Oxidative Stress and Growth Behavior Responses of Marine Diatoms Phaeodactylum Tricornutum and Skeletonema Costatum to Three Typical Persistent Organic Pollutants

To study the oxidative stress responses and growth behavior of marine diatom to persistent organic pollutants (POPs), Phaeodactylum tricornutum and Skeletonema costatum, two species of algae which are potentially harmful to marine environment as red tide algae, were chosen as test diatoms against three common kinds of POPs in the ocean: Aroclor 1254, benzo[a]pyrene (BaP), and dichlorodiphenyltrichloroethane (DDT). The two algae were cultivated in three concentrations of 50, 100 and 500 μg L-1 for 72 h; and the temporal production of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) and peroxidase (POD) were determined. Results showed that MDA responded quicker than SOD in P. tricornutum and S. costatum, a peak of MDA was detected after 2 h of exposure, while the activity of SOD peaked after 12 h of exposure. For studying the growth behavior of diatoms in the bi-algal culture to POPs, two species in different initial cell densities were investigated in 28-day exposure to the three POPs in concentrations of 15 and 50 μg L^-1. The growth of P. tricornutum increased significantly only in the medium enriched with 50 μg L^-1 DDT (ratiomax = 148%). On contrast, the cell density of S. costatum increased during the most time of exposure regardless of initial cell density. The results demonstrate that POPs toxicity could cause oxidative stress even cell damage in both P. tricornutum and S. costatum, but algal growth was promoted by the POPs in the mixed culture, which indicated that the presence of pollutants in the sea was an important inducement of the species groups change. The results of this study may provide valuable help for detailed studies of oxidative stress and growth behavior responses of marine diatom to POPs.