AME 46:225-237 (2007)  -  doi:10.3354/ame046225

ABSTRACT: A laboratory experiment was conducted to study differences in the use of varying phosphorus sources by the bloom-forming filamentous cyanobacteria Aphanizomenon flos-aquae and Nodularia spumigena. Axenic strains were grown in typical bloom-time light regimes under phosphate-replete, added organic phosphorus phosphate-depleted and completely phosphorus-depleted conditions. Responses to the treatments differed clearly. A. flos-aquae growth was dependent on an ample supply of inorganic dissolved phosphorus, whereas N. spumigena grew equally well in all treatments. Cellular N:P ratios showed high plasticity for both species and phosphorus deficiency did not seem to affect nitrogen fixation of either species. Regarding bloom formation, the results call attention to the importance of the omnipresence, eurythermal growth and deeper vertical positioning of A. flos-aquae in comparison to N. spumigena. N. spumigena is able to form and sustain bloom biomasses relying on cellular phosphorus storage and effective remineralization of organic phosphorus compounds.

KEY WORDS: Filamentous cyanobacteria · Aphanizomenon flos-aquae · Nodularia spumigena · Phosphorus source · Phosphorus limitation · Organic phosphorus · Baltic Sea