Distinct Siderophores Contribute to Iron Cycling in the Mesopelagic at Station ALOHA

Bundy, Randelle M.; Boiteau, Rene; McLean, Craig; Turk‐Kubo, Kendra A.; McIlvin, Matthew R.; Saito, Mak A.; Mooy, Benjamin A. S. Van; Repeta, Daniel J.

doi:10.3389/fmars.2018.00061

Cited by 89 publications

(171 citation statements)

References 93 publications

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“…In the subtropical North Pacific near Hawaii, ferrioxamine E was detected in low nitrate, low iron surface waters and the DCM rather than in high nitrate high iron waters, while amphibactins were also detected below 200 m depth where dFe was < 0.1 nM but dissolved nitrate was > 0.5 μM (Bundy et al 2018), similar to this study. Finally, Mawji et al (2008) detected only ferrioxamines E and G in surface waters across the North Atlantic, which has higher dFe concentrations (> 0.3 nM) compared to the CCS transition zone and tropical Pacific HNLC region.…”

Section: Distribution Of Siderophores Across the Ccssupporting

confidence: 89%

Patterns of iron and siderophore distributions across the California Current System

Boiteau

Till

Coale

et al. 2018

Limnology & Oceanography

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Coastal upwelling of nutrients and metals along eastern boundary currents fuels some of the most biologically productive marine ecosystems. Although iron is a main driver of productivity in many of these regions, iron cycling and acquisition by microbes remain poorly constrained, in part due to the unknown composition of organic ligands that keep bioavailable iron in solution. In this study, we investigated organic ligand composition in discrete water samples collected across the highly productive California Coastal upwelling system. Siderophores were observed in distinct nutrient regimes at concentrations ranging from 1 pM to 18 pM. Near the shallow continental shelf, ferrioxamine B was observed in recently upwelled, high chlorophyll surface waters while synechobactins were identified within nepheloid layers at 60–90 m depth. In offshore waters characterized by intermediate chlorophyll, iron, and nitrate concentrations, we found amphibactins and an unknown siderophore with a molecular formula of C33H58O8N5Fe. Highest concentrations were measured in the photic zone, however, amphibactins were also found in waters as deep as 1500 m. The distribution of siderophores provides evidence for microbial iron deficiency across a range of nutrient regimes and indicates siderophore production and acquisition is an important strategy for biological iron uptake in iron limited coastal systems. Polydisperse humic ligands were also detected throughout the water column and were particularly abundant near the benthic boundary. Our results highlight the fine‐scale spatial heterogeneity of metal ligand composition in an upwelling environment and elucidate distinct sources that include biological production and the degradation of organic matter in suboxic waters.

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Section: Distribution Of Siderophores Across the Ccssupporting

confidence: 89%

Patterns of iron and siderophore distributions across the California Current System

Boiteau

Till

Coale

et al. 2018

Limnology & Oceanography

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“…Most publications reported a single class of ligands in hydrothermal plumes (Bennett et al, ; Hawkes, Connelly, et al, ; Kleint et al, ) and seawater (Boye et al, , ; Bundy et al, ; Gerringa et al, , ; Hunter & Boyd, ; Ibisanmi et al, ; Kondo et al, ; van den Berg, , ) although more than two ligand classes have also been seen in coastal and open ocean water (Buck et al, , ; Buck & Bruland, ; Bundy et al, , , ; Cullen et al, ; Fitzsimmons, Bundy, et al, ; Hogle et al, ). Here we use one ligand model considering it can provide a better fit to the measured data than two ligand model (see supporting information).…”

Section: Sampling and Methodsmentioning

confidence: 99%

The Size Fractionation and Speciation of Iron in the Longqi Hydrothermal Plumes on the Southwest Indian Ridge

et al. 2019

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The distribution and composition of Fe in hydrothermal plumes are crucial for understanding the contribution of hydrothermal venting to the oceanic Fe inventory. In this study, we conduct the first complete investigation of the size fractions of Fe and Fe‐binding ligands in the Longqi hydrothermal plumes on the Southwest Indian Ridge, combining the approaches of the size partitioning and reverse titration‐competitive ligand exchange‐adsorptive cathodic stripping voltammetry. Concentrations of all the Fe fractions were very high in the plume samples, and dissolved Fe (<0.2 μm) constituted a significant portion (48.7 ± 7.9%) of total Fe, which might be related to the existence of colloidal Fe oxyhydroxides and sulfides, as well as organic Fe complexes. Dissolved Fe consisted of colloidal Fe (10 kDa to 0.2 μm, ~70.2%) and soluble Fe (<10 kDa, ~29.8%). Colloidal Fe mainly contained Fe oxyhydroxides and sulfides (86.4 ± 6.2%), while most of the soluble Fe were organic Fe complexes (65.7 ± 5.4%). Fe speciation analyses showed that dissolved ligand concentrations were high in the hydrothermal plumes but were significantly lower than the dissolved Fe concentrations. Inferring from previous studies in the Longqi hydrothermal field, the ligands were most likely derived from the diffuse flow adjacent to the hydrothermal vents. The conditional stability constants (logK′FeL) of dissolved FeL (20.4 ± 0.5) were slightly higher than those of soluble FeL (19.6 ± 0.4), although they were not statistically different. Based on the ligands' size partitioning, the soluble ligands stabilized ~8.8 ± 3.8% of the hydrothermal Fe, which is over 2 times that of the colloidal ligands, ~4.0 ± 1.8%.

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“…Determining the bioavailability of organically complexed iron (Hassler & Schoemann, 2009;Tagliabue et al, 2009) and vertical variations in ligand concentration would add additional complexity and perhaps lead to better model-data fit. More observations of the types and distribution of ligands in the ASP are necessary to appropriately model their effects on dFe distributions (Bundy et al, 2018;Hassler et al, 2017). Furthermore, our model does not explicitly include microbially mediated processes, which influence iron and cobalamin colimitation (Bertrand et al, 2015) nor does it include bacterial community structure, which may be important to the decline of the bloom (Delmont et al, 2014).…”

Section: Low Winter Dfe Scenariomentioning

confidence: 99%

Modeling Iron and Light Controls on the Summer Phaeocystis antarctica Bloom in the Amundsen Sea Polynya

Oliver

St‐Laurent

Sherrell

et al. 2019

Global Biogeochemical Cycles

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Of all the Antarctic coastal polynyas, the Amundsen Sea Polynya is the most productive per unit area. Observations from the 2010–2011 Amundsen Sea Polynya International Research Expedition (ASPIRE) revealed that both light and iron can limit the growth of phytoplankton (Phaeocystis antarctica), but how these controls manifest over the bloom season is poorly understood, especially with respect to their climate sensitivity. Using a 1‐D biogeochemical model, we examine the influence of light and iron limitation on the phytoplankton bloom and vertical carbon flux at 12 stations representing different bloom stages within the polynya. Model parameters are determined by Bayesian optimization and assimilation of ASPIRE observations. The model‐data fit is most sensitive to phytoplankton physiological parameters, which among all model parameters are best constrained by the optimization. We find that the 1‐D model captures the basic elements of the bloom observed during ASPIRE, despite some discrepancies between modeled and observed dissolved iron distributions. With this model, we explore the way iron availability, in combination with light availability, controlled the rise, peak, and decline of the bloom at the 12 stations. Modeled light limitation by self‐shading is very strong, but iron is drawn down as the bloom rises, becoming limiting in combination with light as the bloom declines. These model results mechanistically confirm the importance of climate‐sensitive controls like stratification and meltwater on phytoplankton bloom development and carbon export in this region.

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Distinct Siderophores Contribute to Iron Cycling in the Mesopelagic at Station ALOHA

Cited by 89 publications

References 93 publications

Patterns of iron and siderophore distributions across the California Current System

Patterns of iron and siderophore distributions across the California Current System

The Size Fractionation and Speciation of Iron in the Longqi Hydrothermal Plumes on the Southwest Indian Ridge

Modeling Iron and Light Controls on the Summer Phaeocystis antarctica Bloom in the Amundsen Sea Polynya

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