Chronic toxicity of a pure and technical grade pentachlorophenol to Daphnia magna

Chronic toxicity test procedures (static, with renewal) were used to determine the chronic toxicity of sublethal concentrations of a technical formulation of pentachlorophenol (PCP) and pure pentachlorophenol to Daphnia magna. Test organisms 48 +/- 12 h old were exposed for their entire lifespan (i.e., until death) to 0.01, 0.05, 0.1 and 0.5 mg technical PCP/L and 0.01, 0.087 and 0.1 mg pure PCP/L. Criteria used to assess chronic toxicity were mean time to appearance of the primiparous instar in the brood chamber, mean number of days to release of the first brood, mean number of broods produced per female, mean brood size per female, mean number of reproductive days, mean number of young produced per reproductive day per female and survivorship. Pentachlorophenol differentially affected maturation and reproduction but not survivorship or longevity. Mean number of broods produced per daphnid, length of the reproductive period, longevity and survivorship were insensitive criteria relative to mean time to appearance of the primiparous instar, time to release of first brood, brood size, and number of young produced per daphnid per reproductive day. Generally, there was little difference in toxicity of the three concentrations of pure PCP, for they significantly reduced mean brood size and rate of reproduction of young and significantly but differentially affected maturation. Technical PCP, at the highest concentration of 0.5 mg/L, significantly reduced mean brood size and the rate of production of young, and significantly delayed both time to appearance of the primiparous instar and release of the first brood. When differences in toxicity occurred, generally, pure PCP was more toxic than comparable concentrations of technical PCP. Although enhanced maturation was observed there was no compensatory reproduction.(ABSTRACT TRUNCATED AT 250 WORDS)