Effects Of Benzo[α] Pyrene On The Toxicity And Physiology Of Marine Microalgae

Polycyclic aromatic compounds is a persistent organic pollutant. BaP as arepresentative of the pollutants with the features of carcinogenic、teratogenic、mutagenic、 highly toxic and bioaccumulative, which was widespread in the marineenvironment. Seven common Microalgae preserved in microalgae culture collectioncenter, were selected as the subject of study. The cell growth and cell characteristicsof different marine microalgae treated by BaP were analyzed. According to theprinciple of biomarker screening, the effect of BaP on microalgae detoxificationenzymes, antioxidant enzymes and DNA damage were analyzed. Our researchprovides the basis to explore the toxic effects and the detoxification mechanism. Theresults showed:1. The sensitivity of seven microalgae to BaP is different. Isochrysiszhanjiangensis、Tahitian Isochrysis galbana and Chaetoceros muelleri were sensitiveto BaP. Platymonas subcordiformis、 Pyramidomonas sp.、 Phaeodactylumtricornutum and Nitzschia closterium f.minutissima were higher tolerance to BaP.The inhibitory of BaP exists difference among the experimented microalgae species,of which, the Chrysophyta is the most sensitive algae for BaP.2. The results showed that BaP significantly inhibited the growth of three speciesof algae. The96-h median effective concentrations of BaP for Isochrysiszhanjiangensis, Tahitian Isochrysis galbana and Chaetoceros miielleri were17.00μg/L,25.18μg/L and83.06μg/L, respectively. After96h contaminated of highconcentration of BaP, the cell volume and the internal cellular granularity of threespecies of algae were increased, while the chlorophyll content decreased with the BaPconcentration increases, which shows that BaP can significantly impact the algalmorphology and the photosynthetic capacity and inhibite the growth of algal cells.3. Under the exposure of low concentration of BaP, the detoxification enzymes(EROD, GST) and antioxidant enzymes (SOD, CAT) showed different activities, however the activity of GPx showed no significant change. However the activites ofdifferent enzymes in the two species of microalgae showed various trands. Theactivity of EROD showed the trand which was increased firstly and then decreasedwith the increasing in concentration of BaP and the extend of exposure time. Howeverrefer to the activity of EROD decreased within the late expose, which means thePhaeodactylum tricornutum has a high activity of EROD. The activities of GST in thetwo species of microalgae gradually increase with the increasing of exposureconcentration and time. The activity of SOD in Isochrysis zhanjiangensis which issensitive to BaP increase with the increasing of BaP concentration,however decreasewith the expend of exposure time. The highest value of SOD increased1.90foldduring the exposure time. The activity of CAT increased with the increasing ofexposure concentration and time. The highest value of CAT increased1.77fold duringthe exposure time. However the activity of GPx showed no significant changes.Phaeodactylum tricornutum which was tolerant to BaP showed no significantdifference in the activity of SOD. But the basic activity of Phaeodactylumtricornutum was about4times of Isochrysis zhanjiangensis. The activity of CATshowed the same trend to Isochrysis zhanjiangensis. The highest value of CATincreased2.22fold during the exposure time. The activity of GPx showed nosignificant changes. Results show that the activities of detoxification enzymes andantioxidant enzyme in Phaeodactylum tricornutum were higher than in Isochrysiszhanjiangensis. Therefore, the changes of EROD、GST and CAT of microalgae can beused as sensitive biomarkers at the molecule level of the stress of BaP.4. In the concentration range of0.5μg/L~18μg/L, the content of MDA and theDNA damage in the two species of microalgae are different. There was no significantdamage in Phaeodactylum tricornutum. The content of MDA and the DNA damagewas significantly increased on the stress of BaP. The results show that thedetoxification enzymes and antioxidant enzymes in Phaeodactylum tricornutum canefficiently protect the algae cells.