Application of flow cytometry in marine phytoplankton research: current applications and future perspectives

A brief overview is given of current applications of flow cytometry (FCM) in marine phytoplankton research. This paper presents a selection of highlights and various technical and analytical problems we encountered during the past 10 years. In particular, the conversion of the relative values obtained in terms of size and fluorescence applying FCM to quantitative estimates of cell size, pigment concentration, genome size etc., is addressed. The introduction of DNA -cell-cycle analysis made easily assessable by flow cytometry has been of great importance, allowing in situ measurement of species specific growth rates. Key questions in ecology such as factors determining the wax and wane of phytoplankton bloom can now be better answered in terms of species specific growth and mortality. Finally, flow cytometry provides detailed information of the physiological status of the individual algal cells. New staining methods enable us to distinguish between viable and non-viable cells and so will help us to elucidate the importance of "automortality" in aquatic ecosystems.