Effects of multigenerational exposures of D. magna to environmentally relevant concentrations of pentachlorophenol.

The re-emergence of schistosomiasis has given rise to ubiquitous concentrations of the primary control agent pentachlorophenol (PCP) in the environment, especially in the surface waters of China. In this study, the effects of environmentally relevant concentrations of PCP, namely, 0.0002, 0.002, 0.02, 0.2, and 2 μmol/L on survival, age at first reproduction, fecundity, length of mothers, and number of molts of Daphnia magna were studied over three generations. The survival of D. magna exposed to 2 μmol/L was significantly affected in the three generations. Toxic effects were enhanced in later generations. Age at first reproduction of F1 and F2 D. magna was significantly slower than that of the controls. The total number of offspring per female exposed to concentrations of 0.002 μmol/L or greater was less (23.5 to 67.6, 9.4 to 73.7, and 3.6 to 83.7%) than that of the controls in the F0, F1, and F2 generations, respectively. The body length of mothers significantly decreased (4.7 to 6.8, 9.6 to 15.1, and 13.3 to 23.2%) after exposure to 0.002 μmol/L or greater than those of unexposed individuals in the F0, F1, and F2 generations, respectively. Dose-response relationships between concentrations of PCP and length and number of molts of D. magna were observed in the F0 to F2 generations. PCP concentrations on the surface waters of China caused adverse effects to D. magna, which increased over successive generations. Significant effects were observed in the third generation. The multigenerational studies were more sensitive than the single-generation experiments. Thus, multigenerational exposure may be more predictive of chronic exposure under field conditions.