Using phytoplankton and flow cytometry to analyze grazing by marine organisms

Phytoplankton can, through their autofluorescent characteristics, be thought of as tracer particles in much the same way as fluorescent microspheres when used in particle uptake experiments. Flow cytometric techniques can be used to differentiate phytoplankton from other suspended particles by the two primary autofluorescing photosynthetic pigments, chlorophyll and phycoerythrin. Based on these characteristics, phytoplankton assemblages have been used to assess grazing rates, particle selectivity, and endocytotic abilities in various marine species, from single-celled organisms to higher invertebrates.