Oxygen consumption in fathead minnows (Pimephales promelas) following acute exposure to water-borne selenium

Following determination of a concentration of selenate-Se lethal during 24-hr exposures at 22 degrees C, routine oxygen consumption was measured in fathead minnows (Pimephales promelas) exposed to various sublethal concentrations of Se for 24 hr. A median lethal concentration for 24-hr exposures (24-hr LC50) of fathead minnows equalled 82 mg Se/l with 95% fiducial limits of 76-89 mg Se/l. Mean weight-specific oxygen consumption rates of minnows exposed to 0, 15, 40 and 60 mg Se/l for 24-hr ranged from 0.43 to 0.49 mg O2/g-1/hr-1 and were not significantly different. These results indicate that acute exposure to Se does not affect oxygen consumption; however, observations during respirometry trials suggest that minnows at the highest Se concentration may have physiologically compensated to maintain oxygen consumption rates.