Marie Boye | University Pierre and Marie Curie (original) (raw)
Papers by Marie Boye
Biogeosciences, 2011
Page 1. Biogeosciences, 8, 2947–2959, 2011 www.biogeosciences.net/8/2947/2011/ doi:10.5194/bg-8-2... more Page 1. Biogeosciences, 8, 2947–2959, 2011 www.biogeosciences.net/8/2947/2011/ doi:10.5194/bg-8-2947-2011 © Author(s) 2011. CC Attribution 3.0 License. Biogeosciences Nitrogen uptake by phytoplankton in the Atlantic sector of the ...
Marine Chemistry, 2011
The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) wer... more The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58' S and 57°33' S along the Greenwich Meridian during the austral summer 2008 in ...
Journal of Geophysical Research, 2011
1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone sout... more 1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone south of South Africa during a hydrographic transect, are described using a large set of measurements including full depth hydrography, Acoustic Doppler Current Profiler velocities, biogeochemical tracers, air-sea fluxes and altimetric sea surface height. Both eddies have a subtropical origin. The anticyclone is an Agulhas ring with convected core water of ∼12°C, and swirl velocities of 1 m s −1 . It was 9.5 months old when sampled and had crossed the Agulhas Ridge. Though sampled in summer, it was releasing ∼200 W m −2 (sensible plus latent heat flux) to the atmosphere. It was observed adjacent to the Subantarctic Front, illustrating the usual encounters of such structures with this front. The cyclone, marked by pronounced low oxygen and CFC anomalies revealing an origin at the continental slope, was 4.5 months old. It had swirl speeds of 0.3 m s −1 , and was coupled with the anticyclone when observed. From their kinematics and water mass properties both structures were found to transport subtropical water down to ∼900 m, the water trapped below this depth being either from the northern Subantarctic Zone, or local water. The two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the Subantarctic Zone.
1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone sout... more 1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone south of South Africa during a hydrographic transect, are described using a large set of measurements including full depth hydrography, Acoustic Doppler Current Profiler velocities, biogeochemical tracers, air-sea fluxes and altimetric sea surface height. Both eddies have a subtropical origin. The anticyclone is an Agulhas ring with convected core water of ∼12°C, and swirl velocities of 1 m s −1 . It was 9.5 months old when sampled and had crossed the Agulhas Ridge. Though sampled in summer, it was releasing ∼200 W m −2 (sensible plus latent heat flux) to the atmosphere. It was observed adjacent to the Subantarctic Front, illustrating the usual encounters of such structures with this front. The cyclone, marked by pronounced low oxygen and CFC anomalies revealing an origin at the continental slope, was 4.5 months old. It had swirl speeds of 0.3 m s −1 , and was coupled with the anticyclone when observed. From their kinematics and water mass properties both structures were found to transport subtropical water down to ∼900 m, the water trapped below this depth being either from the northern Subantarctic Zone, or local water. The two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the Subantarctic Zone.
Limnology and Oceanography, 2014
The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to ... more The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to 703S at 203E. Dissolved iron concentrations were low at 0.1}0.6 nM, with average concentrations of 0.25$0.13 nM. Organic iron complexing ligands were found to occur in excess of the dissolved iron concentration at 0.72$0.23 nM (equivalent to an excess of 0.5 nM), with
Global Biogeochemical Cycles, 2014
ABSTRACT Dissolved cobalt (DCo; < 0.2μm; 14 to 93 pM) and the apparent particulate cobalt ... more ABSTRACT Dissolved cobalt (DCo; < 0.2μm; 14 to 93 pM) and the apparent particulate cobalt (PCo; > 0.2μm; < 1 to 15 pM) were determined in the upper water-column (< 1000 m) of the Western Atlantic Ocean along the GEOTRACES-A02 section (64°N to 50°S). The lowest DCo concentrations, typical of a nutrient-type distribution were observed in surface waters of the subtropical domains. Strong linear relationships between DCo and phosphate (P) as well as meridional gradients of decreasing DCo from high latitudes were characterized and both linked to the Co biological requirement. External sources such as the Amazon and the atmospheric deposition were found to contribute significantly (> 10%) to the DCo stock of the mixed layer in the equatorial and north subtropical domains. Biotic and abiotic processes as well as the physical terms involved in the biogeochemical cycle of Co were defined and estimated. This allowed establishing the first global budget of DCo for the upper 100 m in the Western Atlantic. The biological DCo uptake flux was the dominant sink along the section, as reflected by the overall nutrient-type behavior of DCo. The regeneration varied widely vary within the different biogeochemical domains, accounting for 10% of the DCo-uptake rate in the subarctic gyre and for up to 85% in southern subtropical domain. These findings demonstrated that the regeneration is likely the prevailing source of DCo in the surface waters of the Western Atlantic, except in the subpolar domains where physically-driven sources can sustain the DCo biological requirement.
An iron enrichment experiment was carried out in the Polar Frontal Zone of the Southern Ocean dur... more An iron enrichment experiment was carried out in the Polar Frontal Zone of the Southern Ocean during the austral late spring on board of the german RV Polarstern (Nov. 2000). An eddy structure was selected to initiate the Fe-fertilized patch. In order to understand the Fe-dynamics, the complete physical and chemical speciation of iron was studied for first time in the upper-water column (0-100 m) of the fertilized-patch in the course of the bloom development over 23 days and compared to the ambient non-fertilized waters. The physical speciation of iron was investigated in several size-fractionated pools, as defined as: particulate>0.2 microm, dissolved <0.2 microm, 200kDa < colloids <0.2 microm and truly dissolved <200 kDa, using ultrafiltration technique and Fe(III)-detection by the FIA- Chemiluminescence method. The organic speciation of iron was studied in the dissolved and ultrafiltered truly dissolved (<200 kDa) samples using voltametric technique. The redox-s...
Marine Chemistry, 2011
The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) wer... more The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58&amp;#x27; S and 57°33&amp;#x27; S along the Greenwich Meridian during the austral summer 2008 in ...
Marine Chemistry, 2003
A transect across the eastern North Atlantic from 42jN, 23jW towards the European continental she... more A transect across the eastern North Atlantic from 42jN, 23jW towards the European continental shelf and English Channel shows a gradient of increasing concentrations of dissolved iron (0.7 -1.9 nM), iron-binding ligands and iron(II) across the continental rise. Other data, notably aluminium and manganese, indicate that the increases are part of a front in the metal concentrations, which is due to admixture of bottom waters. Metal fronts in shelf waters are well known, but it was not known that this may include iron(II) and organic iron-complexing ligands. The iron gradient covered a narrow salinity band between 35 and 36, and was linearly related to salinity indicating conservative behaviour, possibly caused by organic complexation keeping the iron in solution. The open ocean iron(II) levels were low but a major proportion of the increased iron levels in the shelf and coastal waters was found to occur as iron(II), and the increase in the overall iron concentration was matched by increased ligand concentrations causing the iron to remain organically complexed. A sedimentary origin for the iron(II) in the surface waters would require iron(II) to be more stable than expected, perhaps through complexation -stabilization. D
Marine Chemistry, 2005
An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone an... more An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone and fertilized a patch of water within an eddy of the Antarctic Circumpolar Current (EisenEx, Nov. 2000). During the experiment, a physical speciation technique was used for iron analysis in order to understand the changes in iron distribution and size-fractionations, including soluble Fe (b200 kDa), colloidal Fe (200 kDa-0.2 Am) and labile particle Fe (N0.2 Am), throughout the development of the phytoplankton bloom.
Marine Chemistry, 2005
... Southern Ocean. Marine Chemistry.) and significant Fe(II) levels (Croot, PL, Laan, P., Nishio... more ... Southern Ocean. Marine Chemistry.) and significant Fe(II) levels (Croot, PL, Laan, P., Nishioka, J., Strass, V., Cisewski, B., Boye, M., Timmermans, KR, Bellerby, RG, Goldson, L., Nightingale, P., de Baar, HJW, in press. Spatial and ...
Marine Chemistry, 2005
Measurements of Fe(II) and H 2 O 2 were carried out in the Atlantic sector of the Southern Ocean ... more Measurements of Fe(II) and H 2 O 2 were carried out in the Atlantic sector of the Southern Ocean during EisenEx, an iron enrichment experiment. Iron was added on three separate occasions, approximately every 8 days, as a ferrous sulfate (FeSO 4 ) solution. Vertical ...
Marine Chemistry, 2010
Vertical distributions of iron and iron binding ligands were determined in 2 size classes (dissol... more Vertical distributions of iron and iron binding ligands were determined in 2 size classes (dissolved b0.2 μm, soluble b 200 kDa, e.g.,~0.03 μm) in the Southern Ocean. Colloidal iron and complexing capacity (N 200 kDa-b 0.2 μm) were inferred as the difference between the dissolved and soluble fractions. Dissolved iron and ligands exist primarily in the soluble size range in the surface waters, although iron-complexing colloids still represent a significant portion of the dissolved pool and this fraction increases markedly with depth. This work presents evidence for the colloidal nature of a significant portion (37-51% on average) of the 'dissolved' organic Fe pool in these oceanic waters. From the data it was not possible to discern whether iron colloids exist as discrete organic complexes and/or inorganic amorphous colloids. Iron-complexing colloids are the most saturated with iron at the thermodynamic equilibrium, whereas soluble organic ligands occur in larger excess compared to soluble iron. It suggests that the exchangeable fraction for iron uptake through dissociation of Fe complexes likely occurs in the soluble fraction, and that soluble ligands have the potential to buffer iron inputs to surface waters whereas iron colloids may aggregate and settle. Expectations based on Fe diffusion rates, distributions and the stability of the soluble iron complexes and iron colloids also suggest that the weaker soluble Fe complexes may be more bio-available, while the strongest colloids may be a major route for iron removal from oceanic waters. Investigations of the size classes of the dissolved organic iron thus can significantly increase our understanding of the oceanic iron cycle.
Marine Chemistry, 2007
Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the wat... more Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced up to 4 nmol L − 1 dFe, 3 nmol L − 1 dMn and 40 nmol L − 1 dAl and returned to 0.6 nmol L − 1 dFe, 0.5 nmol L − 1 dMn and 10 nmol L − 1 dAl towards the end of the cruise three weeks later. A simple steady state model (MADCOW, [Measures, C.I., Brown, E.T., 1996. Estimating dust input to the Atlantic Ocean using surface water aluminium concentrations. In: Guerzoni. S. and Chester. R. (Eds.), The impact of desert dust across the Mediterranean, Kluwer Academic Publishers, The Netherlands, pp. 301-311.]) was used which relies on surface ocean dAl as a proxy for atmospheric deposition of mineral dust. We estimated dust input at 1.8 g m − 2 yr − 1 (range 1.0-2.9 g m − 2 yr − 1 ) and fluxes of dFe, dMn and dAl were inferred. Mixed layer steady state residence times for dissolved metals were estimated at 1.3 yr for dFe (range 0.3-2.9 yr) and 1.9 yr for dMn (range 1.0-3.8 yr). The dFe residence time may have been overestimated and it is shown that 0.2-0.4 yr is probably more realistic. Using vertical dFe versus Apparent Oxygen Utilization (AOU) relationships as well as a biogeochemical two end member mixing model, regenerative Fe:C ratios were estimated respectively to be 20 ± 6 and 22 ± 5 μmol Fe:mol C. Combining the atmospheric flux of dFe to the upper water column with the latter Fe:C ratio, a 'new iron' supported primary productivity of only 15% (range 7%-56%) was deduced. This would imply that 85% (range 44-93%) of primary productivity could be supported by regenerated dFe. The open ocean surface data suggest that the continental shelf is probably not a major source of dissolved metals to the surface of the adjacent open ocean. Continental shelf concentrations of dMn, dFe, and to a lesser extent dAl, were well correlated with salinity and express mixing of a fresher continental end member with Atlantic Ocean water flowing onto the shelf. This means probably that diffusive benthic fluxes did not play a major role at the time of the cruise.
Marine Chemistry, 2007
The chemistry of dissolved Fe(III) was studied in the Scheldt estuary (The Netherlands). Two disc... more The chemistry of dissolved Fe(III) was studied in the Scheldt estuary (The Netherlands). Two discrete size fractions of the dissolved bulk (< 0.2 μm and <1 kDa) were considered at three salinities (S = 26, 10 and 0.3).
Marine Chemistry, 2000
The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only wit... more The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only with nitrate and Ž . phosphate N and P without chelating agents to control metal speciation. Growth was slow in a ''low-iron'' culture containing 1.3 nM iron and was found to be iron-limited, growth-accelerating when a 1-nM iron addition was made. The Ž . y1 growth rate in a ''high-iron'' culture 5.4 nM iron was greater, reaching 0.4 div day but this culture too was found to have become iron-limited when a 9-nM iron addition was made on day 17 of the incubation. Both cultures were found to release iron-complexing ligands in excess of the iron concentration, 6 nM in the low-iron culture, and 10 nM in the high-iron culture. More ligands were produced after the iron addition taking the ligand concentration to 11 nM in the low-iron culture. The data show that the ligands are released in response to the iron addition, when at least some of the iron had already been taken up. This type of release is contrary to the concept of a siderophore, which is supposed to be released in periods of lack of iron; however the increase in the ligand concentration is similar to that released by the natural community in response to w the iron addition in the IRON-EX II experiment Rue, E.L., Bruland, K.W., 1997. The role of organic complexation on ambient iron chemistry in the equatorial Pacific Ocean and the response of a mesoscale iron addition experiment. Limnol.
Marine Chemistry, 2003
A shipboard analytical intercomparison of dissolved (< 0.2 Am) iron in the surface waters of the ... more A shipboard analytical intercomparison of dissolved (< 0.2 Am) iron in the surface waters of the Atlantic Ocean was undertaken during October 2000. A single underway surface (1 -2 m) seawater sampling and filtration protocol was used, in order to minimise differences from possible sample contamination. Over 200 samples (1/h) were collected over 12 days and analysed immediately using four different analytical methods, based on three variants of flow injection with luminol chemiluminescence (FI -CL) and cathodic stripping voltammetry (CSV). Dissolved iron concentrations varied between 0.02 and 1.61 nM during the intercomparison. On average, CSV [Electroanalysis 12 565] measured 0.08 nM higher iron concentrations than one FI -CL method [Anal. Chim. Acta 361 (1998) 189], which measured 0.13 nM higher iron values than the other two [Anal. Chem. 65 (1993) 1524; Anal. Chim. Acta 377 ]. Statistical analyses (paired two-tailed t-test) showed that each analytical method gave significantly different dissolved iron concentrations at the 95% confidence interval. These data however, represent a significant improvement over earlier intercomparison exercises for iron. The data have been evaluated with respect to accuracy and overall inter-laboratory replicate precision, which was generally better than the 95% confidence intervals reported for the NASS Certified Reference Materials. Systematic differences between analytical methods were probably due to the extraction of different physico-chemical forms of iron during preconcentration, either on the microcolumn resin (in the FI methods) or with competing ligand equilibration (in the CSV method). Small systematic concentration differences may also have resulted from protocols used for quantification of the analytical blank and instrument calibration. D
Biogeosciences, 2011
Page 1. Biogeosciences, 8, 2947–2959, 2011 www.biogeosciences.net/8/2947/2011/ doi:10.5194/bg-8-2... more Page 1. Biogeosciences, 8, 2947–2959, 2011 www.biogeosciences.net/8/2947/2011/ doi:10.5194/bg-8-2947-2011 © Author(s) 2011. CC Attribution 3.0 License. Biogeosciences Nitrogen uptake by phytoplankton in the Atlantic sector of the ...
Marine Chemistry, 2011
The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) wer... more The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58&amp;#x27; S and 57°33&amp;#x27; S along the Greenwich Meridian during the austral summer 2008 in ...
Journal of Geophysical Research, 2011
1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone sout... more 1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone south of South Africa during a hydrographic transect, are described using a large set of measurements including full depth hydrography, Acoustic Doppler Current Profiler velocities, biogeochemical tracers, air-sea fluxes and altimetric sea surface height. Both eddies have a subtropical origin. The anticyclone is an Agulhas ring with convected core water of ∼12°C, and swirl velocities of 1 m s −1 . It was 9.5 months old when sampled and had crossed the Agulhas Ridge. Though sampled in summer, it was releasing ∼200 W m −2 (sensible plus latent heat flux) to the atmosphere. It was observed adjacent to the Subantarctic Front, illustrating the usual encounters of such structures with this front. The cyclone, marked by pronounced low oxygen and CFC anomalies revealing an origin at the continental slope, was 4.5 months old. It had swirl speeds of 0.3 m s −1 , and was coupled with the anticyclone when observed. From their kinematics and water mass properties both structures were found to transport subtropical water down to ∼900 m, the water trapped below this depth being either from the northern Subantarctic Zone, or local water. The two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the Subantarctic Zone.
1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone sout... more 1] Two eddies, one anticyclonic and the other cyclonic, intersected in the Subantarctic Zone south of South Africa during a hydrographic transect, are described using a large set of measurements including full depth hydrography, Acoustic Doppler Current Profiler velocities, biogeochemical tracers, air-sea fluxes and altimetric sea surface height. Both eddies have a subtropical origin. The anticyclone is an Agulhas ring with convected core water of ∼12°C, and swirl velocities of 1 m s −1 . It was 9.5 months old when sampled and had crossed the Agulhas Ridge. Though sampled in summer, it was releasing ∼200 W m −2 (sensible plus latent heat flux) to the atmosphere. It was observed adjacent to the Subantarctic Front, illustrating the usual encounters of such structures with this front. The cyclone, marked by pronounced low oxygen and CFC anomalies revealing an origin at the continental slope, was 4.5 months old. It had swirl speeds of 0.3 m s −1 , and was coupled with the anticyclone when observed. From their kinematics and water mass properties both structures were found to transport subtropical water down to ∼900 m, the water trapped below this depth being either from the northern Subantarctic Zone, or local water. The two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the Subantarctic Zone.
Limnology and Oceanography, 2014
The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to ... more The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to 703S at 203E. Dissolved iron concentrations were low at 0.1}0.6 nM, with average concentrations of 0.25$0.13 nM. Organic iron complexing ligands were found to occur in excess of the dissolved iron concentration at 0.72$0.23 nM (equivalent to an excess of 0.5 nM), with
Global Biogeochemical Cycles, 2014
ABSTRACT Dissolved cobalt (DCo; < 0.2μm; 14 to 93 pM) and the apparent particulate cobalt ... more ABSTRACT Dissolved cobalt (DCo; < 0.2μm; 14 to 93 pM) and the apparent particulate cobalt (PCo; > 0.2μm; < 1 to 15 pM) were determined in the upper water-column (< 1000 m) of the Western Atlantic Ocean along the GEOTRACES-A02 section (64°N to 50°S). The lowest DCo concentrations, typical of a nutrient-type distribution were observed in surface waters of the subtropical domains. Strong linear relationships between DCo and phosphate (P) as well as meridional gradients of decreasing DCo from high latitudes were characterized and both linked to the Co biological requirement. External sources such as the Amazon and the atmospheric deposition were found to contribute significantly (> 10%) to the DCo stock of the mixed layer in the equatorial and north subtropical domains. Biotic and abiotic processes as well as the physical terms involved in the biogeochemical cycle of Co were defined and estimated. This allowed establishing the first global budget of DCo for the upper 100 m in the Western Atlantic. The biological DCo uptake flux was the dominant sink along the section, as reflected by the overall nutrient-type behavior of DCo. The regeneration varied widely vary within the different biogeochemical domains, accounting for 10% of the DCo-uptake rate in the subarctic gyre and for up to 85% in southern subtropical domain. These findings demonstrated that the regeneration is likely the prevailing source of DCo in the surface waters of the Western Atlantic, except in the subpolar domains where physically-driven sources can sustain the DCo biological requirement.
An iron enrichment experiment was carried out in the Polar Frontal Zone of the Southern Ocean dur... more An iron enrichment experiment was carried out in the Polar Frontal Zone of the Southern Ocean during the austral late spring on board of the german RV Polarstern (Nov. 2000). An eddy structure was selected to initiate the Fe-fertilized patch. In order to understand the Fe-dynamics, the complete physical and chemical speciation of iron was studied for first time in the upper-water column (0-100 m) of the fertilized-patch in the course of the bloom development over 23 days and compared to the ambient non-fertilized waters. The physical speciation of iron was investigated in several size-fractionated pools, as defined as: particulate>0.2 microm, dissolved <0.2 microm, 200kDa < colloids <0.2 microm and truly dissolved <200 kDa, using ultrafiltration technique and Fe(III)-detection by the FIA- Chemiluminescence method. The organic speciation of iron was studied in the dissolved and ultrafiltered truly dissolved (<200 kDa) samples using voltametric technique. The redox-s...
Marine Chemistry, 2011
The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) wer... more The spatial distribution, biogeochemical cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58&amp;#x27; S and 57°33&amp;#x27; S along the Greenwich Meridian during the austral summer 2008 in ...
Marine Chemistry, 2003
A transect across the eastern North Atlantic from 42jN, 23jW towards the European continental she... more A transect across the eastern North Atlantic from 42jN, 23jW towards the European continental shelf and English Channel shows a gradient of increasing concentrations of dissolved iron (0.7 -1.9 nM), iron-binding ligands and iron(II) across the continental rise. Other data, notably aluminium and manganese, indicate that the increases are part of a front in the metal concentrations, which is due to admixture of bottom waters. Metal fronts in shelf waters are well known, but it was not known that this may include iron(II) and organic iron-complexing ligands. The iron gradient covered a narrow salinity band between 35 and 36, and was linearly related to salinity indicating conservative behaviour, possibly caused by organic complexation keeping the iron in solution. The open ocean iron(II) levels were low but a major proportion of the increased iron levels in the shelf and coastal waters was found to occur as iron(II), and the increase in the overall iron concentration was matched by increased ligand concentrations causing the iron to remain organically complexed. A sedimentary origin for the iron(II) in the surface waters would require iron(II) to be more stable than expected, perhaps through complexation -stabilization. D
Marine Chemistry, 2005
An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone an... more An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone and fertilized a patch of water within an eddy of the Antarctic Circumpolar Current (EisenEx, Nov. 2000). During the experiment, a physical speciation technique was used for iron analysis in order to understand the changes in iron distribution and size-fractionations, including soluble Fe (b200 kDa), colloidal Fe (200 kDa-0.2 Am) and labile particle Fe (N0.2 Am), throughout the development of the phytoplankton bloom.
Marine Chemistry, 2005
... Southern Ocean. Marine Chemistry.) and significant Fe(II) levels (Croot, PL, Laan, P., Nishio... more ... Southern Ocean. Marine Chemistry.) and significant Fe(II) levels (Croot, PL, Laan, P., Nishioka, J., Strass, V., Cisewski, B., Boye, M., Timmermans, KR, Bellerby, RG, Goldson, L., Nightingale, P., de Baar, HJW, in press. Spatial and ...
Marine Chemistry, 2005
Measurements of Fe(II) and H 2 O 2 were carried out in the Atlantic sector of the Southern Ocean ... more Measurements of Fe(II) and H 2 O 2 were carried out in the Atlantic sector of the Southern Ocean during EisenEx, an iron enrichment experiment. Iron was added on three separate occasions, approximately every 8 days, as a ferrous sulfate (FeSO 4 ) solution. Vertical ...
Marine Chemistry, 2010
Vertical distributions of iron and iron binding ligands were determined in 2 size classes (dissol... more Vertical distributions of iron and iron binding ligands were determined in 2 size classes (dissolved b0.2 μm, soluble b 200 kDa, e.g.,~0.03 μm) in the Southern Ocean. Colloidal iron and complexing capacity (N 200 kDa-b 0.2 μm) were inferred as the difference between the dissolved and soluble fractions. Dissolved iron and ligands exist primarily in the soluble size range in the surface waters, although iron-complexing colloids still represent a significant portion of the dissolved pool and this fraction increases markedly with depth. This work presents evidence for the colloidal nature of a significant portion (37-51% on average) of the 'dissolved' organic Fe pool in these oceanic waters. From the data it was not possible to discern whether iron colloids exist as discrete organic complexes and/or inorganic amorphous colloids. Iron-complexing colloids are the most saturated with iron at the thermodynamic equilibrium, whereas soluble organic ligands occur in larger excess compared to soluble iron. It suggests that the exchangeable fraction for iron uptake through dissociation of Fe complexes likely occurs in the soluble fraction, and that soluble ligands have the potential to buffer iron inputs to surface waters whereas iron colloids may aggregate and settle. Expectations based on Fe diffusion rates, distributions and the stability of the soluble iron complexes and iron colloids also suggest that the weaker soluble Fe complexes may be more bio-available, while the strongest colloids may be a major route for iron removal from oceanic waters. Investigations of the size classes of the dissolved organic iron thus can significantly increase our understanding of the oceanic iron cycle.
Marine Chemistry, 2007
Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the wat... more Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced up to 4 nmol L − 1 dFe, 3 nmol L − 1 dMn and 40 nmol L − 1 dAl and returned to 0.6 nmol L − 1 dFe, 0.5 nmol L − 1 dMn and 10 nmol L − 1 dAl towards the end of the cruise three weeks later. A simple steady state model (MADCOW, [Measures, C.I., Brown, E.T., 1996. Estimating dust input to the Atlantic Ocean using surface water aluminium concentrations. In: Guerzoni. S. and Chester. R. (Eds.), The impact of desert dust across the Mediterranean, Kluwer Academic Publishers, The Netherlands, pp. 301-311.]) was used which relies on surface ocean dAl as a proxy for atmospheric deposition of mineral dust. We estimated dust input at 1.8 g m − 2 yr − 1 (range 1.0-2.9 g m − 2 yr − 1 ) and fluxes of dFe, dMn and dAl were inferred. Mixed layer steady state residence times for dissolved metals were estimated at 1.3 yr for dFe (range 0.3-2.9 yr) and 1.9 yr for dMn (range 1.0-3.8 yr). The dFe residence time may have been overestimated and it is shown that 0.2-0.4 yr is probably more realistic. Using vertical dFe versus Apparent Oxygen Utilization (AOU) relationships as well as a biogeochemical two end member mixing model, regenerative Fe:C ratios were estimated respectively to be 20 ± 6 and 22 ± 5 μmol Fe:mol C. Combining the atmospheric flux of dFe to the upper water column with the latter Fe:C ratio, a 'new iron' supported primary productivity of only 15% (range 7%-56%) was deduced. This would imply that 85% (range 44-93%) of primary productivity could be supported by regenerated dFe. The open ocean surface data suggest that the continental shelf is probably not a major source of dissolved metals to the surface of the adjacent open ocean. Continental shelf concentrations of dMn, dFe, and to a lesser extent dAl, were well correlated with salinity and express mixing of a fresher continental end member with Atlantic Ocean water flowing onto the shelf. This means probably that diffusive benthic fluxes did not play a major role at the time of the cruise.
Marine Chemistry, 2007
The chemistry of dissolved Fe(III) was studied in the Scheldt estuary (The Netherlands). Two disc... more The chemistry of dissolved Fe(III) was studied in the Scheldt estuary (The Netherlands). Two discrete size fractions of the dissolved bulk (< 0.2 μm and <1 kDa) were considered at three salinities (S = 26, 10 and 0.3).
Marine Chemistry, 2000
The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only wit... more The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only with nitrate and Ž . phosphate N and P without chelating agents to control metal speciation. Growth was slow in a ''low-iron'' culture containing 1.3 nM iron and was found to be iron-limited, growth-accelerating when a 1-nM iron addition was made. The Ž . y1 growth rate in a ''high-iron'' culture 5.4 nM iron was greater, reaching 0.4 div day but this culture too was found to have become iron-limited when a 9-nM iron addition was made on day 17 of the incubation. Both cultures were found to release iron-complexing ligands in excess of the iron concentration, 6 nM in the low-iron culture, and 10 nM in the high-iron culture. More ligands were produced after the iron addition taking the ligand concentration to 11 nM in the low-iron culture. The data show that the ligands are released in response to the iron addition, when at least some of the iron had already been taken up. This type of release is contrary to the concept of a siderophore, which is supposed to be released in periods of lack of iron; however the increase in the ligand concentration is similar to that released by the natural community in response to w the iron addition in the IRON-EX II experiment Rue, E.L., Bruland, K.W., 1997. The role of organic complexation on ambient iron chemistry in the equatorial Pacific Ocean and the response of a mesoscale iron addition experiment. Limnol.
Marine Chemistry, 2003
A shipboard analytical intercomparison of dissolved (< 0.2 Am) iron in the surface waters of the ... more A shipboard analytical intercomparison of dissolved (< 0.2 Am) iron in the surface waters of the Atlantic Ocean was undertaken during October 2000. A single underway surface (1 -2 m) seawater sampling and filtration protocol was used, in order to minimise differences from possible sample contamination. Over 200 samples (1/h) were collected over 12 days and analysed immediately using four different analytical methods, based on three variants of flow injection with luminol chemiluminescence (FI -CL) and cathodic stripping voltammetry (CSV). Dissolved iron concentrations varied between 0.02 and 1.61 nM during the intercomparison. On average, CSV [Electroanalysis 12 565] measured 0.08 nM higher iron concentrations than one FI -CL method [Anal. Chim. Acta 361 (1998) 189], which measured 0.13 nM higher iron values than the other two [Anal. Chem. 65 (1993) 1524; Anal. Chim. Acta 377 ]. Statistical analyses (paired two-tailed t-test) showed that each analytical method gave significantly different dissolved iron concentrations at the 95% confidence interval. These data however, represent a significant improvement over earlier intercomparison exercises for iron. The data have been evaluated with respect to accuracy and overall inter-laboratory replicate precision, which was generally better than the 95% confidence intervals reported for the NASS Certified Reference Materials. Systematic differences between analytical methods were probably due to the extraction of different physico-chemical forms of iron during preconcentration, either on the microcolumn resin (in the FI methods) or with competing ligand equilibration (in the CSV method). Small systematic concentration differences may also have resulted from protocols used for quantification of the analytical blank and instrument calibration. D