First studies of pico- and nanoplankton populations by a laser scanning flow cytometer

The innovative laser scanning flow cytometer (LSFC) CLASS, developed at ENEA Research Center of Frascati, merges the ability to perform very fast analyses on a statistically significant number of particles to the capability of characterizing, from a morphological and optical point of view, cells even if they are not fluorescent. In this work two cultured populations of picoplankton and nanoplankton have been analyzed by means of CLASS to evaluate the future applicability of this system as a tool for the early detection of algal blooms. The analyses were performed on a red pigmented Synechococcus sp. and C hlamydomonas reinhardtii by measuring simultaneously the side scattering, scattering in the wide angular range 5–100°, fluorescence in two spectral bands and depolarization of the laser light by every single cell contained in the sample. The results highlighted the ability of CLASS to characterize cell populations in which standard flow cytometers encounter difficulties and in which the use of traditional time-consuming image analyses is often required, such as those characterized by different morphologies in a small size with little or no fluorescence. In particular the system presented was demonstrated to be suitable for the study of composition and changes in a phytoplankton population. ► New LSFC for angular distribution of scattering, side scattering and fluorescence. ► Parametric resolution of the ILSP for retrieving of size and n data. ► Experiments on picoplankton and nanoplankton. ► Size, n and fluorescence to single out populations and physiological states.