Bioenergetic effects of sodium sulfate on the freshwater crustacean, Ceriodaphnia dubia

I tested the hypothesis that if sodium sulfate alters the bioenergetics of Ceriodaphnia dubia, concentrations that cause reduced fecundity in the short (7-day) and long (5 generations) term should also cause changes in feeding rate and/or metabolism, measured as oxygen consumption. In addition, to test the hypothesis that an altered bioenergetic level caused by sodium sulfate exposure will affect the response of that organism to another toxicant, I measured the acute toxicity of phenol to C. dubia in the presence and absence of both food and sodium sulfate. Sodium sulfate reduced the filter-feeding rate of C. dubia, which was associated with significantly reduced oxygen consumption. This decreased energy level appeared to result in a consistent but decreased level of fecundity over a number of generations and the reproductive impairment was dose-dependent. These effects occurred at concentrations much lower than those at which acute (mortality) effects have been observed, a finding that may have regulatory implications. In addition, whereas phenol toxicity to C. dubia was exacerbated by the addition of food, increased phenol toxicity, likely induced by an increase in filtering or metabolic rate due to food addition, was negated when sodium sulfate was added to the test medium.