Comparison of bioaccumulation of metals and induction of metallothioneins in two marine bivalves (Mytilus edulis and Mya arenaria)

The St. Lawrence maritime estuary (Quebec, Canada) is subjected to mixed inputs of pollutants and the study of the induction of metallothionein in species of economic and ecologic importance such as Mytilus edulis and Mya arenaria was pertinent to assess the consequences of pollution in this northern estuary. Bivalves from an area devoid of anthropogenic influences but characterized by background metal contamination (Franquelin) were actively transplanted within this location and in a site contaminated by urban, industrial and endogenous pollutants, Baie-Comeau (Baie-des-Anglais). Spatial differences in metal concentrations were shown between sites. Cu and Zn concentrations were higher in mussels from Baie-des-Anglais at the beginning of the transfer and after 1 and 2 months. In clams, Zn concentrations were significantly higher in gills and digestive gland tissues for organisms transplanted in Baie-des-Anglais thus showing that spatio-temporal variations of metal concentrations were different between the two species studied. Mussels and clams partitioning of metals were shown to be different depending of the species, metal and/or tissue studied. In mussels, Cd and Cu concentrations decreased in both organs and both groups after the 3-month transfer in the polluted site. In mussels, total metal and metallothionein (MT) concentrations were positively correlated in digestive gland while in clams a positive correlation was only observed in gills.