Availability of iron from iron‐storage proteins to marine phytoplankton

Castruita, Madeli; Shaked, Yeala; Elmegreen, Lauren A.; Stiefel, Edward I.; Morel, François M. M.

doi:10.4319/lo.2008.53.3.0890

Cited by 10 publications

(4 citation statements)

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“…Biologically produced Fe-binding organic ligands are (i) related to alleviation of Fe stress [bacterially-produced siderophores (Rue and Bruland, 1995;Trick et al, 1995;Mawji et al, 2008;Velasquez et al, 2011), the toxin domoic acid produced by the diatom Nitzschia Maldonado et al, 2002)], (ii) retention of episodic iron input (Adly et al, 2015;Westrich et al, 2016), or (iii) ligands produced through biological recycling or basal biological activity such as hemes , ferritin (Castruita et al, 2008), polysaccharides (Ozturk et al, 2004;Hassler et al, 2011a), and EPS (Nichols et al, 2004;Hassler et al, 2011b;Norman et al, 2015). Interestingly, amongst most of these organic ligands, only EPS were reported to contribute to the pool of HS-like substances which is not surprising given that EPS and HS are polyfunctional macromolecules.…”

Section: Organic Ligands Distribution-sources Production and Loss Pmentioning

confidence: 99%

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

2017

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Iron-binding ligands are paramount to understanding iron biogeochemistry and its potential to set the productivity and the magnitude of the biological pump in >30% of the ocean. However, the nature of these ligands is largely uncharacterized and little is known about their sources, sensitivity to photochemistry and biological transformation, or scavenging behavior. Despite many uncertainties, there is no doubt that ligands are produced by a wide range of biotic and abiotic processes, and that the bulk ligand pool encompasses a diverse range of molecules. Despite widespread recognition of the likelihood of a continuum of ligand classes making up the bulk ligand pool, studies to date largely focused on the dominant ligand. Thus, most studies have overlooked the need to assess where these targeted molecules fit across the spectrum of ligands that comprise the bulk ligand pool. Here we summarize present knowledge to critically assess the source(s), function(s), production pathways, and loss mechanisms of three important iron-binding organic ligand groups in order to assess their distinctive characteristics and how they link with observed ligand distributions. We considered that ligands are contained in broad groupings of exopolymer substances (EPS), humic substances (HS), and siderophores; using literature data for speciation modeling suggested that this adequately described the iron speciation reported in the ocean. We hypothesize that a holistic viewpoint of the multi-faceted controls on ligands dynamics is essential to begin to understand why some ligands can be expected to dominate in particular oceanic regions, depth strata, or exhibit seasonality and/or lateral gradients. We advocate that the development of a regional classification will enhance our understanding of the changing composition of the bulk ligand pool across the global ocean and to help address to what extent seasonality influences the makeup of this pool. This classification, based on selected functional ligand classes, can act as a bridge to use future ligand datasets to fill in the gaps in the continuum.

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Section: Organic Ligands Distribution-sources Production and Loss Pmentioning

confidence: 99%

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

2017

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“…We performed a similar experiment with ferrihydrite sequestered in the iron-storage protein Dps (23). It has been shown that phytoplankton can take up Fe from Dps and that the uptake rate depends on the dissolution of the colloidal protein core that releases Fe (24). Our experimental results were slightly less noisy than those with ferrihydrite and showed no significant effect of pH on the kinetics of Fe uptake by T. weissflogii (P = 0.43, one-way ANOVA) (Fig.…”

Section: Reportsmentioning

confidence: 99%

Effect of Ocean Acidification on Iron Availability to Marine Phytoplankton

Shi

Hopkinson

et al. 2010

Science

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333

298

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The acidification caused by the dissolution of anthropogenic carbon dioxide (CO2) in the ocean changes the chemistry and hence the bioavailability of iron (Fe), a limiting nutrient in large oceanic regions. Here, we show that the bioavailability of dissolved Fe may decline because of ocean acidification. Acidification of media containing various Fe compounds decreases the Fe uptake rate of diatoms and coccolithophores to an extent predicted by the changes in Fe chemistry. A slower Fe uptake by a model diatom with decreasing pH is also seen in experiments with Atlantic surface water. The Fe requirement of model phytoplankton remains unchanged with increasing CO2. The ongoing acidification of seawater is likely to increase the Fe stress of phytoplankton populations in some areas of the ocean.

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“…Furthermore, complexation of remineralized Fe by EDTA would be expected to reduce Fe bioavailability. Indeed, Castruita et al (2008) found that growth rates of Thalassiosira weissflogii grown on Fe-ferritin complexes were reduced as EDTA was increased from 50 to 200 µmol l -1…”

Section: Bioavailability Of Remineralized Fementioning

confidence: 99%

Remineralization of bioavailable iron by a heterotrophic dinoflagellate

Dalbec¹,

Twining²

2009

Aquat. Microb. Ecol.

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The growth of phytoplankton in oligotrophic ocean waters is largely supported by nutrients remineralized through microzooplankton grazing. The bioavailability of the micronutrient Fe varies as a function of chemical speciation, but the speciation and bioavailability of Fe recycled by protozoan grazers is poorly characterized. We performed laboratory incubation experiments with cultured phytoplankton to examine the bioavailability of Fe produced by the heterotrophic dinoflagellate Oxyrrhis marina grazing on the centric diatom Thalassiosira pseudonana. Three different phytoplankton species (Thalassiosira weissflogii, Emiliania huxleyi and Nannochloris sp.) were grown on the remineralized Fe, and Fe uptake rates (measured with the radiotracer 55 Fe) and cell growth were used to assess bioavailability. Following 14 h of grazing, 1.09 to 1.11 nmol l -1 Fe was remineralized in the presence of O. marina compared to 0.30-0.49 nmol l -1 released in grazer-free controls. The size fractionation of dissolved Fe was similar in the grazed (treatment) and non-grazed (control) cultures. The 0.02 to 0.2 µm fraction was the largest (51 to 70%), followed by the < 0.02 µm fraction (32 to 44%). Remineralized Fe was rapidly accumulated internally by all phytoplankton species, with most accumulation occurring during the first 14 h. More Fe was accumulated in treatments compared to controls for all species, and cellular uptake rates were higher for remineralized Fe. These experiments confirm that microzooplankton grazing is a significant source of bioavailable Fe to marine phytoplankton in the open ocean.KEY WORDS: Iron · Remineralization · Microzooplankton grazing · Recycle · Uptake Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 54: [279][280][281][282][283][284][285][286][287][288][289][290] 2009 compounds in the ocean (e.g. Hutchins et al. 1999). Efforts to characterize Fe-binding ligands with chromatography and mass spectrometry have revealed the presence of functional groups characteristic of siderophores (Macrellis et al. 2001, Gledhill et al. 2004), but porphyrrin compounds have not yet been directly measured in open ocean waters. Refractory carboxyl-rich molecules may also constitute a significant portion of Fe-binding compounds (Hertkorn et al. 2006).The magnitude of external Fe inputs to ocean waters varies widely across the global ocean. Most of the external Fe entering the open ocean is derived from the aeolian deposition of dust from arid continental regions; however, upwelling and horizontal advection can also be important sources. In low-Fe HNLC systems, remineralization may be the most significant source of dissolved Fe (Hutchins et al. 1993. Previous studies have shown that remineralization can account for 30 to 100% of total Fe supplied to the euphotic zone (Bowie et al. 2001. Furthermore, the rapid cycling of Fe by grazing compared to the longer timescales of external particulate Fe input and dissolution indicates that much of the dissolved Fe present in H...

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Availability of iron from iron‐storage proteins to marine phytoplankton

Cited by 10 publications

References 50 publications

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

Effect of Ocean Acidification on Iron Availability to Marine Phytoplankton

Remineralization of bioavailable iron by a heterotrophic dinoflagellate

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