Influence of organic complexation on dissolved iron distribution in East Antarctic pack ice

Genovese, Cristina; Grotti, Marco; Jessica, Pittaluga; Ardini, Francisco; Janssens, Julie; Wuttig, Kathrin; Moreau, Sébastien; Lannuzel, Delphine

doi:10.1016/j.marchem.2018.04.005

Cited by 21 publications

(33 citation statements)

References 83 publications

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“…Within the sea ice, Fe can be converted into more readily available forms via abiotic (photoreduction and chemical complexation) and biotic (biological and enzymatic reduction at the cell surface) processes (Genovese et al., 2018; Kaplan & Ward, 2013; Tagliabue et al., 2009). Fe dissolution reactions could be augmented by freezing processes.…”

Section: Discussionmentioning

confidence: 99%

Nutrient Distribution in East Antarctic Summer Sea Ice: A Potential Iron Contribution From Glacial Basal Melt

et al. 2020

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Phytoplankton growth can be limited by the availability of the essential nutrient iron (Fe; Baar et al., 1990, 1995). The Southern Ocean (SO) is a classic example where high concentrations of macronutrients (nitrate, phosphate, and silicic acid) do not support the expected level of primary production due to low Fe concentrations. The SO has therefore been designated as a High Nutrient Low Chlorophyll (HNLC) area (Martin, 1990). In this context, sea ice plays a pivotal role as a natural and biogeochemically active Fe reservoir due to the high levels of Fe and organic matter concentrated from seawater during its formation

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Section: Discussionmentioning

confidence: 99%

Nutrient Distribution in East Antarctic Summer Sea Ice: A Potential Iron Contribution From Glacial Basal Melt

et al. 2020

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“…Lannuzel et al (2015) showed that the solubility of Fe in sea ice, snow, and brines was controlled by the presence of organic ligands, with high concentrations of up to 80 neq M Fe, and with the same logK′ as in seawater. Recently, Genovese et al (2018) made similar observations in east Antarctic pack ice. Ice algae and bacteria are considered to be the ligand source and when the ice melts, Fe and ligands are released into the ocean where the ligands continue to play a role in maintaining Fe solubility (Lannuzel et al, 2015 Even at the borders of the polynya, where sea ice was melting this did not result in detectable elevations of DFe-binding organic ligands.…”

Section: Relations Between Ligands and Water Mass Sediments And Sea Icementioning

confidence: 52%

The organic complexation of iron in the Ross sea

et al. 2019

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The Ross Sea Polynya (RSP) has the highest primary production of Antarctic waters. Iron (Fe) is one of the most important growth limiting factors in the Southern Ocean. Dissolved iron (DFe)binding organic ligands play an important ecological role because they increase the residence time of the scarce Fe. Therefore, we studied the DFe-binding organic ligands in the vicinity of the Ross Sea during a cruise between 20 December 2013 and 5 January 2014. The DFe-binding organic ligands were measured using Competing Ligand Exchange Cathodic Stripping Voltammetry (CLE-CSV) with TAC as competing ligand. The DFe-binding organic ligand concentrations always exceeded the DFe concentrations except in the bottom nepheloid layer of the RSP. No relationship was found between depth and DFe-binding organic ligand concentrations in the RSP indicating that these ligands are resistant to degradation and are probably exported by high salinity shelf water into the circumpolar current. DFe-binding organic ligand concentrations were highest in the RSP and the Antarctic Circumpolar Current (ACC) west of the Ross Sea, in association with seasonal phytoplankton blooms, although no correlation was found with parameters reflecting phytoplankton abundance or species. Phytoplankton sources and sinks of DFe-binding organic ligands are likely related to the seasonal progression of the bloom. In 39% of the samples, two DFe-binding organic ligand groups were distinguished based on the difference in binding strength. The distinction was especially clear in the RSP and in the ACC west of the RSP (54 and 77% of the samples, respectively) where blooms occurred and much less in the low biomass waters of the ACC east of the RSP and ice covered eastern part of the Ross Sea (15 and 10% of the samples, respectively). In these waters, other environmental factors, like sea ice melt, probably explain the absence of distinct relationships between primary production and ligand characteristics.

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“…Approximately 62% of the Fe-binding ligands are humics in the TPD flow path in the Arctic (Sukekava et al, 2018), and thus [L t ] TAC is probably underestimated for the NN method, the influence of HS on the results obtained were only for measurements at high NN concentrations when HS possibly cannot compete with NN (Laglera et al, 2011). However, NN ([NN] = 5 µM; log D = 2.9) has successfully been used to assess DFe speciation in Antarctic sea ice (Lannuzel et al, 2015;Genovese et al, 2018).…”

Section: One-ligand Modelmentioning

confidence: 99%

Iron Speciation in Fram Strait and Over the Northeast Greenland Shelf: An Inter-Comparison Study of Voltammetric Methods

et al. 2021

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Competitive ligand exchange – adsorptive cathodic stripping voltammetry (CLE-AdCSV) is a widely used technique to determine dissolved iron (Fe) speciation in seawater, and involves competition for Fe of a known added ligand (AL) with natural organic ligands. Three different ALs were used, 2-(2-thiazolylazo)-p-cresol (TAC), salicylaldoxime (SA) and 1-nitroso-2-napthol (NN). The total ligand concentrations ([Lt]) and conditional stability constants (log K′Fe’L) obtained using the different ALs are compared. The comparison was done on seawater samples from Fram Strait and northeast Greenland shelf region, including the Norske Trough, Nioghalvfjerdsfjorden (79N) Glacier front and Westwind Trough. Data interpretation using a one-ligand model resulted in [Lt]SA (2.72 ± 0.99 nM eq Fe) > [Lt]TAC (1.77 ± 0.57 nM eq Fe) > [Lt]NN (1.57 ± 0.58 nM eq Fe); with the mean of log K′Fe’L being the highest for TAC (log ′KFe’L(TAC) = 12.8 ± 0.5), followed by SA (log K′Fe’L(SA) = 10.9 ± 0.4) and NN (log K′Fe’L(NN) = 10.1 ± 0.6). These differences are only partly explained by the detection windows employed, and are probably due to uncertainties propagated from the calibration and the heterogeneity of the natural organic ligands. An almost constant ratio of [Lt]TAC/[Lt]SA = 0.5 – 0.6 was obtained in samples over the shelf, potentially related to contributions of humic acid-type ligands. In contrast, in Fram Strait [Lt]TAC/[Lt]SA varied considerably from 0.6 to 1, indicating the influence of other ligand types, which seemed to be detected to a different extent by the TAC and SA methods. Our results show that even though the SA, TAC and NN methods have different detection windows, the results of the one ligand model captured a similar trend in [Lt], increasing from Fram Strait to the Norske Trough to the Westwind Trough. Application of a two-ligand model confirms a previous suggestion that in Polar Surface Water and in water masses over the shelf, two ligand groups existed, a relatively strong and relatively weak ligand group. The relatively weak ligand group contributed less to the total complexation capacity, hence it could only keep part of Fe released from the 79N Glacier in the dissolved phase.

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Influence of organic complexation on dissolved iron distribution in East Antarctic pack ice

Cited by 21 publications

References 83 publications

Nutrient Distribution in East Antarctic Summer Sea Ice: A Potential Iron Contribution From Glacial Basal Melt

Nutrient Distribution in East Antarctic Summer Sea Ice: A Potential Iron Contribution From Glacial Basal Melt

The organic complexation of iron in the Ross sea

Iron Speciation in Fram Strait and Over the Northeast Greenland Shelf: An Inter-Comparison Study of Voltammetric Methods

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