Cadmium accumulation in coastal demersal fish

The hepatic Cd burden, measured on 291 individuals of 4 species of demersal fish (Gadus morhua, Reinhardtius hippoglossoides, Hippoglossoides platessoides, and Raja radiata), is 2 to 5 times higher in fish from the open Gulf of St. Lawrence than in fish from the St. Lawrence Estuary, 600 km landward. The higher Cd burden in the open Gulf is not related to the input of anthropogenic Cd, nor can it be attributed to differences in size, sex, sampling season, or state of health, Rather, the Cd burden in demersal fish may be related to sediment diagenesis, since the concentration of authigenic Cd (i.e. Cd minerals formed in the sediments) is higher in the Gulf than in the Estuary, which may lead in turn to Cd-enrichment in sediment-dwelling organisms. Measured Cd burdens in the liver agree with predictions made with a simple biokinetic model that uses realistic estimates of the Cd content of benthic invertebrates in combination with kinetic parameters determined in H. platessoides with in vivo gamma counting. These results strongly suggest that the Cd content of the diet, rather than of the water phase, determines the hepatic Cd burden in these demersal fish species.