Retention of dissolved iron and Fe<i><sup>II</sup></i> in an iron induced Southern Ocean phytoplankton bloom

Croot, Peter; Bowie, Andrew R.; Frew, Russell; Maldonado, Maria T.; Hall, Julie; Safi, Karl; Roche, J. La; Boyd, Philip W.; Law, Cliff S.

doi:10.1029/2001gl013023

Cited by 137 publications

(116 citation statements)

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“…In this study and SOIREE (Croot et al, 2001), Fe(II) was still detectable several days after an iron infusion. In SOIREE, limited measurements for Fe(II) in surface waters was made and no vertical profiles were performed, but there Fe(II) was found to be an appreciable fraction of the surface DFe even up to 4 days after the last infusion (Croot et al, 2001) during a period of low wind mixing. In the present study, we found that during the initial part of the study when wind mixing was lowest, Fe(II) was still detectable 7 days after the initial infusion (Fig.…”

Section: Fe(ii) Horizontal Distributionmentioning

confidence: 75%

“…9). Sunlight, and in particular UV radiation (Rijkenberg et al, in press), may however be a more important mechanism under normal low iron conditions in the open ocean (Croot et al, 2001). …”

Section: Model Resultsmentioning

confidence: 99%

“…Organic complexation of Fe II in seawater is suspected (Croot et al, 2001), based on slower Fe II oxidation rates, but as yet no definitive evidence has been presented. Fe(II) has been shown to be formed from photochemical processes in seawater, noticeably in the presence of uronic acids (Kuma et al, 1992;Ö ztü rk et al, 2004).…”

Section: Iron Speciation In Seawatermentioning

confidence: 99%

“…At the low temperatures found in high latitude waters and in the deep sea, it now appears that three key factors may influence iron redox speciation: (1) Significantly longer half-lives for Fe(II) (Croot et al, 2001) compared to tropical waters. (2) Increased solubility of inorganic Fe(III) species (Liu and Millero, 2002).…”

Section: Implications For Iron Redox Speciation In Seawatermentioning

confidence: 99%

“…The overall process causes a loss of dissolved iron (half-life 10-30 h; Gordon et al, 1998), as seen in early mesoscale iron enrichments performed in the Equatorial Pacific IronEX I (Gordon et al, 1998), IronEX II (Coale et al, 1996) and the Southern Ocean (Bowie et al, 2001). In the cold waters of the Southern Ocean, the oxidation rate for Fe II is significantly slower (Croot et al, 2001) and Fe II can became a significant proportion of the iron species in seawater. The present work examines the spatial and temporal changes in Fe II and H 2 O 2 , a key oxidant of Fe II , during the EisenEx experiment.…”

Section: Introductionmentioning

confidence: 99%

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Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. concentrations increased at the depth of the chlorophyll maximum when iron concentrations returned to pre-infusion concentrations (b80 pM) possibly due to biological production related to iron reductase activity.In this work, Fe(II) and dissolved iron were used as tracers themselves for subsequent iron infusions when no further SF 6 was added. EisenEx was subject to periods of weak and strong mixing. Slow mixing after the second infusion allowed significant concentrations of Fe(II) and Fe to exist for several days. During this time, dissolved and total iron in the infusion plume behaved almost conservatively as it was trapped between a relict mixed layer and a new rain-induced mixed layer. Using dissolved iron, a value for the vertical diffusion coefficient K z =6.7F0.7 cm 2 s À1 was obtained for this 2-day period. During a subsequent surface survey of the iron-enriched patch, elevated levels of Fe(II) were found in surface waters presumably from Fe(II) dissolved in the rainwater that was falling at this time.Model results suggest that the reaction between uncomplexed Fe(III) and O 2 À was a significant source of Fe(II) during EisenEx and helped to maintain high levels of Fe(II) in the water column. This phenomenon may occur in iron enrichment experiments when two conditions are met: (i) When Fe is added to a system already saturated with regard to organic complexation and (ii) when mixing processes are slow, thereby reducing the dispersion of iron into under-saturated waters. D

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Section: Fe(ii) Horizontal Distributionmentioning

confidence: 75%

Section: Model Resultsmentioning

confidence: 99%

Section: Iron Speciation In Seawatermentioning

confidence: 99%

Section: Implications For Iron Redox Speciation In Seawatermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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The impact of changing surface ocean conditions on the dissolution of aerosol iron

Fishwick

Sedwick

Lohan

et al. 2014

Global Biogeochemical Cycles

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The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 μm) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 μm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

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Adaptive Mechanisms of the Model Photosynthetic Organisms, Cyanobacteria, to Iron Deficiency

Jiang

Deng

et al. 2020

Microbial Photosynthesis

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Retention of dissolved iron and Fe^II in an iron induced Southern Ocean phytoplankton bloom

Abstract: Abstract.During

Cited by 137 publications

References 25 publications

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

The impact of changing surface ocean conditions on the dissolution of aerosol iron

Adaptive Mechanisms of the Model Photosynthetic Organisms, Cyanobacteria, to Iron Deficiency

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Retention of dissolved iron and FeII in an iron induced Southern Ocean phytoplankton bloom

Abstract: Abstract.During

Cited by 137 publications

References 25 publications

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

The impact of changing surface ocean conditions on the dissolution of aerosol iron

Adaptive Mechanisms of the Model Photosynthetic Organisms, Cyanobacteria, to Iron Deficiency

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Retention of dissolved iron and Fe^II in an iron induced Southern Ocean phytoplankton bloom