A Pair of Crucial Florida Coral Species Declared 'Functionally Extinct' Following Devastating Ocean Heatwave

Researchers have found that two of the primary coral species forming Florida's reef have become functionally extinct after a intense ocean heatwave led to catastrophic losses.

What '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.

Functional extinction is a stage preceding global extinction, a threat that now hangs for many coral species.

Scientists this month alerted that a critical threshold had been reached, whereby corals globally are likely to be wiped out due to climate change, which is increasing ocean temperatures to intolerable levels.

Expert Insight

"Time is running out," stated Ross Cunning of the recent research. "Extreme heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to reduce ocean heating and enhance coral survival, we face the danger of the disappearance of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

The new research, published in the Science journal, examined the outcome of staghorn coral 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 highest levels in over 150 years.

The two species are complex, reef-building corals and are named because they look like, in turn, the antlers of stags and elk.

However, researchers 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.

Regional Impact

• In the Florida Keys, mortality rates reached ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In south-east Florida, where temperatures have been cooler, death rates were reduced, at about 38%.

Historical and Current Dangers

The two Acropora species had already suffered from many years of localized impacts in Florida, such as contaminated water from contaminants that run off the land, as well as illness.

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

The 2023 heat event caused the ninth episode of 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 die off entirely.

Global 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 essentially the rainforests of the sea.
• Millions of people who rely on corals to sustain fish that they can eat 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.

Preservation Efforts

In a desperate attempt to prevent a decline of threatened corals, scientists have created repositories of Acropora in aquariums and offshore coral nurseries.

Attempts have been undertaken to replant corals on reefs in Florida, too, in an effort to restore some of the ninety percent of coral cover lost off the state in the last forty years.

But as global heating continues to intensify, there is slim chance of long-term survival of these species absent significant actions, researchers warn.

Additional Researcher Insight

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

"They were once common 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 altogether."