Isotope dilution models of uptake and remineralization of ammonium by marine plankton1

Open Access
Publisher Website
Google Scholar
Abstract
The utility of 15N isotope dilution models for the calculation of uptake and remineralization of NH4+ by marine phytoplankton was examined in light of model limitations when applied to field data either when ambient NH4+ levels border on our limit of detection or when there is no statistically significant difference between ambient NH4+ at the beginning and end of an incubation. Through specific examples of field and laboratory data we show that the limitations are a function both of analytical error inherent in the methodology and of changes in rates of uptake and remineralization over the course of a given experiment. We propose modifications to the existing models of NH4+ uptake and remineralization which overcome some of these limitations. The results show that uptake rates have been traditionally underestimated by a factor of ≈2 in routine 15N uptake methodology and that regeneration of NH4+ over relatively brief periods can supply the daily nitrogen requirements of the phytoplankton when there are no losses from the system.

This publication has 0 references indexed in Scilit: