Differential remineralization of major and trace elements in sinking diatoms

Twining, Benjamin S.; Nodder, Scott D.; King, Andrew L.; Hutchins, David A.; LeCleir, Gary R.; DeBruyn, Jennifer M.; Maas, Elizabeth W.; Vogt, Stefan; Wilhelm, Steven W.; Boyd, Philip W.

doi:10.4319/lo.2014.59.3.0689

Cited by 93 publications

(105 citation statements)

References 54 publications

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“…The gradient for the remaining sub-surface data appeared to fall on a slightly lower slope ( Figure 13F), suggesting either that less Cu is required, relative to Zn, in the deep euphotic zone, or that Zn is preferentially remineralized below the euphotic zone (Twining et al, 2014), although the difference in slopes was not statistically significant. These inter-element relationships provide novel quantitative clues as to the cellular composition of Phaeocystis antarctica.…”

Section: Relative Biological Removal Of Trace Metals and Macronutrienmentioning

confidence: 77%

Dynamics of dissolved iron and other bioactive trace metals (Mn, Ni, Cu, Zn) in the Amundsen Sea Polynya, Antarctica

Sherrell

Lagerström

Forsch

et al. 2015

Elementa: Science of the Anthropocene

123

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The Amundsen Sea Polynya is experiencing large increases in glacial meltwater input and hosts an extremely productive and long-lasting summer phytoplankton bloom, suggesting a crucial role for natural Fe fertilization. Early summer distributions and dynamics of the dissolved bioactive metals Fe, Mn, Zn, Cu and Ni were investigated during a three week period in 2010-2011, using GEOTRACES-compliant methods. Dissolved Fe was very low (0.06-0.12 nmol kg −1 ) in the upper 20 m of the central polynya, suggesting that the sub-maximal rates of in situ primary productivity reported previously for this growth phase of the bloom are attributable to insufficient Fe availability. Weeks after the sampling period, phytoplankton biomass accumulated to peak bloom conditions, implying a continuous supply of bioavailable Fe to the euphotic zone. The dominant biologically-relevant Fe source was meltwater-enriched seawater flowing from the Dotson Ice Shelf cavity and delivering Fe at 0.7 nmol kg −1 to the broader polynya. The modest Fe content of Circumpolar Deep Water (CDW; 0.3 nmol kg −1 ), invading through cross-shelf troughs, was strongly augmented by benthic Fe inputs, which may combine with glacial meltwater dFe in the Dotson outflow. Sea ice melting provided a modest local Fe flux, insufficient to drive large annual blooms. Dissolved Mn was strongly reduced in surface waters, but displayed a subsurface maximum likely advected through the region from shallow coastal sediments. Nutrient-type elements Zn, Cu and Ni had large to small dynamic ranges, respectively, and increasing concentrations with depth, indicating uptake and remineralization within the polynya system. Surface water drawdown ratios of metals and nutrients provided novel estimates of metal quotas (metal/P) for the dominant bloom phytoplankton, Phaeocystis antarctica. At one unique mature bloom station, Zn and Cu were scavenged to low concentrations throughout the 350 m water column, a possible result of intense removal onto sinking Phaeocystis biodetritus. The Amundsen Sea appears to be a model region for studying the biogeochemical consequences of increased glacial meltwater inputs.

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Section: Relative Biological Removal Of Trace Metals and Macronutrienmentioning

confidence: 77%

Dynamics of dissolved iron and other bioactive trace metals (Mn, Ni, Cu, Zn) in the Amundsen Sea Polynya, Antarctica

Sherrell

Lagerström

Forsch

et al. 2015

Elementa: Science of the Anthropocene

123

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“…We also assume that PO 4 and dFe are remineralized with the same Martin curve and in the same ratio in which they were utilized. The recent work by Twining et al (2014) suggests that sinking diatoms release phosphorus higher in the water column than iron, but we do not have sufficient information to model these effects. Given the large uncertainties in the external iron sources, the neglected details are likely of second order for estimating the large-scale dFe concentration.…”

Section: Discussion and Caveatsmentioning

confidence: 89%

Inverse-model estimates of the ocean's coupled phosphorus, silicon, and iron cycles

Pasquier

Holzer

2017

Biogeosciences

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Abstract. The ocean's nutrient cycles are important for the carbon balance of the climate system and for shaping the ocean's distribution of dissolved elements. Dissolved iron (dFe) is a key limiting micronutrient, but iron scavenging is observationally poorly constrained, leading to large uncertainties in the external sources of iron and hence in the state of the marine iron cycle.Here we build a steady-state model of the ocean's coupled phosphorus, silicon, and iron cycles embedded in a dataassimilated steady-state global ocean circulation. The model includes the redissolution of scavenged iron, parameterization of subgrid topography, and small, large, and diatom phytoplankton functional classes. Phytoplankton concentrations are implicitly represented in the parameterization of biological nutrient utilization through an equilibrium logistic model. Our formulation thus has only three coupled nutrient tracers, the three-dimensional distributions of which are found using a Newton solver. The very efficient numerics allow us to use the model in inverse mode to objectively constrain many biogeochemical parameters by minimizing the mismatch between modeled and observed nutrient and phytoplankton concentrations. Iron source and sink parameters cannot jointly be optimized because of local compensation between regeneration, recycling, and scavenging. We therefore consider a family of possible state estimates corresponding to a wide range of external iron source strengths. All state estimates have a similar mismatch with the observed nutrient concentrations and very similar large-scale dFe distributions. However, the relative contributions of aeolian, sedimentary, and hydrothermal iron to the total dFe concentration differ widely depending on the sources.Both the magnitude and pattern of the phosphorus and opal exports are well constrained, with global values of 8.1 ± 0.3 Tmol P yr −1 (or, in carbon units, 10.3 ± 0.4 Pg C yr −1 ) and 171. ± 3. Tmol Si yr −1 . We diagnose the phosphorus and opal exports supported by aeolian, sedimentary, and hydrothermal iron. The geographic patterns of the export supported by each iron type are well constrained across the family of state estimates. Sedimentary-iron-supported export is important in shelf and large-scale upwelling regions, while hydrothermal iron contributes to export mostly in the Southern Ocean. The fraction of the global export supported by a given iron type varies systematically with its fractional contribution to the total iron source. Aeolian iron is most efficient in supporting export in the sense that its fractional contribution to export exceeds its fractional contribution to the total source. Per source-injected molecule, aeolian iron supports 3.1 ± 0.8 times more phosphorus export and 2.0 ± 0.5 times more opal export than the other iron types. Conversely, per injected molecule, sedimentary and hydrothermal iron support 2.3 ± 0.6 and 4. ± 2. times less phosphorus export, and 1.9 ± 0.5 and 2. ± 1. times less opal export than the other iron types.

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“…Copper efflux has also been documented in marine prokaryotic and eukaryotic phytoplankton (Foster, 1977;Hall et al, 1979;Croot et al, 2003;Quigg et al, 2006;Semeniuk et al, 2015;Walsh et al, 2015), suggesting that Cu efflux might be a common physiological mechanism of Cu homeostasis in marine microorganisms. In addition, micrograzing and bacterial remineralization might mediate fast exchange of Cu between the dissolved and the particulate pools, as recently shown for Ni and Zn (Twining et al, 2014). Therefore, fast biological Cu uptake and efflux, as wells as efficient micrograzing and bacterial remineralization of Cu in surface waters might have significant impacts on the cycling of Cu in the sea.…”

Section: Dissolved-particulate Cu Cycling and Cu Residence Timesmentioning

confidence: 91%

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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Differential remineralization of major and trace elements in sinking diatoms

Cited by 93 publications

References 54 publications

Dynamics of dissolved iron and other bioactive trace metals (Mn, Ni, Cu, Zn) in the Amundsen Sea Polynya, Antarctica

Dynamics of dissolved iron and other bioactive trace metals (Mn, Ni, Cu, Zn) in the Amundsen Sea Polynya, Antarctica

Inverse-model estimates of the ocean's coupled phosphorus, silicon, and iron cycles

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

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