Physiological Effects Of Dibutyl Phthalate And Anti-oxidant On The Two Marine Microalgaes

Dibutyl phthalate (DBP), which is one of the main plasticizers in the plastic industry, is a kind of very important phthalate esters (PAEs). As an environmental hormone substance, DBP can interfere with the endocrine system of humans and animals at very low concentrations. DBP has teratogenic, carcinogenic and mutagenic effects at large doses, which also can enrich and amplify in organism. Both China National Environmental Monitoring Centre (CNEMC) and U.S. Environmental Protection Agency (EPA) list this compound as priority of pollutant for environment control. In order to study the ecological toxic effect of DBP on the marine microalgaes, Phaeodactylum tricornutum and Pavlova viridis were exposed to DBP at 2.5,3,3.5, 4,5,7.5 mg·L-1 and a acetone control. Growth rate, photosynthetic pigment contents, protein, chlorophyll fluorescence and MDA were measured. The protective effect of glutathione and vitamin C on the two marine microalgaes under DBP exposure was also studied. The main results were as follows:(1) All the treat groups had inhibition effect on the growth of P. tricornutum dramatically, and P.tricornutum could not tolerate DBP of 7.5 mg·L-1. When the concentration of DBP was 5 mg·L-1, P. tricornutum had hardly grown for the first two days. It, however, began to grow again on the third day, and soon entered the exponential growth phase. The similar effects also occurred to chlorophyll a, chlorophyll c, carotenoids and protein, that is, with the increase of DBP concentrations, the contents of chlorophyll a, chlorophyll c, carotenoids and protein were gradually reduced. As DBP concentrations raised, the maximal photochemical efficiency of PSII (Fv/Fm), the potential activity of PSII (Fv/F0), the actual photochemical efficiency (Yield) as well as the electron transport rate (ETR) all declined. But the similar change had not obviously happened to the low concentration treatment groups (<4 mg·L-1), compared with the control group. While, after 12 hours of DBP stress, Fv/Fm, Fv/F0, Yield and ETR of the experimental group of 5 mg·L-1 were gradually increased, with the parameter values even exceeding the other treatment groups. The MDA content of P. tricornutum were significantly higher than the control after DBP exposure in the expermental period.(2) The exposure group of DBP had inhibition effect on growth of P. viridis. When the concentrations of DBP were 5 and 7.5 mg·L-1 respectively, the algae cells were completely died. DBP had the same effects on the contents of the chlorophyll a, carotenoids and protein. As DBP concentration increases, the maximal photochemical efficiency of PSII (Fv/Fm), the potential activity of PSII (Fv/F0), the actual photochemical efficiency of PSII in the light (Yield) and the electron transport rate (ETR) were significantly reduced. Weanwhile, the MDA content of P.viridis increased, following the deepening of lipid peroxidation and the increasing of cell damage.(3) Glutathione and vitamin C can effectively alleviate the toxic effect of DBP on the two kinds of marine microalgae, and then improve their anti-reversibility.100 mg·L-1 glutathione and 80 mg·L-1 vitamin C were the best protection concentrations to P. tricornutum under stress of 4.48 mg·L-1 DBP, While P. viridis had the strongest ability to withstand 2.9 mg·L-1 DBP when treated by 40 mg·L-1 glutathione and 15 mg·L-1 vitamin C.(4) When P. tricornutum was exposed to DBP 24 hours,100 mg·L-1 glutathione and 80 mg·L-1 vitamin C promoted the algae's growth and reproduction, and with the extension of the culture time, this promoted effect represented obviously. The content of chlorophyll a decreased at the start, and then gradually increased. The antioxidant significantly increased the content of chlorophyll a. Compared with control, the soluble protein content of 100 mg·L-1 glutathione and 80 mg·L-1 vitamin C treatment increased 39.88% and 59.08%,60.22% and 82.73%,63.18% and 102.18%,55.12% and 87.7% at 24,48,72 and 96 hours of DBP stress respectively. The addition of antioxidants also significantly reduced the content of MDA, indicating that the degree of injury was reduced. In the experimental period, the MDA content of the control group was increased and then decreased, which reached the highest at 48 hours. The MDA of the 100 mg·L-1 glutathione experimental group reached the highest value at 24 hours, after they gradually decreased.80 mg·L-1 of vitamin C treated group had been reduced all the time.