Inorganic nutrients uptake and organic phosphorus utilization by Ostreopsis cf. ovata.

Although nutrient implication in bloom dynamics has not yet been clarified, in Ostreopsis cf. ovata cultures the importance of nutrient concentrations (N and P) for cell growth and toxicity has been remarked. Nutrient uptake pattern in cultured strains also evidenced the need for balanced N/P ratios for optimal growth of this species; moreover it appears that the intracellular nutrient ratios tend towards balanced conditions independently by concentrations (N/P ratio) in the external medium. The present study was therefore performed in order to get better insights into nutrient utilization by O. cf. ovata. The characterization of the nutrient uptake kinetics showed that this species has higher Vmax and higher affinity values for P uptake than for N. In addition, a study performed with cultures grown at different N/P ratios, showed that alkaline phosphatase activity was induced when external P was depleted or present in low amounts. These findings attest to the high efficiency of O. cf. ovata in both inorganic and organic P acquisition, an aspect that could confer advantages towards competing species.