Trophic magnification of legacy persistent organic pollutants and emergent contaminants within a terrestrial food-web of an avian apex predator, the Cooper’s Hawk (Accipiter cooperii)

Several types of legacy and lipophilic persistent organic pollutants (POPs), such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), and emergent proteinophilic POPs like perfluorinated compounds (PFCs) are released from multiple sources into the environment and negatively impact endocrine functions within exposed wildlife. Protocols to assess bioaccumulation of these persistent chemicals within terrestrial systems are far less developed compared to aquatic systems. Consequently, regulatory agencies in Canada, the United States, and the European Union use only aquatic information to assess bioaccumulation potential of chemicals. However, recent studies have shown that some chemicals that are not bioaccumulative in aquatic food-webs do biomagnify in terrestrial food-webs. To better understand the bioaccumulation behaviour of chemicals in terrestrial systems, we assessed the biomagnification of lipophilic and proteinophilic POPs in a terrestrial food-web that included an avian apex predator, the Cooper’s Hawk (Accipiter cooperii). Over 100 samples were collected from various trophic levels of the food-web including hawk eggs, songbirds, invertebrates, and berries. We estimated the trophic position of each organism using stable isotope analysis of δ13C and δ15N signatures of the hawks, songbirds, invertebrates, and berries. We analyzed the biota samples for concentrations of 38 PCB congeners, 20 OCPs, 20 PBDE congeners, 7 other brominated flame retardants (BFRs), and 18 PFCs listed on the Government of Canada's Chemicals Management Plan. We used censored regression by maximum likelihood estimation to assess the relationship between the natural logarithm of each contaminant concentration and trophic position. Trophic magnification factors (TMFs) were determined as the antilog of the regression slope. We determined TMFs for contaminants that were detected at appreciable levels in all of the biota samples (i.e. had 50% or greater detection frequency) and compared these terrestrial TMFs to those observed in aquatic systems. TMFs of legacy and lipophilic POPs ranged from 0.77 to 15.66, indicating that the majority of those POPs are biomagnifying. TMFs of PFCs ranged from 13.02 – 86.19, indicating PFCs are also readily biomagnifying and perhaps at a greater extent than lipophilic POPs. Terrestrial TMFs for legacy POPs were comparable or higher than aquatic TMFs; whereas, terrestrial TMFs for PFCs were considerably higher than aquatic TMFs.