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DAO 132:109-124 (2019)  -  DOI: https://doi.org/10.3354/dao03308

Assessing Karenia brevis red tide as a mortality factor of sea turtles in Florida, USA

Allen M. Foley1,*, Brian A. Stacy2, Paul Schueller3, Leanne J. Flewelling4, Barbara Schroeder5, Karrie Minch6, Deborah A. Fauquier7,8, Jerris J. Foote7,9, Charles A. Manire7,10, Karen E. Atwood4,11, April A. Granholm4, Jan H. Landsberg4

1Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Jacksonville Field Laboratory, Jacksonville, Florida 32218, USA
2NOAA, National Marine Fisheries Service, Office of Protected Resources, University of Florida (duty station), Gainesville, Florida 32611, USA
3Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Center for Biostatistics and Modeling, Gainesville, Florida 32653, USA
4Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, Florida 33701, USA
5NOAA, National Marine Fisheries Service, Office of Protected Resources, Silver Spring, Maryland 20910, USA
6Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, c/o Marine Discovery Center, New Smyrna Beach, Florida 32169, USA
7Mote Marine Laboratory, Sarasota, Florida 34236, USA
8Present address: National Marine Fisheries Service, Office of Protected Resources, Silver Spring, Maryland 20910, USA
9Present address: Operational Management, Sarasota County Government, Parks, Recreation and Natural Resources, Natural Area Parks and Preserves, Sarasota, Florida 34231, USA
10Present address: Loggerhead Marinelife Center, Juno Beach, Florida 33408, USA
11Present address: University of South Florida, Sarasota-Manatee, Sarasota, Florida 34243, USA
*Corresponding author:

ABSTRACT: Data on Karenia brevis red tides (≥105 cells l-1) and on dead or debilitated (i.e. stranded) Kemp’s ridleys Lepidochelys kempii, loggerheads Caretta caretta, green turtles Chelonia mydas, hawksbills Eretmochelys imbricata, and leatherbacks Dermochelys coriacea documented in Florida during 1986-2013 were evaluated to assess red tides as a sea turtle mortality factor. Unusually large numbers of stranded sea turtles were found coincident with red tides primarily along Florida’s Gulf coast but also along a portion of Florida’s Atlantic coast. These strandings were mainly adult and large immature loggerheads and Kemp’s ridleys, and small immature green turtles and hawksbills. Unusually large numbers of stranded leatherbacks never coincided with red tide. For the 3 most common species, results of stranding data modeling, and of investigations that included determining brevetoxin concentrations in samples collected from stranded turtles, all indicated that red tides were associated with greater and more frequent increases in the numbers of stranded loggerheads and Kemp’s ridleys than in the number of stranded green turtles. The mean annual number of stranded sea turtles attributed to K. brevis red tide was 80 (SE = 21.6, range = 2-338). Considering typical stranding probabilities, the overall mortality was probably 5-10 times greater. Red tide accounted for a substantial portion of all stranded loggerheads (7.1%) and Kemp’s ridleys (17.7%), and a smaller portion of all stranded green turtles (1.6%). Even though K. brevis red tides occur naturally, the mortality they cause needs to be considered when managing these threatened and endangered species.


KEY WORDS: Sea turtles · Karenia brevis · Mortality · Brevetoxin · Red tide · Florida


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Cite this article as: Foley AM, Stacy BA, Schueller P, Flewelling LJ and others (2019) Assessing Karenia brevis red tide as a mortality factor of sea turtles in Florida, USA. Dis Aquat Org 132:109-124. https://doi.org/10.3354/dao03308

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