Rapid algal toxicity assay using variable chlorophyll fluorescence for Chlorella kessleri (chlorophyta)

• Published in: Environmental toxicology 2010-12, Vol.25 (6), p.554-563
• Main Author: KVIDEROVA, Jana
• Format: Article
• Language: English
• Subjects: algae; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; cell density; Chlorella - cytology; Chlorella - drug effects; Chlorella kessleri; Chlorophyll - analysis; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Fluorescence; Fundamental and applied biological sciences. Psychology; General aspects; microassay; Spectrophotometry - methods; toxicity; Toxicity Tests - methods; variable chlorophyll fluorescence
• ISSN: 1520-4081; 1522-7278; 1522-7278
• DOI: 10.1002/tox.20516

Three methods of algal assays—the standard assay, microassay, and the proposed fluorescence assay—are compared from the point of view of reliability of EC50 detection, the minimum required time for the detection, sensitivity of individual measurement, i.e. at which cell density the particular assay can be used for EC50 estimation, and the time stability of the EC50 values. The assays were performed with green alga Chlorella kessleri strain LARG/1 growing in potassium dichromate solution in Z‐medium ranging from 0.01 to 100 mg Cr L⁻¹. The inoculation cell density was set according to the standards to 10⁴ cells mL⁻¹ and according to spectrophotometer/plate reader detection limit. The average EC50 ranged from 0.096 to 0.649 mg Cr L⁻¹ and there were no significant differences in EC50 between the assay type and the inoculation methods with the exception of the significant difference between ECc50₇₂ (EC50 established from biomass measured as chlorophyll a concentration after 72 h of cultivation) in the standard assay and ECr50 (EC50 derived from growth rate) in the microassay in the standard inoculation experiment due to low variability of their values. The ECf50 (EC50 derived from variable fluorescence measurement) values correspond to EC50 values derived from the growth rates. Fluorescence measurement revealed the toxic effect of the chromium after 24 h of exposure at cell density of 5 × 10⁴ cells mL⁻¹, less by half than other used assay methods. The positive correlation of ECf50 and time was found in the standard inoculation experiment but opposite effect was observed at the spectrophotometric one.