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Title: The behaviour of iron and other trace elements during the IronEx-I and PlumEx experiments in the Equatorial Pacific,
Description: Dissolved (< 0.4 μm) and particulate (0.4-5 μm and > 5 μm, leachable and refractory) trace elements were measured during the IronEx I and PlumEx experiments in October and November 1993 near the Galapagos Islands. Iron was measured in the enriched patch and at control stations over a 9 day period following fertilization. The dissolved iron was initially depleted at a rate that gave an iron half-life of 28-40 h. The loss rate gradually decreased, and dissolved iron concentrations did not decrease below about 0.25 nmol kg-1 throughout the experiment. These results were most consistent with a kinetic model that was second order in iron concentration for the scavenging removal of each iron fraction. Other trace elements measured did not change significantly either in concentration or partitioning during the IronEx I experiment. Biological production tracked iron concentrations over time, which suggests that productivity within the fertilized patch was regulated by the availability of iron. The PlumEx study consisted primarily of two transects, a meridional course to the east of the Galapagos Islands and a zonal section to the west. Surface dissolved iron was very low at all stations except those near the Galapagos Islands. Sections of trace metal and other properties distinctly confirm the upwelling of the Equatorial Undercurrent as it intersects the islands. This upwelling has a great effect on the surface distributions of the trace metals on the west side of the islands. Productivity within the mixed layer of this region is highly correlated with iron and nitrate. West of the islands highest productivity is found at stations with the highest iron. North of the Equatorial front, in nitrate-depleted waters, elevated iron concentrations do not enhance productivity., Cited By (since 1996):58, Oceanography, CODEN: DSROE, ,
Author: Gordon, Johnson, Coale
Date: 1998-01-01T00:00:00Z

Title: A rosette system for the collection of trace metal clean seawater,
Description: We designed a large-volume rosette sampler for collecting seawater with minimal trace metal contamination. The system uses eight modified 30-liter Go-Flo bottles secured to a Nylon II-coated stainless steel frame. The instrument is deployed with a dedicated winch with polyurethane-coated, three-conductor Kevlar hydroline. A prototype was used as part of the U.S. JGOFS Equatorial Pacific sampling program during spring and fall 1992. A redesigned model was used during the 1993 IronEx experiments and is currently being deployed in the Arabian Sea. The results of trace metal analyses collected on these cruises indicate that samples recovered are comparable to current single Go-Flo casts., Cited By (since 1996):28, CODEN: LIOCA, , , Oceanography, Downloaded from: www.aslo.org/lo/toc/vol_41/issue_6/1367.pdf (23 June 2014).
Author: Hunter, Gordon, Fitzwater, Coale
Date: 1996-01-01T00:00:00Z

Title: Iron deficiency and phytoplankton growth in the equatorial Pacific,
Description: Several experiments were conducted in the equatorial Pacific at 140°W during the Joint Global Ocean Flux Study, equatorial Pacific, 1992 Time-series I (TS-I, 23 March-9 April). Time-series II (TS-II, 2-20 October) and FeLINE II cruises (10 March-14 April), to investigate the effects of added Fe on phytoplankton communities. Seven series of deckboard iron-enrichment experiments were performed, with levels of added Fe ranging from 0.13 to 1000 nM. Time-course measurements included nutrients, chlorophyll a and HPLC pigments. Results of these experiments showed that subnanomolar (sub-nM) additions of Fe increased net community specific growth rates, with resultant chlorophyll a increases and nutrient decreases. Community growth rates followed Michaelis Menten type kinetics resulting in maximum rates of 0.99 doublings per day and a half-saturation constant of 0.12 nM iron. The dominant group responding to iron enrichment was diatoms., Cited By (since 1996):62, CODEN: DSROE, ,
Author: Fitzwater, Coale, Gordon, Johnson, Ondrusek
Date: 1996-01-01T00:00:00Z

Title: Iron distributions in the equatorial Pacific: Implications for new production,
Description: Several recent studies have shown that phytoplankton growth rate and production at 0°, 140°W is physiologically limited by iron. Therefore, changes in iron supply to the euphotic zone will result in variations in phytoplankton growth. We show that the flux of iron to this region is dominated by upwelling of the iron-rich Equatorial Undercurrent waters. Variations in the depth and strength of upwelling and changes in iron concentrations at the base of the euphotic zone will account for variations in primary and new production in this region. We determined dissolved and particulate iron profiles for the upper water column of the eastern equatorial Pacific including a vertical section from 9°N to 3°S along 140°W. One of the more prominent features of the section was a peak in dissolved and particulate iron associated with the Equatorial Undercurrent. The possible lithogenic origin of this iron is substantiated by the vertical section of particulate aluminum and manganese, which is consistent with a shallow hydrothermal source in the western equatorial Pacific. A simple one-dimensional model was used to calculate iron fluxes into the euphotic zone at the equator. Upwelling rates and dissolved iron concentrations were coupled to estimate the upwelling iron flux at 120 m (0.1% light level). Diffusive and atmospheric inputs of iron were also considered but were less significant than the upwelling flux. Iron-based potential new production was estimated to be 10-82 mmol C m-2 d-1 with C: Fe ratios of 100,000500,000: 1. In a similar manner, nitrate-based potential new production was 99-106 mmol C m-2 d-1. This demonstrates that iron supply limits new production to only 9-83% of the nitrate-based potential., Cited By (since 1996):103, CODEN: LIOCA, , , Downloaded from: aslo.org/lo/toc/vol_42/issue_3/0419.pdf (9 June 2014).
Author: Gordon, Coale, Johnson
Date: 1997-01-01T00:00:00Z

Title: On the formation of the manganese maximum in the oxygen minimum,
Description: A simple model that accounts for the formation of the Mn maximum in the oxygen minimum is presented here. In this model, Mn is proposed to cycle in a constant proportion to carbon, as do nitrogen and phosphorous. Superimposed on the Mn-carbon cycle is the removal of Mn(II) via scavenging onto sinking particles and transport by vertical diffusion. Scavenging is assumed to follow the rate law observed in the laboratory for Mn(II) oxidation. Manganese (II) concentrations were calculated with the model at stations in the Pacific and Atlantic Oceans and compared with measurements of dissolved Mn. All parameters in the model were based on laboratory measurements or field observations. The model reproduced Mn(II) maxima of the correct concentration and at the correct depth. This agreement was observed at a range of oxygen concentrations. The calculations demonstrate that the Mn maximum can form because of a reduction in the pseudo-first order scavenging rate constant (k′) within the oxygen minimum. The value of k′ will decrease in regions of the water column with low oxygen and pH (k′ = k0 [O2] {OH-}2). These regions will accumulate higher dissolved Mn(II) concentrations before the rate of Mn(II) removal, k′ [Mn(II)], equals the input from remineralization of POC and a steady state is reached. An additional source of Mn, such as flux from continental margin sediments or dissolution of Mn oxides, is not necessary to account for formation of the Mn maximum., Cited By (since 1996):51, ,
Author: Johnson, Coale, Berelson, Gordon
Date: 1996-01-01T00:00:00Z

Title: Southern Ocean Iron Enrichment Experiment,
Description: The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide., Cited By (since 1996):316, Oceanography, CODEN: SCIEA, ,
Author: Coale, Johnson, Chavez, Buesseler, Barber, Brzezinski, Cochlan, Millero, Falkowski, Bauer, Wanninkhof, Kudela, Altabet, Hales, Takahashi, Landry, Bidigare, Wang, Chase, Strutton, Friederich, Gorbunov, Lance, Hilting, Hiscock, Demarest, Hiscock, Sullivan, Tanner, Gordon, Hunter, Elrod, Fitzwater, Jones, Tozzi, Koblizek, Roberts, Herndon, Brewster, Ladizinsky, Smith, Cooper, Timothy, Brown, Selph, Sheridan, Twining, Johnson
Date: 2004-01-01T00:00:00Z

Title: Developing standards for dissolved iron in seawater
Description: Cited By (since 1996):114
Author: Johnson, Boyle, Bruland, Coale, Measures, Moffett, Aguilar-Islas, Barbeau, Bergquist, Bowie, Buck, Cai, Chase, Cullen, Doi, Elrod, Fitzwater, Gordon, King, Laan, Laglera-Baquer, Landing, Lohan, Mendez, Milne, Obata, Ossiander, Plant, Sarthou, Sedwick, Smith, Sohst, Tanner, Van den Berg, Wu
Date: 2007-01-01T00:00:00Z

Title: A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean
Description: The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability., Cited By (since 1996):930, Oceanography
Author: Coale, Johnson, Fitzwater, Gordon, Tanner, Chavez, Ferioli, Sakamoto, Rogers, Millero, Steinberg, Nightingale, Cooper, Cochlan, Landry, Constantinou, Rollwagen, Trasvina, Kudela
Date: 1996-01-01T00:00:00Z

Title: Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean,
Description: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km 2 in the open equatorial Pacific Ocean with iron. This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production. Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturaly enriched in iron. These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean., Cited By (since 1996):749, Oceanography, CODEN: NATUA, ,
Author: Martin, Coale, Johnson, Fitzwater, Gordon, Tanner, Hunter, Elrod, Nowicki, Coley, Barber, Lindley, Watson, Van Scoy, Law, Liddicoat, Ling, Stanton, Stockel, Collins, Anderson, Bidigare, Ondrusek, Latasa, Millero, Lee, Yao, Zhang, Friederich, Sakamoto, Chavez, Buck, Kolber, Greene, Falkowski, Chisholm, Hoge, Swift, Yungel, Turner, Nightingale, Hatton, Liss, Tindale
Date: 1994-01-01T00:00:00Z

Title: Control of community growth and export production by upwelled iron in the equatorial Pacific Ocean
Description: The iron hypothesis states that phytoplankton growth and biomass are limited by low concentrations of available iron in large regions of the world's oceans where other plant nutrients are abundant. Such limitation has been demonstrated by experiments in which iron has been added to both enclosed and in situ (un-enclosed) phytoplankton populations. A corollary of the iron hypothesis is that most 'new' iron is supplied by atmospheric deposition, and it has been suggested that changes in the deposition rates of iron-bearing dust have led to changes in biological productivity and, consequently, global climate. Here we report surface-water measurements in the equatorial Pacific Ocean which show that the main iron source to equatorial waters at 140°W is from upwelling waters. Shipboard in vitro experiments indicate that sub-nanomolar increases in iron concentrations can cause substantial increases in carbon export to deeper waters in this region. These findings demonstrate that equatorial biological production is controlled not solely by atmospheric iron deposition, but also by processes which influence the rate of upwelling and the iron concentration in upwelled water., Cited By (since 1996):221 Seaweeds, CODEN: NATUA
Author: Coale, Fitzwater, Gordon, Johnson, Barber
Date: 1996-01-01T00:00:00Z

Title: The distribution and behavior of dissolved and particulate iron and zinc in the Ross Sea and Antarctic circumpolar current along 170°W,
Description: Dissolved and particulate iron and zinc were measured in water samples collected from the Antarctic Circumpolar Current (ACC) region and the Ross Sea during the US JGOFS Antarctic Environment Southern Ocean Process Study (AESOPS). Dissolved and particulate zinc showed strongly seasonal variation, indicating efficient recycling in the upper 150 m of the water column in both regions. Seasonal zinc utilization is 21-118 μmol m-2 in the ACC and 134-192 μmol m-2 in the Ross Sea. Only 10-25% of the particulate zinc is exported below 150 m. Generally low dissolved (<0.05 nmol kg -1) and particulate iron concentrations (<0.2 nmol kg -1) were observed in the mixed layer year-around in the ACC region whereas seasonal depletion of dissolved iron and relatively high particulate iron (>1 nmol kg-1) were found in the Ross Sea. Seasonal iron utilization is 7-45 μmol m-2 in the ACC and 450-938 μmol m -2 in the Ross Sea, which yields an estimated Fe/C ratio of 15 and 100 (μmol Fe:mol C) for the ACC and the Ross Sea, respectively. More than 50% of the total iron production is exported below 150 m in the ACC region. Iron input through vertical mixing was minimal, in contrast to the vertical input of dissolved zinc and macronutrients in the ACC region. Upwelling may supply 50% of the export production of iron near the Southern ACC Front. In the Ross Sea, more iron is available due to the variety of inputs, in contrast to the ACC region. In addition to the input of dissolved and particulate iron from melting sea-ice, there is substantial input of particulate iron from the suspended materials of sediments. © 2004 Elsevier Ltd. All rights reserved., Cited By (since 1996):42, Oceanography, CODEN: DRORE, Antarctica, ,
Author: Coale, Gordon, Wang
Date: 2005-01-01T00:00:00Z

Title: Iron distributions in the equatorial Pacific: Implications for new production
Description: Several recent studies have shown that phytoplankton growth rate and production at 0°, 140°W is physiologically limited by iron. Therefore, changes in iron supply to the euphotic zone will result in variations in phytoplankton growth. We show that the flux of iron to this region is dominated by upwelling of the iron-rich Equatorial Undercurrent waters. Variations in the depth and strength of upwelling and changes in iron concentrations at the base of the euphotic zone will account for variations in primary and new production in this region. We determined dissolved and particulate iron profiles for the upper water column of the eastern equatorial Pacific including a vertical section from 9°N to 3°S along 140°W. One of the more prominent features of the section was a peak in dissolved and particulate iron associated with the Equatorial Undercurrent. The possible lithogenic origin of this iron is substantiated by the vertical section of particulate aluminum and manganese, which is consistent with a shallow hydrothermal source in the western equatorial Pacific. A simple one-dimensional model was used to calculate iron fluxes into the euphotic zone at the equator. Upwelling rates and dissolved iron concentrations were coupled to estimate the upwelling iron flux at 120 m (0.1% light level). Diffusive and atmospheric inputs of iron were also considered but were less significant than the upwelling flux. Iron-based potential new production was estimated to be lo-82 mmol C rnd2 d-l with C : Fe ratios of 100,000- 500,000: 1. In a similar manner, nitrate-based potential new production was 99-106 mmol C m-2 d-l. This demonstrates that iron supply limits new production to only 9-83% of the nitrate-based potential.
Author: Gordon, Coale, Johnson