Fremlin, KM; Elliott, JE; Droulliard, K; Martin, PA; Gobas, FAPC; Green, D
Several types of legacy persistent organic pollutants (POPs), such as PCBs and DDE, and emerging POPs like cyclic volatile methyl siloxanes (cVMS) are released from multiple sources into the ambient environment and are known to negatively impact endocrine and physiological functions within exposed wildlife. Protocols to assess bioaccumulation of these persistent chemicals within terrestrial systems are far less developed compared to aquatic systems. Presently, regulatory agencies in Canada, the USA, and the EU use only bioaccumulation information for fish to assess the 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 food-webs, we aim to produce a food-web model to assess the biomagnification of POPs in an apex avian predator, the Cooper’s hawk. Over 100 samples were collected from various trophic levels of the food-web including hawk eggs, songbirds, invertebrates, and berries. All samples were analyzed for a number of contaminants listed as priorities for monitoring by the Chemical Management Plan of the Canadian federal government. Stable isotope analysis of δ13C and δ15N signatures of hawks, songbirds, invertebrates, and berries was used to estimate the trophic position of each organism. Censored regression by maximum likelihood estimation was used to assess the relationship between the natural logarithm of each contaminant lipid equivalent concentration and trophic position. Trophic magnification factors (TMFs) were determined for cVMS and legacy POPs for comparison. TMFs of PCBs, PBDEs, and OCPs ranged from 1.20 to 15.66, 3.11 to 7.32, and 0.77 to 7.79, respectively. Indicating that most legacy POPs are biomagnifying in this terrestrial food-web. TMFs of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) were estimated at 0.77 (0.12 SE), 1.17 (0.18 SE), 1.29 (0.23 SE), respectively, indicating that cVMS are either diluting or not biomagnifying in this terrestrial system. Overall, terrestrial TMF values for legacy POPs were comparable to or slightly higher than TMF values determined for several aquatic systems; however, the terrestrial TMF values for the cVMS were lower than TMF values reported in aquatic systems.