Sizing-up nutrient uptake kinetics: Combining a physiological trade-off with size-scaling of phytoplankton traits

Abstract

We present a new model for the kinetics of nutrient uptake by phytoplankton, which we derive by combining existing models: (1) a size-based modeling framework that accounts for the effects of extra-cellular diffusive limitation, and (2) a model of optimal resource allocation that maximizes uptake rate subject to a physiological trade-off. We show that the new model, unlike either of its pre-existing components, is able to reproduce the observed range of variation in the half-saturation constant for nitrate uptake as a function of both ambient nitrate concentration and cell size. Our results illustrate that the combination of mechanistic trait-based modeling and physiological trade-offs can greatly advance our understanding of plankton ecology.