Toxic Effects of the Organophosphorus Insecticide Fenthion on Growth and Chlorophyll Production Activity of Unicellular Marine Microalgae Tetraselmis suecica: Comparison between Observed and Predicted Endpoint Toxicity Data

Abstract

This chapter provides the results of a laboratory ecotoxicological study conducted to assess the acute toxicity of the organophosphorus pesticide fenthion toward the marine microalgal species Tetraselmis suecica. Bioassays were performed, and algal densities and chlorophyll pigments fractions were measured in the exponential phase after 96 h of exposure to fenthion. Two quantitative structure activity relationships (QSARs) were used to estimate the toxicity of 13 primary metabolites and degradation products of fenthion toward the selected organism; the first was based on the use of the n-octanol/water partition coefficient, whereas the second was based on the solubility of the compound in water. Results revealed that fenthion can have marked effects on the growth and photosynthesis of the target primary producers of marine ecosystems T. suecica. The parent pesticide toxicant was found not toxic to the tested algal species up to 1.00 mg L -1 , while higher treatment concentrations not only affected algal densities and significantly decreased specific growth rate values (μ) (p < 0.05) but also decreased the contents of photosynthetic pigments. The comparison between the observed and the predicted toxicity values of the parent compound fenthion indicated that the predictive capability of the QSARs applied can be considered highly satisfactory. Consequently, both QSAR models were used for the prediction of toxicity data of fenthion's principal metabolites and degradation products.