Depth and wavelength dependence of phytoplankton photosynthesis: implications for the remote sensing of marine primary production

A detailed profile of the photosynthetic parameters and the action spectra was obtained in the Sargasso Sea during late summer, when the upper water column was strongly stratified. Significant depth variation in their magnitudes was present in the lower part of the euphotic zone. The consequences of such vertical structure on the estimation of water column primary production by remote sensing on ocean color are evaluated by sensitivity analysis using a spectra irradiance model. The errors in estimated primary production at depth assuming constant values of the photosynthetic parameters can be of several fold. However, for estimates of daily water-column primary production the errors are generally less than 10 percent.