Isotopic constraints on biogeochemical cycling of copper in the ocean

Takano, Shotaro; Tanimizu, Masaharu; Hirata, Takafumi; Sohrin, Yoshiki

doi:10.1038/ncomms6663

Cited by 98 publications

(128 citation statements)

References 37 publications

(55 reference statements)

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“…Given the total dissolved surface Cu concentrations across Line P varied by ∼2-fold (1.46-2.79 nM), we estimate the residence time for Cu in the mixed layer (mixed layer [Cu] diss ÷ estimated net loss) along Line P between 2.5 and 8 years. This is similar to other independent surface layer residence time estimates in the tropical Atlantic Ocean (3-12 years; Helmers and Schrems, 1995) and the North Pacific Ocean (∼9 years; Takano et al, 2014). The surface residence time is much longer than other bioactive metals, such as Fe (6-150 days; Bergquist and Boyle, 2006;Ellwood et al, 2014), or Co (∼100 days; Saito and Moffett, 2002), and reflects the higher total dissolved Cu concentrations in surface waters (0.2-3 nM) compared to other bioactive metals (0.01-0.2 nM).…”

Section: Dissolved-particulate Cu Cycling and Cu Residence Timessupporting

confidence: 75%

Using 67Cu to Study the Biogeochemical Cycling of Copper in the Northeast Subarctic Pacific Ocean

et al. 2016

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Microbial copper (Cu) nutrition and dissolved Cu speciation were surveyed along Line P, a coastal to open ocean transect that extends from the coast of British Columbia, Canada, to the high-nutrient-low-chlorophyll (HNLC) zone of the northeast subarctic Pacific Ocean. Steady-state size fractionated Cu uptake rates and Cu:C assimilation ratios were determined at in situ Cu concentrations and speciation using a 67 Cu tracer method. The cellular Cu:C ratios that we measured (∼30 μmol Cu mol C −1 ) are similar to recent estimates using synchrotron x-ray fluorescence (SXRF), suggesting that the 67 Cu method can determine in situ metabolic Cu demands. We examined how environmental changes along the Line P transect influenced Cu metabolism in the sub-microplankton community. Cellular Cu:C assimilation ratios and uptake rates were compared with net primary productivity, bacterial abundance and productivity, total dissolved Cu, Cu speciation, and a suite of other chemical and biological parameters. Total dissolved Cu concentrations ([Cu] d ) were within a narrow range (1.5-2.8 nM), and Cu was bound to a ∼5-fold excess of strong ligands with conditional stability constants (K cond 2 ) of ∼10 14 .CuL,Cu + Free Cu 2+ concentrations were low (pCu 14.4-15.1), and total and size fractionated net primary productivity (NPP ; g C L −1 d −1 V μ ) were negatively correlated with inorganic Cu concentrations ([Cu ]). We suggest this is due to greater Cu drawdown by faster growing phytoplankton populations. Using the relationship between [Cu ] drawdown and NPP V , we calculated a regional photosynthetic Cu:C drawdown export ratio between 1.5 and 15 μmol Cu mol C −1 , and a mixed layer residence time (2.5-8 years) that is similar to other independent estimates (2-12 years). Total particulate Cu uptake rates were between 22 and 125 times faster than estimates of Cu export; this is possibly mediated by rapid cellular Cu uptake and efflux by phytoplankton and bacteria or the effects of grazers and bacterial remineralization on dissolved Cu. These results provide a more detailed understanding of the interactions between Cu speciation and microorganisms in seawater, and suggest that marine phytoplankton modify Cu speciation in the open ocean.

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Section: Dissolved-particulate Cu Cycling and Cu Residence Timessupporting

confidence: 75%

Using 67Cu to Study the Biogeochemical Cycling of Copper in the Northeast Subarctic Pacific Ocean

et al. 2016

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“…Cu solution-phytoplankton ≈ 0) is consistently observed in the pH range of modern oceans, for both prokaryotes and eukaryotes (16,28). In our sample suite, δ…”

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confidence: 82%

“…Cu values in post-GOE shales are readily explained by continental weathering processes (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) delivering dissolved riverine Cu with a δ 65 Cu signature of up to ∼0.7‰ (26,(39)(40)(41) to the oceans, as today (28).…”

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confidence: 98%

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Cu isotopes in marine black shales record the Great Oxidation Event

Fru

Rodríguez

Partin

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The oxygenation of the atmosphere ∼2.45–2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth’s redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (δ65CuERM-AE633) in organic carbon-rich shales spanning the period 2.66–2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in 65Cu, along with the preferential removal of 65Cu by iron oxides, left seawater and marine biomass depleted in 65Cu but enriched in 63Cu. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy δ65Cu values coincides with a shift to negative sedimentary δ56Fe values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary δ65Cu values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.

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“…Hitherto, a large number of studies regarding theoretical, experimental and application data sets of Cu isotope compositions have been published. These studies have largely improved our knowledge on Cu biogeochemical behaviors in biosphere, hydrosphere and lithosphere, and to different extent on Cu isotopic fractionation mechanisms in various geochemical, biological and metabolism processes [15,16,17,18,19,20,21]. …”

Section: Introductionmentioning

confidence: 99%

Cu Isotopic Composition in Surface Environments and in Biological Systems: A Critical Review

Wang

Chen

Zhang

2017

IJERPH

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Copper (Cu) is a transition metal and an essential micronutrient for organisms, but also one of the most widespread toxic inorganic contaminants at very high content. The research on Cu isotopes has grown rapidly in the last decade. Hitherto, a large number of studies have been published on the theoretical fractionation mechanisms, experimental data and natural variations of Cu isotopes in variable environments and ecosystems. These studies reported a large variation of δ65Cu (−16.49 to +20.04‰) in terrestrial samples and showed that Cu isotopes could be fractionated by various biogeochemical processes to different extent. Several papers have previously reviewed the coupling of Cu and Zn isotope systematics, and we give here a tentative review of the recent publications only on Cu isotopesin variable surface repositories, animals and human beings, with a goal to attract much attention to research on Cu (and other metals) behaviors in the environment and biological systems.

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Isotopic constraints on biogeochemical cycling of copper in the ocean

Cited by 98 publications

References 37 publications

Using 67Cu to Study the Biogeochemical Cycling of Copper in the Northeast Subarctic Pacific Ocean

Using 67Cu to Study the Biogeochemical Cycling of Copper in the Northeast Subarctic Pacific Ocean

Cu isotopes in marine black shales record the Great Oxidation Event

Cu Isotopic Composition in Surface Environments and in Biological Systems: A Critical Review

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