T9 AM Bioaccumulation and Biomagnification
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 339-340

(GEW-1117-855218) Application of a food web model to evaluate the mechanisms controlling polychlorinated naphthalene concentrations in a Lake Ontario food web.

Gewurtz, S¹, Helm, P², Gandhi, N¹, Bhavsar, S¹, Diamond, M¹, Marvin, C³, Whittle, D⁴, ¹ University of Toronto, Toronto, Ontario, Canada² Ontario Ministry of the Environment, Toronto, Ontario, Canada³ Environment Canada, Toronto, Ontario, Canada⁴ Fisheries and Oceans Canada, Toronto, Ontario, Canada

ABSTRACT- Polychlorinated naphthalenes (PCNs) have been less studied compared to legacy contaminants such as PCBs and, as a result, the processes controlling their dynamics are not well known. A recent study found that PCNs bioaccumulate in a Lake Ontario food web (Helm et al. 2005). We used this data set in a model in order to further assess the mechanisms controlling PCN dynamics in aquatic food webs. Model performance was first evaluated with persistent PCB congeners and the model predicted PCB concentrations within the error associated with the measured data. In contrast, the model over-predicted concentrations of all PCNs, even the congeners which have no vicinal carbon atoms unsubstituted with chlorine that are not typically metabolized in aquatic organisms. We hypothesized that this occurred because PCNs are planar compounds and thus show stronger sorption to sediment then would be expected based on equilibrium partitioning. PCN biota-sediment accumulation factors for benthic invertebrates were consistently less than those for PCBs, providing support for this hypothesis. After calibrating the model to account for decreased bioavailability of PCNs from sediment, the model predicted concentrations of the PCN congeners which have no vicinal carbon atoms unsubstituted with chlorine within the error associated with the measured data. However, even after this model modification, measured concentrations of the less persistent PCNs with 2 vicinal carbon atoms unsubstituted with chlorine were still over predicted in fish. We hypothesized that this occurred as a result of metabolic degradation of these less persistent PCNs in the higher trophic levels. We then used the food web model to provide estimated rates of metabolic degradation.

Key words: bioaccumulation, polychlorinated naphthalenes, food web model, Lake Ontario