A strain of Cyclotella meneghiniana was isolated from the River Danube. The optimum irradiance and temperature for growth were determined in batch cultures. The optimum temperature for growth was 25 °C. The estimated saturated irradiance was near 125 uE m 2 s 1 . The calculated I k for growth and photosynthesis were 30 ± 3 and 44 ± 6 uE nr 2 s 1 respectively. A continuous culture technique was used to test the growth and cell composition at the transition state between batch, nutrient

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... y, and a low rate of nutrient supply. Algal response was characterized by high intracellular N and C with negative growth rate. At a low dilution rate (0.06 d 1 ), the continuous culture theory was not followed. This critical rate is characterized by low chlorophyll-a content per cell and may depend on the mode of nutrition.