Controls on iron distributions in the deep water column of the North Pacific Ocean: Iron(III) hydroxide solubility and marine humic‐type dissolved organic matter

Kitayama, Soichiro; Kuma, Kenshi; Manabe, Eri; Sugie, Koji; Takata, Hyoe; Isoda, Yutaka; Toya, Kenji; Saitoh, Sei–Ichi; Takagi, Shohgo; Kamei, Yoshihiko; Sakaoka, Keiichiro

doi:10.1029/2008jc004754

Cited by 47 publications

(109 citation statements)

References 85 publications

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“…These results are consistent with alter native concepts presented by studies on digestion of biogenic DOM in oceanic waters (Amon and Benner, 1994;Tanoue, 1996). It would be of interest to know how the organic ligands detected in the present study are related to fluorescent dissolved organic matter produced in situ in the ocean inte rior and with processes related to the degradation of sinking particles or DOM (Yamashita and Tanoue, 2008) or whether these ligands could overlap with those for iron(III) recently reported (e.g., Kitayama et al, 2009).…”

Section: Vertical Distributions Of Organic Ligandssupporting

confidence: 79%

Vertical distribution and chemical nature of strong ligands for copper(II) in the western North Pacific

貴¹,

英一郎²

2012

Pap. Meteor. Geophys.

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We investigated the vertical distribution and chemical nature of strong ligands for copper (II) in the western NorthPacific based on measurements of organically complexed copper(II) with two experimental procedures having dif ferent properties. The first involved fractionation of copper(II) complexes on the basis of their stability: exclusion of copper(II) complexed with weak ligands and, consequently, extraction of only highly stable copper(II) complexed with strong ligands (conditional stability constant of log Kʹ CuL > 14) by use of a ligand exchange reaction with ethylenedi aminetetraacetic acid. We also detected two weaker ligand classes having log Kʹ CuL = 9−10 (L 1 ) and log Kʹ CuL ~ 7 (L 2 ) with the copper(II) titration of an aliquot of the concentrated and desalted seawater. The second procedure involved the separation of hydrophobic copper(II) complexes from the original seawater by adsorption onto a resin. We determined the conditional stability constant of the hydrophobic copper(II) complex to be log Kʹ CuL ≤ 10.26 based on measurements of copper(II) complexes collected after copper(II) titration.We detected strong ligands (log Kʹ CuL > 14) at all depths from the surface to 1000 m, and we determined their con centrations to be 0.02−0.19 nM. The concentrations of hydrophobic ligands were lower than those of strong ligands at most depths, especially in surface waters. The vertical profile of strong ligands showed small maxima in the euphotic zone that did not coincide with chlorophyll a maxima. We estimated strong ligands to be present quantitatively (> 99.9 %) in the form of copper(II) complexes throughout the entire 1000 m water column based on the concentrations of in organic copper(II) measured by means of hydrophobic chromatography. In contrast, the copper(II) complexed fraction of the hydrophobic ligands (log Kʹ CuL = 10.26) varied from 15% at 120 m to 78% at 1000 m and was positively correlat ed with the concentration of inorganic copper(II). Strong ligands appeared to have different ligand sites and different structural units in their environments compared to the hydrophobic ligands. The strong ligands appeared to be relatively hydrophilic because their ligand sites were multidentate and were composed of several polar functional groups.We characterized at least three types of organic ligands with different affinities for copper(II) and different hydro phobic properties. Each ligand was associated with copper(II) with a different efficiency that varied with depth in the oceanic water column. In surface layers it appeared that strong ligands played an important role that enabled copper (II) to be present stably in seawater as a soluble form, whereas at depth, hydrophobic ligands also contributed to the cop per(II) speciation. Knowledge of ligand speciation is of noteworthy importance to the investigation of the abundance, distribution, and dynamics of copper(II) and organic ligands in the ocean.

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Section: Vertical Distributions Of Organic Ligandssupporting

confidence: 79%

Vertical distribution and chemical nature of strong ligands for copper(II) in the western North Pacific

貴¹,

英一郎²

2012

Pap. Meteor. Geophys.

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“…Thus, the decrease in D-Fe concentrations from the shelf region to the slope and basin regions (Fig. 4b,c) can be explained by the removal of colloidal Fe from the water by aggregation and particle scavenging2293033. The D-Fe concentrations above the Fe(III) hydroxide solubility in the HL at D4, which are higher than those at A8 (B1), C5, and D5 (Figs 2g and 5a), are inferred to reflect a balance in the interplay between input and removal processes within this water mass330.…”

Section: Resultsmentioning

confidence: 95%

“…Subsurface D-Fe maxima in the upper HL of the slope and basin regions, especially far from the shelf, may be maintained primarily by complexation of D-Fe with organic Fe-binding ligands such as humic DOM, which controls the Fe(III) hydroxide solubility in seawater229303132 (Fig. 5a).…”

Section: Resultsmentioning

confidence: 99%

Laterally spreading iron, humic-like dissolved organic matter and nutrients in cold, dense subsurface water of the Arctic Ocean

Hioki

Kuma

Morita

et al. 2014

Sci Rep

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The location and magnitude of oceanic iron sources remain uncertain owing to a scarcity of data, particularly in the Arctic Ocean. The formation of cold, dense water in the subsurface layer of the western Arctic Ocean is a key process in the lateral transport of iron, macronutrients, and other chemical constituents. Here, we present iron, humic-like fluorescent dissolved organic matter, and nutrient concentration data in waters above the continental slope and shelf and along two transects across the shelf–basin interface in the western Arctic Ocean. We detected high concentrations in shelf bottom waters and in a plume that extended in the subsurface cold dense water of the halocline layer in slope and basin regions. At σθ = 26.5, dissolved Fe, humic-like fluorescence intensity, and nutrient maxima coincided with N* minima (large negative values of N* indicate significant denitrification within shelf sediments). These results suggest that these constituents are supplied from the shelf sediments and then transported laterally to basin regions. Humic dissolved organic matter probably plays the most important role in the subsurface maxima and lateral transport of dissolved Fe in the halocline layer as natural Fe-binding organic ligand.

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“…Therefore, iron supply is thought to regulate primary production in coastal and oceanic regions where the surface waters are deficient in iron. In addition, many recent studies on the Fe(III) hydroxide solubility in seawater [5][6][7][8][9] suggest that Fe(III) solubility is controlled by organic complexation, which plays an important role in regulating dissolved Fe concentrations, [D-Fe], in seawater [9][10][11][12][13][14][15][16][17]. In previous studies [5,18], the Fe(III) solubility limit, [Fe(III) 0 ], for inorganic Fe(III) hydrolysis species, Fe(III) 0 , of fresh solid amorphous Fe(III) hydroxide in ultraviolet (UV)-irradiated open-ocean waters (free of organic ligands) was 0.08 ± 0.03 nM.…”

Section: Introductionmentioning

confidence: 99%

Effects of Mn and Fe on growth of a coastal marine diatom Talassiosira weissflogii in the presence of precipitated Fe(III) hydroxide and EDTA-Fe(III) complex

2011

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The significance of Mn and Fe for the growth of the coastal marine diatom Thalassiosira weissflogii was investigated by culture experiments in the presence of precipitated Fe(III) hydroxide [am-Fe(III)] and EDTAFe(III) complex with or without Mn addition. The culture experiments in all media without any added Mn(II) resulted in the very low phytoplankton growth for cell density and chlorophyll a (Chl a) concentration. In contrast, sufficient Mn addition (25 nM) induced the maximum growth both for cell generation and Chl a production. By using an approach in which further iron uptake by T. weissflogii from external iron in the culture media is prevented by adding hydroxamate siderophore desferrioxamine B (DFB) during cultivation, we examined the ability of T. weissflogii to grow on intracellularly stored Fe after the DFB addition. The addition of DFB after 3-and 5-days of cultivation resulted in the lower growth rate and lower maximum yields for cell density and Chl a concentration in solid 7-day-aged am-Fe(III) medium than in freshly precipitated am-Fe(III) medium. The longer aging time of am-Fe(III) in medium reduced the supply of bioavailable iron in the medium by the slower dissolution rate of am-Fe(III) with the longer aging time. In addition, phytoplankton growth for cell generation in EDTA-Fe(III) complex media in the presence of insufficient Mn (0 and 5 nM) is strongly influenced by the bioavailable iron supply through the dissociation of EDTA-Fe(III). These results may suggest that T. weissflogii in longer aged am-Fe(III) medium and in EDTA-Fe(III) medium with a higher ratio of EDTA:Fe(III) is in Fe-limitation of growth, which probably increases the production rate of the reactive oxygen species (ROS), and the corresponding up-regulation of the superoxide dismuting enzyme Mn-SOD increases the requirement for Mn.

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Controls on iron distributions in the deep water column of the North Pacific Ocean: Iron(III) hydroxide solubility and marine humic‐type dissolved organic matter

Cited by 47 publications

References 85 publications

Vertical distribution and chemical nature of strong ligands for copper(II) in the western North Pacific

Vertical distribution and chemical nature of strong ligands for copper(II) in the western North Pacific

Laterally spreading iron, humic-like dissolved organic matter and nutrients in cold, dense subsurface water of the Arctic Ocean

Effects of Mn and Fe on growth of a coastal marine diatom Talassiosira weissflogii in the presence of precipitated Fe(III) hydroxide and EDTA-Fe(III) complex

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