Acute and Chronic Toxicity of Copper to Four Species of Daphnia

Abstract

The sensitivity of Daphnia magna, D. pulex, D. parvula, and D. ambigua to acute and chronic copper stresses was evaluated under laboratory conditions. Using 72-h LC50 values as the index, the two larger species were significantly less sensitive to an acute copper stress than were the two smaller species. All four species exhibited reductions in survival at Cu concentrations > 40 μg/liter. Daphnia magna exhibited a decrease in the instantaneous rate of population growth (r) at Cu concentrations > 60 μg/liter; r decreased in the other three species at concentrations > 40 μg/liter. Daphnia ambigua produced significantly smaller broods at Cu concentrations > 40 μg/liter, whereas mean bood sizes did not decrease in D. pulex and D. parvula until the Cu concentration exceeded 60 μg/liter. Daphnia magna did not exhibit any reduction in mean brood size related to copper concentration; reproduction in this latter species was inhibited only as a consequence of females dying before they reached reproductive maturity at concentrations > 80 μg/liter. Application factors, based on the highest concentration that did not reduce survival and 72-h LC50 values, ranged from 0.47 to 0.59 and were not significantly different for the four species. We concluded that the four species do not differ in their susceptibility to a chronic copper stress.