The effects of short time exposure to mercury (Hg2+), cadmium (Cd2+), and copper (Cu2+) ions on the metabolic activity of gill tissue from the freshwater bivalve Elliptio complanata were investigated by isothermal calorimetry and respirometry. Metabolic heat rates were altered following exposure of gill tissue to these ions over the concentration range from 10(-6) to 10(-3) M, The effects of metal ions on metabolic heat rates were metal ion specific and time and concentration dependent. Treatment of tissue with low concentrations of Hg2+ and Cu2+ for short times caused stimulation of metabolic heat rates. Longer exposures and higher concentrations caused inhibition, Cadmium was inhibitory under all conditions tested, Treatment of mitochondria isolated from gill and muscle tissues showed a similar pattern of stimulation of respiratory rate at low concentration and inhibition at higher concentration, Analysis of CO2, and O-2 from the headspaee gasses in the calorimeter ampule showed an enhancement of respiratory quotient (RQ, i.e., R(CO2)/R(O2) where R = rate) following addition of 10(-3) M Cd2+ for 30 min. The microcalorimetric method proved to be a useful technique to assess toxicity of heavy metals on the Kills of a freshwater bivalve.
