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Organic ligands control the concentrations of dissolved iron in Antarctic sea ice

Citation

Lannuzel, D and Grotti, M and Abelmoschi, ML and Van Der Merwe, P, Organic ligands control the concentrations of dissolved iron in Antarctic sea ice, Marine Chemistry, 174 pp. 120-130. ISSN 0304-4203 (2015) [Refereed Article]

Copyright Statement

Copyright 2015 Elsevier B.V.

DOI: doi:10.1016/j.marchem.2015.05.005

Abstract

The organic complexation of dissolved iron (DFe) was assessed in 5 snow, 34 sea ice, 12 brine and 24 under-ice seawater samples collected during a 22day time series in the East Antarctic sector in austral summer 2009. Similar to seawater, over 99% of DFe was bound to organic ligands in snow, sea ice and brines throughout the study. Dissolved organic ligand and Fe concentrations were higher in the brines and sea ice than in snow and seawater samples. In sea ice, [DFe] ranged from 2.1 to 81.0nM and organic Fe complexing ligands ([Lt]) ranged from 4.5 to 72.1nM, with complex stability log KFeL=21.023.0. Estimated concentrations of inorganic Fe ([Fe′]) in sea ice ranged from 0.1 to 98.2pM. In brines, [DFe] ranged from 0.3 to 34.6nM and [Lt] ranged from 5.9 to 41.4nM, with complex stability log KFeL=21.022.0. Estimated concentrations of inorganic Fe (Fe′) in brines ranged from 0.70 to 7.2pM. Organic ligands were nearly saturated with Fe in both sea ice and brines, with positive linear relationships observed between [DFe] and [Lt]: [Lt]=0.90 [DFe]+4.24 (R2=0.93, n=34) in sea ice and [Lt]=1.08[DFe]+4.86 (R2=0.98, n=12) in brines. Our results therefore suggest that the organic ligands produced by sea ice algae and bacteria keep Fe in the dissolved phase therefore enhancing its availability for the sea ice algal community. When DFe concentrations become higher than the ligand concentrations, non-organically bound Fe is transferred into the particulate phase by scavenging, biological uptake or precipitation processes. As sea ice starts to melt, DFe is released into seawater together with organic ligands, potentially increasing the residence time of Fe in Antarctic surface waters and its bio-availability for the phytoplankton community.

Item Details

Item Type:Refereed Article
Keywords:sea ice, organic ligands, Fe, iron
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Physical and Chemical Conditions of Water
Objective Field:Physical and Chemical Conditions of Water in Marine Environments
Author:Lannuzel, D (Dr Delphine Lannuzel)
Author:Van Der Merwe, P (Mr Pier Van Der Merwe)
ID Code:103854
Year Published:2015
Web of Science® Times Cited:6
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2015-10-28
Last Modified:2017-10-31
Downloads:0

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