Transport limited nutrient uptake rates in Ditylum brightwellii1

The analysis of diffusional transport limitation of nutrient uptake rates by phytoplankton, derived earlier for spherical cells, is extended to include, in an approximate manner, cylindrical and disk‐shaped cells. Transport limitation of nutrient (NO3− and NO2−) uptake rates by the marine diatom, Ditylum brightwellii, was demonstrated experimentally at low nutrient concentrations in quiescent media. The effect of transport limitation was decreased by mixing and eliminated completely when the organism was cultured in a medium being sheared at a high enough rate. It also disappeared at high enough nutrient concentrations.