Dynamics of lipids and polychlorinated biphenyls in a Baltic amphipod (Monoporeia affinis): a field study

Processes such as accumulation and elimination, which control tissue concentration of polychlorinated biphenyls (PCBs), were examined over time in an in situ study of the amphipod Monoporeia affinis. These processes were studied with respect to individual PCB congeners, percentage lipid and composition, and body weight. A secondary objective was to examine the impact of seasonal variability in percentage lipids and lipid composition on PCB concentration in two coexisting Baltic amphipods, M. affinis and Pontoporeia femorata. Polycholorinated biphenyl concentrations tended to be higher in P. femorata than in M. affinis, possibly because of P. femorata's lower respiration rate and larger size. The net accumulation of PCBs was congener dependent and negatively correlated to lipid concentration. The relation between the net concentration change rate of 16 PCB congeners over time and log Kow was not significant during the spring and summer months, a time when lipid accumulation and strong growth occur. In contrast, the net concentration change rate of the corresponding PCB congeners over time during autumn and early winter, that is, from the period before gonad maturation to the period after mating and early embryogenesis, showed a significant relation to tog Kow (r2 = 0.62, p < 0.001, n = 16). During the latter period, amphipod lipid weight was reduced while the PCB body burden increased. Results strongly indicate that elimination rather than accumulation is the main process controlling amphipod body burden. This pattern results in a transfer of PCBs from the female to the developing embryos, which is reflected in high PCB body burden in newly released offspring.