METAL AND OXYGEN UPTAKE IN THE GREEN MUSSEL PERNA VIRIDIS UNDER DIFFERENT METABOLIC CONDITIONS

Coupled respirometric and radiotracer techniques were applied to simultaneously measure the rates of oxygen and metal uptake in the green mussel Perna viridis. This was performed under different metabolic conditions by varying the ambient oxygen partial pressure (Po₂), temperature, air exposure, and body size. When the mussels were tested under different hypoxic and anoxic conditions, Cd and Zn uptake decreased with decreasing Po₂, accompanied by a decrease in the ventilation activity of mussels. Significant reduction in metal uptake was observed at a Po₂ level of 3 kPa. Under anoxic conditions, the uptake of Cd and Zn was 1.6 to 2.7 times and 2.8 times, respectively, lower than those measured under normoxia. In contrast, both the absorption efficiencies of Cd and Zn and the oxygen extraction efficiency increased significantly with decreasing Po₂. There were significant correlations between the rates of Cd/Zn and O₂ uptake by the mussels when quantified under various Po₂ levels. The uptake of Cd and Zn was temperature dependent and increased with temperature over a range of 15 to 30°C. Significant correlations between the rates of Cd/Zn and O₂ uptake were also found in the temperature experiments. With reimmersion of mussels after aerial exposure, the mussels experienced an apparent O₂ debt. Metal uptake also increased within the first 15 min followed by gradual recovery to the control levels. Similarly, the quantified uptake rates of Zn were significantly correlated with the O₂ uptake in experiments with different sizes of mussels. These results strongly suggest that Cd and Zn uptake are coupled with oxygen uptake in the mussels; thus, physiological processes need to be considered in studying metal accumulation. © 2005 SETAC.