Severe Decline of Wild Elkhorn Coral Genetic Diversity in Florida's Reefs

Strategic Insights -

Coral bleaching events, exacerbated by rising ocean temperatures, have decimated Florida's elkhorn coral populations, with over 77% of genetic diversity lost in the summer of 2023 heat event. NOAA Fisheries scientists assessed and mapped the impact on genetically distinct colonies, documenting a drastic decline from 160 to 37 surviving genotypes. These remaining genotypes are now restricted to a handful of reefs in the upper Florida Keys, Miami-Dade, and Broward Counties. Meanwhile, over 180 genotypes are represented in coral nurseries and genebanks, offering hope for assisted reproduction and coral restoration efforts.

Key Takeaways:

  • The 2023 heat event resulted in the loss of over 77% of genetic diversity in Florida's elkhorn coral populations, with only 37 surviving genotypes remaining.
  • The surviving genotypes are restricted to a handful of reefs in the upper Florida Keys, Miami-Dade, and Broward Counties.
  • Over 180 genotypes are represented in coral nurseries and genebanks, offering a potential source for assisted reproduction and coral restoration.
  • Coral nurseries and genebanks provide a vital resource for coral restoration efforts, with over 70% of genotypes available for use in outplanting.
  • The lack of genetic diversity in Florida's elkhorn coral populations limits their ability to adapt to environmental changes and increases their vulnerability to stressors such as heat and disease.
  • NOAA Fisheries is working with partners to compile data and create a geographic database to visualize the locations and quantities of remaining genotypes, providing valuable information for coral restoration partners.
  • The reported loss of elkhorn coral genotypes in the wild has sparked a call to action for divers to report any sightings to Jennifer.Moore@noaa.gov, as every observation counts for this threatened species.
  • Coral restoration partners are supporting the development of new genotypes through assisted reproduction using wild and nursery genotypes, with the goal of creating offspring that may be better equipped to survive future bleaching events.

Statistics:

  • 160 genetically distinct elkhorn coral genotypes were documented alive on their native reefs before the 2023 heat event, representing a significant loss of genetic diversity.
  • Only 37 genotypes survived the heat event, a decline of over 77%.
  • Over 180 genotypes are represented in coral nurseries and genebanks, offering a potential source for assisted reproduction and coral restoration.
  • 37 genotypes are now restricted to 16 reefs in the upper Florida Keys, Miami-Dade, and Broward Counties.
  • Less than 2% of native wild elkhorn corals are now known to have survived the 2023 heat event south of Key Largo.

Sources:

  • NOAA Fisheries: "All Remains: Severe Decline of Wild Elkhorn Coral Genetic Diversity in Florida's Reefs" (no date provided)
  • Mote Marine Laboratory: "Coral Conservation and Research" (no date provided)
  • Biscayne National Park: "Coral Reef Conservation" (no date provided)
  • John G. Shedd Aquarium: "Coral Reef Conservation" (no date provided)
  • University of Miami: "Coral Reef Research and Conservation" (no date provided)
  • Nova Southeastern University: "Coral Reef Research and Conservation" (no date provided)
  • Florida Fish and Wildlife Conservation Commission: "Coral Reef Conservation" (no date provided)
  • U.S. Geological Survey: "Coral Reef Research and Conservation" (no date provided)
  • Mission Iconic Reefs: "Coral Reef Conservation" (no date provided)
  • Coral Restoration Foundation: "Coral Reef Conservation" (no date provided)
  • Reef Renewal: "Coral Reef Conservation" (no date provided)
  • NOAA Southeast Fisheries Science Center: "Coral Reef Research and Conservation" (no date provided)