Toxicity response of Chlorella microalgae to glyphosate herbicide exposure based on biomass, pigment contents and photosynthetic efficiency

Somruthai Kaeoboon; Rungcharn Suksungworn; Nuttha Sanevas

Toxicity response of Chlorella microalgae to glyphosate herbicide exposure based on biomass, pigment contents and photosynthetic efficiency

2021

Somruthai Kaeoboon (Department of Botany, Faculty of Science, Kasetsart University, Bangkean, Bangkok 10900, Thailand / Department of Biology and Health Science, Mahidol Wittayanusorn School, Salaya, Nakhon Pathom 73160, Thailand) | Rungcharn Suksungworn (Department of Botany, Faculty of Science, Kasetsart University, Bangkean, Bangkok 10900, Thailand) | Nuttha Sanevas (Department of Botany, Faculty of Science, Kasetsart University, Bangkean, Bangkok 10900, Thailand)

The extensive use of glyphosate (N-(phosphonomethyl) glycine) herbicide in agriculture is accompanied by the risk of environmental contamination of aquatic ecosystems. In this study, the effects of glyphosate at different concentrations (50–500 µg ml-1) on three Chlorella species including Chlorella ellipsoidea, Chlorella sorokiniana and Chlorella vulgaris especially in relation to the biomass, pigment contents and photosynthetic efficiency were assessed. After treatment for 24 hr, the acute toxicity results showed that C. vulgaris (IC50 = 449.34 ± 6.20 µg ml-1) was more tolerant to glyphosate than C. ellipsoidea (IC50 = 288.23 ± 23.53 µg ml-1) and C. sorokiniana (IC50 = 174.28 ± 0.50 µg ml-1). After a 72-hr chronic toxicity treatment with glyphosate, glyphosate concentrations decreased to 400–500 µg ml-1 in C. ellipsoidea, 200–300 µg ml-1 in C. sorokiniana and 200–500 µg ml-1 in C. vulgaris respectively. During 24-hr acute toxicity exposure to glyphosate, the pigment contents and maximum quantum efficiency of photosystem II (Fv/Fm) decreased as the concentration of glyphosate increased. Overall, the biomass, pigment contents and photosynthetic efficiency presented a high positive correlation. It is worthwhile to mention that our study provides detailed information on the toxicity and sensitivity of these Chlorella species to glyphosate.

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