Habitat-Based PCB Environmental Quality Criteria for the Protection of Endangered Killer Whales (Orcinus orca)

Abstract

The development of an area-based polychlorinated biphenyl (PCB) food-web bioaccumulation model enabled a critical evaluation of the efficacy of sediment quality criteria and prey tissue residue guidelines in protecting fish-eating resident killer whales of British Columbia and adjacent waters. Model-predicted and observed PCB concentrations in resident killer whales and Chinook salmon were in good agreement, supporting the model's application for risk assessment and criteria development. Model application shows that PCB concentrations in the sediments from the resident killer whale's Critical Habitats and entire foraging range leads to PCB concentrations in most killer whales that exceed PCB toxicity threshold concentrations reported for marine mammals. Results further indicate that current PCB sediment quality and prey tissue residue criteria for fish-eating wildlife are not protective of killer whales and are not appropriate for assessing risks of PCB-contaminated sediments to high trophic level biota. We present a novel methodology for deriving sediment quality criteria and tissue residue guidelines that protect biota of high trophic levels under various PCB management scenarios. PCB concentrations in sediments and in prey that are deemed protective of resident killer whale health are much lower than current criteria values, underscoring the extreme vulnerability of high trophic level marine mammals to persistent and bioaccumulative contaminants.

Food Web Bioaccumulation Model for Resident Killer Whales from the Northeastern Pacific Ocean as a Tool for the Derivation of PBDE-Sediment Quality Guidelines

“…Because critical habitat is so important for feeding, resident killer whales spend a considerable portion of their lives in these areas. This has implications for the disposal of potentially contaminated materials into that habitat (Lachmuth et al 2010;Alava et al 2012a). Under SARA, critical habitat is legally protected from degradation, and advice from science is needed to justify management decisions designed to protect all of resident killer whale habitat under the Fisheries Act.…”

“…The structure of the resident killer whale food webs, including organisms' feeding preferences and composition of prey items, was described and is available elsewhere (Lachmuth et al 2010;Alava et al 2012a). A schematic diagram of organisms included in the coastal food web and the representative trophic interactions considered is provided in Fig.…”

“…Tables S1 and S2 indicate sites where sediment and water PBDE data were obtained and these data were used in the food web model. Second, the wildlife species included in the model are distributed over large areas of the Strait of Georgia region and most of them are year-round residents of the region, except for the oceanic stage of Chinook salmon and winter foraging areas of resident killer whales (Lachmuth et al 2010;Alava et al 2012a). Third, the model accounts for PBDE binding to organic carbon in the water column and sediments, which causes the PBDE to become less bioavailable.…”

“…The development of the PBDE bioaccumulation model of the coastal food webs for killer whales was based on the application of a food web bioaccumulation model for PCBs developed for killer whales' critical habitats in the marine region of British Columbia, Canada (Lachmuth et al 2010;Alava et al 2012a), explained in detail in the supporting information. Briefly, the description of the food web bioaccumulation model expressing the net accumulation of PBDE in killer whales as function of uptake and elimination is represented by the following mass balance, steady state equation:…”

“…BSAF values are used to ''forward'' and ''backward'' calculate PBDE concentrations. The model application involving forward and backward calculations are applied to conduct exposure and health risk assessments and risk management, respectively (Gobas and Arnot 2010;Alava et al 2012a). These applications are detailed in the supporting information.…”