Possible Causes of Extreme Variation of Benzo[a]pyrene Acute Toxicity Test on Daphnia magna

There are enormous differences in benzo[a]pyrene (BaP) acute toxicity tests on <i>Daphnia magna</i>, according to previous publications. The explanations of the reasons for this extreme variation are necessary. In this context, the acute toxicity tests of different experiment conditions (light/dark, culture medium, and solvent) were conducted on <i>Daphnia magna</i> with BaP as the toxicant of concern. Based on the experiments above, molecular dynamics (MD) simulations were employed to investigate the mechanisms of action. According to our results, the significant influence of light exposure on the acute toxicity test of BaP (<i>p</i> < 0.05) on <i>D. magna</i> was recorded. On the basis of the MD simulations, it was possible that BaP may not affect the normal operation of Superoxide Dismutase and Catalase directly, and it could be quickly transferred from the body through Glutathione S-transferase and Cytochromes P450. Therefore, when exposed to light, the oxidative stress process intensifies, causing damage to <i>Daphnia magna</i>. Apparently, the ecotoxicity tests based on inhibition for <i>D. magna</i> cannot adequately reflect the toxic effects of BaP.