Phototoxicity of Polycyclic Aromatic Hydrocarbons to Marine Diatom Skeletonema Costatum

Many toxicology studies particularly in the discipline of aquatic toxicology indicated that the toxicity of polycyclic aromatic hydrocarbons(PAHs) was enhanced in the presence of solar ultraviolet radiation.Marine diatom Skeletonema costatum,a predominant phytoplankton species in the Yangtze estuary in China,was exposed for 72 h to a series of PAHs including 2-ring naphthalene,3-ring phenanthrene and anthracene,4-ring fluoranthene and pyrene in the laboratory. The toxicity of each PAH on this alga was compared in the absence of simulated solar UV radiation and its presence.When UV radiation was added to the system,the 72 h EC_(50) decreased about(1.9) times for naphthalene,(8.4) times for phenanthrene,(13.0) times for anthracene,(6.5) times for fluoranthene,and(5.7) times for pyrene comparing with those in the absence of UV light.Under the fluorescent radiation(lacking UV),the dose-response curves based on chemical concentrations revealed that the order of toxic strength was fluoranthene pyrene anthracene phenanthrene naphthalene,while under the UV radiation it became fluoranthene ≈ anthracene pyrene phenanthrene naphthalene.The results indicated that the UV illumination could not only enhance the PAH toxicity,but also change their relative toxicity to marine diatom.