Bioaccumulation and differential partitioning of polychlorinated biphenyls in freshwater, planktonic food webs

The planktonic food chain phytoplankton - zooplankton - young-of-the-year roach (Rutilus rutilus) was studied in 19 lakes in southern Sweden to investigate the bioaccumulation of polychlorinated biphenyls (PCBs). The ΣPCB concentrations did not steadily increase with increasing trophic level. The ΣPCB concentrations in zooplankton (400 ng·g lipid -1 ) were lower than in both phytoplankton (660 ng·g lipid -1 ) and fish (890 ng·g lipid -1 ), which did not differ significantly. Lipid content explained 40% of the total variation in dry weight normalised ΣPCB concentrations in the samples. The PCBs were differentially partitioned between the trophic levels. The logBMFs (biomagnification factors, concentration in predator/concentration in prey) were a function of the logK ow of the PCB congeners. The logBMF zoo/phyto values were < 0 for all PCB congeners on a lipid weight basis, and the logBMF fish/zoo values were < 0 for PCB congeners with logK ow > 6. We conclude that no PCBs had higher lipid-normalised concentrations in zooplankton than in phytoplankton and the most lipophilic PCBs had moderately higher concentrations in roach than in zooplankton. PCBs with logK ow > 6 decreased in concentration from phytoplankton to zooplankton to roach. We suggest that the concept of biomagnification did not apply to the planktonic food chain investigated in these lakes.