A simple metabolic model of phytoplankton physiology: quantifying energetic trade-offs for diatoms.

We have developed a simplified, metabolic flux model for phytoplankton which resolves macro-molecular composition and employs mass, redox, and energy balance constraints. The model qualitatively and quantitatively captures, and interprets, relationships between growth rate, environment and elemental composition when constrained with laboratory data. The synthesis of model and data suggests a coupling of metabolic rate and light intensity. The energetic framework can be used to explore the relative costs of specific physiological traits. It has been hypothesized that the success of diatoms may be related to the energy efficiency of the production of a silica frustule relative to an organic structure. We explicitly quantify this energy saving through comparative simulations for cells with silicic and organic cell walls.