Proceedings Article | 6 February 1997
Proc. SPIE. 2963, Ocean Optics XIII
KEYWORDS: Absorption, Packaging, Algorithm development, Ocean optics, Magnesium, Absorbance, Bragg cells, Water, Chromophores, Remote sensing
The absorption of light by phytoplankton at a single wavelength, aph((lambda) ), is reduced with the increased packaging of the light absorption material. A common method of estimating the package effect is to divide aph((lambda) ) by the light absorption of the intracellular material after it has been extracted in an organic solvent. The absorption of the extract is often assumed to be representative of the true absorption of the cellular material in a dissolved state, asol((lambda) ). However, asol((lambda) ) is affected by the process of removing the light absorptive material from the organic matrix of the cell, the destruction of the pigment-protein complexes, and the solvent interference with the excited states of the chromophore. What is actually being measured by these extraction methods to determine asol((lambda) ), is aom((lambda) ), i.e., the absorption of light by the pigment material in the organic medium of the experiment. A solvation factor, S, that is the ratio of the true asol((lambda) ) to the measured aom((lambda) ) is needed before the package effect can be determined. We have developed an internally consistent measure of aph((lambda) ), aom(lambda), chlorophyll a concentration, and pheopigment concentration to determine the ratio asol((lambda) ):aom((lambda) ) and the package effect, Qa equals aph/at 675 nm. These parameters are used to determine a functional relationship between chlorophyll a concentrations and light absorption for high- light adapted, natural phytoplankton populations in optically clear waters. The packaging effect in these waters is negligible at the red peak of the spectrum. Exclusion of the weight specific absorption of pheopigments and the assumption of a zero aph(675) at a zero pigment concentration produces a misleading chlorophyll a-specific absorption and a false determination of pigment packaging. An algorithm is developed and validated for predicting chlorophyll a concentration from aph(675) in high-light, optically clear waters.
