Later, fluorescence techniques such as epifluorescence
microscopy and flow cytometry played a key role in the
discovery of picoplankton (Waterbury et al., 1979;
Chisholm et al., 1988). Flow cytometry, initially borrowed
from the biomedical field, has become the method of choice
to estimate cell abundance in the field, since it permits the
counting and classification of several thousand cells per
minute.