Computation of aquatic primary production: Extended formalism to include effect of angular and spectral distribution of light

Abstract

With a new spectral model of the underwater light field and an extended formalism for the light#x2010;saturation curve, it is shown that the angular distribution of underwater light has to be considered to account correctly for light absorption and utilization by algal cells. Neglecting the effect of angular distribution on the light absorbed by phytoplankton can lead to underestimation of primary production. For the stations studied as examples, the minimum correction required is 5–13% for daily, column#x2010;integrated production. For instantaneous primary production, the error is greater when the solar zenith angle is larger (higher latitudes, early morning, and late afternoon). In the extended formalism, models of photosynthesis based on light absorbed are shown to have a more rigorous foundation than those based on light available.