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Light absorption by phytoplankton and the vertical light attenuation: ecology and physiological significance
Schanz, F.; Senn, P.; Dubinsky, Z. (1997). Light absorption by phytoplankton and the vertical light attenuation: ecology and physiological significance. Oceanogr. Mar. Biol. Ann. Rev. 35: 71-95
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218; e-ISSN 2154-9125, more
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  • Schanz, F.
  • Senn, P.
  • Dubinsky, Z.

    The chlorophyll a specific light attenuation coefficient k c, (in m²mg-1 chl a), is an apparent optical property of the underwater light field, resulting from the interaction between sunlight and the phytoplankton suspended in natural waters. The determination of kc is carried out under the natural light conditions of a water body, whereas the specific light absorption coefficient of chlorophyll a, a*ph (in m²mg -1 chl a, is an inherent optical property of the phytoplankton. That parameter, a*ph, is determined using a laboratory spectrophotometer. Both kc and a*ph are necessary to calculate the quantum requirement of phytoplankton photosynthesis from alpha, the linear part of the photosynthesis versus irradiation curve. The spectral distribution of kc(?) and a*ph(?) contains information about the species composition of the phytoplankton community. Different ways to determine kc or a*ph are presented. It is relatively easy to evaluate mean of kc (=mean of kc(PAR)), the wavelength-average over the photosynthetically available radiation (PAR) range, assumed to be from 400 nm to 700 nm. Alternatively, in the literature such values were also calculated from the much more difficult to measure kc(?) -spectrum, and the spectral distribution of underwater irradiance, E(?). The values of kc and a*ph are influenced by technical, physical and biological factors: the method of chlorophyll determination, the filter loading, the light properties of the water bodies, the species composition of the phytoplankton community, including cell geometry and size, the ultrastructure of chloroplasts and the physiological status of the cells, resulting from senescence, nutrient limitation or photoacclimation.

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