THE BIOMAGNIFICATION OF POLYCHLORINATED-BIPHENYLS, TOXAPHENE, AND DDT COMPOUNDS IN A LAKE-MICHIGAN OFFSHORE FOOD WEB

The biomagnification of polychlorinated biphenyls (PCB), toxaphene, and the DDT family of metabolites was investigated in the epibenthic Mysis relicta (mysid), the benthic Pontoporeia hoyi (amphipod), plankton, particulate flux, surficial sediments, and Myoxocephalus thompsoni (deepwater sculpin) in southeastern Lake Michigan. DDE was the most strongly biomagnified compound, increasing 28.7 times in average concentration from plankton to fish. PCB increased 12.9 times in average concentration from plankton to fish while toxaphene increased by an average factor of 4.7. Particle flux was comprised of lower chlorinated PCB homologues (average chlorine number = 3.8) than the biota (4.5-5.0) and sediments (4.6), possibly reflecting strong influences from atmospheric deposition and/or zooplankton egestion. The percent of higher chlorinated PCB homologues (5 and 6 chlorine atoms per PCB molecule) increased from 54-56% of the total PCB in plankton and M. relicta, to 61% in P. hoyi, to 74% in sculpins. Amphipods contained greater concentrations than mysids of PCB, DDT residues, and toxaphene, possibly reflecting differences in habitat (benthic vs epibenthic) and diet (detritus vs plankton). Based on estimates of average areal biomass and contaminant concentration, offshore Lake Michigan P. hoyi populations contain approximately 15.0 times as much toxaphene, 9.5 times as much total DDT, and 12.0 times as much PCB as the offshore M. relicta populations. Thus, amphipods may represent a greater reservoir than mysids for contaminant storage and subsequent recycling in offshore Lake Michigan.