Kinetics of bioaccumulation of heavy metals in Odontesthes bonariensis is explained by a single and common mechanism

Fish are often considered a very sensitive indicator of heavy metal contamination in aquatic ecosystems; however, the detailed mechanisms of bioaccumulation remain unclear. Here, we study the bioaccumulation processes of three relevant heavy metals (Cd2+, Cu2+ and Cr6+) in Odontesthes bonariensis using mathematical modelling. We developed a general compartmental kinetic model that describes the transport of heavy metals between the surrounding water and the gills and liver of fish. The general model was reduced to a simple one still capable of reproducing previous experimental data and suggesting a common mechanism for the three metals. The modelling results indicate that bioaccumulation of Cd2+, Cu2+, and Cr6+ is described by a combination of a concentration-independent and saturable uptake kinetics in both organs with a unidirectional path of elimination from gills to liver to waterborne. Finally, the good agreement between the parameter values predicted by the model and previously published data suggests that our modelling approach may shed light on the mechanisms of heavy metal bioaccumulation in other species.