Search results | Digital Commons of Moss Landing Marine Laboratories

Title: Vertex: Phytoplankton/iron studies in the Gulf of Alaska,
Description: VERTEX studies were performed in the Gulf of Alaska in order to test the hypothesis that iron deficiency was responsible for the phytoplankton's failure to remove major plant nutrients from these waters. In view of the observed Fe distributions and the results of phytoplankton Fe enrichment experiments, it was concluded that Gulf of Alaska atmospheric Fe input rates are sufficient to support moderately high rates of primary productivity; however, not enough Fe is available to support the high growth rates that would lead to normal major nutrient depletion. Enhanced Fe input does occur along the Alaska continental margin, where normal NO 3 surface depletion is observed. Coccolithophorids appear to be best able to cope with low Fe conditions; however, they cannot compete with diatoms when Fe is readily available. Iron may be more important than available N in determining global rates of phytoplankton new production. Offshore Pacific Ocean water, replete with major nutrients, appears to be infertile without supplemental iron from the atmosphere or continental margin. © 1989., Cited By (since 1996):399, ,
Author: Martin, Gordon, Fitzwater, Broenkow
Date: 1989-01-01T00:00:00Z

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 in north-east Pacific waters,
Description: Although Fe is an element of great biological 1 and geochemical 2 importance, little is known about its distribution in the sea. The reasons for this are: (1) contamination is extremely difficult to avoid during sampling and laboratory procedures, not only because of man's wide use of this element, but also because it is fourth most abundant element in the Earth's crust (5.63%) 3; (2) the chemistry of Fe is very complex, and its form (or forms) in seawater is poorly known, hence whether one preconcentration technique will work for existing species is questionable. Iron also appears to be very insoluble 4 in oxygenated ocean water, and most (90%) 5 precipitates out in association with dissolved organics during estuarine mixing processes 5-8. Indeed, some argue that truly dissolved Fe does not exist in seawater and that the fraction found in filtrates is totally colloidal 9. We have been attempting oceanic dissolved Fe measurements for the past four years and report here three vertical Fe profiles (Fig. 1) that have the following features in common: Fe is severely depleted (0.15-0.30 nmol kg -1) in surface waters; Fe maxima (up to 2.6 nmol kg -1) occur in association with oxygen minima; and, Fe levels appear to vary little in mid-depth waters (0.5-1.0 nmol kg -1)., Cited By (since 1996):33, ,
Author: Gordon, Martin, Knauer
Date: 1982-01-01T00:00:00Z

Title: Iron deficiency limits phytoplankton growth in Antarctic waters,
Description: Enrichment experiments were performed in the Ross Sea to test the hypothesis that iron deficiency is responsible for the phytoplankton's failure to use up the luxuriant major nutrient supplies found in these and all other offshore Antarctic ocean waters. The results suggest that Fe deficiency is the primary reason that the present-day southern ocean biological pump is shut off. In contrast, iron was 50 times more abundant during the last glacial maximum; greater Fe availability may have stimulated the biological pump and contributed to the ice age drawdown of atmospheric CO 2. These results also imply that large-scale southern ocean Fe fertilization is feasible, at least in terms of the total amounts of Fe required; i.e., 100 000 to 500 000 tons yr -1., Cited By (since 1996):277, , , Downloaded from: http://onlinelibrary.wiley.com/doi/10.1029/GB004i001p00005/pdf (9 June 2014).
Author: Martin, Fitzwater, Gordon
Date: 1990-01-01T00:00:00Z

Title: The case for iron,
Description: Excess major nutrients occur in offshore areas ranging from the tropical equatorial Pacific to the polar Antarctic. In spite of the great ecological differences in these environments, they share a common trait: iron deficiency. All of these areas are far from Fe-rich terrestrial sources and atmospheric dust loads in these regions are amongst the lowest in the world. Experiments were performed in three nutrient-rich areas: The Gulf of Alaska, the Ross Sea, and the equatorial Pacific. In general, populations without added Fe doubled at rates 11-40% of the expected maxima at various temperatures. The addition of nanomole quantities of Fe increased these doubling rates by factors of 2-3. In spite of the lack of Fe, tightly coupled phytoplankton/zooplankton communities seem to inhabit these major nutrient-rich areas. -from Authors, Cited By (since 1996):341, Oceanography, , , Downloaded from: aslo.org/lo/toc/vol_36/issue_8/1793.pdf (16 June 2014).
Author: Martin, Gordon, Fitzwater
Date: 1991-01-01T00:00:00Z

Title: Cobalt in north-east Pacific waters,
Description: Significant understanding has been gained recently about the biogeochemical cycling of trace metals in the ocean. This knowledge has mostly resulted from the accurate measurement of dissolved species in oceanic water columns. We report here that cobalt's vertical distribution is similar to that exhibited 1-3 by Mn; that is, its surface enrichment/deep depletion (Fig. 1). However, amounts of Co (1-7 ng 1 -1) are ∼10-20 times less than those for Mn (Table 1), as might be expected from crustal abundance estimates 4 for these elements (Mn=950; Co=25 μg per g). The similarity between Mn and Co profiles implies the same biogeochemical pathways. The Co excess in nearshore surface waters probably results from continental weathering input processes, as suggested by the remarkable Co-salinity mirror-image relationship shown in Fig. 1, and the Co-salinity scatter diagram in Fig. 2a. The steady decrease in Co concentrations also indicates that Co is usually scavenged rather than regenerated at depth, as is the case with Mn (Fig. 1; Table 1). © 1982 Nature Publishing Group., Cited By (since 1996):47 Oceanography, ,
Author: Knauer, Martin, Gordon
Date: 1982-01-01T00:00:00Z

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: Iron, nutrient and phytoplankton biomass relationships in upwelled waters of the California coastal system,
Description: We report measurements of dissolvable and particulate iron, particulate Al, nutrients and phytoplankton biomass in surface waters during the termination of one upwelling event and the initiation of a second event in August 2000. These events occurred in the area of the Año Nuevo upwelling center off the coast of central California. The first event was observed after ∼8 days of continuous upwelling favorable winds, while the second event was observed through the onset of upwelling favorable winds to wind reversals ∼3 days later. Coincident with the upwelling signatures of low temperature and high salinity were significantly elevated concentrations of nitrate and silicate with average concentrations greater than 15 and 20 μM, respectively, during both upwelling events. Dissolvable Fe concentrations (TD-Fe) were significantly higher in the second event, 6.5 versus 1.2 nM Fe found in the first event. Nitrate was reduced by ∼5 μM day-1 within this second upwelled plume as compared to a drawdown of ∼2 μM day-1 within the first plume. Silicate was reduced in a ratio of 1.2 mol Si:mol NO3 in the high Fe waters of the second plume as compared to a ratio of 2.2 in the lower Fe waters of the first plume. The observed differences in nutrient utilization are consistent with some degree of iron limitation. The area of increased dissolvable Fe in the second upwelling event was coincident with elevated particulate Fe concentrations, indicating the particulate pool as a possible source of the observed increase in TD-Fe. The elevated particulate Fe in surface waters was a result of resuspended sediments in the bottom boundary layer (BBL) of the shallow shelf being transported to the surface during upwelling. Particulate (and dissolvable) iron concentrations were significantly reduced as upwelling continued. This was most probably due to a decoupling of the BBL from upwelled source waters as the upwelling front moved offshore and/or reduced turbulence in the BBL as upwelling continued. The observed reduction in both particulate and dissolvable Fe, as upwelling continued to deliver macronutrients to surface waters, may result in varying levels of Fe limitation., Cited By (since 1996):35, CODEN: CSHRD, ,
Author: Fitzwater, Johnson, Elrod, Ryan, Coletti, Tanner, Gordon, Chavez
Date: 2003-01-01T00:00:00Z

Title: Mytilus californianus as a bioindicator of trace metal pollution: Variability and statistical considerations,
Description: Trace metal variability was evaluated in two populations of Mytilus californianus through the analysis of individual specimens. Samples were collected for two areas in the Southern California Bight and analysed for their Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn content. Analysis of the data revealed that population variability was not the same between the two sites, indicating that variability may need to be evaluated for each population (site) studied. In general, the analysis of 10 to 30 individuals was necessary to yield maximum resolution in terms of trace metal concentrations between population means while maintaining cost effectiveness., Cited By (since 1996):29, CODEN: MPNBA, ,
Author: Gordon, Knauer, Martin
Date: 1980-01-01T00:00:00Z

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: Iron in Antarctic waters,
Description: WE are testing the hypothesis that Antarctic phytoplankton suffer from iron deficiency 1-3 which prevents them from blooming and using up the luxuriant supplies of major nutrients found in vast areas of the southern ocean. Here we report that highly productive 4 (∼3 g Cm -2 day -1), neritic Gerlache Strait waters have an abundance of Fe (7.4 nmol kg -1) which facilitates phytoplankton blooming and major nutrient removal, while in low-productivity 4 (∼0.1 g Cm -2 day -1), offshore Drake Passage waters, the dissolved Fe levels are so low (0.16 nmol kg -1) that the phytoplankton are able to use less than 10% of the major nutrients available to them. The verification of present-day Fe deficiency is of interest as iron-stimulated phytoplankton growth may have contributed to the drawing down of atmospheric CO 2 during glacial maxima 2,3; it is also important because oceanic iron fertilization aimed at the enhancement of phytoplankton production may turn out to be the most feasible method of stimulating the active removal of greenhouse gas CO 2 from the atmosphere, if the need arises (J.H.M., manuscript in preparation)., Cited By (since 1996):449, CODEN: NATUA, ,
Author: Martin, Gordon, Fitzwater
Date: 1990-01-01T00:00:00Z

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: Primary productivity and trace-metal contamination measurements from a clean rosette system versus ultra-clean Go-Flo bottles,
Description: Primary productivity rates, measured during the 1992 United States Joint Global Ocean Flux Study (U.S. JGOFS) Equatorial Pacific (EqPac) process study with a new Trace-Metal clean rosette system (TM rosette) designed to be trace-metal clean, agreed within 5% with those determined using ultra-clean procedures that were previously shown to be trace-metal clean. The TM rosette system did not inhibit phytoplankton primary productivity rates. Using the TM rosette system, there was no contamination of Co, Ni, Cu, Cd or Pb, and only slight contamination of Fe and Zn, relative to ultra-clean collection. However, the slight contaminations were below levels that affect primary productivity rates. Therefore, systematic phytoplankton inhibition by trace-metal contamination appears to have been successfully eliminated with water collected using the TM rosette system. © 1995., Cited By (since 1996):16, CODEN: DSROE, ,
Author: Sanderson, Hunter, Fitzwater, Gordon, Barber
Date: 1995-01-01T00:00:00Z

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: Silver distributions and fluxes in north-east Pacific waters,
Description: In recent years, significant knowledge has been gained about the oceanic distributions of several trace elements 1,2. However, relatively little is known about amounts of Ag in the ocean, and how this element cycles through it. We report here that Ag levels are relatively low near the surface (∼1 pmol kg -1), and that concentrations more or less steadily increase with depth; for example, 23 pmol kg -1 at 2,440 m, the deepest sample we collected. In general, Ag depth profiles are similar to those observed for Cu (Fig. 1). The near-surface cycles of Ag appears to be involved with particulate organic matter uptake-sinking-regeneration processes. © 1983 Nature Publishing Group., Cited By (since 1996):39, Oceanography, ,
Author: Martin, Knauer, Gordon
Date: 1983-01-01T00:00:00Z

Title: Surface ocean-lower atmosphere interactions in the Northeast Pacific Ocean Gyre: Aerosols, iron, and the ecosystem response,
Description: Here we report measurements of iron and aluminum in surface and subsurface waters during late March and late May of 2001 on transects between central California and Hawaii. A large cloud of Asian dust was detected during April 2001, and there was a clear signal in surface water iron due to aerosol deposition on the May transect. Iron and aluminum concentrations increased synchronously by 0.5 and 2 nM along the southern portion of the transect, which includes the Hawaii Ocean Time series (HOT) station, from background values in March (0.1 to 0.2 nM Fe). These changes occured in a ratio that is close to the crustal abundance ratio of the metals, which indicates a soil aerosol source. A vertical profile of dissolved iron was also measured at the HOT station in late April and this profile also shows a large increase near the surface. Direct observations of aerosol iron concentration at Mauna Loa Observatory on Hawaii indicate that aerosol concentrations were significantly lower than climatological values during this period. Soil aerosol concentrations along the transect were estimated using the real-time Navy Aerosol Analysis and Prediction System (NAAPS). The NAAPS results show a large meridional gradient with maximum concentrations in the boundary layer north of 30°N. However, the deposition of iron and aluminum to surface waters was highest south of 25°N, near Hawaii. There were only weak signals in the ecosystem response to the aerosol deposition., Cited By (since 1996):64, Oceanography, , , Downloaded from: http://onlinelibrary.wiley.com/doi/10.1029/2002GB002004/pdf (16 June 2014).
Author: Johnson, Elrod, Fitzwater, Plant, Chavez, Tanner, Gordon, Westphal, Perry, Wu, Karl
Date: 2003-01-01T00:00:00Z

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-enrichment bottle experiments in the equatorial Pacific: Responses of individual phytoplankton cells,
Description: Iron-enrichment bottle experiments were monitored using flow cytometry to investigate the hypothesis that phytoplankton in the equatorial Pacific are iron-limited. Iron-enriched Synechococcus, ultraphytoplankton, nanophytoplankton, pennate diatoms, and coccolithophorids had higher fluorescence and/or forward light scatter per cell than control cells; for Prochlorococcus the trends were the same although the differences were not significant. This suggests that most phytoplankton cells were physiologically affected by the low iron concentrations in this region. However, only pennate diatoms showed significant increases in cell concentrations due to iron enrichment. The sum of chlorophyll fluorescences of individual cells measured by flow cytometry yielded patterns similar to those of extracted bulk chlorophyll, with increases of up to 10-fold in iron-enriched bottles but at most 3-fold in control bottles; pennate diatoms accounted for most of the increase in chlorophyll in iron-enriched bottles., Cited By (since 1996):39, CODEN: DSROE, ,
Author: Zettler, Olson, Binder, Chisholm, Fitzwater, Gordon
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 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