Seasonal iron depletion in temperate shelf seas

Antony J. Birchill*, Angela Milne, E. Malcolm S. Woodward, Carolyn Harris, Amber Annett, Dagmara Rusiecka, Eric P. Achterberg, Martha Gledhill, Simon J. Ussher, Paul J. Worsfold, Walter Geibert, Maeve C. Lohan

*Corresponding author for this work

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Our study followed the seasonal cycling of soluble (SFe), colloidal (CFe), dissolved (DFe), total dissolvable (TDFe), labile particulate (LPFe), and total particulate (TPFe) iron in the Celtic Sea (NE Atlantic Ocean). Preferential uptake of SFe occurred during the spring bloom, preceding the removal of CFe. Uptake and export of Fe during the spring bloom, coupled with a reduction in vertical exchange, led to Fe deplete surface waters (<0.2 nM DFe; 0.11 nM LPFe, 0.45 nM TDFe, and 1.84 nM TPFe) during summer stratification. Below the seasonal thermocline, DFe concentrations increased from spring to autumn, mirroring NO3 and consistent with supply from remineralized sinking organic material, and cycled independently of particulate Fe over seasonal timescales. These results demonstrate that summer Fe availability is comparable to the seasonally Fe limited Ross Sea shelf and therefore is likely low enough to affect phytoplankton growth and species composition.

Original languageEnglish
Pages (from-to)8987-8996
Number of pages10
JournalGeophysical Research Letters
Issue number17
Early online date14 Sept 2017
Publication statusPublished - 26 Sept 2017


  • Celtic Sea
  • colloidal iron
  • dissolved iron
  • nitrate
  • particulate iron
  • shelf sea biogeochemistry
  • UKRI
  • NERC
  • NE/L501840/1
  • NE/K001779/1
  • NE/K002023/1
  • NE/K001973/1
  • NE/K002058/1


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