The effects of 4-nonylphenol and ethanol on acute toxicity, embryo development, and reproduction in Daphnia magna

The mean 48-h EC50 (n=3) of 4-nonylphenol (NP) using ethanol as the carrier solvent was 155 μg/L, compared to a mean 48-h EC50 (n=3) of 281 μg/L without ethanol. The 96-h EC50ʹs for embryo lethality (arrested egg development) and deformities (curved or unextended shell spines and undeveloped second antennae) were 738 and 263 μg/L, respectively. Reproduction studies were conducted using conditions that stimulate male production (i.e., reduced photoperiod and food levels). An increase in neonate deformities was observed at 50 μg/L (without ethanol), but no changes were observed in fecundity or sex ratios. A decrease in sex ratios was observed at 25 and 50 μg/L (with ethanol) compared to the ethanol control. However, an increase in sex ratios was observed in the ethanol control compared to media controls. The use of ethanol as a solvent carrier confounds the effects of 4-NP on acute toxicity and male production in daphnids.