Samperio-Ramos, Guillermo; Santana-Casiano, Juana Magdalena; González-Dávila, Melchor (2018): Pseudo-first order oxidation rate, apparent oxidation rate and half-life time of Fe(II) under different pH conditions for seawater enriched with nutrients (SWEN) and seawater enriched organic exudates (SWEX) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.924610
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Abstract:
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 pCO2 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) 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 KFeCHO+ = 3.68 ± 0.81/M) and the oxidation rate (log kFeCHO+ = 3.28 +- 0.41/M/min) 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 1013 and 1016. 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/pCO2 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 CO2 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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Supplement to:
Samperio-Ramos, Guillermo; Santana-Casiano, Juana Magdalena; González-Dávila, Melchor (2018): Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II) Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach. Frontiers in Marine Science, 5, https://doi.org/10.3389/fmars.2018.00210
Related to:
Samperio-Ramos, Guillermo; González-Dávila, Melchor; Santana-Casiano, Juana Magdalena (2018): Impact on the Fe redox cycling of organic ligands released by Synechococcus PCC 7002, under different iron fertilization scenarios. Modeling approach. Journal of Marine Systems, 182, 67-78, https://doi.org/10.1016/j.jmarsys.2018.01.009
Samperio-Ramos, Guillermo; Santana-Casiano, Juana Magdalena; Gonzalez Davila, Melchor (2016): Effect of ocean warming and acidification on the Fe(II) oxidation rate in oligotrophic and eutrophic natural waters. Biogeochemistry, 128(1-2), 19-34, https://doi.org/10.1007/s10533-016-0192-x
Samperio-Ramos, Guillermo; Santana-Casiano, Juana Magdalena; González-Dávila, Melchor (2018): Variability in the production of organic ligands, by Synechococcus PCC 7002, under different iron scenarios. Journal of Oceanography, 74(3), 277-286, https://doi.org/10.1007/s10872-017-0457-6
Samperio-Ramos, Guillermo; Santana-Casiano, Juana Magdalena; González-Dávila, Melchor; Ferreira, Sonia; Coimbra, Manuel A (2017): Variability in the organic ligands released by Emiliania huxleyi under simulated ocean acidification conditions. AIMS Environmental Science, 4(6), 788-808, https://doi.org/10.3934/environsci.2017.6.788
Further details:
Gattuso, Jean-Pierre; Epitalon, Jean-Marie; Lavigne, Héloïse; Orr, James C; Gentili, Bernard; Proye, Aurélien; Soetaert, Karline; Rae, James (2016): seacarb: seawater carbonate chemistry with R. R package version 3.1. https://cran.r-project.org/package=seacarb
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Comment:
In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2018-05-23.
Parameter(s):
License:
Creative Commons Attribution 4.0 International (CC-BY-4.0)
Status:
Curation Level: Enhanced curation (CurationLevelC)
Size:
512 data points