Elevated Accumulation of Tributyltin and Its Breakdown Products in Bottlenose Dolphins (<i>Tursiops truncatus</i>) Found Stranded along the U.S. Atlantic and Gulf Coasts

Butyltin compounds, including mono- (MBT), di- (DBT), and tributyltin (TBT), were determined in the liver, kidney, and muscle of bottlenose dolphins (Tursiops truncatus) found stranded along the southeast U.S. Atlantic and Gulf coasts during 1989−1994. Total butyltin (BTs: MBT + DBT + TBT) concentrations in dolphin liver ranged between 110 and 11 340 ng/g (wet wt) with a mean value of 1400 ng/g. Butyltin concentrations in bottlenose dolphins were higher than those reported from other locations. The liver of a adult male dolphin collected in 1989 had the highest BT concentration (11 340 ng/g wet wt) reported. The concentrations of butyltins increased during the early life stages until maturity, for both sexes, and then tended to remain constant. Analysis of fish muscle collected from the Gulf of Mexico indicated the existence of recent inputs of TBT. The biomagnification factor of BTs in dolphins, on average, was 1.0 with the highest value of 6.8. In addition to polychlorinated biphenyls (PCBs), the presence of noticeable concentrations of TBT and DBT, which are potential immunosuppressing agents, might have also contributed to bottlenose dolphin mortality events in the U.S. Atlantic and Gulf coasts.