Author: Roman Majchrowski, last updated: 26 April 2016
Absorption by phytoplankton for wavelength 675 nm
The coefficient of light absorption in phytoplankton cells by all pigments for wavelength 675 nm corresponds to the maximum in the red part of the spectrum. This coefficient gives the maximum light absorption in the red band of the spectrum. Its value is determined mainly by the chlorophyll a contained in phytoplankton cells.
Absorption coefficients for 675 nm are determined for specified depths (i.e. 0, 1, 3, 5, 10, 20 and 30 m) in the water.
Coefficients of light absorption by phytoplankton for 675 nm at selected depths in the Baltic are calculated using the DESAMBEM model (Woźniak et al., 2008). The relevant formulas for determining spectral coefficients of light absorption by phytoplankton in the Baltic can be found in the articles by Woźniak et al. (2008) and Ficek et al. (2004).
The averaged light absorption by phytoplankton for 675 nm was validated with respect to the surface and selected depths in the Baltic.
Measurements of 154 spectral coefficients of light absorption by phytoplankton in the surface layer of the Baltic and more than a dozen depth profiles were performed in 2010-2014 during cruises, mainly in the southern Baltic.
The spectral coefficients of light absorption by phytoplankton were measured using a non-extractive, spectrophotometric method on a UNICAM UV 4-100 spectrophotometer equipped with an RSA-UC40 (LABSPHERE) integrating sphere.
The statistical logarithmic error (see the Table) s+ of the method of determining the coefficient of light absorption by phytoplankton for light wavelength 675 nm using the DESAMBEM algorithm is rather small: depending on depth it is from 36.3% at the surface to 28.7% at 10 m depth.
Table 1. Systematic and statistical errors of estimated coefficients of absorption by phytoplankton for 675 nm at selected depths z in the Baltic in arithmetic and logarithmic statistics when the surface chlorophyll a concentration, measured from on board ship, is the input datum for the DESAMBEM algorithm. N denotes the number of estimated values at a given depth.