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La cinetica de oxidacion de Fe(II) se estudio en el area del volcan submarino Tagoro, El Hierro y... more La cinetica de oxidacion de Fe(II) se estudio en el area del volcan submarino Tagoro, El Hierro y en el Oceano Atlantico Norte Subartico. En el area del volcan submarino Tagoro, las emisiones de Fe(II) fueron intermitentes e inversamente correlacionadas con los valores de pH. Las velocidades de oxidacion de Fe(II) fueron mas altas que las esperadas en aguas oligotroficas. Estas velocidades pueden explicarse por el efecto de las concentraciones de nutrientes de las muestras de agua de mar, en particular los silicatos. Los estudios de la cinetica de oxidacion de Fe(II) en condiciones naturales llevadas a cabo en el Atlantico Subartico y en el Mar de Labrador muestran que la temperatura, el pH y la salinidad fueron las variables maestras que controlaron la cinetica de oxidacion de Fe(II). Sin embargo, las fuentes y las caracteristicas de la materia organica presente son factores importantes que influyen en la oxidacion de Fe(II), mostrando efectos tanto positivos como negativos sobre l...
El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado d... more El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado de afección y la recuperación sobre el ecosistema marino del volcán submarino de la isla de El Hierro, haciéndolo extensible a otras regiones canarias de posible interés hidrotermal o vulcanológico. En este sentido, se ha investigado además el volcán de "Enmedio", entre las islas de Gran Canaria y Tenerife. Para ello, se realizará un estudio completo de las propiedades físico-químicas, biológicas y geológicas en las dos áreas descritas (Figura 1).
El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado d... more El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado de afección y la recuperación sobre el ecosistema marino del volcán submarino de la isla de El Hierro, haciéndolo extensible a otras regiones canarias de posible interés hidrotermal o vulcanológico. En este sentido, se ha investigado además el volcán de “enmedio”, entre las islas de Gran Canaria y Tenerife y el sur de La Palma (Fuentesanta). Para ello, se realizará un estudio completo de las propiedades físico-químicas, biológicas y geológicas en las áreas descritasIE
Biogeosciences, 2020
The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist almost exclusive... more The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist almost exclusively of Fe(III)-ligand complexes. Yet in most aqueous environments a poorly defined fraction of DFe also exists as Fe(II), the speciation of which is uncertain. Here we deploy flow injection analysis to measure in situ Fe(II) concentrations during a series of mesocosm/microcosm/multistressor experiments in coastal environments in addition to the decay rate of this Fe(II) when moved into the dark. During five mesocosm/microcosm/multistressor experiments in Svalbard and Patagonia, where dissolved (0.2 µm) Fe and Fe(II) were quantified simultaneously, Fe(II) constituted 24 %-65 % of DFe, suggesting that Fe(II) was a large fraction of the DFe pool. When this Fe(II) was allowed to decay in the dark, the vast majority of measured oxidation rate constants were less than calculated constants derived from ambient temperature, salinity, pH, and dissolved O 2. The oxidation rates of Fe(II) spikes added to Atlantic seawater more closely matched calculated rate constants. The difference between observed and theoretical decay rates in Svalbard and Patagonia was most pronounced at Fe(II) concentrations < 2 nM, suggesting that the effect may have arisen from organic Fe(II) ligands. This apparent enhancement of Fe(II) stability under post-bloom conditions and the existence of such a high fraction of DFe as Fe(II) challenge the assumption that DFe speciation in coastal seawater is dominated by ligand bound-Fe(III) species.
Biogeosciences Discussions, 2018
The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist exclusively of F... more The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist exclusively of Fe(III)-ligand complexes. Yet in most aqueous environments a poorly defined fraction of DFe also exists as Fe(II). Here we deploy flow injection analysis to measure in-situ Fe(II) concentrations during a series of mesocosm/microcosm experiments in coastal environments in addition to the decay rate of this Fe(II) when moved into the dark. During 5 mesocosm/microcosm experiments in Svalbard and Patagonia, where dissolved (0.2 µm) Fe and Fe(II) were quantified simultaneously, Fe(II) constituted 24-65% of DFe suggesting that Fe(II) was a large fraction of the DFe pool. When this Fe(II) was allowed to decay in the dark, the vast majority of measured oxidation rate constants were retarded relative to calculated constants derived from ambient temperature, salinity, pH and dissolved O 2. The oxidation rates of Fe(II) spikes added to Atlantic seawater more closely matched calculated rate constants. The difference between observed and theoretical decay rates in Svalbard and Patagonia was most pronounced at Fe(II) concentrations <2 nM and attributed to a stabilising effect of cellular exudates upon Fe(II). This enhanced stability of Fe(II) under post-bloom conditions, and the existence of such a high fraction of DFe as Fe(II), challenges the assumption that DFe speciation is dominated by ligand bound-Fe(III) species.
Marine Chemistry, 2017
The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Isla... more The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in the waters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruises were carried out two years after the eruptive process in October 2013, March 2014 and May 2015. The results from these cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pH F,is (pH in free scale, at in situ conditions) located in the proximity of the main cone. Maximum values in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle resuspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over the main and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pH F,is values. Observations showed an important variability in both pH F,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t 1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pH F,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.
Marine Chemistry, 2018
The Fe(II) oxidation rate was studied in different water masses present in the subartic North Atl... more The Fe(II) oxidation rate was studied in different water masses present in the subartic North Atlantic ocean along the 59.5ºN transatlantic section. Temperature, pH, salinity and total organic carbon (TOC) in natural conditions, fixed temperature conditions and both fixed temperature and pH conditions, were considered in order to understand the combined effects of the variables that control the Fe(II) oxidation kinetics in the ocean. The study shows that in natural conditions, temperature was the master variable which controled 75% of the pseudo-first order kinetics rate (k'). This value rose to 90% when pHF (free scale) and salinity were also considered. At a fixed temperature, 72% of k' was controlled by pH and at both fixed temperature and pH, salinity controled 62% of the Fe(II) oxidation rate. Sources and characteristics of TOC are important factors influencing the oxidation of Fe(II). The organic matter had both positive and negative effects on Fe(II) oxidation. In surface and coastal waters, TOC accelerated k', decreasing the Fe(II) half-life time (t1/2). In Subpolar Mode Water, Labrador Sea Water (for the Irminger Basin) and Denmark Straight Overflow Water, TOC slowed down k', increasing Fe(II) t1/2. This shifting behaviour where TOC affects Fe(II) oxidation depending on its marine or terrestrial origin, depth and remineralization stage proves that TOC cannot be used as a variable in an equation describing k'. The temperature dependence study indicated that the energy requirement for Fe(II) oxidation in surface waters was 32% lower than the required for bottom waters at both pH 7.7 and 8.0. This variability confirmed the importance of the organic matter composition of the selected samples. The Fe(II) oxidation rate constants in the region can be obtained from an empirical equation considering the natural conditions of temperature, pHF and salinity for the area, producing an error of estimation of 0.0072 min-1. This equation should be incorporated in global Fe models.
&lt;p&gt;Iron is an essential nutrient that limits primary productivity in up to ... more &lt;p&gt;Iron is an essential nutrient that limits primary productivity in up to 30% of the world&amp;#8217;s ocean. Redox and complexation reactions control its solubility and therefore the fraction of dissolved and bioavailable iron. The iron (II) oxidation kinetic process was studied at 25 stations in coastal seawater of the Macaronesia region (around Cape Verde, the Canary Islands and Madeira). Laboratory experiments were carried out to study the pseudo-first-order oxidation rate constant (&lt;em&gt;k&amp;#8217;&lt;/em&gt;, min&lt;sup&gt;-1&lt;/sup&gt;) over a range of pH (7.8-8.1) and temperature (T; 10-25&amp;#186;C). Measured k&amp;#8217; varied from the calculated &lt;em&gt;k&amp;#8217;&lt;/em&gt; (&lt;em&gt;k'&lt;/em&gt;&lt;sub&gt;cal&lt;/sub&gt;) at the same T, pH and salinity (S) at most stations. Measured iron (II) half-life times (t&lt;sub&gt;1/2&lt;/sub&gt;=ln2/&lt;em&gt;k&amp;#8217;&lt;/em&gt;; min) at the 25 stations ranged from 1.8-3.5 min (mean 1.9&amp;#177;0.8 min) and for all but two stations were lower than the theoretically calculated t&lt;sub&gt;1/2&lt;/sub&gt; of 3.2&amp;#177;0.2 min. The biogeochemical context was considered by analysing nutrients and variables associated with the organic matter spectral properties (CDOM and FDOM). A multilinear regression model indicated that &lt;em&gt;k&amp;#8217;&lt;/em&gt; can be described (R=0.921, SEE=0.064 for pH=8 and T=25&amp;#186;C) from a linear combination of three organic variables.&lt;/p&gt;&lt;p&gt;&lt;em&gt;k&amp;#8217;&lt;sup&gt;OM&lt;/sup&gt;&lt;/em&gt; = &lt;em&gt;k&amp;#8217;&lt;/em&gt;&lt;sub&gt;cal&lt;/sub&gt; -0.11* TDN + 29.9 * &lt;em&gt;b&lt;/em&gt;&lt;sub&gt;DOM&lt;/sub&gt; + 33.4 * C1&lt;sub&gt;humic&lt;/sub&gt;&lt;/p&gt;&lt;p&gt;where TDN is the total dissolved nitrogen, &lt;em&gt;b&lt;/em&gt;&lt;sub&gt;DOM&lt;/sub&gt; is the spectral peak obtained from coloured DOM analysis when protein-like or tyrosine-like components are present and C1&lt;sub&gt;humic&lt;/sub&gt; is the component associated with humic-like compounds obtained from the parallel factor analysis (PARAFAC) of the fluorescent DOM. Experimentally, &lt;em&gt;k&amp;#8217;&lt;/em&gt; and &lt;em&gt;k&lt;/em&gt;&amp;#8217;&lt;sup&gt;OM &lt;/sup&gt;provide the net result between the compounds that accelerate the process and those that slow it down. Results show that compounds with nitrogen in their structures mainly explain the observed &lt;em&gt;k&amp;#8217;&lt;/em&gt; increase for most of the samples, although other components could also present a relevant role.&lt;/p&gt;
La cinetica de oxidacion de Fe(II) se estudio en el area del volcan submarino Tagoro, El Hierro y... more La cinetica de oxidacion de Fe(II) se estudio en el area del volcan submarino Tagoro, El Hierro y en el Oceano Atlantico Norte Subartico. En el area del volcan submarino Tagoro, las emisiones de Fe(II) fueron intermitentes e inversamente correlacionadas con los valores de pH. Las velocidades de oxidacion de Fe(II) fueron mas altas que las esperadas en aguas oligotroficas. Estas velocidades pueden explicarse por el efecto de las concentraciones de nutrientes de las muestras de agua de mar, en particular los silicatos. Los estudios de la cinetica de oxidacion de Fe(II) en condiciones naturales llevadas a cabo en el Atlantico Subartico y en el Mar de Labrador muestran que la temperatura, el pH y la salinidad fueron las variables maestras que controlaron la cinetica de oxidacion de Fe(II). Sin embargo, las fuentes y las caracteristicas de la materia organica presente son factores importantes que influyen en la oxidacion de Fe(II), mostrando efectos tanto positivos como negativos sobre l...
El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado d... more El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado de afección y la recuperación sobre el ecosistema marino del volcán submarino de la isla de El Hierro, haciéndolo extensible a otras regiones canarias de posible interés hidrotermal o vulcanológico. En este sentido, se ha investigado además el volcán de "Enmedio", entre las islas de Gran Canaria y Tenerife. Para ello, se realizará un estudio completo de las propiedades físico-químicas, biológicas y geológicas en las dos áreas descritas (Figura 1).
El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado d... more El objetivo principal del proyecto VULcanología CAnaria submariNA, VULCANA, es evaluar el grado de afección y la recuperación sobre el ecosistema marino del volcán submarino de la isla de El Hierro, haciéndolo extensible a otras regiones canarias de posible interés hidrotermal o vulcanológico. En este sentido, se ha investigado además el volcán de “enmedio”, entre las islas de Gran Canaria y Tenerife y el sur de La Palma (Fuentesanta). Para ello, se realizará un estudio completo de las propiedades físico-químicas, biológicas y geológicas en las áreas descritasIE
Biogeosciences, 2020
The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist almost exclusive... more The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist almost exclusively of Fe(III)-ligand complexes. Yet in most aqueous environments a poorly defined fraction of DFe also exists as Fe(II), the speciation of which is uncertain. Here we deploy flow injection analysis to measure in situ Fe(II) concentrations during a series of mesocosm/microcosm/multistressor experiments in coastal environments in addition to the decay rate of this Fe(II) when moved into the dark. During five mesocosm/microcosm/multistressor experiments in Svalbard and Patagonia, where dissolved (0.2 µm) Fe and Fe(II) were quantified simultaneously, Fe(II) constituted 24 %-65 % of DFe, suggesting that Fe(II) was a large fraction of the DFe pool. When this Fe(II) was allowed to decay in the dark, the vast majority of measured oxidation rate constants were less than calculated constants derived from ambient temperature, salinity, pH, and dissolved O 2. The oxidation rates of Fe(II) spikes added to Atlantic seawater more closely matched calculated rate constants. The difference between observed and theoretical decay rates in Svalbard and Patagonia was most pronounced at Fe(II) concentrations < 2 nM, suggesting that the effect may have arisen from organic Fe(II) ligands. This apparent enhancement of Fe(II) stability under post-bloom conditions and the existence of such a high fraction of DFe as Fe(II) challenge the assumption that DFe speciation in coastal seawater is dominated by ligand bound-Fe(III) species.
Biogeosciences Discussions, 2018
The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist exclusively of F... more The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist exclusively of Fe(III)-ligand complexes. Yet in most aqueous environments a poorly defined fraction of DFe also exists as Fe(II). Here we deploy flow injection analysis to measure in-situ Fe(II) concentrations during a series of mesocosm/microcosm experiments in coastal environments in addition to the decay rate of this Fe(II) when moved into the dark. During 5 mesocosm/microcosm experiments in Svalbard and Patagonia, where dissolved (0.2 µm) Fe and Fe(II) were quantified simultaneously, Fe(II) constituted 24-65% of DFe suggesting that Fe(II) was a large fraction of the DFe pool. When this Fe(II) was allowed to decay in the dark, the vast majority of measured oxidation rate constants were retarded relative to calculated constants derived from ambient temperature, salinity, pH and dissolved O 2. The oxidation rates of Fe(II) spikes added to Atlantic seawater more closely matched calculated rate constants. The difference between observed and theoretical decay rates in Svalbard and Patagonia was most pronounced at Fe(II) concentrations <2 nM and attributed to a stabilising effect of cellular exudates upon Fe(II). This enhanced stability of Fe(II) under post-bloom conditions, and the existence of such a high fraction of DFe as Fe(II), challenges the assumption that DFe speciation is dominated by ligand bound-Fe(III) species.
Marine Chemistry, 2017
The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Isla... more The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in the waters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruises were carried out two years after the eruptive process in October 2013, March 2014 and May 2015. The results from these cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pH F,is (pH in free scale, at in situ conditions) located in the proximity of the main cone. Maximum values in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle resuspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over the main and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pH F,is values. Observations showed an important variability in both pH F,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t 1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pH F,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.
Marine Chemistry, 2018
The Fe(II) oxidation rate was studied in different water masses present in the subartic North Atl... more The Fe(II) oxidation rate was studied in different water masses present in the subartic North Atlantic ocean along the 59.5ºN transatlantic section. Temperature, pH, salinity and total organic carbon (TOC) in natural conditions, fixed temperature conditions and both fixed temperature and pH conditions, were considered in order to understand the combined effects of the variables that control the Fe(II) oxidation kinetics in the ocean. The study shows that in natural conditions, temperature was the master variable which controled 75% of the pseudo-first order kinetics rate (k'). This value rose to 90% when pHF (free scale) and salinity were also considered. At a fixed temperature, 72% of k' was controlled by pH and at both fixed temperature and pH, salinity controled 62% of the Fe(II) oxidation rate. Sources and characteristics of TOC are important factors influencing the oxidation of Fe(II). The organic matter had both positive and negative effects on Fe(II) oxidation. In surface and coastal waters, TOC accelerated k', decreasing the Fe(II) half-life time (t1/2). In Subpolar Mode Water, Labrador Sea Water (for the Irminger Basin) and Denmark Straight Overflow Water, TOC slowed down k', increasing Fe(II) t1/2. This shifting behaviour where TOC affects Fe(II) oxidation depending on its marine or terrestrial origin, depth and remineralization stage proves that TOC cannot be used as a variable in an equation describing k'. The temperature dependence study indicated that the energy requirement for Fe(II) oxidation in surface waters was 32% lower than the required for bottom waters at both pH 7.7 and 8.0. This variability confirmed the importance of the organic matter composition of the selected samples. The Fe(II) oxidation rate constants in the region can be obtained from an empirical equation considering the natural conditions of temperature, pHF and salinity for the area, producing an error of estimation of 0.0072 min-1. This equation should be incorporated in global Fe models.
&lt;p&gt;Iron is an essential nutrient that limits primary productivity in up to ... more &lt;p&gt;Iron is an essential nutrient that limits primary productivity in up to 30% of the world&amp;#8217;s ocean. Redox and complexation reactions control its solubility and therefore the fraction of dissolved and bioavailable iron. The iron (II) oxidation kinetic process was studied at 25 stations in coastal seawater of the Macaronesia region (around Cape Verde, the Canary Islands and Madeira). Laboratory experiments were carried out to study the pseudo-first-order oxidation rate constant (&lt;em&gt;k&amp;#8217;&lt;/em&gt;, min&lt;sup&gt;-1&lt;/sup&gt;) over a range of pH (7.8-8.1) and temperature (T; 10-25&amp;#186;C). Measured k&amp;#8217; varied from the calculated &lt;em&gt;k&amp;#8217;&lt;/em&gt; (&lt;em&gt;k'&lt;/em&gt;&lt;sub&gt;cal&lt;/sub&gt;) at the same T, pH and salinity (S) at most stations. Measured iron (II) half-life times (t&lt;sub&gt;1/2&lt;/sub&gt;=ln2/&lt;em&gt;k&amp;#8217;&lt;/em&gt;; min) at the 25 stations ranged from 1.8-3.5 min (mean 1.9&amp;#177;0.8 min) and for all but two stations were lower than the theoretically calculated t&lt;sub&gt;1/2&lt;/sub&gt; of 3.2&amp;#177;0.2 min. The biogeochemical context was considered by analysing nutrients and variables associated with the organic matter spectral properties (CDOM and FDOM). A multilinear regression model indicated that &lt;em&gt;k&amp;#8217;&lt;/em&gt; can be described (R=0.921, SEE=0.064 for pH=8 and T=25&amp;#186;C) from a linear combination of three organic variables.&lt;/p&gt;&lt;p&gt;&lt;em&gt;k&amp;#8217;&lt;sup&gt;OM&lt;/sup&gt;&lt;/em&gt; = &lt;em&gt;k&amp;#8217;&lt;/em&gt;&lt;sub&gt;cal&lt;/sub&gt; -0.11* TDN + 29.9 * &lt;em&gt;b&lt;/em&gt;&lt;sub&gt;DOM&lt;/sub&gt; + 33.4 * C1&lt;sub&gt;humic&lt;/sub&gt;&lt;/p&gt;&lt;p&gt;where TDN is the total dissolved nitrogen, &lt;em&gt;b&lt;/em&gt;&lt;sub&gt;DOM&lt;/sub&gt; is the spectral peak obtained from coloured DOM analysis when protein-like or tyrosine-like components are present and C1&lt;sub&gt;humic&lt;/sub&gt; is the component associated with humic-like compounds obtained from the parallel factor analysis (PARAFAC) of the fluorescent DOM. Experimentally, &lt;em&gt;k&amp;#8217;&lt;/em&gt; and &lt;em&gt;k&lt;/em&gt;&amp;#8217;&lt;sup&gt;OM &lt;/sup&gt;provide the net result between the compounds that accelerate the process and those that slow it down. Results show that compounds with nitrogen in their structures mainly explain the observed &lt;em&gt;k&amp;#8217;&lt;/em&gt; increase for most of the samples, although other components could also present a relevant role.&lt;/p&gt;