Effects of red tide on dolphins, sea turtles and sea birds
By Deborah Fauquier, DVM, PhD student,
University of California, Santa Cruz

"Zach", a loggerhead turtle rescued near Boca Grande, Florida on September 8, 2006. He was treated for red tide toxicosis at Mote and then released on November 17, 2006.

      We have been investigating the impacts of red tide on Sarasota Bay dolphins, sea turtles and sea birds over the last several years.  Although the Sarasota Bay area did not experience a red tide bloom during 2007 we are still investigating the impacts of the severe red tide blooms in 2005 and 2006 on these species.  We have collected data from stranded dolphins, sea turtles, and sea birds to determine brevetoxin (the toxin produced by red tide organisms) levels in these species and the effects brevetoxin has on increasing morbidity and mortality in these species.  In sea turtles and sea birds we have been able to collect blood and/or fecal samples from live animals suffering from brevetoxicosis and determine how quickly or slowly these animals clear the toxin from their blood.   
      Seventy-six percent of dolphins stranding during 2006-2007 (n=21) had brevetoxin levels above the detection limit and were classified as brevetoxin positive animals.  Of these positive animals, 30% were determined to have died from brevetoxin intoxication or it was implicated as a contributory factor to death.  
      Sea birds and sea turtles stranding during 2005 and 2006 had clinical signs of red tide intoxication including circling, paralysis, and seizures.  Red tide intoxication appeared to be the primary cause of stranding in 46 of 74 (62%) live stranded sea birds and 30 of 40 (75%) sea turtles.  Sea birds were able to clear the toxin from their blood in 10 days, while it took up to 50 days for some sea turtles to clear the toxin due to their lower metabolic rate.
      Findings from this study are only preliminary, but the fact that the majority of the live and dead sea birds and sea turtles sampled during the 2005 and 2006 red tide events were positive for the red tide toxin indicates that red tide intoxication plays a larger role in the morbidity and mortality of sea bird and sea turtles off the west coast of Florida than previously recognized.  In addition, the information that sea birds can clear the red tide toxin from their bodies within 10 days of rehabilitation whereas it may take up to 50 days for sea turtles to clear the toxin can be used by rehabilitators to modify treatment plans for animals suspected of suffering from red tide intoxication.  This modification of treatment plans may lead to increased success in the rehabilitation of these animals.
      Our research was supported by funding from the John H. Prescott Grant Program, Morris Animal Foundation and the Florida Sea Turtle License Plate Sea Turtle Grants Program.