In vivo absorption properties of algal pigments

Estimates of the in vivo specific absorption coefficients (m2 mg-1; 400-750 nm, 2 nm intervals)for the major algal pigment groups (chlorophylls, carotenoids and physobilins)are presented. 'Unpackaged' absorption coefficients were initially obtained by measuring the absorption properties of pure pigment standards spectrophotometrically and 'shifting' their absorption maxima to match in vivo positions. Two approaches for estimating the phytoplankton absorption coefficient (spectral reconstruction and spectral decomposition)are compared by linear regression analysism incorporating concurrent measurements of particulate absorption and pigmentation performed in the Sargasso Sea. Results suggest that 'pigment package' effects are minimal for natural assemblages of open-oceanic phytoplankton and that accessory pigments do not always co-vary with chlorophyll a over depth and time.