• One-fourth of all ocean life that depends on what are essentially the marine rainforests.
• Millions of people who depend upon corals to sustain fish that they can consume and gain an income from.

Corals also serve as a barrier to protect our shorelines from powerful storms, which are themselves being intensified by rising global temperatures.

Conservation Attempts

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

Attempts have been undertaken to replant corals on reefs in Florida, too, in an effort to regain some of the ninety percent 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.

Additional Researcher Insight

"Elkhorn corals, in particular, are some of the most important wave-breaking coral species in the region," said Andrew Baker, a marine biologist at the Miami University.

"They were once abundant on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals completely."