EFFECTS OF HEAVY-METALS ON OXYGEN-CONSUMPTION AND AMMONIA EXCRETION IN GREEN-LIPPED MUSSELS (PERNA-VIRIDIS)

Physiological responses (oxygen consumption and ammonia excretion) of the green-lipped mussel (Perna viridis) exposed to four concentrations of Cd (0.15, 0.32, 0.70 and 1.50 ppm) and four concentrations of Zn ( 0.60, 1.29, 2.79 and 6.00 ppm) were monitored for 21 days. Changes occ urred in the ammonia excretion rates and O:N ratios with individual mu ssels experiencing different metal concentrations over time. Oxygen co nsumption rate decreased significantly with time for Cd-exposed indivi duals and also decreased significantly with the interaction between th e concentration of Zn and time for Zn-exposed individuals. Although lo w O:N ratios (<30) were obtained in most of the treatments, no predict able correlation was found between concentrations of metals and values of O:N obtained. The value of using O:N ratio as a stress index is qu estioned.