Ten-year simulations were performed using a coupled physical-biological-optical ocean ecosystem model with both simple analytic and accurate EcoLight numerical computations of the in-water irradiances. The predicted chlorophyll concentrations differed by tens of percent over the course of 10-year simulations. The EcoLight code runs with less than a 30% increase in nm time, which providing several advantages than cannot he obtained with an analytic light model. These advantages are as follows. ...