Delineation of Pb contamination pathways in two Pectinidae: the variegated scallop Chlamys varia and the king scallop Pecten maximus.

Bioaccumulation of Pb was determined in Chlamys varia and Pecten maximus exposed to (210)Pb via seawater, food and sediment. Both scallops readily concentrated dissolved Pb with whole-body 7-d concentration factors of 250+/-40 and 170+/-70, respectively. In both species, more than 70% of Pb taken up from seawater was strongly retained within tissues (biological half-life>1.5 month) whereas Pb ingested with phytoplankton was poorly assimilated (<20%). As P. maximus lives buried in the sediment, this exposure pathway was assessed and showed low bioaccumulation efficiency for sediment-bound Pb (transfer factor <0.015). Despite the poor transfer efficiency of Pb from food and sediment, the use of a global bioaccumulation model indicated that the particulate pathway (food and/or sediment) constituted the major bioaccumulation route of Pb in both scallops. Whatever the exposure pathway, the digestive gland and kidneys always played a major role in Pb accumulation. In scallop tissues, Pb was predominantly associated with the insoluble subcellular fraction, suggesting a low bioavailability of Pb for scallop consumers.