Influence of nutrient conditions on the growth and intracellular storage capacities (nitrogen and phosphorus) of Planktothrix agardhii isolated from eutrophic El Kansera impoundment waters (Morocco)

The effects of nutrient conditions on the growth and intracellular nitrogen and phosphorus quotas of filamentous Cyanobacteria Planktothrix agardhii, isolated from eutrophic El Kansera waters were studied in batch culture. The deficiency in nitrogen affects the biomass more severely than the deficiency in phosphorus, with more marked effects on chlorophyll a content. Intracellular nitrogen (QN) and phosphorus (QP) quotas, determined experimentally, show that this alga is capable of storing quantities of N and P, which explains the delay observed between the onset in deficiency of the culture and the stoppage of growth. The values of ON, of QP, as well as those of QChl (chlorophyll a contents by filament) vary between a minimum (Q(o)) and a maximum (Q(m)) that correspond to a situation of deficiency and a nutritive supply respectively. The resumption of growth after the addition of the limiting element is discussed in relation to the added initial dose and to the instantaneous nitrogen and phosphorus quotas.