Response of photosynthesis and the antioxidant defense system of two microalgal species (Alexandrium minutum and Dunaliella salina) to the toxicity of BDE-47.

Polybrominated diphenyl ethers (PBDEs), a persistent organic pollutant are ubiquitous in aquatic ecosystems, which are causing serious environmental concerns. In this study, we chose BDE-47 as a representative PBDEs, to investigate its toxic effects on two microalgal species and the response of their antioxidant system. The results indicated Alexandrium minutum (a dinoflagellate) was more sensitive to BDE-47 than Dunaliella salina (a chlorophyte), as determined by growth rates, cellular structure and photosynthetic parameters. Cellular reactive oxygen species (ROS) levels were significantly elevated under the exposure of BDE-47 in both species, corresponding to an increase of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) activities, while glutathione peroxidase (GPX) activities decreased in D. salina and increased in A. minutum. The different enzymes responses between the two species indicated different mechanisms in their antioxidant system, and we deduced that A. minutum might have a higher efficiency for scavenging H2O2 than D. salina.