DETERMINATION OF THE MAJOR GROUPS OF PHYTOPLANKTON PIGMENTS FROM THE ABSORPTION-SPECTRA OF TOTAL PARTICULATE MATTER

The contributions of detrital particles and phytoplankton to total lig ht absorption are retrieved by nonlinear regression on the absorption spectra of total particles from various oceanic regions. The model use d explains more than 96% of the variance in the observed particle abso rption spectra. The resulting absorption spectra of phytoplankton are then decomposed into several Gaussian bands reflecting absorption by p hytoplankton pigments. Such a decomposition, combined with high-perfor mance liquid chromatography data on phytoplankton pigment concentratio ns, allows the computation of specific absorption coefficients for chl orophylls a, b, and c and carotenoids. The spectral values of these in vivo absorption coefficients are then discussed, considering the effe cts of secondary pigments which were not measured quantitatively. We s how that these coefficients can be used to reconstruct the absorption spectra of phytoplankton at various locations and depths. Discrepancie s that do occur at some stations are explained in terms of particle si ze effect. These coefficients can be used to determine the concentrati ons of phytoplankton pigments in the water, given the absorption spect rum of total particles.