Disruption of the algal cell membrane was visualized and analysed by counting 24 random views under the fluorescent microscope after SYTOX Green staining. SYTOX Green has a high affinity to nucleic acid in the cells and can emit bright green fluorescence light when excited with a 450–490 nm source (Sato et al., 2004). Since it is a large molecule, SYTOX Green could only penetrate into membrane damaged cells. Autofluorescence of chlorophyll was observed simultaneously, which allowed the discrimination of membrane damaged cells and intact cells. The
linear correlation for M8 species between the actual and measured percentage of live algae was confirmed prior to this study (data not shown here). An increase in the ratio of damaged to intact cells was observed in all the systems over the 48 h pretreatment (Table 1).