An Assessment of the Value of Shell Thickening in Crassostrea Gigas as an Indicator of Exposure to Tributyltin

Data from laboratory and field studies on the effects of tributyltin (TBT) on the oyster Crassostrea gigas are presented in order to provide a framework for the use of the species as a bioindicator when monitoring for environmental concentrations of TBT, and for monitoring for harmful effects of TBT on marine ecosystems. Concentrations of TBT in tissues have been demonstrated to reflect concentrations of TBT in the water column. Shell thickness index and accompanying loss of meat yield in the oysters have been shown to be related to tissue concentrations of TBT or concentrations of TBT in the water column in a readily predictable way. In field transplanting experiments, tissue concentrations of TBT >0.2–0.3 µg g-1 occurred concomitantly with a decrease in shell thickness index in the oysters, demonstrating that harm was occurring to a valuable marine resource. Deployment of C. gigas in the field has been shown to be a useful component in programs designed to monitor long-term changes in TBT concentrations. It is proposed that the presence of normally shaped C. gigas oysters yielding good meats are indicative of concentrations of TBT of <10 ng l-1