Nunclon microplates

The toxicity of TEB and 124T to phytoplankton was examined in inhibition tests with the unicellular green microalgae Raphidocelis subcapitata (formerly Selenastrum capricornutum and Pseudokirchneriella subcapitata). The endpoint was inhibition of growth measured after 72 h of incubation as described in ISO 8692 (2012 ). R. subcapitata (MicroBioTests Inc.) was cultivated in alga test medium at 22 ± 2 °C and continuous illumination at 6500 lx (ISO 8692 , 2012 ). Two-fold dilutions of TEB or 124T were prepared in 96-well clear Nunclon microplates (Thermo Scientific) by serially diluting 150 µL of an aqueous solution with the chemical in 150 µL algal test medium. After transfer of the chemicals, 150 µL of diluted R. subcapitata culture (1:50) was added to each well resulting in a final liquid volume of 300 µL in each well. Plates were incubated for 72 h at 22 ± 2 °C on a shaker at 70 rpm with continuous illumination (6500 lx). Growth was measured after 0, 24 h, 48 h, and 72 h as absorbance at 450 nm using a Thermo Multiskan Plate Reader (Thermo Scientific). The bioassay with R. subcapitata included eight replicates of blanks (medium only), controls (no test chemical), and 10 nominal concentrations of TEB and 124T. The toxicity of TEB to R. subcapitata was examined before and after exposure of aqueous solutions to different VUV/UVC irradiation regimes.

The toxicity of glyphosate to phytoplankton was examined in inhibition tests with the unicellular green microalga Raphidocelis subcapitata (formerly Selenastrum capricornutum and Pseudokirchneriella subcapitata; ISO 8692, 2012)¹⁷ . The endpoint was inhibition of growth measured after 72 h of incubation (ISO 8692, 2012)¹⁷ . R. subcapitata (MicroBioTests Inc.) was cultivated in test medium at 23 ± 2 °C and continuous illumination at 6500 lx (ISO 8692, 2012)¹⁷ . Diluted culture was exposed in 96-well clear Nunclon microplates (Thermo Scientific) to different concentrations of glyphosate with or without prior UV irradiation (0.098, 0.195, 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 mg/L). Eight replicates were included for blanks (medium), controls (no glyphosate), and each glyphosate concentration. Plates were incubated for 72 h at 23 °C on a shaker at 70 rpm with continuous illumination (6500 lx). Growth was measured after 0, 24 h, 48 h and 72 h as absorbance at 450 nm using a Thermo Multiskan Plate Reader (Thermo Scientific). Growth measurements for selected samples was verified by measuring cell sizes (µm) and cell abundance (cells/mL) using a Multisizer 4e Coulter Counter (Beckman Coulter).