A seasonal study of dissolved cobalt in the Ross Sea, Antarctica: micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P

Saito, Mak A.; Goepfert, Tyler J.; Noble, Abigail E.; Bertrand, Erin M.; Sedwick, Peter N.; DiTullio, Giacomo R.

doi:10.5194/bg-7-4059-2010

Cited by 77 publications

(189 citation statements)

References 94 publications

(201 reference statements)

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“…The sources and the cycle of the organic Co-binding ligands in the ocean are not well known (Saito et al, 2001(Saito et al, , 2005(Saito et al, , 2010. In the present study, the relative [L] maxima observed within or close to the Chl-a rich layers in the subtropical domain and the northern subantarctic zone (stations L1, S1, L2, S2; int.…”

Section: Cycle Of the Organic Ligands Along The Sectionmentioning

confidence: 79%

“…growth by iron and cobalt contained in vitamin B 12 in the Ross Sea during early austral summer (Bertrand et al, 2007). In that latter study, the colimitation could be related to the absence of vitamin B 12 produced by bacteria and archaea during austral spring (Saito et al, 2010), or to a decrease in the biosynthesis of vitamin B 12 due to low cobalt concentrations (Gordon and Sullivan, 2008).…”

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confidence: 99%

“…of the Atlantic Ocean (Bown et al, 2011;Jakuba et al, 2008;Saito and Moffett, 2001) or in the Ross Sea (Saito et al, 2010) to scavenged-like as found in the North Pacific (Knauer et al, 1982) or conservative like in the Southern Ocean (Bown et al, 2011). In surface waters of the Atlantic and the Southern Ocean, DCo concentrations can be low (5-25 pM, Bown et al, 2011;Ellwood et al, 2005;Saito and Moffett, 2001;Saito et al, 2010), and such low concentrations can impact the phytoplankton growth.…”

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confidence: 99%

“…The chemical nature of the ligands is not known, but it has been suggested that vitamin B 12 and its degradation products can strongly bind Co (Saito et al, 2002(Saito et al, , 2010, since Co is the structural atom of this vitamin. Siderophores, such as desferrioxamine B or siderophore-like compounds, can also form extremely strong complexes with Co (Duckworth et al, 2009).…”

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confidence: 99%

“…In surface waters of the Atlantic and the Southern Ocean, DCo concentrations can be low (5-25 pM, Bown et al, 2011;Ellwood et al, 2005;Saito and Moffett, 2001;Saito et al, 2010), and such low concentrations can impact the phytoplankton growth. Recent field observation evidenced co-limitation of diatoms and Phaeocystis antarctica sp.…”

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confidence: 99%

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New insights on the role of organic speciation in the biogeochemical cycle of dissolved cobalt in the southeastern Atlantic and the Southern Ocean

2012

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Abstract. The organic speciation of dissolved cobalt (DCo) was investigated in the subtropical region of the southeastern Atlantic, and in the Southern Ocean in the Antarctic Circumpolar Current (ACC) and the northern Weddell Gyre, between 34°25´ S and 57°33´ S along the Greenwich Meridian during the austral summer of 2008. The organic speciation of dissolved cobalt was determined by competing ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV) using nioxime as a competing ligand. The concentrations of the organic ligands (L) ranged between 26 and 73 pM, and the conditional stability constants (log K'CoL) of the organic complexes of Co between 17.9 and 20.1. Most dissolved cobalt was organically complexed in the water-column (60 to >99.9%). There were clear vertical and meridional patterns in the distribution of L and the organic speciation of DCo along the section. These patterns suggest a biological source of the organic ligands in the surface waters of the subtropical domain and northern subantarctic region, potentially driven by the cyanobacteria, and a removal of the organic Co by direct or indirect biological uptake. The highest L:DCo ratio (5.81 ± 1.07 pM pM−1) observed in these surface waters reflected the combined effects of ligand production and DCo consumption. As a result of these combined effects, the calculated concentrations of inorganic Co ([Co']) were very low in the subtropical and subantarctic surface waters, generally between 10−19 and 10−17 M. In intermediate and deep waters, the South African margins can be a source of organic ligands, as it was suggested to be for DCo (Bown et al., 2011), although a significant portion of DCo (up to 15%) can be stabilized and transported as inorganic species in those DCo-enriched water-masses. Contrastingly, the distribution of L does not suggest an intense biological production of L around the Antarctic Polar Front where a diatom bloom had recently occurred. Here [Co'] can be several orders of magnitude higher than those reported in the subtropical domain, suggesting that cobalt limitation was unlikely in the ACC domain. The almost invariant L:DCo ratio of ~1 recorded in these surface waters also reflected the conservative behaviours of both L and DCo. In deeper waters higher ligand concentrations were observed in waters previously identified as DCo sources (Bown et al., 2011). At those depths the eastward increase of DCo from the Drake Passage to the Greenwich Meridian could be associated with a large scale transport and remineralisation of DCo as organic complexes; here, the fraction stabilized as inorganic Co was also significant (up to 25%) in the low oxygenated Upper Circumpolar Deep Waters. Organic speciation may thus be a central factor in the biogeochemical cycle of DCo in those areas, playing a major role in the bioavailability and the geochemistry of Co.

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Section: Cycle Of the Organic Ligands Along The Sectionmentioning

confidence: 79%

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confidence: 99%

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New insights on the role of organic speciation in the biogeochemical cycle of dissolved cobalt in the southeastern Atlantic and the Southern Ocean

2012

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Biogeochemical cycling of dissolved zinc along the GEOTRACES South Atlantic transect GA10 at 40°S

Wyatt

Milne

Woodward

et al. 2014

Global Biogeochemical Cycles

108

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The biogeochemical cycle of zinc (Zn) in the South Atlantic, at 40°S, was investigated as part of the UK GEOTRACES program. To date there is little understanding of the supply of Zn, an essential requirement for phytoplankton growth, to this highly productive region. Vertical Zn profiles displayed nutrient-like distributions with distinct gradients associated with the water masses present. Surface Zn concentrations are among the lowest reported for the world's oceans (< 50 pM). A strong Zn-Si linear relationship was observed (Zn (nM) = 0.065 Si (μM), r 2 = 0.97, n = 460). Our results suggest that the use of a global Zn-Si relationship would lead to an underestimation of dissolved Zn in deeper waters of the South Atlantic. By utilizing Si* and a new tracer Zn* our data indicate that the preferential removal of Zn in the Southern Ocean prevented a direct return path for dissolved Zn to the surface waters of the South Atlantic at 40°S and potentially the thermocline waters of the South Atlantic subtropical gyre. The importance of Zn for phytoplankton growth was evaluated using the Zn-soluble reactive phosphorus (SRP) relationship. We hypothesize that the low Zn concentrations in the South Atlantic may select for phytoplankton cells with a lower Zn requirement. In addition, a much deeper kink at~500m in the Zn:SRP ratio was observed compared to other oceanic regions.

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Contrasting biogeochemical cycles of cobalt in the surface western Atlantic Ocean

Dulaquais

Boyé

Middag

et al. 2014

Global Biogeochemical Cycles

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Dissolved cobalt (DCo; <0.2 μm; 14 to 93 pM) and the apparent particulate cobalt (PCo; >0.2 μm; <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 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.

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A seasonal study of dissolved cobalt in the Ross Sea, Antarctica: micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P

Cited by 77 publications

References 94 publications

New insights on the role of organic speciation in the biogeochemical cycle of dissolved cobalt in the southeastern Atlantic and the Southern Ocean

New insights on the role of organic speciation in the biogeochemical cycle of dissolved cobalt in the southeastern Atlantic and the Southern Ocean

Biogeochemical cycling of dissolved zinc along the GEOTRACES South Atlantic transect GA10 at 40°S

Contrasting biogeochemical cycles of cobalt in the surface western Atlantic Ocean

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