Chambering in the Pacific oyster, Crassostrea gigas, and its relationship to tributyltin

Studies have documented a relationship between tributyltin (TBT) exposure and the occurrence of shell chambering in Crassostrea gigas. The studies conducted in the 1980s presented exposures where TBT water concentrations were many times higher than current concentrations in the USA. Through an ongoing field study, the incidence of chambering is evaluated to determine if it is correlated with current environmental concentrations of TBT, and to any declines in oyster health. Interestingly, condition and weight showed no significant relationship with TBT residues or number of chambers. In other words, despite increases in the number of chambers, neither the weight nor condition of the oysters declined from that observed in the baseline population or from those transplanted to fish/shellfish areas. This indicates that TBT may be eliciting a response, but perhaps not an ecologically significant effect.