The redfield ratio and phytoplankton growth rate

Goldman, McCarthy & Peavey (1979) argued that phytoplankton chemical composition close to the Redfield ratio (C:N:P of 106:16:1) implies near maximal growth rate. According to the Droop Cell-Quota model it is possible for algae to exhibit this chemical composition whilst growing slowly because of light limitation. This is demonstrated by the results of an experiment with the haptophyte Pavlova lutheri in continuous culture, and by observations made on natural populations of phytoplankton: the blue-green alga Oscillatoria bourrellyi in the freshwater English lake, Windermere in summer; and a spring bloom dominated by the diatom Skeletonema costatum in the Scottish sea-loch Creran. The conclusions of Goldman et al. concerning the growth rate of phytoplankton in oligotrophic oceans are discussed in the light of these results and the problems of determining precise elemental ratios for phytoplankton.