Carbon limitation of ammonium uptake by heterotrophic bacteria in the subarctic Pacific

• Published in: Limnology and Oceanography
• Main Authors: Kirchman, David L., Keil, Richard G., Wheeler, Patricia A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1990
• Subjects: Pacific; Subarctic
• Online Access: http://dx.doi.org/10.4319/lo.1990.35.6.1258; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.1990.35.6.1258; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1990.35.6.1258

The purpose of this study was to test the hypothesis that NH 4 + uptake by heterotrophic bacteria in the subarctic Pacific is C limited. Addition of glucose (0.5–1.0 µ M) stimulted NH 4 + uptake in unfractionated water but had no effect on bacterial abundance. Glucose stimulation of NH 4 + uptake was even greater in the bacterial size fraction (<0.8 µ m). Regeneration of 15 NH 4 + from added [ 15 N] amino acids was measurable in the bacterial size fraction, but glucose additions prevented net NH 4 + excretion because of increased uptake of NH 4 + . In the subarctic Pacific, NH 4 + concentrations range from undetectable (≤0.05 µ M) to 0.4 µ M, whereas the maximal estimate of monosaccharide concentrations was 0.025 M. These results indicate that the supply of C compounds like glucose can limit NH 4 + uptake by heterotrophic bacteria.