EFFECTS OF DIFFERENT PROTECTIVE AGENTS ON THE PHOTOTOXICITY OF FLUORANTHENE TO DAPHNIA-MAGNA

Some compounds, accumulated by organisms, are transformed into toxic f orms when irradiated with UV light. The polycyclic aromatic hydrocarbo n (PAH) fluoranthene is one such compound of environmental importance. In this study on Daphnia magna, fluoranthene toxicity increased signi ficantly after a 2 h exposure to solar-simulating UV light, if organis ms were allowed to accumulate the substance for 24 h prior to irradiat ion. Since no enhanced toxicity was observed if the solutions were irr adiated before the daphnids were added and only a slight decrease in t oxicity was observed if the daphnids were transferred to pure dilution water prior to exposure, it was concluded that the acute phototoxicit y of fluoranthene was predominantly due to photoactivation of accumula ted or adsorbed molecules. Thus, the enhanced toxicity of fluoranthene by UV light is thought to act through the production of either single t oxygen or free radicals. Possible effects of different protective ag ents (antioxidants, free radical scavengers and UV-screening compounds ) were examined in two cultured populations of Daphnia magna. One popu lation received a synthetic diet and the other dried baker's yeast. Th e yeast-fed population became progressively more sensitive to the phot oinduced toxicity of fluoranthene, and after 14 days it was significan tly more sensitive than the population that received the synthetic fee d. It was not obvious whether any of the additives influenced the UV-i nduced toxicity significantly, although, alpha-tocopherol, a known ant ioxidant, was the best candidate. (C) 1998 Elsevier Science Inc. All r ights reserved.