Chromoprotein- and pigment dependent modeling of spectral light absorption in two dinoflagellates, Prorocentrum minimum and Heterocapsa pygmaea

  • Johnsen G
  • Nelson N
  • Jovine R
 et al. 
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Pigment- and chromoprotein-dependent spectral models, designed to
accurately reconstruct whole cell absorption spectra for photosynthetic
dinoflagellates, were assessed. Measured spectral absorption properties
(400 to 700 nm) included signatures from whole cells,dispersed thylakoid
fragments (unpacked absorption),isolated chromoproteins and individual
pigments from high (500 mu mol m(-2) s(-1)) and low (35 mu mol m(-
2) s(- 1)) light-adapted cells of the dinoflagellates Prorocentrum
minimum and Heterocapsa pygmaea grown in continuous light at 15 degrees
C.For model verification, we also developed a procedure to measure
unpackaged cell absorption,free of solvent and light-scattering effects.
Maximum measured chl a- specific absorption at 675 nm appears to
be closer to 0.027 than a predicted value of 0.0203 m(2) mg(-1) chl
a based on absorption from chl a in 90 % acetone.The percent fractional
absorption of 'in vivo' weight- specific absorption coefficients
of individual pigments relative to total weighted absorption (all
pigments) was estimated to indicate the light-harvesting capabilities
of the different pigments as a function of photoadaptive status and
water color.Correspondingly, the weighted absorption of each pigment
fraction has been estimated in theoretical white Light and in 'clearest'
green coastal and blue oceanic waters.Independent of water color,peridinin
was by far the most important light-harvesting pigment,followed by
chl c(2) and chl a.The photoprotective diadinoxanthin absorbed most
efficiently in the blue part of the visible spectrum. Results indicate
that the chromoprotein model (1) overcame spectral distortions inherent
in more general pigment-dependent models and,when combined with corrections
for pigment packaging effects,(2) provided accurate spectral estimates
of in vivo absorption coefficents and (3) worked equally well for
dinoflagellate species with or without the major light- harvesting
peridinin-chlorophyll-protein complex, PCP.Findings are discussed
in the context of modeling of bio- optical characteristics in dinoflagellates,their
photoecology and implications for the in situ optical monitoring
of red tides

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  • G. Johnsen

  • N. B. Nelson

  • R. V.M. Jovine

  • B. B. Prezelin

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