Effects of sublethal Zn++ and Cd ++ concentrations on filtration rate, absorption efficiency and scope for growth in Donax trunculus (Bivalvia; Donacidae).

Physiological parameters (filtration rate measured as clearance rate; absorption efficiency measured as Conover index) and energy balance [scope for growth (SFG)] where determined under Zn++ (essential metal) and Cd++ (nonessential metal) at different concentration levels and timing. The toxic effect observed on Donax trunculus was higher for Cd++ than for Zn++ in almost all the parameters studied. The SFG is proposed as an integrated environmental biomarker to be used like a tool with others from different organization levels to obtain a more comprehensive vision of the ecological consequences of pollutants.