Florida’s Iconic Elkhorn and Staghorn Corals Now “Functionally Extinct”
A new study reveals that rising ocean temperatures have pushed two crucial coral species in Florida to the brink, signaling a dire warning for reefs worldwide.
For millennia, elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) corals once flourished throughout the Florida reef system, their branching structures resembling antlers rising from the seabed. But a grim reality has emerged: these foundational species are now considered “functionally extinct” in the region, following record-breaking ocean temperatures. A study released Thursday details the devastating impact of marine heatwaves on these vital ecosystems.
A Legacy of Decline
These coral species, responsible for building and maintaining the Florida reef system for the past 10,000 years, were already critically endangered due to a confluence of stressors. Diseases, pollution, hurricanes, and the overarching threat of ocean warming had steadily weakened their resilience. However, an unprecedented marine heatwave appears to have delivered a fatal blow.
During the summer of 2023, water temperatures in Florida soared to over 32°C (89.6°F), the highest recorded in the region in at least 150 years. This extreme heat inflicts lethal stress on corals, causing them to expel the symbiotic algae that provide them with color and energy. This process, known as coral bleaching, leaves behind a skeletal, lifeless structure. While corals can recover if temperatures return to normal, prolonged and intense heatwaves dramatically increase mortality rates.
Extensive Monitoring Reveals Catastrophic Loss
Researchers meticulously monitored over 52,300 Acropora corals – encompassing both elkhorn and staghorn varieties – throughout the 563-kilometer (350-mile) Florida reef system, stretching from Dry Tortugas and the Florida Keys in the southwest to St. Lucie Inlet on the east coast. The monitoring occurred during the peak of the 2023 heatwave.
By March 2024, the results were stark. Between 98% and 100% of coral colonies in the southern portion of the system had perished, according to the study led by the Coral Reef Watch program of the National Oceanic and Atmospheric Administration (NOAA) and the Shedd Aquarium in Chicago.
The report underscores that this heatwave marks the “functional extinction” of these colonies – a stage often preceding the complete disappearance of a species. While some elkhorn and staghorn corals remain, they are no longer present in sufficient densities to fulfill their ecological role: constructing and maintaining the reef structure.
Cascading Impacts on the Ecosystem
Remaining colonies, primarily located in the northern reaches of the reef system, remain vulnerable to disease, predation, and storm damage. The loss of these corals triggers “cascading impacts,” as explained by Ross Cunning, a research biologist at the Shedd Aquarium and the study’s author. “The growth of the reef slows down, the complexity of the habitat decreases, and fish and invertebrates lose the shelter and resources they depend on,” he stated. The diminished reefs also leave coastlines more exposed to storms and erosion.
The findings serve as “a stark warning for the future of coral reefs worldwide,” the study authors wrote in an accompanying statement. A recent study from the University of Exeter found that warm-water coral reefs globally have already passed a critical tipping point due to climate change, with large-scale reef loss inevitable unless global warming is reversed.
A Bleak Outlook for Recovery
Natural recovery of Acropora corals in Florida is deemed unlikely, the new report concludes. Climate projections suggest severe bleaching events will occur annually by 2040. As oceans continue to warm, other coral species are also likely to succumb. The report warns of potential “true global extinctions” of multiple coral species across the Caribbean region in the coming decades.
Scientists have attempted to bolster Florida’s coral populations through artificial propagation, cultivating colonies in both land-based and offshore nurseries. However, the success of these efforts hinges on the frequency and severity of future bleaching events. A graph illustrating the projected increase in bleaching events under different climate scenarios would be beneficial here.
A Call to Action, Not Despair
Keri O’Neil, director and chief scientist of the Coral Conservation Program at the Florida Aquarium, who was not involved in the study, emphasized the significance of the findings. “These findings are extremely significant and underscore the importance of taking immediate action to reduce pollution that warms the planet.”
However, she added that functional extinction does not equate to complete species extinction. “Human intervention, combined with an improvement in ocean conditions, can reverse this trend.”
Cunning echoed this sentiment, urging against despair. “The window to prevent further losses is rapidly closing, but targeted interventions and aggressive climate action can still make a difference.” He stressed that the report should be viewed as a call to action, not a surrender.
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