Action of the organophosphorous insecticide parathion on the free-living marine dinoflagellate Prorocentrum micans Ehrbg.

Growth of cultures of the dinoflagellate Prorocentrum micans Ehrbg. was slowed by parathion greater than 1 ppm. Parathion also decreased chlorophyll content and perturbed cellular ultrastructure, eliciting especially plastoglobuli in their chloroplasts. Toxicity of this organophosphorous insecticide is unlikely to be due to its anticholinesterase activity since P. micans appears not to contain cholinesterase. Fluorescence kinetics show that parathion affects the photosynthetic system, particularly photosystem II.