Stock solutions were prepared in DV culture media. Atrazine and
diuron were dissolved in 0.05% dimethyl sulfoxide (DMSO) obtained
from Sigma-Aldrich (St Louis, MO 63103, USA) and sonicated for
30 min before adding the DV media. The toxicity of 0.05% DMSO to
diatoms was assessed in the DV medium prior to the bioassay implementation and no effect was detected.