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Ammonium uptake and incorporation by Chesapeake Bay phytoplankton: Short term uptake kinetics 1
Author(s) -
Wheeler Patricia A.,
Glibert Patricia M.,
McCarthy James J.
Publication year - 1982
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1982.27.6.1113
Subject(s) - ammonium , chemistry , phytoplankton , chesapeake bay , trichloroacetic acid , saturation (graph theory) , kinetics , environmental chemistry , assimilation (phonology) , chromatography , nutrient , biology , ecology , estuary , organic chemistry , physics , mathematics , combinatorics , quantum mechanics , linguistics , philosophy
Using 15 N‐labeled NH 4 + , we assessed the time‐course of NH 4 + uptake, the parameters of saturation kinetics, and the rates of incorporation of NH 4 + into trichloroacetic acid‐insoluble material by Chesapeake Bay phytoplankton. The amount of NH 4 + taken up by the phytoplankton increased linearly with time for 2 h for all samples growing on or exposed to high concentrations (>1 µ g‐atom N · liter −1 ) of NH 4 + , but extrapolations to time zero did not intercept the origin. These results could be explained by rapid isotopic equilibration of internal and external NH 4 + pools. For stations for which ambient NH 4 + bordered on detection limits, rapid but nonsaturable uptake was observed in 1‐ and 5‐min incubations, whereas saturation was attained in 15–60‐min incubations. The experiments on rates of NH 4 + incorporation into TCA‐insoluble material demonstrated that most (>85%) of the 1 5 N label was incorporated into the macromolecular fraction by ≈15 min. These data thus demonstrate that rates of NH 4 + uptake may become limited within minutes by rates of assimilation and incorporation into macromolecules and that reported kinetic parameters reflect these metabolic rates rather than transport rates.