Bioaccumulation kinetics of PCB 31, 49 and 153 in the blue mussel, Mytilus edulis L as a function of algal food concentration

Uptake and depuration kinetics of a tri, a tetra and a hexa chlorobiphenyl (IUPAC no. 31, 49 and 153) in Baltic Sea blue mussels (Mytilus edulis L.) were determined at different algal food rations. Differences in food concentration markedly influenced the water pumping and filtration rates of the mussels. This indicates that physiologically-based (PB) rather than simple equilibrium partitioning bioaccumulation models are more appropriate to use when describing the influence of differences in food ration on PCB bioaccumulation in mussels. A PB bioaccumulation model was used to describe the gradual shift in PCB exposure with increasing food concentration from apparently dissolved to food-associated PCBs. This change in the route of PCB exposure was owing to the combined effect of PCB partitioning to algae and regulation of the rates of water pumping and algae filtration by the mussels. Differences in food ration significantly influenced the PCB uptake rate, whereas PCB depuration was mainly unaffected by differences in algal food concentration. The observed differences in PCB uptake were primarily caused by the influence of food ration on the physiological activity of the mussels and only to a lesser degree by changes in PCB bioavailability owing to PCB partitioning between water and algal food. Calculated bioaccumulation factors (BAFs) varied up to two orders of magnitude over the food ration interval studied. Maximum BAFs of 4.92 10(5), 1.10 10(6), and 6.91 10(6) ml g(-1) DW were obtained for PCB 31, 49 and 153, respectively, at a food concentration of 0.076 mg particulate organic carbon per litre. Thus, differences in food ration affects both the route and the rate of contaminant exposure and uptake. This emphasises the importance of controlling particulate food concentrations when designing bioaccumulation and toxicity studies with suspension-feeding organisms. Long-term changes in food availability may also affect contaminant accumulation and cycling in field populations of suspension-feeding mussels.