Fundamental studies for chemical speciation of iron in seawater with an improved analytical method

Obata, Hajime; Karatani, Hajime; Matsui, Masanao; Nakayama, Eiichiro

doi:10.1016/s0304-4203(96)00082-5

Cited by 112 publications

(79 citation statements)

References 31 publications

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“…The data collected here on several occasions show significant differences between DFe, as measured by the luminol H 2 O 2 chemiluminescence method (de Jong et al, 1998;Obata et al, 1993Obata et al, , 1997, and Fe(II) as measured by luminol chemiluminescence (Croot and Laan, 2002). The main reason for this discrepancy appeared to be the long half-life of the Fe(II) and the loading pH employed with the Fe(III) method.…”

Section: Implications For Iron Measurementsmentioning

confidence: 63%

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. concentrations increased at the depth of the chlorophyll maximum when iron concentrations returned to pre-infusion concentrations (b80 pM) possibly due to biological production related to iron reductase activity.In this work, Fe(II) and dissolved iron were used as tracers themselves for subsequent iron infusions when no further SF 6 was added. EisenEx was subject to periods of weak and strong mixing. Slow mixing after the second infusion allowed significant concentrations of Fe(II) and Fe to exist for several days. During this time, dissolved and total iron in the infusion plume behaved almost conservatively as it was trapped between a relict mixed layer and a new rain-induced mixed layer. Using dissolved iron, a value for the vertical diffusion coefficient K z =6.7F0.7 cm 2 s À1 was obtained for this 2-day period. During a subsequent surface survey of the iron-enriched patch, elevated levels of Fe(II) were found in surface waters presumably from Fe(II) dissolved in the rainwater that was falling at this time.Model results suggest that the reaction between uncomplexed Fe(III) and O 2 À was a significant source of Fe(II) during EisenEx and helped to maintain high levels of Fe(II) in the water column. This phenomenon may occur in iron enrichment experiments when two conditions are met: (i) When Fe is added to a system already saturated with regard to organic complexation and (ii) when mixing processes are slow, thereby reducing the dispersion of iron into under-saturated waters. D

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Section: Implications For Iron Measurementsmentioning

confidence: 63%

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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“…dfo-mpo.gc.ca/). For measurements of dissolved iron (DFe) concentrations, 0.22-μm filtered seawater sampled at 0, 10, 20, 30, and 40 m depth was collected in acid-washed 250-mL low-density polyethylene bottles and buffered to pH 3.5 for 1-2 h before FIA chemiluminescent analysis following the method of Obata et al (47,48). Iron concentrations represent the average value of the five depth samples.…”

Section: Methodsmentioning

confidence: 99%

Unveiling a phytoplankton hotspot at a narrow boundary between coastal and offshore waters

Ribalet

Marchetti

Hubbard

et al. 2010

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

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In terrestrial ecosystems, transitional areas between different plant communities (ecotones) are formed by steep environmental gradients and are commonly characterized by high species diversity and primary productivity, which in turn influences the foodweb structure of these regions. Whether comparable zones of elevated diversity and productivity characterize ecotones in the oceans remains poorly understood. Here we describe a previously hidden hotspot of phytoplankton diversity and productivity in a narrow but seasonally persistent transition zone at the intersection of iron-poor, nitrate-rich offshore waters and iron-rich, nitrate-poor coastal waters of the Northeast Pacific Ocean. Novel continuous measurements of phytoplankton cell abundance and composition identified a complex succession of blooms of five distinct size classes of phytoplankton populations within a 100-km-wide transition zone. The blooms appear to be fueled by natural iron enrichment of offshore communities as they are transported toward the coast. The observed succession of phytoplankton populations is likely driven by spatial gradients in iron availability or time since iron enrichment. Regardless of the underlying mechanism, the resulting communities have a strong impact on the regional biogeochemistry as evidenced by the low partial pressure of CO 2 and the nearly complete depletion of nutrients. Enhanced phytoplankton productivity and diversity associated with steep environmental gradients are expected wherever water masses with complementary nutrient compositions mix to create a region more favorable for phytoplankton growth. The ability to detect and track these important but poorly characterized marine ecotones is critical for understanding their impact on productivity and ecosystem structure in the oceans.ecotone | transition zone | iron | high-nitrate, low-chlorophyll | flow cytometry

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“…The filtrate (100 ml) for Fe concentration analysis was buffered at pH 3.2 with a 10 mol l -1 formic acid, 2.4 mol l -1 ammonium formate buffer solution (0.5 ml 100 ml -1 filtrate). The Fe concentration in buffered filtrate (≤2 nmol l -1 ) was determined with an automated Fe analyzer (Kimoto Electric) by placing various concentrations on an 8-hydroxyquinoline chelating column and using luminol-hydrogen peroxide chemiluminescence (CL) detection in a closed flow-through system (Obata et al 1993(Obata et al , 1997. The concentrations of NO 3 +NO 2 , PO 4 , and Si(OH) 4 in the filtered seawater measured by a Technicon autoanalyzer were less than 0.5, 0.1, and 5 µmol l -1 , respectively, which are negligible compared with the concentrations added in the culture experiments (see below).…”

Section: Methodsmentioning

confidence: 99%

Effect of high iron concentrations on iron uptake and growth of a coastal diatom Chaetoceros sociale

Iwade¹,

Kuma

Isoda³

et al. 2006

Aquat. Microb. Ecol.

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The growth and iron uptake of the coastal marine diatom Chaetoceros sociale were experimentally measured in batch experiments at 10°C to which an acidic Fe(III) stock solution was added. The direct input of Fe(III) into the culture media induced the highest iron uptake rate (~3.4 to 4.2 × 10–16 mol Fe cell–1 d–1) by C. sociale during the first day of the incubation, resulting from the supply of bioavailable inorganic Fe(III) species at levels above its expected equilibrium value (~0.1 nmol l–1) with solid amorphous Fe(III) hydroxide in seawater. The iron uptake rate during the first day of incubation in solid amorphous Fe(III) hydroxide medium aged for 1 d at 10°C was approximately 50% lower than that in the direct Fe(III) input media. We used a modified approach in which further iron uptake by C. sociale from external iron in the direct Fe(III) input media was prevented by adding hydroxamate siderophore desferrioxamine B (DFB) during cultivation. After the addition of DFB, the highest growth rate (~0.5 to 0.6 d–1) of C. sociale by intracellularly stored Fe in the direct Fe(III) input media was maintained for a few days since no iron uptake was observed after the DFB addition. The growth rate was independent of the amount of intracellularly stored Fe. However, the maximal cell yields appeared to be relatively dependent on the amount of intracellularly stored Fe, suggesting the presence of a critical concentration of intracellular Fe (minimum cellular Fe for growth) for phytoplankton growth (~1 × 10–16 mol Fe cell–1 for C. sociale). In the present study, maximal and minimal Fe quotas were 3.4 to 4.2 × 10–16 and ~1 × 10–16 mol Fe cell–1 (the maximal/minimal Fe ratio of 3.4 to 4.2), respectively. The high iron uptake and storage capacity in C. sociale allows this species to accumulate excess iron at high concentrations of bioavailable inorganic Fe species and to support up to 1.8 to 2.1 cell divisions without any additional iron uptake. In addition, we attempted to model the effect of luxury uptake on growth, as biodilution of cellular Fe eventually decreases the Fe quota to a critical threshold

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Fundamental studies for chemical speciation of iron in seawater with an improved analytical method

Cited by 112 publications

References 31 publications

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Unveiling a phytoplankton hotspot at a narrow boundary between coastal and offshore waters

Effect of high iron concentrations on iron uptake and growth of a coastal diatom Chaetoceros sociale

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