Productivity in the ocean is viewed from the perspective of its three components: biomass, yield (new production), and the rate of production. The three components are ordered along a time scale and a fundamental time scale is defined for the rate of production at the diel (24 h). Two optical properties, the absorption by phytoplankton and particle scattering, are presented and it is argued that they provide a means to unite the rate of production with biomass and yield at the diel scale.