A SPECTRALLY AVERAGED MODEL OF LIGHT PENETRATION AND PHOTOSYNTHESIS

A model was developed which predicts the daily photosynthesis of a vertical pigment profile divided into a number of homogeneous layers. A spectral model (irradiance divided into a large number of wavebands) was used to derive simple empirical equations for calculating spectrally averaged values of two parameters-the vertical light attenuation coefficient and the chlorophyll-specific absorption of algae-for each layer as a function of its pigment content and position in the water column. The empirical equations are not dependent on the layer depths chosen, i.e. the same equations can be used for any given set of depths. The spectrally averaged parameters can be used with analytic integrals to give a computationally rapid and accurate result. The model is therefore ideally suited for general circulation models.