A simple model of ocean color1

Drawing upon principles of reflectance spectroscopy, we present a model of ocean color which consists of two optical components, water and phytoplankton. Diffuse spectral reflec-tance immediately below the sea surface is calculated from the diffuse absorption and diffuse backscattering coefficients for water and phytoplankton. Coefficients for phytoplankton were determined from measurements with a spectrophotometer of cells grown in the laboratory, coefficients for water calculated from optical measurements made in the oligotrophic waters of the Sargasso Sea. Broad spectral changes in diffuse reflectance of the model ocean were cffccted by increases in the total absorption and backscattering coefficients of the phytoplank-ton crop. These spectral changes are a function not only of crop size, but also of the age or physiological state of the cells. The study concludes with a derivation of a dichromatic func-tion for calculating diffuse absorption by the phytoplankton crop from measured values of rc’-flectance in a two-component ocean and a comparison of the model with field measurements. The effect of varying phytoplankton crop upon ocean color spectra has bee