The origin, composition, and reactivity of dissolved iron(III) complexes in coastal organic- and iron-rich sediments

Beckler, Jordon S.; Jones, Morris; Taillefert, Martial

doi:10.1016/j.gca.2014.12.017

Cited by 27 publications

(24 citation statements)

References 99 publications

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“…Theoretical predictions (Millero et al 1987) are displayed for comparison. The first-order rate constant, k, has been adjusted to find the best fit of data to a first-order rate (FOR) equation (plot a), [Fe] t = [Fe] 0 9 e -kt , from which the half-lives, t 1/2 (min), are displayed in plot (b) sediments studied here also means that there is no evidence for any significant concentrations of Fe(III) organic complexes as reported for anoxic porewaters in estuarine systems (Jones et al 2011;Beckler et al 2015).…”

Section: Discussionmentioning

confidence: 70%

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

et al. 2017

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Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2-5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe,\0.15 lm) mainly ([85%) consisted of Fe(II) and gradually increased from 0.4 to 15 lM at the sediment surface to *100-170 lM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) ([85% sFe, \0.02 lm). Sub-surface dFe(II) maxima were enriched in light isotopes (d 56 Fe -2.0 to -1.5%), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to -3.0%). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water Responsible Editor: Martin Solan.Electronic supplementary material The online version of this article (doi:10.1007/s10533-017-0309-x) contains supplementary material, which is available to authorized users. 49-67 DOI 10.1007/s10533-017-0309-x oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after [7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23-31 lmol m -2 day -1 ) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas.

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Section: Discussionmentioning

confidence: 70%

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

et al. 2017

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“…As expected from thermodynamic considerations (Froelich et al, 1979), the onset of Fe(III) reduction was located below the Mn 21 production zone (45 mm), and Fe 21 reached concentrations as high as 600 mM at 65 mm then gradually decreasing with depth. Soluble organic-Fe(III) complexes, hypothesized to be produced during microbial Fe(III) reduction (Beckler et al, 2015), mirrored the Fe 21 profile, reached current intensities as high as 400 nA around 90 mm, then remained constant throughout the rest of the measured depths ( Fig. 1A and 6 mM and between 7 and 12 mM, respectively ( Fig.…”

Section: Resultsmentioning

confidence: 77%

Microbial manganese(III) reduction fuelled by anaerobic acetate oxidation

Szeinbaum

Lin

Brandes

et al. 2017

Environmental Microbiology

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Soluble manganese in the intermediate +III oxidation state (Mn ) is a newly identified oxidant in anoxic environments, whereas acetate is a naturally abundant substrate that fuels microbial activity. Microbial populations coupling anaerobic acetate oxidation to Mn reduction, however, have yet to be identified. We isolated a Shewanella strain capable of oxidizing acetate anaerobically with Mn as the electron acceptor, and confirmed this phenotype in other strains. This metabolic connection between acetate and soluble Mn represents a new biogeochemical link between carbon and manganese cycles. Genomic analyses uncovered four distinct genes that allow for pathway variations in the complete dehydrogenase-driven TCA cycle that could support anaerobic acetate oxidation coupled to metal reduction in Shewanella and other Gammaproteobacteria. An oxygen-tolerant TCA cycle supporting anaerobic manganese reduction is thus a new connection in the manganese-driven carbon cycle, and a new variable for models that use manganese as a proxy to infer oxygenation events on early Earth.

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“…Dissolved organic Fe(III) is a preferred electron acceptor for Fe(III)-reducing microorganisms, and it accelerated Fe cycling in the vegetated mesocosms because dissolved organic Fe(III) complexes are generally re duced more rapidly than solid-phase Fe(III) minerals (Beckler et al 2015). Although dissolved organic Fe(III) was not measured in our study, relatively high concentrations of dissolved organic Fe(III) have been found in saltmarsh creek sediments in previous studies (Koretsky et al 2008, Jones et al 2011, Beckler et al 2015.…”

Section: Influence Of Plants On Sediment Geochemistrymentioning

confidence: 99%

“…Both FeRR and SRR may be underestimated in sealed laboratory incubations, because the rapid reoxidation of Fe(II) and sulfides by sedge root activity, advective groundwater processes, and tidal pumping are not taken into account (Kristensen et al 2000, Tallifert et al 2007, Beckler et al 2015. In addition, dissolved organic substrate-mediated Fe(II)−Fe(III) cycling cannot occur in closed containers because roots are excluded (Beckler et al 2015).…”

Section: Total Anaerobic Metabolismmentioning

confidence: 99%

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Iron dynamics in a subtropical estuarine tidal marsh: effect of season and vegetation

Luo¹,

Huang²,

Tong³

et al. 2017

Mar. Ecol. Prog. Ser.

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The origin, composition, and reactivity of dissolved iron(III) complexes in coastal organic- and iron-rich sediments

Cited by 27 publications

References 99 publications

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

Microbial manganese(III) reduction fuelled by anaerobic acetate oxidation

Iron dynamics in a subtropical estuarine tidal marsh: effect of season and vegetation

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