The Functional and Optical Absorption Cross-Sections of Phytoplankton Photosynthesis

Abstract

Phytoplankton, like all photosynthetic organisms, have highly complex light-harvesting systems, consisting of pigment beds arranged on asymmetrical membranes. These pigment arrays, or ``antennae'', as well as any other cellular, light-absorbing structures and compounds have a definite probability ``cloud'' for absorbing impinging photons. This wavelength-dependent probability may be quantified as a cross-section, with dimensions of area per unit of compound. These in vivo cross-sections are invariably smaller than those of the same substance, for example, chlorophyll a, when extracted by any suitable solvent, brought into solution, and purified. The optical in-vivo cross-section of these pigments varies considerably between species, as well as within the same species, in response to such environmental factors as ambient light and nutrient status.