Parameterization of phytoplankton spectral absorption coefficients in the Baltic Sea: general, monthly and two-component variants of approximation formulas

• Published in: Ocean science Vol. 14; no. 6; pp. 1523 - 1545
• Main Authors: Meler, Justyna, Wozniak, Slawomir B, Ston-Egiert, Joanna, Wozniak, Bogdan
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 11-12-2018; Copernicus Publications
• Subjects: Absorption; Absorption by phytoplankton; Absorption coefficient; Absorption spectra; Absorptivity; Approximation; Chlorophyll; Chlorophyll a; Coefficients; Composition; Electromagnetic absorption; Empirical equations; Environmental aspects; Exponential functions; Geographical variations; Light absorption; Mathematical analysis; Parameterization; Physiological aspects; Phytoplankton; Plankton; Sea surface; Spectral absorption; Surface water; Temperature (air-sea); Variability; Wavelengths; Baltic Sea
• ISSN: 1812-0792; 1812-0784; 1812-0792
• DOI: 10.5194/os-14-1523-2018

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.