The use of DAPI for identifying and counting aquatic microflora1

A highly specific and sensitive fluorescing DNA stain, 4′6-diamidino-2-phenylindole (DAPI) was compared with acridine orange (AO) for counting aquatic microflora. Use of DAPI improved visualization and counting of <1-µm bacteria and blue-green algae in seston-rich samples and extended sample storage to at least 24 weeks.