The use of metallothioneins as biomarker of metal contamination: variability between sites and organs in the oyster Crassostrea gigas.

Heavy metals (Cd, Cu, Hg and Zn) and metallothionein levels were determined in oysters Crassostrea gigas from two sites: the Gironde Estuary (contamin ated site) and Bourgneuf Bay (uncontaminated site). Metallothionein levels led us to suspect the presence of cadmium in the environment when quantifie d in the gills. Soluble cadmium and metallothioneins were positively correl ated in the digestive gland of oysters from Gironde (contaminated site), bu t metallothionein levels in this organ were not significantly different fro m levels observed in the digestive gland of oysters from Bourgneuf Bay (unc ontaminated site). Conversely, no correlation was noticed between metals an d metallothioneins in the gills of oysters from Gironde despite metallothio nein levels significantly higher than levels observed in oyster gills from Bourgneuf Bay. This significant difference of metallothionein levels is att ributed to a higher ratio of soluble metals (Cd, Cu, Zn) in the gills of oy sters from Gironde. The generalization of the use of metallothioneins as bi omarkers of metal contamination of aquatic environments is questioned. (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.