Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section

Wyatt, Neil J.; Milne, Angela; Achterberg, Eric P.; Browning, Thomas J.; Bouman, Heather A.; Woodward, E. Malcolm S.; Lohan, Maeve C.

doi:10.5194/bg-18-4265-2021

Cited by 7 publications

(3 citation statements)

References 83 publications

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“…In the deep Pacific (depth ≥2000 m) the average dCo concentration was 27 ± 11 pM (n=166), with large regions of the deep Pacific consistently under 25 pM dCo, particularly in the South Pacific. In contrast, the Atlantic Ocean has greater deep-dCo concentrations on average Wyatt et al, 2021), with the North and South Atlantic basins displaying deep-dCo concentrations of 57 ± 12 pM (n=166) and 40 ± 9 pM (n=184), respectively (Schlitzer et al, 2018). On GP15, dCo exhibited a heterogeneous distribution within the deep ocean, often with clear vertical regimes of elevated dCo that extend from the mesopelagic to the seafloor.…”

Section: Dissolved Cobalt Distributions In the Pacific Oceanmentioning

confidence: 99%

Distributions and perturbations of the marine dissolved cobalt cycle in a changing ocean

Chmiel¹

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Cobalt is a necessary nutrient for many marine phytoplankton, but its hybrid-type nature results in small marine inventories that make it one of the scarcest bioactive trace metals in the oceans. This study examines the marine dissolved cobalt cycle in two regions: the Pacific Ocean and Antarctic coastal seas. In the North Pacific, elevated cobalt stoichiometries among phytoplankton were linked to nitrogen, iron and phosphate stress protein biomarkers at the boundaries of oceanographic provinces and upwelling zones, providing insight into the flexibility of cobalt stoichiometry. In both regions, perturbations to the marine cobalt cycle were either predicted or observed; in the equatorial Pacific, the dissolved cobalt inventory was predicted to increase by up to 28% due to the expansion of oxygen minimum zones in a warmer ocean, while in the Antarctic, melting ice shelves have the potential to shift the nutrient regime from iron limitation towards zinc and vitamin B12 limitation, resulting in higher cobalt demand and a lower dissolved cobalt inventory. When the global cobalt cycle was estimated throughout four of Earth’s systems (the lithosphere, biosphere, hydrosphere and the anthroposphere – the human environment), it was determined that the scale of the cobalt flux through the anthroposphere is only one order of magnitude lower than the inventory of the entire hydrosphere (10(9) mol Co yr-1 and 10(10) mol Co, respectively), revealing a vulnerability to anthropogenic perturbation of the marine cobalt inventory through human mining, use and disposal of cobalt if appropriate pollution abatement, disposal and recycling infrastructure is not established. In light of observed and predicted changes to cobalt biogeochemistry, this research suggests that the marine cobalt cycle is particularly vulnerable to anthropogenic perturbation from both global climate change and pollution due to its low ocean inventory and interconnection to other nutrient biogeochemical cycles.

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Section: Dissolved Cobalt Distributions In the Pacific Oceanmentioning

confidence: 99%

Distributions and perturbations of the marine dissolved cobalt cycle in a changing ocean

Chmiel¹

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“…Within the poorly ventilated OMZ regions, elevated dCo plumes are formed when there is a source of dCo via remineralization in the mesopelagic but little to no loss of dCo via scavenging onto Mn oxide particles (see Sect. (Dulaquais et al, 2014a;Noble et al, 2017;Wyatt et al, 2021), with the North and South Atlantic basins displaying deep dCo concentrations of 57 ± 12 pM (n = 166) and 40 ± 9 pM (n = 184), respectively (Schlitzer et al, 2018). On GP15, dCo exhibited a heterogeneous distribution within the deep ocean, often with clear vertical regimes of elevated dCo that extend from the mesopelagic to the seafloor.…”

Section: Hydrographic Settingmentioning

confidence: 99%

Major processes of the dissolved cobalt cycle in the North and equatorial Pacific Ocean

Chmiel

Lanning

Laubach

et al. 2021

Preprint

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Abstract. Over the past decade, the GEOTRACES and wider trace metal geochemical community have made substantial contributions towards constraining the marine cobalt (Co) cycle and its major biogeochemical processes. However, few Co speciation studies have been conducted in the North and equatorial Pacific Ocean, a vast portion of the world’s oceans by volume and an important endmember of deep thermohaline circulation. Dissolved Co (dCo) samples, including total dissolved and labile Co, were measured at-sea during the GEOTRACES Pacific meridional transect (GP15) along the 152° W longitudinal from 56° N to 20° S. Along this transect, upper ocean dCo was linearly correlated to dissolved phosphate (slope = 82 ± 2 µM:M) due to phytoplankton uptake and remineralization. As depth increased, dCo concentrations became increasingly decoupled from phosphate concentrations due to co-scavenging with manganese oxide particles in the mesopelagic. The transect revealed an organically-bound coastal source of dCo to the Alaskan Stream associated with low salinity waters. An intermediate-depth hydrothermal flux of dCo was observed off the Hawaiian coast at the Loihi Seamount, and the elevated dCo was correlated to estimated xs3He at and above the vent site; however, the Loihi Seamount likely did not represent a major source of Co to the Pacific basin. Elevated concentrations of dCo within oxygen minimum zones (OMZs) in the equatorial North and South Pacific were consistent with the suppression of oxidative scavenging, and we estimate that future deoxygenation could increase the OMZ dCo inventory by 13–28 % over the next century. In North Pacific Deep Water (NPDW), a fraction of elevated ligand-bound dCo appeared protected from scavenging by the high biogenic particle flux in the North Pacific basin. This finding is counter to previous expectations of low dCo concentrations in the deep Pacific due to scavenging over thermohaline circulation. Compared to a Co global biogeochemical model, the observed transect displayed more extreme inventories and fluxes of dCo than predicted by the model, suggesting a highly dynamic Pacific Co cycle.

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“…However, ocean model simulations require that Zn is additionally reversibly scavenged onto particles, further coupling Zn-Si and decoupling Zn-P, in order to replicate field observations (10,12). Despite the implied importance of Zn scavenging, little is known about pZn speciation and the particle components that are important for carrying Zn from the photic zone to the deep ocean (4,6,(17)(18)(19)(20).…”

mentioning

confidence: 99%

Biogenic-to-lithogenic handoff of particulate Zn affects the Zn cycle in the Southern Ocean

Duan,

Cloete,

Loock

et al. 2024

Science

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Zinc (Zn) is vital to marine organisms. Its active uptake by phytoplankton results in a substantial depletion of dissolved Zn, and Zn bound to particulate organic matter replenishes dissolved Zn in the ocean through remineralization. However, we found that particulate Zn changes from Zn bound to phosphoryls in cells to recalcitrant inorganic pools that include biogenic silica, clays, and iron, manganese, and aluminum oxides in the Southern Ocean water column. The abundances of inorganic pools increase with depth and are the only phases preserved in sediments. Changes in the particulate-Zn speciation influence Zn bioavailability and explain the decoupling of Zn and phosphorus and the correlation of Zn and silicon in the water column. These findings reveal a new dimension to the ocean Zn cycle, implicating an underappreciated role of inorganic Zn particles and their impact on biological productivity.

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Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section

Cited by 7 publications

References 83 publications

Distributions and perturbations of the marine dissolved cobalt cycle in a changing ocean

Distributions and perturbations of the marine dissolved cobalt cycle in a changing ocean

Major processes of the dissolved cobalt cycle in the North and equatorial Pacific Ocean

Biogenic-to-lithogenic handoff of particulate Zn affects the Zn cycle in the Southern Ocean

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