The Utermöhl method (Utermöhl, 1931) was employed
using 5 and 10 ml HYDRO-BIOS settling
chambers depending on the densities. Each sample
for each dilution was settled in triplicate and 10 fields
in each chamber were counted. At least 100 cells per
sample were counted and the average value of the
resulting 30 fields was used for a 48hLD50 calculation.
Light microscopic/visual identification at 250×
magnification was employed.