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Blood Monitoring Supports Response and Rehabilitation of Algae-poisoned Sea Turtles

Sea turtles in the Gulf of Mexico are long-lived animals that are valuable indicator species of environmental health. They are subject to multiple hazards, such as pollutants and natural toxins, including the algae-produced brevetoxin. NCCOS scientists who pioneered the use of blood collection cards are working in cooperation with wildlife managers in Florida to measure brevetoxin in live sea turtles. During two extensive red tide events along the central west coast of Florida, blood collection cards from stranded sea turtles helped to diagnose whether or not they were exposed to brevetoxin. These cards were used as part of a study to be published in the June issue of the Journal of Zoo and Wildlife Medicine.

Response data showed that live stranded sea turtles showed signs of brevetoxin poisoning and 93% (52 of 56) had measurable brevetoxin in their blood. Dead stranded sea turtles were 98% (42 of 43) positive for brevetoxin. This indicates that during red tide events, sea turtles are susceptible to brevetoxins, which can cause serious health problems or death. For live animals, knowing whether or not they are positive helps to properly diagnose them and treat them during rehabilitation so they can be released safely back into the wild.

Pictures of the three common sea turtle species found in the Gulf of Mexico

Loggerhead (Caretta caretta) (left) retain brevetoxins up to four times longer than Green (Chelonia mydas) (center) or Kemp’s ridley (Lepidochelys kempii) (right). Green turtles had the highest success of rehabilitation after red tide poisoning. Photo SEFSC Beaufort Lab.

Rehabilitation data showed the toxin cleared from sea turtle blood more slowly in some species than others, with loggerheads retaining the toxin up to four times longer than Green turtles and Kemp Ridleys.  Those animals that could eliminate the toxin had the highest survival rates. The majority of animals that survived rehabilitation eliminated 80% of toxin from blood by day 20, whereas animals that died in rehabilitation eliminated only 40-60% of toxin over the same time period.   Factors that enhance toxin elimination remain to be determined, but may include metabolic rate, age or diet.

The use of blood collection cards, a Center for Disease Control (CDC) method for blood collection and sample archiving, was developed by NCCOS for biomonitoring brevetoxin exposure in humans and wildlife species, including sea birds, sea turtles, manatees and dolphins. The blood card method used as part of this study could be a reliable means of monitoring brevetoxin levels to assess wildlife mortality events in the Gulf of Mexico, as well as to establish “baseline” levels during non-bloom periods.

Contributing partners in this study include Mote Marine Laboratory, Florida Fish and Wildlife Conservation Commission, Loggerhead Marinelife Center, the University of Illinois Zoological Pathology Program and the University of Florida College of Veterinary Medicine. The Morris Animal Foundation and Florida Sea Turtle Grants Program funded this research.

For more information, contact John.Ramsdell@noaa.gov.

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