A new staining technique for dual identification of plankton and detritus in seawater

A new method is described that employs dual staining and epifluorescencemicroscopy for the identification of plankton and detritus inseawater. The staining technique uses the fluorochromes propidiumiodide (PI) and 4'.6-diamidino-2-phenylindole (DAPI) in conjunctionwith UV excitation. PI/DAPI staining identifies living matterdistinct from non-living matter by selectively staining detritusa deep orange color while cells are either blue-white or pink,depending upon stain and cell type. Comparison of this techniquewith existing epifluorescence techniques and staining reagentsindicates that PI/DAPI offers an improved approach for Stainingdetritus and plankton when evaluation of both is desired. Thisstep is a prerequisite for quantitation of the volumes of detritusand plankton, preliminary to independent estimates of theircarbon and nitrogen pools in aquatic ecosystems.