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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. [ABSTRACT FROM AUTHOR]

The paper presents approximate formulas 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 nine 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 analysed empirical material was characterized by a wide range of variability: the total chlorophyll a concentration (Tchla) varied between 0.3 and > 140 mg m-3, the ratio of the sum of all accessory pigment concentrations to chlorophyll a (ΣCi/Tchla) varied between 0.21 and 1.5, and the absorption coefficients aph (λ) at individual light wavelengths varied over almost three orders of magnitude. Different versions of the parameterization formulas were derived on the basis of the data gathered: a one-component parameterization in the "classic" form of a power function with Tchla as the only variable, and a two-component formula - the product of the power and exponential functions, with Tchla and ΣCi/Tchla as variables. There were distinct differences between the general version of the one-component parameterization and its variants developed for individual months of the year. In contrast to the general parameterization, both the monthly and the two-component variants enable, at least partially, the variability of pigment composition occurring throughout the year in the Baltic phytoplankton populations examined here to be taken into account. [ABSTRACT FROM AUTHOR]

This study presents three alternative models for estimating the absorption properties of chromophoric dissolved organic matter aCDOM(λ). For this analysis we used a database containing 556 absorption spectra measured in 2006-2009 in different regions of the Baltic Sea (open and coastal waters, the Gulf of Gdansk and the Pomeranian Bay), at river mouths, in the Szczecin Lagoon and also in three lakes in Pomerania (Poland) -- Obłęskie, Łebsko and Chotkowskie. The variability range of the chromophoric dissolved organic matter (CDOM) absorption coefficient at 400nm, aCDOM(400), lay within 0.15-8.85m-1. The variability in aCDOM(λ) was parameterized with respect to the variability over 3 orders of magnitude in the chlorophyll a concentration Chl a (0.7-119 mg m-3). The chlorophyll a concentration and aCDOM(400) were correlated, and a statistically significant, nonlinear empirical relationship between these parameters was derived (R² = 0.83). On the basis of the covariance between these parameters, we derived two empirical mathematical models that enabled us to design the CDOM absorption coefficient dynamics in natural waters and reconstruct the complete CDOM absorption spectrum in the UV and visible spectral domains. The input variable in the first model was the chlorophyll a concentration, and in the second one it was aCDOM(400). Both models were fitted to a power function, and a second-order polynomial function was used as the exponent. Regression coefficients for these formulas were determined for wavelengths from 240 to 700nm at 5nm intervals. Both approximations reflected the real shape of the absorption spectra with a low level of uncertainty. Comparison of these approximations with other models of light absorption by CDOM demonstrated that our parameterizations were superior (bias from -1.45 to 62%, RSME from 22 to 220 %) for estimating CDOM absorption in the optically complex waters of the Baltic Sea and Pomeranian lakes. [ABSTRACT FROM AUTHOR]

This paper reports on detailed studies of the relationship between the inherent optical properties (IOPs) of suspended particulate matter populations occurring in southern Baltic Sea waters, and the basic biogeochemical and morphological quantities enabling these populations to be generally characterized. Specifically, these IOPs are the spectral absorption coefficients by all particulate matter, phytoplankton pigments and detritus, the spectral scattering and backscattering coefficients by particles, and the backscattering ratio. The biogeochemical properties of suspended matter populations are characterized by measuring concentrations of suspended particulate matter (SPM), particulate organic matter (POM) and particulate inorganic matter (PIM), as well as concentrations of various phytoplankton pigments, including chlorophyll a (Chl a). We also take particle size distributions (PSDs) into account. This diverse empirical material is used to describe how the typical relationships between the IOPs of suspended matter and the concentrations of the main water constituents (SPM or Chl a) can be influenced by differences in the general composition and size distributions of the suspended matter. We statistically describe the possible impact on these relationships of the variability of composition ratios, such as POM/SPM and Chl a /SPM, as well as the impact of the variability of certain characteristics calculated on the basis of PSDs: the average particle diameter weighted by the particle's projected area (D A), the average apparent density of particles (ρ a), the average intracellular concentration of chlorophyll a (c i), and the corresponding products of these quantities. We also demonstrate the significant variability of the specific IOPs (SIOPs) by attempting to determine them in the classical way for our southern Baltic data, and we give a possible interpretation of this variability. On the basis of these analyses, we derive new, multicomponent IOP parameterizations that are functions of several variables. These new parameterizations enable the IOPs of suspended matter to be characterized and predicted with better accuracy than with the often-used standard one-component relationships. • the optically complex waters of the southern Baltic Sea, • detailed measurements of optical and biogeochemical properties of suspended matter, • influence of particle composition and size distributions on optical properties, • interpretation of the variability of the specific inherent optical properties, • new, multicomponent parameterizations of inherent optical properties. [ABSTRACT FROM AUTHOR]