The purpose of this investigation was to determine the effect of continuous exposure of pre-adult Daphnia magna to low, presumably sub-lethal doses of phenol. The experimental data were obtained through use of a standard 24-hour toxicity bioassay and a modified long-term toxicity bioassay. Control and test animals were cultured in a synthetic pond water and fed with dried yeast. Six concentrations of phenol were tested. Data were applied to least squares linear regression analysis, multiple linear regression analysis, crossed covariance analysis, and several related tests in order to quantitatively interpret the total effects of the chronic poisoning. It was found that phenol exhibited strong interaction with temperature of the culture medium and with the age of the individual to retard ecdysis. This results in a prolonged generation time. Mortality was also increased and reproduction was greatly inhibited. Combinations of these effects act to greatly reduce population growth rates. It is concluded that even minute amounts of phenol introduced into a natural environment may have deleterious effects on the ecological balance of an ecosystem.
