Marine phytoplankton distributions measured using shipboard flow cytometry

Abstract Flow cytometry is an alternative to traditional methods of studying the distribution and abundance of phytoplankton that allows rapid, objective analysis of light scattering and fluorescence of individual cells in a natural water sample. We report here the first flow cytometric analysis of phytoplankton communities carried out at sea. Light scatter and autofluorescence of individual cells were measured in water samples from the Gulf Stream. These flow cytometric ‘signatures’ allowed us to discriminate between different groups of phytoplankton, enumerate them, and detect changes in average pigment fluorescenee resulting from changes in population structure. The results indicate that flow cytometric techniques can be used on board ship with minimal modification of available equipment. They also show promise for automated analyses of plankton and particles in the sea.