Bioaccumulation and detoxification processes of Hg in the king scallop Pecten maximus: field and laboratory investigations

Hg bioaccumulation was investigated in the king scallop Pecten maximus in the laboratory and in the field. In controlled conditions, scallops were exposed to (203)Hg through seawater, sediment and food in order to determine its uptake and depuration kinetics. In the field, Hg and metallothionein (MT) concentrations and the metal subcellular distribution were determined in scallops from two sites of the Bay of Seine (France) differently subjected to the Seine river inputs. While Hg concentrations in the whole soft parts and kidneys (viz. the highest accumulator organ) did not differ between scallops from both sites (74-156 ng g(-1)dry wt), they did for the digestive gland and the gills. According to the experimental results, a higher exposure to dissolved Hg might occur in the site close to the estuary whereas Hg would be mainly incorporated via the dietary pathway in the site away from the estuary. Within the cells of wild scallops, Hg was mainly associated to the cytosolic fraction in the digestive gland and gills (60-100%). However, the lack of relationship between Hg and MT levels suggests that Hg detoxification in P. maximus involves other, non-MT, soluble compounds. In kidneys, insoluble compounds played an important role in Hg sequestration. No effect of scallop age was observed neither on Hg and MT concentrations nor on the subcellular distribution of the metal. Finally, according to FAO/WHO recommendations (maximum weekly Hg intake), our results clearly indicate that the low Hg contents in the edible part of the king scallops from the Bay of Seine prevent any risk for human consumers.