Wavelength dependency of the maximum quantum yield of carbon fixation for two red tide dinoflagellates, Heterocapsa pygmaea and Prorocentrum minimum (Pyrrophyta): Implications for measuring photosynthetic rates

  • Schofield O
  • Prézelin B
  • Johnsen G
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The influence of photoadaptive state on the spectral dependency of
the maximum quantum yield for carbon fixation was determined for
two red tide dinoflagellates, Heterocapsa pygmaea Loeblich, Schmidt,
et Sherley and Prorocentrum minimum Pavillard. Cultures were aclimated
to green, blue, red and white light. The spectral dependency in the
light-limited slope of the photosynthesis-irradiance curves (alpha)
was measured with carbon action spectra that, when divided by the
spectrally weighted absorption coefficient, provided estimates of
the maximum quantum yield (phi(max)) for carbon fixation. Values
of phi(max) varied with wavelength within each culture condition
as well as between different culture conditions. The degree to which
the spectral dependency in phi(max) was influenced by the presence
of photoprotective carotenoids and/or energy both dinoflagellates.
The impact of photoprotective pigmentation on the spectral dependency
of phi(max) was most significant for cells grown under high light
conditions reflecting the enrichment of diadinoxanthin. Energy imbalances
between the photosystems was assessed by quantifying enhancement
effects on spectral phi(max) in the presence of background illumination.
Under our experimental conditions, enhancement effects on carbon
action spectra were evident for H. pygmaea under nearly all growth
conditions but were not detectable for P. minimum under any growth
condition. We hypothesize that sensitivity to enhancement effects
reflected differences in the structure of the photosynthetic machinery
of these two peridinin-containing dinoflagellates. While measurements
of phi(max) are sensitive to the color of the light within and incubator,
the relative impact on the spectral dependency of alpha was less
than the wavelength dependency associated with the cellular absorption
properties. Finally we used our data to validate an approach proposed
by others to aid in the correction of photosynthetic measurements
where the situ spectral light field cannot be easily mimicked. The
average error using this approach was 8%, which was significantly
less than the error associated with ignoring the spectral dependency
in alpha

Author-supplied keywords

  • Heterocapsa pygmaea
  • Prorocentrum minimum
  • Pyrrophyta
  • action spectra
  • chromatic adaptation
  • photosynthesis
  • quantum yield

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