Kinetics of nitrogen (nitrate, ammonium and urea) uptake by the picoflagellate Micromonas pusilla (Prasinophyceae)

• Published in: Journal of experimental marine biology and ecology Vol. 153; no. 2; pp. 129 - 141
• Main Authors: Cochlan, William P., Harrison, Paul J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.1991; Elsevier Science
• Subjects: Ammonium; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Metabolism; Micromonas pusilla; Nitrate; Nitrogen metabolism; Nutrient uptake kinetics; Picoplankton; Plant physiology and development; Urea; Urea; Micromonas pusilla; Picoplankton; Ammonium; Nitrate; Nutrient uptake kinetics; Marine environment; Algae; Nutrient; Nitrates; Kinetics; Nitrogen; Uptake; Thallophyta
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/0022-0981(91)90220-Q

The kinetics of N (nitrate, ammonium and urea) uptake by the eucaryotic picoflagellate Micromonas pusilla (Butcher) Manton et Parke were investigated using N-replete batch cultures and the 15N tracer technique. Maximum specific uptake rate ( V max) of NH 4 + was 0.13·h −1, > 2 times the V max of NO 3 − or urea (≈ 0.05·h −1). The half-saturation constants ( K s) for urea, NH 4 + and NO 3 − were similar with an average value of 0.4 μg-at N·1 −1 which is within the range reported for small oceanic diatoms. The greater initial slope of the Michaelis-Menten plot for NH 4 + uptake suggests that M. pusilla can utilize low concentrations of NH 4 + more effectively than equivalent concentrations of urea or NO 3 −. The results of this first study of N uptake kinetics by an eucaryotic picoplankter demonstrate the preference for NH 4 + over urea and NO 3 − as a nitrogenous nutrient source, which may contribute to the relative success of picoplankton in oligotrophic oceanic regions.