An inexpensive flow cytometer for the analysis of fluorescence signals in phytoplankton: Chlorophyll and DNA distributions

A flow cytometer suitable for analyzing fluorescence signals from individual phytoplankton cells is described. The instrument was assembled using an epifluorescence microscope, a photomultiplier, a Coulter size distribution analyzer, and an inexpensive quartz capillary flow system as basic components. The performance of the instrument is comparable to that of commercial flow cytometers, and the component parts are easily separated from the system for transport or to serve their alternative functions. To illustrate some of the capabilities of the instrument, experiments are presented in which the relative amounts of DNA/cell and chlorophyll/cell were analyzed in cultures of a marine diatom, a coccolithophore, and a dinoflagellate, growing under varied nutrient and light regimes.