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Bottlenose dolphins (Tursiops truncatus) along the Gulf of Mexico are frequently exposed to blooms of the toxic alga, Karenia brevis, and brevetoxins associated with these blooms have been implicated in several dolphin mortality events. Studies on brevetoxin accumulation in dolphins have typically focused on analyses of carcasses from large-scale die-offs; however, data are scarce for brevetoxin loads in live individuals frequently exposed to K. brevis blooms. This study investigated in vivo brevetoxin exposure in free-ranging bottlenose dolphins resident to Sarasota Bay, Florida, utilizing samples collected during health assessments performed during multiple K. brevis blooms occurring from 2003 to 2005. Brevetoxins were detected by ELISA and LC-MS in 63% of bottlenose dolphins sampled (n = 30) concurrently with a K. brevis bloom. Brevetoxins were present in urine and gastric samples at concentrations ranging from 2 to 9 ng PbTx-3 eq/g, and in feces at concentrations ranging from 45 to 231 ng PbTx-3 eq/g. Samples from individuals (n=12) sampled during nonbloom conditions (≤1,000 cells/L) were negative for brevetoxin activity. Brevetoxin accumulation data from this study complement dolphin carcass and prey fish data from the same study area, and aid in evaluating impacts of harmful algal blooms on sentinel marine animal species along the west Florida coast.