COMPARISON BETWEEN 3 METHODS FOR DETERMINING FLAGELLATE ABUNDANCE IN NATURAL-WATERS

Flagellates were counted in five lakes by three different methods: live, epifluorescence, and MPN (Most Probable Number) counts. Live and epifluorescence counts always gave similar numbers. epifluorescence counts provide the best estimate of total flagellate abundance and live counts are useful because they give a quick and easy estimate. MPN counts always gave lower numbers than the other methods. MPN, however, are interesting because they give an indication of the physiological status of the flagellate assemblage. The effect of several food sources and different conditions of incubation on MPN were assayed. MPN were higher when the incubation most closely resembled the field situation, in our case at 10-degrees-C in the light.