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Distribution and export of particulate organic carbon in East Antarctic coastal polynyas
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  • Lavenia Ratnarajah,
  • Viena Puigcorbé,
  • Sebastien Moreau,
  • Montserrat Roca-Martí,
  • Julie Janssens,
  • Matthew Jeremy Corkill,
  • Luis Paulo Agostino de Magalhaes Duprat,
  • Cristina Genovese,
  • Jan L. Lieser,
  • Pere Masqué,
  • Delphine Lannuzel
Lavenia Ratnarajah
Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool

Corresponding Author:[email protected]

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Viena Puigcorbé
Edith Cowan University
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Sebastien Moreau
Institute for Marine and Antarctic Studies
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Montserrat Roca-Martí
Dalhousie University
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Julie Janssens
Institute for Marine and Antarctic Studies
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Matthew Jeremy Corkill
University of Tasmania
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Luis Paulo Agostino de Magalhaes Duprat
University of Tasmania
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Cristina Genovese
University of Tasmania
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Jan L. Lieser
University of Tasmania
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Pere Masqué
Edith Cowan University
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Delphine Lannuzel
University of Tasmania
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Abstract

Polynyas represent regions of enhanced primary production due to the low, or absent, sea-ice cover coupled with the proximity of nutrient sources. However, studies throughout the Southern Ocean suggest elevated primary production does not necessarily result in increased carbon export. Three coastal polynyas in East Antarctica and an off-shelf region were visited during the austral summer of 2016/2017 to examine the vertical distribution of particulate organic carbon (POC). Carbon export was also examined using thorium-234 (234Th) as a proxy at two of the polynyas. Our results show that concentrations and integrated POC stocks were higher within the polynyas compared to the off-shelf sites. Within the polynyas, vertical POC concentrations were higher in the Mertz and Ninnis polynyas compared to the Dalton polynya. Similarly, higher carbon export was measured in the diatom-dominated Mertz polynya, where large particles (53 μm) represented a significant fraction of the particulate 234Th and POC, compared to the small flagellate-dominated Dalton polynya, where almost all the particulate 234Th and POC were found in the smaller size fraction (1 - 53 μm). The POC to Chlorophyll-a ratios suggests that organic matter below the mixed layer in the polynyas consisted largely of fresh phytoplankton at this time of the year. In combination with a parallel study on phytoplankton production at these sites, we find that increased primary production at these polynyas does lead to greater concentrations and export of POC and a higher POC export efficiency.