Flow cytometric discrimination of phytoplankton classes by fluorescence emission and excitation properties.

The ataxonomic discrimination of phytoplankton species on the basis of fluorescence data obtained by multiwavelength excitation in combination with wavelength selective detection in flow cytometry is demonstrated. The discrimination is based on differences in pigment composition between the species, which are reflected in their spectral characteristics. Classification can be done both by making use of the absolute fluorescence intensities and with fluorescence parameter ratios. The latter approach has the advantage that size-related effects and instrument fluctuations are reduced to a large extent. Photoadaptation does influence the absolute as well as the ratioed parameters that are obtained but does not impede the classification into major ataxonomic groups.