TOXICITY OF ARSENIC, MOLYBDENUM AND SELENIUM COMBINATIONS TO CERIODAPHNIA-DUBIA

Previous research done on the effects of contaminant mixtures has been evaluated primarily by using acute exposures. While this was an impor tant initial step, characterizing the effects of chronic exposures of these mixtures is more environmentally pragmatic. This study examined the sublethal interactive effects of arsenic (As), molybdenum (Mo), an d selenium (Se) on Ceriodaphnia dubia using the three-brood static ren ewal toxicity test. A complete factorial design experiment using four levels (zero, IC12.5, IC25, and IC50 values) of each metal was perform ed to investigate the binary and tertiary interactions of these metals on C. dubia survival and fecundity. Results indicate three-way intera ctive effects in survival and fecundity with the strongest effect exhi bited by Se. Molybdenum and As in binary combinations appear to be str ongly antagonistic in their effects on C. dubia, even at their respect ive IC50 concentrations. However, generally the addition of Se to As-M o mixtures significantly reduced survival and reproduction. The IC50 c oncentrations of either Mo or Se significantly reduced fecundity in al l binary and tertiary mixtures. All tertiary metal mixtures, except th e combination of the IC12.5 concentrations of each metal, significantl y reduced C. dubia fecundity.