Calibration of the Gastrointestinal Magnification Model to Predict Maximum Biomagnification Potentials of Polychlorinated Biphenyls in a Bird and Fish

The gastrointestinal magnification (GI-magnification) model was calibrated in ring doves and Japanese koi using matched data on dietary assimilation and fecal depuration of polychlorinated biphenyls (PCBs). Mass transport parameters describing PCB flux from gut contents to organism (Dgo′; mol d–1 Pa–1) and organism to gut contents (Dog; mol d–1 Pa–1) were quantified to test the hypothesis that the ratio of these two terms approached unity. For birds, Dgo′/Dog ranged from 2.9 to 6.3 and for fish the ratios ranged from 0.7 to 3.1. In both species, the ratio commonly exceeded 1. The GI-magnification model was used to predict maximum PCB biomagnification factors (BMFmax) for each species which ranged from 18.5 to 33.8 for ring doves and 7.9 to 14.8 for Japanese koi. Chemical losses via respiration reduced steady state biomagnification factor (BMFss) estimates by a negligible amount in birds, whereas for fish, predicted BMFss decreased to values from 0.5 to 7.2. This study demonstrated that chemical transfer efficiency during assimilation exceeds organism/feces transfer which contributes to elevated PCB biomagnification potentials in birds and fish. Combined with reduced losses of chemical across respiratory surfaces, higher Dgo′/Dog ratios of birds contribute to elevated biomagnification in birds over fish.