BIOACCUMULATION KINETICS OF PCB-31, PCB-49 AND PCB-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 chlorobiph enyl (IUPAC no. 31, 49 and 153) in Baltic Sea blue mussels (Mytilus ed ulis L.) were determined at different algal food rations. Differences in food concentration markedly influenced the water pumping and filtra tion 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 differen ces in food ration on PCB bioaccumulation in mussels. A PB bioaccumula tion model was used to describe the gradual shift in PCB exposure with increasing food concentration from apparently dissolved to food-assoc iated PCBs. This change in the route of PCB exposure was owing to the combined effect of PCB partitioning to algae and regulation of the rat es of water pumping and algae filtration by the mussels. Differences i n food ration significantly influenced the PCB uptake rate, whereas PC B depuration was mainly unaffected by differences in algal food concen tration. The observed differences in PCB uptake were primarily caused by the influence of food ration on the physiological activity of the m ussels and only to a lesser degree by changes in PCB bioavailability o wing to PCB partitioning between water and algal food. Calculated bioa ccumulation factors (BAFs) varied up to two orders of magnitude over t he 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, re spectively, at a food concentration of 0.076 mg particulate organic ca rbon per litre. Thus, differences in food ration affects both the rout e and the rate of contaminant exposure and uptake. This emphasises the importance of controlling particulate food concentrations when design ing bioaccumulation and toxicity studies with suspension-feeding organ isms. Long-term changes in food availability may also affect contamina nt accumulation and cycling in field populations of suspension-feeding mussels.