NITROGEN AND PHOSPHORUS INTRACELLULAR CAPACITY IN STORAGE BY MICROCYSTIS-AERUGINOSA KUTZ AND SYNECHOCYSTIS SP - TOXIC CYANOBACTERIA OCCASIONALLY FORMING BLOOMS IN MARRAKESCH AREA (MOROCCO)

Nutritive behavior of microalgae Microcystis aeruginosa and Synechocys tis sp., when nutrients are deficient, was evaluated by simultaneous e xperiments of nitrogen and phosphorus deficit and enrichment. These ex periments allowed us of estimation intracellular nutrient reserve stor ed by the two alga strains, which support their growth in the course o f nutrient deficiency. Nutrient storage capacity was determined using natural culture media (lake water, wastewater) and enriched BG 13 medi um. Results showed that the growth of alga strains was rapidly affecte d by nitrogen (N-NO3-)deficiency. Daughter cell number produced from i ntracellular nitrogen stock was similar for all media used. Inversely, in spite of phosphorus deficiency, algal cells continue logarithmic g rowth using their reserve which had not been exhausted before the eigh th day of deficiency. Daughter cell number produced from phosphorus st ock was slightly lower in BG 13 than in natural medium. Cyanobacterial strains store nitrogen and phosphorus in quantities which may maintai n their growth when these nutrients are deficient in their natural hab itats.