Phosphorus storage in Chlorella vulgaris (Trebouxiophyceae, Chlorophyta) cells and its dependence on phosphate supply

It has been postulated that the content of polyphosphates in microalgae call be Used as a biological indicator for eutrophication. Therefore the total cellular phosphorus (TCP) and polyphosphate concentration in the green alga Chlorella vulgaris were investigated ill relation to the amount of available inorganic phosphorus in the medium. Phosphorus starvation was induced by diluting the cultures with P-free medium to study the impact of this Stress situation on phosphorus storage after phosphorus resupply. Increased activity of alkaline phosphatases Was Used as all indicator for actual phosphorus starvation of algal cells. After a P-starvation phase a significant increase ill polyphosphate Content could be observed. This effect was detected by using ill extraction method and microscopic analysis. The variation in phosphate concentration in the medium of a well-supplied culture had much less effect oil the degree of polyphosphate storage than a preceding P-starvation phase. Therefore, the amount of polyphosphate granules in algal Cells is not suitable as in indicator for eutrophication (P-loading) of surface waters. The influence Of P-starvation oil subsequent P-uptake varied between experiments.