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Absorption and photosynthetic action spectra for natural phytoplankton populations: Implications for production in the open ocean 1
Author(s) -
Lewis Marlon R.,
Warnock Roderick E.,
Platt Trevor
Publication year - 1985
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1985.30.4.0794
Subject(s) - photosynthesis , phytoplankton , absorption (acoustics) , spectral line , chlorophyll a , action spectrum , absorption spectroscopy , irradiance , chlorophyll c , atmospheric sciences , chemistry , analytical chemistry (journal) , chlorophyll fluorescence , biology , botany , environmental chemistry , physics , ecology , photochemistry , optics , astronomy , nutrient
The hypothesis that variation in the initial slope of the photosynthesis‐irradiance curve clue to variations in wavelengths of light could be responsible for lower rat es of estimated photosynthesis in the open ocean is tested by direct measurement of photosynthetic action spectra (12‐λ bands, 25‐nm bandpass, eight intensities per band) for natural populations from the well mixed waters containing the spring plankton bloom in the Sargasso Sea. We conclude that this possibility is unlikely, at least at this time of year. The spectral shape of a was similar to that of laboratory diatom or dinoflagellate populations, with a peak at 450 nm, a valley between 500 and 600 nm, and a slight rise at 675 nm. No evidence was found for absorption or photosynthesis by phycobiliproteins and there was little variation with depth. The action spectra covaried with the absorption spectra (determined on glass‐fiber filters) except at 400 nm, where higher absorption and relatively little photosynthetic response was observed. Apparent quantum requirements estimated from absorption and action spectra were spectrally invariant (except 400‐nm band) and ranged from 60 to 200 moles quanta per mole carbon reduced. It is concluded that estimates of open ocean production from chlorophyll‐light models with parameters estimated from laboratory algal cultures are likely to be too high because of a large component of absorption that, while covarying spatially and spectrally with photosynthetic pigment, is itself photosynthetically inactive.