Effect of Biomass Measurements on Toxicity Evaluation in Algal Growth Inhibition Tests.

SUZUKI Yoshihiro, MORISHITA Reiko, TAKAMI Tohru, MARUYAMA Toshiroh

doi:10.11532/proes1992.35.101

General methods for the biomass measurements in algal growth inhibition tests are cell counting, absorbance, and fluorescence, but a standard method is not restricted by the standard procedures. The possibilityof the different evaluation is present in the toxicity test by different biomass determinations.In this study, the toxicity of copper (Cu) and monochloramine (NH₂Cl) as reference toxic substances wereevaluated from the algal growth inhibition test using green alga Selenasturum capricornutum. To determine thebiomass changes, direct cell counting, turbidity, chlorophyll with fluorescence, and ATP methods were used andthe effective concentration of Cu and NH₂Cl were evaluated with each results. The most sensitive method of theevaluation was direct cell counting, then LOEC and EC₅₀ of Cu were 10 and 7 μg/l, and LOEC and EC₅₀ of NH₂Cl were 7 and 19 μg-Cl₂/l, respectively. Turbidity and fluorescence methods showed the same sensitivity for Cu, whereas these were not sensitive for NH₂Cl. In contrast, the sensitivity of ATP method was not good for bothtoxic substances, and the evaluated values of LOEC and EC₅₀ with ATP were several times higher than withcounting method. It is necessary to recognize that the method for biomass measurements in algal growth test hasan effect on the estimation.

Effect of Biomass Measurements on Toxicity Evaluation in Algal Growth Inhibition Tests.

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