The composition of dissolved iron in the dusty surface ocean : an exploration using size-fractionated iron-binding ligands
Fitzsimmons, Jessica N.
Bundy, Randelle M.
Al-Subiai, Sherain N.
Barbeau, Katherine A.
Boyle, Edward A.
MetadataShow full item record
KeywordIron; Iron ligands; CLE-ACSV; Colloids; Ultrafiltration; Trace metals; GEOTRACES; North Atlantic Ocean; Chemical oceanography
The size partitioning of dissolved iron and organic iron-binding ligands into soluble and colloidal phases was investigated in the upper 150 m of two stations along the GA03 U.S. GEOTRACES North Atlantic transect. The size fractionation was completed using cross-flow filtration methods, followed by analysis by isotope dilution inductively-coupled plasma mass spectrometry (ID-ICP-MS) for iron and competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) for iron-binding ligands. On average, 80% of the 0.1-0.65 nM dissolved iron (<0.2 μm) was partitioned into the colloidal iron (cFe) size fraction (10 kDa < cFe < 0.2 μm), as expected for areas of the ocean underlying a dust plume. The 1.3-2.0 nM strong organic iron-binding ligands, however, overwhelmingly (75-77%) fell into the soluble size fraction (<10 kDa). As a result, modeling the dissolved iron size fractionation at equilibrium using the observed ligand partitioning did not accurately predict the iron partitioning into colloidal and soluble pools. This suggests that either a portion of colloidal ligands are missed by current electrochemical methods because they react with iron more slowly than the equilibration time of our CLE-ACSV method, or part of the observed colloidal iron is actually inorganic in composition and thus cannot be predicted by our model of unbound iron-binding ligands. This potentially contradicts the prevailing view that greater than 99% of dissolved iron in the ocean is organically complexed. Untangling the chemical form of iron in the upper ocean has important implications for surface ocean biogeochemistry and may affect iron uptake by phytoplankton.
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Marine Chemistry 173 (2015): 125-135, doi:10.1016/j.marchem.2014.09.002.
Showing items related by title, author, creator and subject.
Song, Jiasheng; Clagett-Dame, Margaret; Peterson, Richard E.; Hahn, Mark E.; Westler, William M.; Sicinski, Rafal R.; DeLuca, Hector F. (National Academy of Sciences, 2002-10-30)The aryl hydrocarbon receptor (AHR) is a ligand-inducible transcription factor that is best known because it mediates the actions of polycyclic and halogenated aromatic hydrocarbon environmental toxicants such as ...
Hestermann, Eli V. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1999-12)Aryl hydrocarbon receptor (AHR) expression and activity was characterized in the teleost hepatoma cell line, PLHC-1. This work was carried out in order to gain insights into mechanisms of halogenated aromatic hydrocarbon ...
Identification of cinnabarinic acid as novel endogenous aryl hydrocarbon receptor ligand that drives IL-22 production Lowe, Margaret M.; Mold, Jeff E.; Kanwar, Bittoo; Huang, Yong; Louie, Alexander; Pollastri, Michael P.; Wang, Cuihua; Patel, Gautam; Franks, Diana G.; Schlezinger, Jennifer; Sherr, David H.; Silverstone, Allen E.; Hahn, Mark E.; McCune, Joseph M. (Public Library of Science, 2014-02-03)The aryl hydrocarbon receptor (AHR) binds to environmental toxicants including synthetic halogenated aromatic hydrocarbons and is involved in a diverse array of biological processes. Recently, the AHR was shown to control ...