Uptake of aqueous and dietary metals by mussel Perna viridis with different Cd exposure histories

The influences of different Cd pre-exposure regimes (route, concentration, and duration of Cd exposure) on the bioavailability of Cd, Ag, Hg, and Zn to the green mussels Perna viridis were quantified in this study. Following pre-exposing the mussels to Cd, we measured the mussel's tissue Cd concentration and clearance rate, as well as the metal dietary assimilation efficiency (AE) and the influx rate from the dissolved phase of the four studied metals. Differences in the route (aqueous and dietary pathways) and the history of pre-exposure (combined Cd concentration and duration) did not significantly affect the subsequent Cd dietary and aqueous uptake. The Cd dietary AEs increased following both the dissolved and dietary Cd pre-exposure. There was a significant correlation between the Cd AE and the accumulated Cd body concentration in the mussels. Dietary assimilation of Hg and Zn also increased slightly (but not significantly) after Cd pre-exposure, but the AEs of Ag remained constant. Except for the significant decrease in the dissolved uptake of Hg, Cd pre-exposure did not apparently affect the uptake of the other three metals from the solution. Metal-metal interactions are likely to be affected by the specificity of metallothionein induction. Our study demonstrated that the Cd body concentration as well as the environmental Cd concentration instead of the history of pre-exposure was more important in affecting the Cd accumulation in the mussels. Such factors need to be considered in interpreting metal body concentrations in biomonitors