Ocean acidification affects iron speciation in seawater

Breitbarth, Eike; Bellerby, Richard; Neill, Craig; Ardelan, Murat Van; Meyerhöfer, Michael; Zöllner, Eckart; Croot, Peter; Riebesell, Ulf

doi:10.5194/bgd-6-6781-2009

Cited by 13 publications

(4 citation statements)

References 54 publications

(44 reference statements)

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“…As has previously been demonstrated (Santana-Casiano et al, 2000;Pullin and Cabaniss, 2003;González et al, 2016), the oxidation rate decreases as a function of the pH (Figure 2), giving minimum oxidation rates at the higher values of studied pH. The data presented here are also comparable with those obtained by Breitbarth et al (2009a) during a coastal seawater mesocosm experiment, where the authors linked the significant increase of Fe(II) half-life time to Fe(II) complexation by biologically mediated organic ligands, especially in the lower pH treatments. According to the results presented here (Figure 1), the organic iron ligands present in SWEX affect the kinetic behavior of iron in the pH-range studied, due to variations in the Fe(II) speciation.…”

Section: Kinetic Studiessupporting

confidence: 90%

“…The results obtained in SWEN are close to those from other studies carried out with North Atlantic seawater enriched with nutrients Samperio-Ramos et al, 2016), confirming that the silicate affected the Fe(II) oxidation rate and the lifetime of Fe(II). This study also shows a lessening in the oxidation rate of Fe(II) due to the presence of the organic ligands released from the coccolitophorid E. huxleyi, proving that the organic matter exuded by phytoplankton can preserve Fe(II) for longer periods in oxygen rich waters, as a result of the formation of ferrous organic complexes (Rijkenberg et al, 2006;Roy et al, 2008;Breitbarth et al, 2009a;González et al, 2014).…”

Section: Kinetic Studiesmentioning

confidence: 53%

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Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II) Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach

2018

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The potential effect of ocean acidification on the exudation of organic matter by phytoplankton and, consequently, on the iron redox chemistry is largely unknown. In this study, the coccolithophorid Emiliania huxleyi was exposed to different pCO 2 conditions (225-900 µatm), in order to determine the role of natural organic ligands on the Fe(II) oxidation rate. Oxidation kinetics of Fe(II) were studied as a function of pH (7.75-8.25) and dissolved organic carbon levels produced (0-141.11 µmol C L −1 ) during the different growth stages. The Fe(II) oxidation rate always decreased in the presence of exudates as compared to that in the exudates-free seawater. The organic ligands present in the coccolithophorid exudates were responsible for this decrease. The oxidation of Fe(II) in artificial seawater was also investigated at nanomolar levels over a range of pH (7.75-8.25) at 25 • C in the presence of different glucuronic acid concentrations. Dissolved uronic acids (DUA) slightly increased the experimental rate compared to control artificial seawater (ASW) which can be ascribed to the stabilization of the oxidized form by chelation. This behavior was a function of the Fe(II):DUA ratio and was a pH dependent process. A kinetic model in ASW, with a single organic ligand, was applied for computing the equilibrium constant (log K FeCHO+ = 3.68 ± 0.81 M −1 ) and the oxidation rate (log k FeCHO+ = 3.28 ± 0.41 M −1 min −1 ) for the Fe(II)-DUA complex (FeCHO + ), providing an excellent description of data obtained over a wide range of DUA concentrations and pH conditions. Considering the Marcus theory the Fe(III) complexing constant with DUA was limited to between 10 13 and 10 16 . For the seawater enriched with exudates of E. huxleyi a second kinetic modeling approach was carried out for fitting the Fe(II) speciation, and the contribution of each Fe(II) species to the overall oxidation rate as a function of the pH/pCO 2 conditions. The influence of organic ligands in the Fe(II) speciation diminished as pH decreased in solution. During the stationary growth phase, the FeCHO + complex became the most important contributor to the overall oxidation rate when pH was lower than 7.95. Because CO 2 levels modify the composition of excreted organic ligands, the redox behavior of Fe in solution may be affected by future acidification conditions.

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Section: Kinetic Studiessupporting

confidence: 90%

Section: Kinetic Studiesmentioning

confidence: 53%

Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II) Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach

2018

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“…The increase in Cu 2þ could lead to a higher toxicity for the growth of phytoplankton (Brand et al, 1986) and bacteria (Schreiber et al, 1985). Recent studies have demonstrated that ocean acidification does increase the availability of Fe in seawater (Breitbarth et al, 2009) and that Cu is toxic to diatoms (Pascal et al, 2010). Recent studies have demonstrated that ocean acidification does increase the availability of Fe in seawater (Breitbarth et al, 2009) and that Cu is toxic to diatoms (Pascal et al, 2010).…”

Section: Effect Of Ocean Acidificationmentioning

confidence: 99%

Physico-Chemical Controls on Seawater

Millero

2014

Treatise on Geochemistry

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“…Alternatively, the erosion of Cretaceous age Coastal Plain deposits that had undergone millions of years of chemical weathering, such as the kaolinite-rich deltaic clays of the Raritan Formation [Groot and Glass, 1960], could have enhanced reactive iron fluxes. Ocean acidification could also have increased iron concentrations [Breitbarth et al, 2009].…”

Section: Comparison To the Modern Amazon Shelfmentioning

confidence: 99%

An Appalachian Amazon? Magnetofossil evidence for the development of a tropical river‐like system in the mid‐Atlantic United States during the Paleocene‐Eocene thermal maximum

et al. 2009

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[1] On the mid-Atlantic Coastal Plain of the United States, Paleocene sands and silts are replaced during the Paleocene-Eocene Thermal Maximum (PETM) by the kaolinite-rich Marlboro Clay. The clay preserves abundant magnetite produced by magnetotactic bacteria and novel, presumptively eukaryotic, ironbiomineralizing microorganisms. Using ferromagnetic resonance spectroscopy and electron microscopy, we map the magnetofossil distribution in the context of stratigraphy and carbon isotope data and identify three magnetic facies in the clay: one characterized by a mix of detrital particles and magnetofossils, a second with a higher magnetofossil-to-detrital ratio, and a third with only transient magnetofossils. The distribution of these facies suggests that suboxic conditions promoting magnetofossil production and preservation occurred throughout inner middle neritic sediments of the Salisbury Embayment but extended only transiently to outer neritic sediments and the flanks of the embayment. Such a distribution is consistent with the development of a system resembling a modern tropical river-dominated shelf.

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Ocean acidification affects iron speciation in seawater

Cited by 13 publications

References 54 publications

Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II) Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach

Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II) Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach

Physico-Chemical Controls on Seawater

An Appalachian Amazon? Magnetofossil evidence for the development of a tropical river‐like system in the mid‐Atlantic United States during the Paleocene‐Eocene thermal maximum

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