Validation of photo synthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliqlals was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystern II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R-2 >= 0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (Phi(M')), photochemical quenching (q(P)) and relative photochemical quenching (q(P(rel))) values. The cells density was also linearly dependent (R-2 = 0.838) oil the relative unquenched fluorescence parameter (UQF((rel))). Non-linear correlation was found (R-2 = 0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF((rel)) > Phi(M') > q(P) > q(P(rel)) > ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants. (C) 2007 Published by Elsevier Ltd.