A Pair of Essential Florida Coral Species Declared 'Functionally Extinct' After Severe Ocean Heatwave

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

What 'Functional Extinction' Means

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they can no longer fulfill their previously crucial role in building and sustaining reef ecosystems that host a diversity of marine life.

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

Researchers this month alerted that a tipping point has been crossed, whereby corals globally are likely to be eradicated due to global heating, which is increasing ocean temperatures to unbearable levels.

Researcher Perspective

"Time is running out," stated the lead author of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to climate change, and without immediate, ambitious actions to reduce ocean heating and boost coral resilience, we risk the extinction of additional coral species from reefs in Florida and around the world."

The New Research

The new research, featured in the journal Science, analyzed the outcome of staghorn and elkhorn 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 over 150 years.

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

However, researchers who conducted underwater surveys of over fifty-two thousand colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often catastrophic, losses.

Regional Effects

• Along the Florida Keys, death rates hit ninety-eight percent and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about 38%.

Past and Current Threats

The two Acropora species had already endured from decades of localized impacts in Florida, such as contaminated water from pollutants that run off the land, as well as illness.

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

The 2023 heat event caused the ninth occurrence 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 stay high, the corals die off completely.

Global Implications

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

This poses a significant danger to:

• One-fourth of all ocean life that depends on what are essentially the rainforests of the sea.
• Hundreds of millions of people who rely on corals to sustain fish that they can eat and earn a livelihood from.

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

Preservation Attempts

In a desperate attempt to avert a decline of endangered corals, scientists have established collections of Acropora in aquariums and offshore coral nurseries.

Attempts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the ninety percent of coral cover disappeared off the state in the last forty years.

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

Additional Researcher Insight

"Elkhorn corals, especially, are some of the most important wave-breaking coral species in the area," noted a study co-author, a ocean scientist at the Miami University.

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