Pigment composition, spectral characterization and photosynthetic parameters in Chryso-chromulma polylepis

Abstract

The photobiological response of an isolate of the prymnesiophyte Chrysochromulina polylepis, obtained from a bloom in the Skagerrak in May-June 1988, was evaluated with respect to pigment composition, spectral dependence of light harvesting, and photosynthetic parameters of cultures grown at 75 to 120 gm01 m-2 S-' irradiance, 16 h day length and 15°C. Results were compared to similarly grown cultures of the diatom Skeletonerna costatum that appeared before and after the C. polylepis bloom. Chl a-specific absorption of light (a,) and chl a-specific absorption of quanta transported to photosystem 11, estimated by means of a scaled fluorescence excitation spectrum (F), were 1.7 to 2.1 times larger in C. polylepis than in S. costatum in the visible spectrum. C. polylepis harvested blue-green light (450 to 500 nm) particularly efficiently. This is related to a high proportion of 19'hexanoyloxyfucoxanthin and chl c3 relative to chl a. Nonetheless, both C. polylepis and S. costatum absorb light more efficiently in 'clearest' blue ocean water than in 'clearest' green coastal water according to calculations based on spectrally corrected absorbed quanta transported to photosystem I1 (F). Carbon-specific light absorption was about the same in the 2 species since the chl a : C ratio in S. costatum was twice as high as in C. polylepis. C. polylepis had a much smaller maximum carbon uptake (P:) than S. costatum. Differences between the 2 species in terms of photosynthetic parameters, pigment composition, and spectral characteristics normalized to chl a, carbon, and cell are discussed.