Phytoplankton carbon fixation, chlorophyll-biomass and diagnostic pigments in the Atlantic Ocean

Alex J. Poulton, Patrick M. Holligan, Anna E. Hickman, Young Nam Kim, Tim R. Adey, Mark C. Stinchcombe, Claire Holeton, Sarah Root, E. Malcolm S. Woodward

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Abstract

We have made daily measurements of phytoplankton pigments, size-fractionated (<2 and >2-μm) carbon fixation and chlorophyll-a concentration during four Atlantic Meridional Transect (AMT) cruises in 2003-04. Surface rates of carbon fixation ranged from <0.2-mmol C m-3 d-1 in the subtropical gyres to 0.2-0.5-mmol C m-3 d-1 in the tropical equatorial Atlantic. Significant intercruise variability was restricted to the subtropical gyres, with higher chlorophyll-a concentrations and carbon fixation in the subsurface chlorophyll maximum during spring in either hemisphere. In surface waters, although picoplankton (<2-μm) represented the dominant fraction in terms of both carbon fixation (50-70%) and chlorophyll-a (80-90%), nanoplankton (>2-μm) contributions to total carbon fixation (30-50%) were higher than to total chlorophyll-a (10-20%). However, in the subsurface chlorophyll maximum picoplankton dominated both carbon fixation (70-90%) and chlorophyll-a (70-90%). Thus, in surface waters chlorophyll-normalised carbon fixation was 2-3 times higher for nanoplankton and differences in picoplankton and nanoplankton carbon to chlorophyll-a ratios may lead to either higher or similar growth rates. These low chlorophyll-normalised carbon fixation rates for picoplankton may also reflect losses of fixed carbon (cell leakage or respiration), decreases in photosynthetic efficiency, grazing losses during the incubations, or some combination of all these. Comparison of nitrate concentrations in the subsurface chlorophyll maximum with estimates of those required to support the observed rates of carbon fixation (assuming Redfield stoichiometry) indicate that primary production in the chlorophyll maximum may be light rather than nutrient limited.

Original languageEnglish
Pages (from-to)1593-1610
Number of pages18
JournalDeep-Sea Research Part II: Topical Studies in Oceanography
Volume53
Issue number14-16
DOIs
Publication statusPublished - Jul 2006

Keywords

  • Atlantic Meridional Transect
  • Carbon fixation
  • Chlorophyll-a
  • Nanoplankton
  • Phytoplankton
  • Picoplankton

ASJC Scopus subject areas

  • Oceanography

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  • Cite this

    Poulton, A. J., Holligan, P. M., Hickman, A. E., Kim, Y. N., Adey, T. R., Stinchcombe, M. C., Holeton, C., Root, S., & Woodward, E. M. S. (2006). Phytoplankton carbon fixation, chlorophyll-biomass and diagnostic pigments in the Atlantic Ocean. Deep-Sea Research Part II: Topical Studies in Oceanography, 53(14-16), 1593-1610. https://doi.org/10.1016/j.dsr2.2006.05.007