Variation in Fe-organic complexation with depth in the Northwestern Atlantic Ocean as determined using a kinetic approach

Witter, Amy E.; Luther, George W.

doi:10.1016/s0304-4203(98)00044-9

Cited by 113 publications

(125 citation statements)

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“…PP IX has previously been found to be a strong Fe chelator by voltammetric studies (Rue and Bruland 1995;Witter and Luther 1998) though more recently this has been bought into question by photochemical (Rijkenberg et al 2006) and bioavailability studies (Sato et al 2007). In the present work, we find little evidence supporting PP IX as a strong Fe chelator in seawater as 100 nM of this ligand was only able to maintain ~2.5 nM in solution.…”

Section: Discussionmentioning

confidence: 99%

“…As shown in numerous works more than 99% of the dissolved Fe (<0.2 μm) is bound by organic ligands throughout the world oceans (Croot and Johansson 2000;Rue and Bruland 1997;Van Den Berg 1995;Witter and Luther 1998;Wu and Luther 1995). Hutchins et al (1999b) concluded that the organic complexation of Fe increases the amount of dissolved Fe species and consequently its biological availability.…”

Section: Introductionmentioning

confidence: 98%

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Application of cross‐flow filtration for determining the solubility of iron species in open ocean seawater

Schlösser

Croot

2008

Limnology & Ocean Methods

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Measurements of soluble iron species (organic and inorganic) are important for understanding the transport of iron within the ocean and its bioavailability. Recent developments in ultrafiltration equipment and analytical detection techniques for low level Fe determination has turned the spotlight on obtaining data on soluble iron species. However there have, until now, been few studies that have characterized the performance of an ultrafiltration system with respect to well described soluble iron complexes. In the present work, we describe a methodological study characterizing the behavior of soluble and colloidal iron species in seawater by combining a crossflow ultrafiltration system (Vivaflow 50 TM ) with a radioisotope ( 55 Fe). During this study, we were able to maintain excellent mass balances by including all components: not only the solution phases (retentate and permeate) but wall-adsorbed and filter-adsorbed iron, which were recovered by an acid-rinsing step. Wall and filter adsorption were unavoidable when solutions were saturated with respect to Fe'. However in undersaturated solutions, such as with an excess of desferrioxamine B, wall and filter adsorption were minimized, indicating that these effects should be slight for natural samples where iron-binding ligands are in excess. Our results have important implications for the use of ultrafiltration membranes for open ocean iron biogeochemical studies.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Application of cross‐flow filtration for determining the solubility of iron species in open ocean seawater

Schlösser

Croot

2008

Limnology & Ocean Methods

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“…Most of dissolved Fe in the ocean is present as organically-complexed forms (Boye et al, 2001, Rue and Bruland, 1997, Witter and Luther III, 1998. However, if an artificially enriched Fe concentration exceeds the organic ligand concentration in situ, excess dissolved Fe may change to the particulate or colloidal form.…”

Section: Mesoscale Iron Fertilization Experiments Generally Increase mentioning

confidence: 99%

Phytoplankton community response to Fe and temperature gradients in the NE (SERIES) and NW (SEEDS) subarctic Pacific Ocean

Kudo

Noiri

Nishioka

et al. 2006

Deep Sea Research Part II: Topical Studies in Oceanography

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Ship-board iron enrichment bottle experiments were carried out with samples collected at the mesoscale iron fertilization experimental site (SERIES) in the subarctic NE Pacific in the summer of 2002. Samples were collected on Day 14 of the experiment outside the patch that was in a typical HNLC (high nitrate and low chlorophyll) condition. The iron concentration in the incubation bottles ranged from 0.1 to 2.0 nM by adding FeCl 3 solution. The increase in Chl-a in the micro (>10 µm) and nano-sized (2-10 µm) fraction was observed as a function of the added iron. Chl-a in the pico-sized fraction (0.7-2 µm) showed no increase with time. Nitrate and silicate were exhausted in the Fe-amended bottles, while those in the control bottle remained at the end of incubation. The relative consumption ratio of silicate to nitrate for the control bottles was significantly higher than that for the Fe-amended bottles. As a hyperbolic relation was found between iron concentration and the rate of increase in Chl-a (specific growth rate) for the micro and nano-sized fraction, the Monod equation was fit to obtain a maximum growth rate (µ max ) and a half-saturation constant for iron (K Fe ).

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“…The kinetics of the complexation reaction with these ligands is quite slow, reaching equilibrium at times between 15 min and Ž several hours van den Berg, 1995;Rue and Bruland, . 1997;Witter and Luther, 1998 . At such slow reaction rates, it is not likely that algae would benefit much from the dissociation of organic iron in the diffusion layer surrounding the cells to enhance pFe X -controlled iron uptake.…”

Section: Introductionmentioning

confidence: 99%

Iron availability and the release of iron-complexing ligands by Emiliania huxleyi

Boyé

Berg

2000

Marine Chemistry

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The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only with nitrate and Ž . phosphate N and P without chelating agents to control metal speciation. Growth was slow in a ''low-iron'' culture containing 1.3 nM iron and was found to be iron-limited, growth-accelerating when a 1-nM iron addition was made. The Ž .y1 growth rate in a ''high-iron'' culture 5.4 nM iron was greater, reaching 0.4 div day but this culture too was found to have become iron-limited when a 9-nM iron addition was made on day 17 of the incubation. Both cultures were found to release iron-complexing ligands in excess of the iron concentration, 6 nM in the low-iron culture, and 10 nM in the high-iron culture. More ligands were produced after the iron addition taking the ligand concentration to 11 nM in the low-iron culture. The data show that the ligands are released in response to the iron addition, when at least some of the iron had already been taken up. This type of release is contrary to the concept of a siderophore, which is supposed to be released in periods of lack of iron; however the increase in the ligand concentration is similar to that released by the natural community in response to w the iron addition in the IRON-EX II experiment Rue, E.L., Bruland, K.W., 1997. The role of organic complexation on ambient iron chemistry in the equatorial Pacific Ocean and the response of a mesoscale iron addition experiment. Limnol.x Oceanogr. 42, 901-910 . The enhanced growth in the cultures when more iron was added indicated that the organically Ž complexed iron present in the cultures was not immediately available to the organisms or at least not at sufficiently high . rate , and that the organisms responded to freshly added, inorganic, iron. q

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Variation in Fe-organic complexation with depth in the Northwestern Atlantic Ocean as determined using a kinetic approach

Cited by 113 publications

References 50 publications

Application of cross‐flow filtration for determining the solubility of iron species in open ocean seawater

Application of cross‐flow filtration for determining the solubility of iron species in open ocean seawater

Phytoplankton community response to Fe and temperature gradients in the NE (SERIES) and NW (SEEDS) subarctic Pacific Ocean

Iron availability and the release of iron-complexing ligands by Emiliania huxleyi

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