Modeling 137Cs bioaccumulation in the salmon-resident killer whale food web of the Northeastern Pacific following the Fukushima Nuclear Accident

To track the long term bioaccumulation of Cs-137 in marine organisms off the Pacific Northwest coast of Canada, we developed a time dependent bioaccumulation model for Cs-137 in a marine mammalian food web that included fish-eating resident killer whales. The model outcomes show that Cs-137 can be expected to gradually bioaccumulate in the food web over time as demonstrated by the increase of the apparent trophic magnification factor of Cs-137, ranging from 0.76 after 1 month of exposure to 2.0 following 30 years of exposure. Cs-137 bioaccumulation is driven by relatively rapid dietary uptake rates, moderate depuration rates in lower trophic level organisms and slow elimination rates in high trophic level organisms. Model estimates of the Cs-137 activity in species of the food web, based on current measurements and forecasts of Cs-137 activities in oceanic waters and sediments off the Canadian Pacific Northwest, indicate that the long term Cs-137 activities in fish species including Pacific herring, wild Pacific salmon, sablefish and halibut will remain well below the current Cs-137-Canada Action Level for consumption (1000 Bq/kg) following a nuclear emergency. Killer whales and Pacific salmon are expected to exhibit the largest long term Cs-137 activities and may be good sentinels for monitoring Cs-137 in the region. Assessment of the long term consequences of Cs-137 releases from the Fukushima aftermath should consider the extent of ecological magnification in addition to ocean dilution. (C) 2015 Elsevier B.V. All rights reserved.