Oxidative stress responses caused by dimethyl phthalate (DMP) and diethyl phthalate (DEP) in a marine diatom Phaeodactylum tricornutum.

A marine diatom (Phaeodactylum tricornutum) was exposed to different concentrations of dimethyl phthalate (DMP) and diethyl phthalate (DEP) for 96 h within a batch-culture system to investigate their toxicities. Results showed that P. tricornutum could remove DMP and DEP effectively with removal rates of 0.20-0.30 and 0.14-0.21 mg L-1 h-1, respectively. In addition, DMP and DEP significantly inhibited the photosynthesis and chlorophyll a biosynthesis of P. tricornutum with 96-h EC50 values of 390.5 mg L-1 and 74.0 mg L-1, respectively. Results of reactive oxygen species (ROS) level suggested that the two PAEs could induce excessive ROS production in the diatom. Moreover, activities of antioxidant enzymes (i.e., SOD and POD) in the diatom increased with the increase of DMP and DEP concentrations. The results will help to understand the toxic mechanisms of PAEs, and provide strong evidences for evaluating their ecological risks in the marine environment.