Utilisation des métallothionéines comme biomarqueur de la contamination métallique : variabilité entre sites et organes chez l'huı̂tre Crassostrea gigas

Heavy metals (Cd, Cu, Hg and Zn) and metallothionein levels were determined in oysters Crassostrea gigas from two sites: the Gironde Estuary (contaminated site) and Bourgneuf Bay (uncontaminated site). Metallothionein levels led us to suspect the presence of cadmium in the environment when quantified in the gills. Soluble cadmium and metallothioneins were positively correlated in the digestive gland of oysters from Gironde (contaminated site), but metallothionein levels in this organ were not significantly different from levels observed in the digestive gland of oysters from Bourgneuf Bay (uncontaminated site). Conversely, no correlation was noticed between metals and metallothioneins in the gills of oysters from Gironde despite metallothionein levels significantly higher than levels observed in oyster gills from Bourgneuf Bay. This significant difference of metallothionein levels is attributed to a higher ratio of soluble metals (Cd, Cu, Zn) in the gills of oysters from Gironde. The generalization of the use of metallothioneins as biomarkers of metal contamination of aquatic environments is questioned.