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| Format: | Dataset Open Access |
| Language: | en |
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PANGAEA
2018
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| Online Access: | https://doi.org/10.1594/PANGAEA.924610 |
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| _version_ | 1867168206803697664 |
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| author | Samperio-Ramos, Guillermo Santana-Casiano, Juana Magdalena González-Dávila, Melchor |
| author_facet | Samperio-Ramos, Guillermo Santana-Casiano, Juana Magdalena González-Dávila, Melchor |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | 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. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_924610 |
| institution | PANGAEA |
| language | en |
| publishDate | 2018 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | 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) Samperio-Ramos, Guillermo Santana-Casiano, Juana Magdalena González-Dávila, Melchor Alkalinity, total; Alkalinity, total, standard error; Apparent oxidation rate; Apparent oxidation rate, standard error; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbon, organic, dissolved; Carbon, organic, dissolved, standard error; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Emiliania huxleyi; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Half-life time; Haptophyta; Laboratory experiment; Laboratory strains; Macro-nutrients; Not applicable; OA-ICC; Ocean acidification; Ocean Acidification International Coordination Centre; Other; Other metabolic rates; Oxygen; Oxygen, standard error; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; Pelagos; pH, total scale; Phytoplankton; Pseudo-first order oxidation rate; Pseudo-first order oxidation rate, standard error; Registration number of species; Salinity; Single species; Species; Temperature, water; Treatment; Type; Uniform resource locator/link to reference; Uronic acids, dissolved; Uronic acids, dissolved, standard error 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. |
| title | 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) |
| topic | Alkalinity, total; Alkalinity, total, standard error; Apparent oxidation rate; Apparent oxidation rate, standard error; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbon, organic, dissolved; Carbon, organic, dissolved, standard error; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Emiliania huxleyi; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Half-life time; Haptophyta; Laboratory experiment; Laboratory strains; Macro-nutrients; Not applicable; OA-ICC; Ocean acidification; Ocean Acidification International Coordination Centre; Other; Other metabolic rates; Oxygen; Oxygen, standard error; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; Pelagos; pH, total scale; Phytoplankton; Pseudo-first order oxidation rate; Pseudo-first order oxidation rate, standard error; Registration number of species; Salinity; Single species; Species; Temperature, water; Treatment; Type; Uniform resource locator/link to reference; Uronic acids, dissolved; Uronic acids, dissolved, standard error |
| url | https://doi.org/10.1594/PANGAEA.924610 |