Chromatic light effects and physiological modeling of absorption properties of Heterocapsa pygmaea (= Glenodinium sp.)

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Abstract
Growth and absorption properties of the marine dinoflagellate Heterocapsa pygmaea (also known as Glenodinium sp.) were defined for batch cultures of populations grown in blue and green light. Log-phase cells exhibited variations in growth rate, cell volume, pigmentation, chlorophyll-specific absorption, absorption cross-sections for photosynthesis and cellular packaging effects that were dependent upon spectral growth irradiances (5 to 150 .mu.Ein m-2 s-1). By combining knowledge of (1) cellular pigmentation, (2) the distribution of specific pigments into discrete light-harvesting components, and (3) newly-derived pigment-specific absorption coefficients for the major pigment-protein complexes in dinoflagellates, it was possible to reconstruct the photosynthetic absorption properties of the dinoflagellate. The degree of fit between measured and reconstructed absorption spectra varied as a function of spectral growth irradiance. In most instances, the majority of the discrepancy was attributable to a wavelength-dependent package effect, which ranged from 1 to 30% depending upon growth irradiance control of cell pigmentation and cell volume. Preliminary results contribute to the development of a model which uses field measurements of pigmentation and cell characteristics to monitor the presence, distribution, and bio-optical properties of red-tide dinoflagellates.