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(13-01) Photoenhanced toxicity of azaarenes to marine phytoplankton. Wiegman, Saskia*,1, Kraak, Michiel1, De Voogt, Pim2, Laane, Remi2, Admiraal, Wim1, 1 UvA, AEE, Kruislaan 320, Amsterdam, The Netherlands2 UvA, MTC, Nieuwe Achtergracht 166, Amsterdam, The Netherlands ABSTRACT- Photoenhanced toxicity of azaarenes to marine phytoplankton. Wiegman S., M.H.S. Kraak, P. de Voogt, R.W.P.M. Laane and W. Admiraal. University of Amsterdam, Amsterdam, The Netherlands.The aim of this study was to analyze the influence of UV radiation on the interaction between phototoxic PAHs and phototrophic organisms. First the toxicity of azaarenes to the marine flagellate Dunaliella tertiolecta was determined. Growth inhibition by azaarenes was well described by molecular volume and log Kow, indicating a narcotic mode of action. The toxicity of acridine and benz[c]acridine was, however, photoenhanced. Next, the photochemical reactivity of azaarenes was determined. The efficiency of photochemical reactions of azaarenes was wavelength dependent, resulting in different photolyse reactions. Especially preexposure of azaarenes to UV-A led to toxic products. We also observed that UV-A was dominant in the photoenhanced toxicity of acridine to Phaeodactylim tricornutum. The UV irradiance absorbed by acridine is proposed here as a key to photo-enhanced toxicity and effectively described the effect of acridine on P. tricornutum in a dose-response dependent manner. This approach may circumvent the variability between studies using different light sources. In the last set of experiments, cultures of P. tricornutum were grown under laboratory light with a different fraction of UV. The two types of light led to changes in the pigment composition and PS I to PS II stoichiometry. Despite the adaptation of the photosynthetic apparatus, long-term exposure to mercury light did not alter the sensitivity of the photosynthetic efficiency of P. tricornutum to the phototoxic acridine. This indicates that the prime receptor of photoenhanced toxicity may be unrelated to the photosynthetic machinery. We argue that the current set of quality criteria for PAHs should be expanded with heterocyclic aromatic compounds and provided the means to incorporate photoenhanced toxicity. Key words: Photoenhanced toxicity , azaarenes, PAHs, phytoplankton |
