VARIABILITY IN THE CHLOROPHYLL-SPECIFIC ABSORPTION-COEFFICIENTS OF NATURAL PHYTOPLANKTON - ANALYSIS AND PARAMETERIZATION

Variability in the chlorophyll (chl) a-specific absorption coefficient s of living phytoplankton a(ph)(lambda) was analyzed using a data set including 815 spectra determined with the wet filter technique in dif ferent regions of the world ocean (covering the chlorophyll concentrat ion range 0.02-25 mg m(-3)). The a(ph) values were observed to decrea se rather regularly from oligotrophic to eutrophic waters, spanning ov er more than 1 order of magnitude (0.18 to 0.01 m(2) mg(-1)) at the bl ue absorption maximum. The observed covariation between a(ph)(lambda) and the field chl a concentration (chl) can be explained considering (1) the level of pigment packaging and (2) the contribution of accesso ry pigments to absorption. Empirical relationships between a(ph)(lamb da) and (chl) were derived by least squares fitting to power functions . These relationships can be used to produce a(ph) spectra as a funct ion of [chl]. Such a simple parameterization, if confirmed with furthe r data, can be used, e.g., for refining estimates of the carbon fixati on rate at global or regional scales, such as those obtained by combin ing satellite pigment concentration maps with primary production model s based on physiological parameters, among which a(ph) is an importan t one.