Chronic Effects of 17 alpha-Ethinylestradiol, Fluoxetine, and the Mixture on Individual and Population-Level End Points in Daphnia magna

摘要

Many pharmaceuticals and personal care products (PPCPs) enter the environment continuously. Because these chemicals are not intended for environmental applications, testing for environmental effects is not mandatory, and thus relatively little is known about their ecological effects, particularly on invertebrate species. To better understand the effects of PPCPs on freshwater invertebrates, we exposed the water flea Daphnia magna to environmentally relevant concentrations of the pharmaceuticals 17 alpha-ethinylestradiol (EE2) and fluoxetine both individually and as a mixture for 40 days. Exposure to EE2 decreased the number of neonates produced per female at 0.1 and 1.0 A mu g/L EE2, whereas fluoxetine increased mortality and neonate production at 100 A mu g/L. Exposure to the mixture of EE2 + fluoxetine increased time to first reproduction in medium and high mixture treatments and decreased time to death and neonate production in the high mixture treatment. When these individual parameters were integrated into a demographic model, population growth rate decreased when D. magna were exposed to 0.1 and 1.0 A mu g/L EE2, 100 A mu g/L fluoxetine, and low and high mixture treatments. When we compared the results of our extended 40 day exposures with data from only the first 21 days, the standard duration of chronic toxicity tests with D. magna, the effects of pharmaceutical exposure were generally significant at lower chemical concentrations during the 21-day period compared with the 40-day exposures, which points to the importance of exposure duration in drawing inferences from toxicity studies.