A comparison of two voltammetric techniques for determining zinc speciation in Northeast Pacific Ocean waters

Donat, John R.; Bruland, Kenneth W.

doi:10.1016/0304-4203(90)90050-m

Cited by 153 publications

(94 citation statements)

References 27 publications

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“…Perhaps, as some results suggest, [58,59] iron binding ligands in deep water are recalcitrant/refractory in nature, and might be analogous to the humic material in terrestrial soil and water that is characteristic of organic matter degradation. The specific nature of iron-binding ligands is also difficult to reconcile with the observation that the chemical speciation of many other transition metals is also dominated by organic complexes, [77,78] including Zn, [79][80][81] Cd, [82] Cu, [83][84][85][86] Ni [85] and Co. [87] As already mentioned, much of this humic material is colloidal in nature in terrestrial environments. This may also be the case in the ocean.…”

Section: The Provenance Of Ligandsmentioning

confidence: 99%

Iron-binding ligands and their role in the ocean biogeochemistry of iron

2007

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Environmental context. It is now well accepted that iron is an essential micronutrient for phytoplankton growth in many areas of the global ocean, even though this element is present in seawater in extremely low abundance. It is also known that most of the iron in seawater is present as complexes formed with ligands of natural organic matter whose nature and origin remain largely unknown. Here we consider how these iron-complexing ligands might have evolved during geological time, what factors may have given rise to their presence and the possible roles that they play in iron biogeochemistry.Abstract. Current knowledge about the role of iron-binding organic ligands in the ocean and their role in determining the biogeochemistry of this biologically active element has been summarised. Some electrochemical measurements suggest the presence of at least two ligand types, a strong binding ligand L 1 found mainly in the mixed layer and a weaker ligand L 2 found mainly in deep water. Speciation of Fe III is dominated by L 1 in the mixed layer and L 2 in the deep ocean. There is some evidence that L 1 is siderophore-like and is specifically generated by marine microbes (i.e. heterotropic bacteria and cyanobacteria). We suggest that this is a specific biological mechanism for sequestering iron in the mixed layer that developed early in the ocean's history (Archaean period, 2500-3500 million years BP), whereas the more ubiquitous L 2 ligand only arose at the close of the Proterozoic (500-2500 million years BP) when eukaryotic organisms evolved to switch on the ocean's biological pump, allowing L 2 ligands to form from the oxidation of sinking biological particles. This development coincided with the complete oxygenation of the ocean's interior which removed the iron-binding sulfide ion and allowed maintenance of the ocean's iron inventory. These speculations are accompanied by various suggestions about avenues for future research to better understand iron biogeochemistry.

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Section: The Provenance Of Ligandsmentioning

confidence: 99%

Iron-binding ligands and their role in the ocean biogeochemistry of iron

2007

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“…Additions of Fe were chosen so that Fe 3ϩ concentrations were approximately constant and nonlimiting for growth. With the high concentration of EDTA, the natural Zn-complexing ligands (Donat and Bruland 1990;Bruland et al 1991;Ellwood and van den Berg 2000) had no effect on the Zn 2ϩ concentrations, whereas natural Co-binding ligands (Zhang et al 1990) played only a minor role (and only in the case of no addition of Co). However, the natural Table 2 for metal speciation details.…”

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confidence: 96%

“…However, the natural Table 2 for metal speciation details. Ϫ9 M and with a log KЈ of 10.5 (Bruland 1989;Donat and Bruland 1990;Ellwood and van den Berg 2000). For natural Co-binding ligands, a concentration of 0.4ϫ10 Ϫ9 M and a log KЈ of 15 was used (Zhang et al 1990 concentrations has been reported for many other marine phytoplankton species (Brand et al 1983;Sunda and Huntsman 1995).…”

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Not all eukaryotic algae can replace zinc with cobalt: Chaetoceros calcitrans (Bacillariophyceae) versus Emiliania huxleyi (Prymnesiophyceae)

Timmermans

Snoek

Gerringa

et al. 2001

Limnology & Oceanography

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Not all eukaryotic algae can replace zinc with cobalt: Chaetoceros calcitrans (Bacillariophyceae) versus Emiliania huxleyi (Prymnesiophyceae)Abstract-Zinc and cobalt are essential trace metals for phytoplankton growth and can substitute for each other metabolically in some eukaryotic algal species, especially in some marine diatoms and coccolithophorids. In the present study, it is reported that in the marine diatom Chaetoceros calcitrans, Co cannot replace Zn: in contrast, Co substitution of Zn was found in Emiliania huxleyi. It is concluded that Co can substitute for Zn but that the phenomenon is species/genera-specific. Differing ability to substitute Zn with Co can be regarded as an additional factor affecting phytoplankton biomass and/ or species composition.

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“…For Zn, this uncertainty has been removed by recent anodic and cathodic stripping voltametric measurements of organic complexation (Bruland 1989;Donat and Bruland 1990). These measurements indicate that Zn is complexed in central North Pacific seawater by a relatively long-lived, high-affinity organic ligand whose concentration is essentially constant (1.2 nM) throughout the upper 500 m of the water column.…”

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Feedback interactions between zinc and phytoplankton in seawater

Sunda

Huntsman

1992

Limnology & Oceanography

263

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In Zn ion-buffered media, oceanic species (Thalassiosira oceanica and Emiliania hu.xZeyi) grew at near-maximal rates at the lowest free Zn ion concentration ([Zn2+] = lo-12,3 M), whereas coastal species (Thalassiosira pseudonana and Thalassiosira weissflogii) were limited at [Zn2+] < lo-" M. The ability of the oceanic species to outgrow coastal ones at low [Zn2+] was due almost entirely to a reduced growth requirement for cellular Zn rather than to an increased capability for uptake. All isolates exhibited similar sigmoidal relationships between cellular Zn: C ratios and [Zn2+] with minimal slopes at [Zn2+] of lO-'o.5 to -1 O-9.5 M and increasing slopes above and below this range. The minimal slopes at intermediate [Zr?+] could be explained by negative feedback regulation of a high-affinity Zn uptake system, while increased slopes at high [Zn2+] appeared to be related to uptake by a low-affinity site. Measured relationships between cellular Zn : C ratios and [Zn'+] agreed well with those computed from a modified Redfield model based on depth profiles for Zn and PO, concentrations and Zn chelation in the nutricline of the North Pacific. This agreement provides evidence that Zn concentrations in the nutricline are controlled by biological uptake and regeneration as occurs for major nutrients.There is mounting evidence that the distribution and chemical speciation of certain trace metal nutrients and the growth and species composition of phytoplankton communities are tightly linked (Morel and Hudson 1984; Sunda 199 1). Like major nutrients, many trace metal nutrients occur at concentrations in surface oceanic waters that are orders of magnitude lower than those in coastal environments. Two of the most important metallic micronutrients, Fe and Zn, occur at lo-lo M or less in oceanic waters, but are present at 100-l ,000 times higher concentrations in coastal and estuarine waters (Bruland and Franks 1983;Evans 1977;Martin and Gordon 1988;Martin et al. 1989). The marked neritic-oceanic differences in the concentrations of these metals are associated with large corresponding variations in the growth requirements of neritic and oceanic algal species for these micronutrients, providing evidence that both metals have had a marked influence on the ' Present address: Office of Naval Research, Code 1123C, Arlington, Virginia 222 17-5000. Reprint requests should be sent to the Beaufort Laboratory. AcknowledgmentsThis work was partially funded by a grant from the Office of Naval Research.We thank Kenneth Bruland, Larry Brand, Francois Morel, and an anonymous referee for reviews of this manuscript.evolution and spatial distribution of phytoplankton species (Brand et al. 1983).Large increases also occur with depth in the concentrations of many trace metal nutrients and nutrient analogs resembling observed increases in major nutrient concentrations. Zn has been found to increase from 0.07 nM in surface waters of the central North Pacific to 8 nM at 1,500 m, and its concentration is linearly correlated with that of silici...

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A comparison of two voltammetric techniques for determining zinc speciation in Northeast Pacific Ocean waters

Cited by 153 publications

References 27 publications

Iron-binding ligands and their role in the ocean biogeochemistry of iron

Iron-binding ligands and their role in the ocean biogeochemistry of iron

Not all eukaryotic algae can replace zinc with cobalt: Chaetoceros calcitrans (Bacillariophyceae) versus Emiliania huxleyi (Prymnesiophyceae)

Feedback interactions between zinc and phytoplankton in seawater

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