Variability Of Particulate Spectral Absorption Coefficients In The Eastern Pacific Ocean

As part of the Optical Dynamics Experiment (ODEX), the spectral absorption coefficient (400-700 nm.) was measured for marine particles sampled at stations in the California current and the eastern edge of the North Central Pacific Gyre. By normalizing the spectral absorption coefficients to the concentration of chlorophyll plus phaeopigments, variability in both the spectral shapes and magnitudes of the specific coefficient can be assessed. Comparisons between samples indicated large variability vertically (mixed layer versus deep euphotic zone), horizontally (near shore versus central gyre) and seasonally (fall versus spring). When compared to chlorophyll specific absorption coefficients for healthy cul-tures, the field data suggest that a large, and variable fraction of particulate absorption in the ocean is due to detrital components. Because the origin of particulate organic material (POM) for these regions can be assumed to be derived from in situ biogenic process-es, the deviation of field spectra from those observed for cultures must in large part be due to the previous history of biological dynamics within a particular water mass.