Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean): Iron biogeochemistry

Loes J. A. Gerringa*, Anne-Carlijn Alderkamp, Patrick Laan, Charles-Edouard Thuroczy, Hein J. W. De Baar, Matthew M. Mills, Gert L. van Dijken, Hans van Haren, Kevin R. Arrigo

*Corresponding author for this work

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Abstract

Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January-February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive continental shelves surrounding the Antarctic continent. However, the polynyas of the Amundsen Sea harbor the highest concentrations of phytoplankton anywhere in Antarctica. Here we present data showing the likely sources of Fe that enable such a productive and long lasting phytoplankton bloom. Circumpolar Deep Water (CDW) flows over the bottom of the shelf into the Pine Island Bay where DFe and TDFe were observed to increase from 0.2 to 0.4 nM DFe and from 0.3-4.0 to 7-14 nM TDFe, respectively. At the southern end of Pine Island Bay, the CDW upwelled under the Pine Island Glacier, bringing nutrients (including Fe) to the surface and melting the base of the glacier. Concentrations of DFe in waters near the Pine Island Glacier and the more westward lying Crosson, Dotson, and Getz Ice Shelves varied between 0.40 and 1.31 nM, depending on the relative magnitude of upwelling, turbulent mixing, and melting. These values represent maximum concentrations since associated ligands (which increase the solubility of Fe in seawater) were saturated with Fe (Thuroczy et al., 2012). The TDFe concentrations were very high compared to what previously has been measured in the Southern Ocean, varying between 3 and 106 nM. In the Pine Island Polynya, macronutrients and DFe were consumed by the phytoplankton bloom and concentrations were very low. We calculate that atmospheric dust contributed

Original languageEnglish
Pages (from-to)16-31
Number of pages16
JournalDeep-Sea research part ii-Topical studies in oceanography
Volume71-76
DOIs
Publication statusPublished - 15-Sep-2012

Keywords

  • Fe
  • Fe fluxes
  • Dissolved Fe
  • Total dissolvable Fe
  • Southern Ocean
  • PINE ISLAND GLACIER
  • EQUATORIAL PACIFIC-OCEAN
  • CATHODIC STRIPPING VOLTAMMETRY
  • DISSOLVED IRON
  • ROSS SEA
  • ORGANIC COMPLEXATION
  • COLLOIDAL IRON
  • FERTILIZATION EXPERIMENT
  • TAXONOMIC VARIABILITY
  • MARINE-PHYTOPLANKTON

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