Functionally Extinct: Florida's Iconic Coral Species Unravel Amidst Climate Crisis

Coral reefs in Florida's lower Keys and Dry Tortugas were thriving in June 2023, but a marine heat wave less than three weeks later caused widespread bleaching and death among transplanted corals. The bleaching was so severe that it led to a global mass bleaching event, with temperatures soaring above 87°F (31°C) for weeks, resulting in the death of nearly all Acroporid corals surveyed. Research published in the journal Science in October 2025 revealed that two of Florida's most important reef-building coral species, staghorn and elkhorn, have become functionally extinct across Florida's coral reef, with less than 3% of transplanted corals surviving. The study's authors, led by Carly D. Kenkel, Associate Professor of Biological Sciences at the University of Southern California, warn that these iconic species' extinction is a result of climate change and has significant implications for the ecosystem and global biodiversity.

Key Takeaways:

• Acroporid corals, including staghorn and elkhorn, suffered a staggering 97.8-100% mortality rate across nearly 400 individual reefs in Florida's Coral Reef during the 2023-2024 heat wave.
• The bleaching event was so severe that it led to a global mass bleaching event, with temperatures soaring above 87°F (31°C) for weeks, resulting in the death of nearly all Acroporid corals surveyed.
• The accumulated heat stress on the corals during the 2023 heat wave was 2.2 to 4 times higher than it had ever been since modern satellite sea-surface temperature recordings began in the 1980s.
• The corals' symbiotic relationship with algae was disrupted, causing them to expel the algae and turn stark white - a sign of bleaching.
• The surviving corals in Florida cannot recover on their own due to the low number of individuals left.
• To restore the reefs, conservation efforts may involve assisted gene flow, mass production of corals through microfragmentation and cryopreservation, and coordinating international exchange of endangered species.

Statistics:

• 97.8-100% mortality rate of Acroporid corals across nearly 400 individual reefs in Florida's Coral Reef during the 2023-2024 heat wave.
• 2.2-4 times higher accumulated heat stress on corals during the 2023 heat wave compared to previous recordings.
• 3% of transplanted corals survived in the Florida Keys transplant experiment.
• Only 50,000 Acroporid corals surveyed across nearly 400 individual reefs before and after the heat wave.

Sources:

• Kenkel, C. D., et al. (2025). "Extinction vortex: the functional extinction of two Caribbean Acroporid coral species." Science, 10.1126/science.adx7825
• "2 iconic coral species are now functionally extinct off Florida, study finds — we witnessed the reef's bleaching and devastation." The Conversation, https://theconversation.com/2-iconic-coral-species-are-now-functionally-extinct-off-florida-study-finds-we-witnessed-the-reefs-bleaching-and-devastation-267958