Continuous culture of marine diatoms under silicon limitation. 3. A model of Si‐limited diatom growth 1

A biochemically based model for simulating silicon‐limited diatom growth has been developed in which silicic acid uptake is described by Michaelis‐Menten kinetics. Utilization of silicon within the cell is a function of silicon available in internal pools, while growth is a function of silica in the frustule. Uptake is frequently limited by the rate of silicon utilization within the cell. That rate may be set by the enzymes, or more likely one key enzyme, which regulates the process of frustule formation. Alternatively, some other factor such as light or another nutrient may limit growth, and this in turn may limit silicon utilization within the cell and silicic acid uptake. The model was designed specifically to simulate steady state and transient behavior of a Si‐limited diatom population growing in a chemostat. Comparison of simulations and actual chemostat results indicate that it is a realistic representation of diatom response under these conditions.