A strain of Cyclotella meneghiniana was isolated from the River Danube. The optimum irradiance and temperature for growthwere determined in batch cultures. The optimum temperature for growth was 25 °C. The estimated saturated irradiance wasnear 125 µE m-2 s-1. The calculated Ik for growth and photosynthesis were 30 ± 3 and 44 ± 6 µE m-2 s-1 respectively. A continuousculture technique was used to test the growth and cell composition at the transition state between batch, nutrient sufficiency, anda low rate of nutrient supply. Algal response was characterized by high intracellular N and C with negative growth rate. At a lowdilution rate (0.06 d-1), the continuous culture theory was not followed. This critical rate is characterized by low chlorophyll-acontent per cell and may depend on the mode of nutrition.
