Flow cytometric analysis of fresh (a) and fixed (b) (formaldehyde, 2% final concentration) subsamples of coastal seawater stained with SYTO 13. The x and y axes show right angle light scatter (RALS) and green fluorescence (FL1) values (arbitrary units), respectively. Large windows on the left were drawn around fluorescent bacterial cells. Fluorescent microbeads (0.94-μm diameter) (small windows, on the upper right) were used as internal standard. Signal processing was triggered on green fluorescence (FL1).