Influence of light-temperature and nutrient conditions on the growth and intracellular storage (nitrogen and phosphorus) of Microcystis aeruginosa Kutzing isolated from the El Kansera (Morocco) eutrophic impoundment

The interdependence between light and temperature was studied in a non axen ic culture of Microcystis aeruginosa, isolated from the El Kansera eutrophi c impoundment. The experiments were performed, in batch culture without bub bling, over a range of light intensities 5 - 500 muE. m(-2)s(-1) provided b y 400 W lamps (phytoclaude) under 15/9 light : dark cycles at various tempe rature from 15 to 30 degreesC. The maximum growth rate (mu max = 0.92 day(- 1)) was recorded for growth conditions at 20 degreesC (+/- 1 degreesC) and a light intensity (Iopt) of 115 muE. m(-2).s(-1). Under non limited nutrient conditions and for suboptimal temperature, a goo d relationship was found (r(2) = 0.98) between optical density (750 mn) and the chlorophyll a values. In case of nutrient deficiency, the pigment cont ent was more affected by nitrogen starvation. Intracellular and cell storage capacity were deduced from experiments. This strain is able to store high quantities of nutrients, and the chlorophyll a content varyies according to the degree of starvation.