Model of the in vivo spectral absorption of algal pigments. Part 1. Mathematical apparatus

Existing statistical models of in vivo light absorption by phytoplankton (Woźniak & Ostrowska 1990, Bricaud et al. 1995, 1998) describe the dependence of the phytoplankton specific spectral absorption coefficient a∗ pl(λ) on the chlorophyll a concentration Ca in seawater. However, the models do not take into account the variability in this relationship due to phytoplankton acclimation. The observed variability in the light absorption coefficient and its components due to various pigments with depth and geographical position at sea, requires further accurate modelling in order to improve satellite remote sensing algorithms and interpretation of ocean colour maps. The aim of this paper is to formulate an improved model of the phytoplankton spectral absorption capacity which takes account of the pigment composition and absorption changes resulting from photo- and chromatic acclimation processes, and the pigment package effect. It is a synthesis of earlier models and the following statistical generalisations: (1) statistical relationships between various pigment group concentrations and light field properties in the sea (described by Majchrowski & Ostrowska 2000, this volume); (2) a model of light absorption by phytoplankton capable of determining the mathematical relationships between the spectral absorption coefficients of the various photosynthetic and photoprotecting pigment groups, and their concentrations in seawater (Woźniak et al. 1999); (3) bio-optical models of light propagation in oceanic Case 1 Waters and Baltic Case 2 Waters (Woźniak et al. 1992a, b, 1995a,b). The generalised model described in this paper permits the total phytoplankton light absorption coefficient in vivo as well as its components related to the various photosynthetic and photoprotecting pigments to be determined using only the surface irradiance PAR(0+) surface chlorophyll concentration Ca(0) and depth z in the sea as input data

Model of the in vivo spectral absorption of algal pigments. Part 2. Practical applications of the model

The article describes applications and accuracy analyses of a statistical model of light absorption by phytoplankton that accounts for the influence of photo- and chromatic acclimation on its absorption properties. Part 1 of this work (seeWoźniak et al. 2000, this volume) describes the mathematical apparatus of the model. Earlier models by Woźniak & Ostrowska (1990) and by Bricaud et al. (1995, 1998) are analysed for comparison. Empirical verification of these three models shows that the new model provides a much better approximation of phytoplankton absorption properties than do the earlier models. The statistical errors in estimating the mean absorption coefficient apl, for example, are σ+ = 36% for the new model, whereas for the earlier models the figures are σ+ = 43% (Bricaud et al. 1995, 1998) and σ+ = 59% (Woźniak & Ostrowska 1990). Example applications are given of the new model illustrating the variability in phytoplankton absorption properties with depth and trophicity of the sea