Methylammonium uptake by Chesapeake Bay phytoplankton: Evaluation of the use of the ammonium analogue for field uptake measurements Public Deposited

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  • The uptake of methylammonium (MA) by Chesapeake Bay phytoplankton was measured in short term experiments by using the 14C radioisotope. This uptake was inversely related to ambient NH4+ concentrations, and the specificity for uptake of both substrates was demonstrated by competitive inhibition. At stations with low ambient NH4+, MA uptake followed saturation kinetics, but the Vmax values decreased over time during 10–60-min incubations. Uptake rates of MA were generally lower than those of NH4+, but in short incubations (10– 15 min) the Vmax values were similar. Although MA and NH4+ are taken up by the same transport system, the utility of MA as an NH4+ analogue is restricted by the strong inhibition of MA uptake by low concentrations of NH4+ and by the fact that in some cases MA uptake primarily reflects membrane transport, whereas NH4+ uptake can also reflect metabolic assimilation. Our results show that in typical uptake experiments, NH4+ uptake is rate-limited by either internal pool filling or metabolic assimilation rather than by the membrane transport system. As a consequence, the kinetic parameters reported in the literature for NH4+ uptake overestimate K8 and underestimate Vmax for the membrane transport system.
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  • Limnol. Oceanogr., 27(G), 1982, 1129-1140
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  • Methods; Results; Discussion
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  • description.provenance : Approved for entry into archive by Linda Lamb(llamb@coas.oregonstate.edu) on 2009-10-05T15:11:48Z (GMT) No. of bitstreams: 1 Wheeler et. al. 1982b.pdf: 1320306 bytes, checksum: 694483803126ee0faea72677bd9c2fe4 (MD5)
  • description.provenance : Made available in DSpace on 2009-10-05T15:11:48Z (GMT). No. of bitstreams: 1 Wheeler et. al. 1982b.pdf: 1320306 bytes, checksum: 694483803126ee0faea72677bd9c2fe4 (MD5) Previous issue date: 1982
  • description.provenance : Submitted by Linda Lamb (llamb@coas.oregonstate.edu) on 2009-10-04T20:56:40Z No. of bitstreams: 1 Wheeler et. al. 1982b.pdf: 1320306 bytes, checksum: 694483803126ee0faea72677bd9c2fe4 (MD5)
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  • 0024-3590

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