A comparison of two N-irradiance interaction models of phytoplankton growth

The N-photoacclimation interaction models of Geider et al. (GM) and Flynn e t al. (FM) are compared by tuning them to data from a light-shift experimen t for a diatom. Both the original model constructs have failings, GM in its Nassimilation component and FM in its photoacclimation component. However, both of these models can be modified readily to overcome these problems. I n addition, hybrid models that use the N-assimilation component of FM and t he photoacclimative component of GM work well. For situations where a model is required to simulate the interaction between a single N source and ligh t, the use of the revised GM structure should be considered first. The revi sed FM is better suited for more complex environmental scenarios-for exampl e where detailed simulations of ammonium-nitrate interactions are required. GM and FM are to be preferred over models that use a fixed Chi: C, because they may both be tuned directly to real chlorophyll a data in ecosystem si mulators.