Modelling the interacting effects of nutrient uptake, light capture and temperature on phytoplankton growth

A model of phytoplankton growth developed by analogy with chemical kinetics (CR model) in Baird and Emsley (J. Plankton Res., 21, 85–126, 1999) is explored further. The CR model parameterizes all biochemical reactions involved in phytoplankton growth by one parameter: the maximum growth rate. Phytoplankton growth rate is then calculated from an interaction of the maximum growth rate, and the physical limit to extracellular nutrient uptake rates and light capture. In this paper, the CR model was re-derived, with two corrections and a number of modifications to increase its generality. During derivation, the model's behaviour was compared with chemostat cultures at a variety of dilution rates, nutrient inputs and temperatures. Model output was then plotted against observations of a semi-continuous culture of Isochrysis galbana. Finally, the CR model was used to predict the growth rate of phytoplankton communities extracted from two temperate lakes under varying nutrient, light and temperature regimes. The CR model explained 37% of the variability of phytoplankton growth rate in cultures at environmental conditions similar to those of the lakes, compared with 25% explained by a non-linear best fit to 324 growth experiments. The following paper in this issue develops the CR model further, using it to predict stable carbon isotope fractionation.