Influence of chemical and biological factors on trophic transfer of persistent organic pollutants in the northwater polynya marine food web

Persistent organic pollutants (POPs) and stable isotopes of nitrogen (delta N-15) were measured in zooplankton (6 species), a benthic invertebrate (An onyx nugax), Arctic cod (Boreogados saida), seabirds (6 species), and ringe d seals (Phoca hispida) collected in 1998 in the Northwater Polynya to exam ine effects of biological and chemical factors on trophic transfer of POPs in an Arctic marine food web. Strong positive relationships were found betw een recalcitrant POP concentrations (lipid corrected) and trophic level bas ed on stable isotopes of nitrogen, providing clear evidence of POP biomagni fication in Arctic marine food webs. Food web magnification factors (FWMFs) , derived from the slope of the POP-trophic level relationship, provided an overall magnification factor for the food web but over and underestimated biomagnification factors (BMFs) based on predator-prey concentrations in po ikilotherms (fish) and homeotherms (seabirds and mammals), respectively. Gr eater biomagnification in homeotherms was attributed to their greater energ y requirement and subsequent feeding rates. Within the homeotherms, seabird s had greater BMFs than ringed seals, consistent with greater energy demand s in birds. Scavenging from marine mammal carcasses and accumulation in mor e contaminated winter habitats were considered important variables in seabi rd BMFs. Metabolic differences between species resulted in lower than expec ted BMFs, which would not be recognized in whole food web trophic level-POP relationships. The use of Sigma POP groups, such as Sigma PCB, is problema tic because FWMFs and BMFs varied considerably between individual POPs. FWM Fs of recalcitrant POPs had a strong positive relationship with log octanol -water partition coefficient (K-ow). Results of this study show the utility of using delta N-15 to characterize trophic level and trophic transfer of POPs but highlight the effects of species and chemical differences on troph ic transfer of POPs that can be overlooked when a single magnification fact or is applied to an entire food web.