How water oxygenation level influences cadmium accumulation pattern in theasiatic clam Corbicula fluminea: A laboratory and field study

The level of O-2 in water is highly variable in the aquatic environment and is a major ventilatory drive in all animals breathing water. Low O-2 parti al pressure (PO2) strongly stimulates ventilatory activity compared to air- equilibrated or O-2-enriched water. We studied the ir fluence of ventilator y activity on the bioaccumulation rate of Cd in the freshwater Asiatic clam Corbicula fluminea for PO2 ranging from 4 to 40 kPa (2-20 mg/L at 15 degre esC) during steady-state exposure to controlled concentrations of Cd of app roximately 2 or 0.5 mug/L under both laboratory and field conditions. The c oncentration of Cd in the expired water and its apparent extraction coeffic ient (Ew(Cd)) from the ventilated water were calculated. Results show that a low PO2 strongly enhanced Cd bioaccumulation rate in the whole soft body and modified the distribution pattern and the relative burden in the organs . Whatever the water PO2, values for the concentration of Cd in the expired water remained close to the Cd concentration in the inspired water and Ew( Cd) varied from 2 to 12%. Because the field results conformed to the labora tory analysis, the suggestion is made that the influence of O-2 on bioaccum ulation patterns of metals in water-breathers should be classified as of pr imary importance.