Mechanism of Biomagnification in Fish under Laboratory and Field Conditions

Abstract

While biomagnification of certain organic contaminants in food chains has been observed in field studies, the mechanism of the biomagnification process is still unresolved. Knowledge of the mechanism by which contaminants are absorbed and biomagnified in food chains is important in environmental risk assessment and studies of chemical bioavailability. In this study, we hypothesize a fugacity based model of the gastrointestinal absorption of contaminants. We test the model in a 73 day laboratory, gastrointestinal magnification study of 2,2‘,4,4‘,6,6‘-hexachlorobiphenyl in adult rainbow trout ( Oncorhynchus mykiss ) and in a field study of the gastrointestinal magnification of PCB congeners in rock bass ( Ambloplites rupestris ). Both studies show that the fugacity of the test chemicals in the gastrointestinal tract (GIT) can increase to levels up to 7−8-fold greater than those in the consumed food. The fugacity increase in the GIT is the result of a drop in the chyme's fugacity capacity for the test chemicals (i.e. approximately 4-fold in this study) and an increase in chemical concentration due to food absorption in the GIT (i.e. approximately 2-fold in this study). Food digestibility and absorption are found to be critical factors controlling biomagnification factors and dietary uptake efficiencies under laboratory and field conditions.