Abstract
Abstract. This paper presents approximate formulas (empirical equations) for parameterizing the coefficient of light absorption by phytoplankton aph(λ) in Baltic Sea surface waters. Over a thousand absorption spectra (in the 350–750 nm range), recorded during 9 years of research carried out in different months of the year and in various regions of the southern and central Baltic, were used to derive these parameterizations. The empirical material was characterized by a wide range of variability: the total chlorophyll a concentration (Tchl a) varied between 0.31 and 142 mg m−3, the ratio of the sum of all accessory pigment concentrations to chlorophyll a (∑Ci/Tchla) ranged between 0.21 and 1.5, and the absorption coefficients aph(λ) at individual light wavelengths varied over almost 3 orders of magnitude. Different versions of the parameterization formulas were derived on the basis of these data: a one-component parameterization in the “classic” form of a power function with Tchl a as the only variable and a two-component formula – the product of the power and exponential functions – with Tchl a and ∑Ci/Tchla as variables. We found distinct differences between the general version of the one-component parameterization and its variants derived for individual months of the year. In contrast to the general variant of parameterization, the new two-component variant takes account of the variability of pigment composition occurring throughout the year in Baltic phytoplankton populations.
Highlights
If we wish to fully describe the process of photosynthesis in the seas and oceans and to correctly interpret remote observations of water bodies, it is important to obtain an accurate quantitative description of the spectral characteristics of light absorption by living phytoplankton, a significant constituent of seawater (e.g. Kirk, 1994; Mobley, 1994; Wozniak and Dera, 2007)
Analysis of pigment composition data obtained for marine phytoplankton assemblages from various ocean and sea waters has revealed a general trend indicating that the proportion of accessory pigments relative to chlorophyll a decreases with increasing chlorophyll a concentration
In an earlier paper by our research team (Meler et al, 2017a), we provided an initial version of the power function parameterization, adjusted to data collected in the southern Baltic Sea
Summary
If we wish to fully describe the process of photosynthesis in the seas and oceans and to correctly interpret remote observations of water bodies, it is important to obtain an accurate quantitative description of the spectral characteristics of light absorption by living phytoplankton, a significant constituent of seawater (e.g. Kirk, 1994; Mobley, 1994; Wozniak and Dera, 2007). If we wish to fully describe the process of photosynthesis in the seas and oceans and to correctly interpret remote observations of water bodies, it is important to obtain an accurate quantitative description of the spectral characteristics of light absorption by living phytoplankton, a significant constituent of seawater There are various accessory pigments, like chlorophylls b and c, carotenoids, and phycobilins. These latter pigments have different spectral absorption characteristics and may be involved in photosynthetic, photoprotective or other processes in marine organisms. Analysis of pigment composition data obtained for marine phytoplankton assemblages from various ocean and sea waters has revealed a general trend indicating that the proportion of accessory pigments relative to chlorophyll a decreases with increasing chlorophyll a concentration (increasing trophicity)
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