COMPARISON OF HALF-SATURATION CONSTANTS FOR GROWTH AND NITRATE UPTAKE OF MARINE PHYTOPLANKTON (2).
Growth rates and rates of nitrate uptake by N-depleted cells were measured for an oceanic diatom, Chaetoceros gracilis, and a neritic diatom, Asterionella japonica, as functions of nitrate concentration of the medium. Both growth and N-uptake rates appeared to be hyperbolic with nitrate concentration and could be fit to an equation of Michaelis-Menten form: where v is rate, V(m) . is the maximum rate, S is nitrate concentration, and Ks is the half-saturation constant. Ks values for uptake and growth were similar if not identical for each species. Uptake experiments can provide a presumptive measure of Ks for growth, thought to be an ecologically significant characteristic of a species.
Institute of Marine Resources, University of California, La Jolla, California 92037.
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Eppley
Institute of Marine Resources, University of California, La Jolla, California 92037.
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Thomas