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The effects of 6 biocides on the growth of Chlamydomonas reinhardii in pure culture were studied. For the batch culture assay of biocides, the growth rate in contro tubes should be compared with in the test tubes and the effective concentration calculated on the basis of the percent decrease in growth rate at the different toxicant concentration. The concentrations at which 50% decrease in growth rate was observed are 40㎍/1 for butachlor and 350㎍/1 for alachlor in herbicide, 900㎍/1 for phenazine-5-oxide and 3,400㎍/1 for isoprothiolane in fungicide, and 3,330㎍/1 for fenthion and 332,500㎍/1 for trichlorfon in insecticide. The inhibitory effect on the growth of Chlamydomonas reinhardii by the treatment of vatious biocide concentrations was decreased in order of herbicide>fungicide>insecticide. ChlorophyⅡ and carotenoid content per cell were increased, whereas chlorophyⅡ a/b ratio was hardly affected by biocides. The effects of biocides on pigment content were also decreased in order of herbicide>fungicide>insecticide, which suggested the relationship between the effect of biocides on the pigment content and inhibition of growth rate.
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