Bioaccumulation of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) was investigated in plankton, crustaceans, and fish from two relatively small Amsterdam lakes, with different levels of contamination. Ratios between contaminant concentrations in organisms and sediments ranged from 0.1 to 41.7. The accumulation of pollutants could not be explained as a simple partitioning between sediment, water, and organisms. Probably, both biomagnification (PCBs and OCPs) and biotransformation (PAHs) affect the bioaccumulation in aquatic organisms. These effects were more pronounced in organisms of the higher trophic levels of the aquatic food-chain.
Mixed function oxygenase (MFO) activity of liver microsomal fractions was determined in three fish species (roach, eel, and pike) and compared with those of similar fish taken from a less contaminated lake that served as a reference. Despite the low level of contaminants present in the two lakes, an induction of both cytochrome P-450 and ethoxy-resorufin-O-deethylase (EROD) activity was observed in all three fish species involved. Pentoxyresorufin-O-depentylase (PROD) activity was induced in pike and eel only. Both the 3-methylcholan-threne-type inducible isozymes (P-450IA) and the phenobarbital-type inducible isozymes (P-450IIB) seem to be induced in the fish. These findings suggest that MFO enzyme activity in fish liver may be a suitable and sensitive indicator for the presence of trace organics in the aquatic environment. Despite the enzyme induction, no significant liver enlargement was observed in the fish species investigated, which can be interpreted as the absence of some pathological changes.
A relationship between MFO activities and PCB and OCP levels was observed in fish. No such relationship was found for PAH, because these compounds are biotransformed readily in fish. Through enhanced metabolism, accumulation of these chemicals is further reduced when MFO systems are induced. The interaction between bioaccumulation and enzyme induction demonstrates the importance of an integrated study of these phenomena in field research.