Bioaccumulation and biomagnification of polycyclic aromatic hydrocarbons in aquatic organisms

Uptake and degradation of polycyclic aromatic hydrocarbons were studied in a laboratory scale food chain consisting of Dunaliella tertiolecta (microalga), Mytilus galloprovincialis (mussel) and Dicentrarchus labrax (fish), in tanks supplied with open water flow. The toxicants, benzo(a)pyrene and 7,12-dimethyl benz(a)anthracene, were added and samples were taken every ten days. Bioaccumulation of toxicants in the food chain steps and the physiological response of organisms' xenobiotic-metabolizing enzyme systems were tested. Mixed-function oxygenase enzymes were evaluated through quantitation of benzo(a)pyrene-monooxygenase in the mussels and ethoxyresorufin-O-diethylase in the fish. In the mussels benzo(a)pyrene and 7,12-dimethyl benz(a)anthracene are bioaccumulated in contrast with the seabasses in which only negligible quantities were found. These different responses among mussels and fish are probably caused by the very efficient detoxification enzymatic system located in the liver of the fish. The mussel is confirmed as a biomonitor of hydrocarbons in the environment because of its ability to bioaccumulate, whereas seabass shows a strategy of survival in contaminated environments based on an active oxidative enzymatic system.