Search results | Digital Commons of Moss Landing Marine Laboratories

Title: The flux of iron from continental shelf sediments,
Description: The flux of dissolved iron from sediments to the water column was measured with flux chambers along the California coast over a five-year period. High fluxes were observed from sediments on the continental shelf. The measured fluxes were an average of 75 times larger than flux values derived from pore-water iron gradients. The iron flux was significantly correlated with the oxidation of organic matter, which allows an extrapolation to the global shelf. The input from shelf sediments is at least as significant as the global input of dissolved iron from aerosols, which has been presumed to be the dominant external iron source. Evidence of this input is seen 100's of kilometers offshore where it can enable the high productivity of broad coastal regions seen in satellite images. Copyright 2004 by the American Geophysical Union., Cited By (since 1996):125, Oceanography, CODEN: GPRLA, ,
Author: Elrod, Berelson, Coale, Johnson
Date: 2004-01-01T00:00:00Z

Title: Determination of subnanomolar levels of iron(II) and total dissolved iron in seawater by flow injection analysis with chemiluminescence detection
Description: A highly sensitive technique for the rapid determination of Fe( I I) and total dlssolved iron in seawater has been developed. The technlque employs flow Injection analysis and chemiluminescence detectlon (FIA-CL). The light Is emitted by the reaction of brilliant sulfoflavin with hydrogen peroxlde and Fe( I I ) in a neutral medlum. A cation-exchange column Is used to preconcentrate the Iron from seawater. The detection limit was 0.45 nmol/L when 4.4 mL of sample was passed through the column. Lower detectlon llmlts are attainable wlth larger sample volumes. The relative standard deviation is 2-5% for concentrations greater than 2.5 nmd/L. A typical analysis can be performed In 5 mln. The technique was determlned to be accurate based on the analysis of the trace metal standard seawater solutions NASS and CASS. Shipboard analyses provided oceanographically consistent profiles for total iron and also revealed some of the first profiles for Fe(I1) in hydrothermal plume samples. A typical profile of 12 samples, together with blanks and standards, can be analyzed In triplicate in 4.5 h.
Author: Elrod, Johnson, Coale

Title: The flux of iron from continental shelf sediments: A missing source for global budgets
Description: The flux of dissolved iron from sediments to the water column was measured with flux chambers along the California coast over a five-year period. High fluxes were observed from sediments on the continental shelf. The measured fluxes were an average of 75 times larger than flux values derived from pore-water iron gradients. The iron flux was significantly correlated with the oxidation of organic matter, which allows an extrapolation to the global shelf. The input from shelf sediments is at least as significant as the global input of dissolved iron from aerosols, which has been presumed to be the dominant external iron source. Evidence of this input is seen 100’s of kilometers offshore where it can enable the high productivity of broad coastal regions seen in satellite images.
Author: Elrod, Berelson, Coale, Johnson

Title: Oxidation kinetics of manganese (II) in sea water at nanomolar concentrations,
Description: Manganese oxidation rates were determined at low (∼20 nM) concentrations in seawater by measuring dissolved manganese (Mn(II)) using flow injection analysis with chemiluminescence detection. Mn(II) was measured in samples that had been filtered (0.2 μm) and kept in the dark under controlled temperature and pH conditions for time periods up to 6 months. Eight 9 L carboys with mean pH values ranging from 8 to 8.7 were held at 25°C, another carboy (pH = 9.32) was kept at 5°C. Oxidation followed the Morgan (1967) homogeneous rate equation (d[Mn(II)]/dt = k1 [O2][OH-]2 [Mn(II)]). The mean rate constant k1 = 1.7 ± 0.7 × 1012 M-3 d-1 (95% CI), determined using hydroxide ion activities determined with pH measurements on the NBS scale, was in agreement with work by Morgan (1967; k1 = 4 × 1012 M-3 d-1) and Davies and Morgan (1989; k1 = 1.1 × 1012 M-3 d-1) in dilute solutions. The rate constant at 5°C was 1.3 ± 0.3 × 1012 M-3 d-1. If free hydroxide concentrations (based on the free proton pH scale) are used, then the rate constant at 25°C was k*1 = 0.34 ± 0.14 × 1012 M-3 d-1. Autocatalytic increases in Mn(II) oxidation rates, as predicted by a heterogeneous reaction mechanism (Morgan, 1967) (d[Mn(II)]/dt = k′2[Mn(II)][MnO2]) were not observed, indicating that the homogeneous reaction dominates Mn(II) oxidation at low nM concentrations in seawater. Bacteria were enumerated by 4′,6-diamidino-2-phenylindole (DAPI) staining during the experiments. No significant correlation between bacterial concentrations and Mn(II) oxidation rates was found. Copyright © 1997 Elsevier Science Ltd., Cited By (since 1996):26, ,
Author: Von Langen, Johnson, Coale, Elrod
Date: 1997-01-01T00:00:00Z

Title: Determination of zinc in seawater using flow injection analysis with fluorometric detection,
Description: A sensitive technique for the shipboard determination of zinc in seawater has been developed. The technique couples flow injection analysis with fluorometric detection (FIA-FL). A cation exchange column was used to separate zinc from interfering alkali and alkaline earth ions and to concentrate Zn from seawater. The organic indicator ligand, p-tosyl-8-aminoquinoline, was used to form a complex with zinc, the fluorescence of which was determined with a flow-through fluorometer. The detection limit (defined as three times the standard deviation of the blank, n = 4) was 0.1 nM for a 4.4-mL sample. The precision based on the replicate analysis of samples containing 4.3 nM Zn was ±6% (n = 5). A single sample can be analyzed in 6 min. The technique was determined to be accurate on the basis of analysis of the standard seawater solutions CASS-2 and N ASS-2 and by comparison with previous reliable investigations. A typical profile of 12 samples along with standards and blanks can be completed in triplicate in 5.5 h., Cited By (since 1996):31, CODEN: ANCHA, ,
Author: Nowicki, Johnson, Coale, Elrod, Lieberman
Date: 1994-01-01T00:00:00Z

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: Manganese flux from continental margin sediments in a transect through the oxygen minimum,
Description: The flux of manganese from continental margin sediments to the ocean was measured with a free-vehicle, benthic flux chamber in a transect across the continental shelf and upper slope of the California margin. The highest fluxes were observed on the shallow continental shelf. Manganese flux decreased linearly with bottom water oxygen concentration, and the lowest fluxes occurred in the oxygen minimum zone (at a depth of 600 to 1000 meters). Although the flux of manganese from continental shelf sediments can account for the elevated concentrations observed in shallow, coastal waters, the flux from sediments that intersect the oxygen minimum cannot produce the subsurface concentration maximum of dissolved manganese that is observed in the Pacific Ocean., Cited By (since 1996):47, Oceanography, CODEN: SCIEA, ,
Author: Johnson, Berelson, Coale, Coley, Elrod, Fairey, Iams, Kilgore, Nowicki
Date: 1992-01-01T00:00:00Z

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: In situ observations of dissolved iron and manganese in hydrothermal vent plumes, Juan de Fuca Ridge,
Description: , , , In situ measurements of dissolved manganese and total dissolved iron were conducted in hydrothermal plumes over the Juan de Fuca Ridge using a submersible chemical analyzer (Scanner). The Scanner was deployed as part of a CTD/transmissometer/rosette instrument package on both tow-yos and vertical casts during the VENTS Leg I cruise in 1989. Dissolved manganese and total dissolved iron concentrations, along with temperature and light attenuation anomalies, were determined over the ridge crest every 5 s. Discrete samples for laboratory analyses of dissolved iron II, total dissolved iron II+ III and manganese were also collected. Metal to heat ratios (Me:Q) measured in situ were extremely variable in one steady state plume, while an event plume had constant Me:Q. Uniform values of Mn:Q in the event plume demonstrate that Mn behaves conservatively in the near-field plume. Variability in the Mn:Q ratios in a steady state plume indicated the presence of at least two hydrothermal sources with distinct Me:Q values. A simple mixing model shows that the contribution of Mn from high Me:Q sources, with a composition characteristic of black smoker vents, varies between 1% and 99% within the core of the steady state plume with an average value of 55%. On average, over 50% of the excess heat within the plume originates from low Me:Q ratio sources, with a composition characteristic of low-temperature, diffuse flow vent fluids. Less than 4% of the volume of hydrothermal fluids in the plume originates from black smokers. The Fe II concentrations were used to provide an estimate of plume age on a transect across the ridge axis. Plume ages were about 2.5 days on axis and > 12 days off axis. These plume ages were modeled to provide estimates of plume transport and horizontal diffusion and show excellent agreement with ages determined using 222Rn., ,
Author: Chin, Coale, Elrod, Johnson, Massoth, Baker
Date: 1994-01-01T00:00:00Z

Title: Iron photochemistry in seawater from the equatorial Pacific,
Description: Cited By (since 1996):141, CODEN: MRCHB, The photochemistry of iron in surface waters, and its implications to iron bioavailability, was examined on two cruises to the equatorial Pacific. Decktop incubations were performed with equatorial seawater to which iron was added in various chemical forms. Results showed clear diurnal patterns in measurable iron levels, with the highest levels occurring midday. These results are consistent with a model of iron cycling involving the photo-reductive dissolution of colloidal iron and its subsequent oxidation and biological uptake of dissolved iron(III). Model calculations were based on independently determined rate constants. We suggest that photochemical reactions may have a significant impact on iron availability to phytoplankton in the open ocean., ,
Author: Johnson, Coale, Elrod, Tindale
Date: 1994-01-01T00:00:00Z

Title: An evaluation of ISFET sensors for coastal pH monitoring applications
Description: Abstract The accuracy and precision of ion sensitive field effect transistor (ISFET) pH sensors have been well documented, but primarily by ocean chemistry specialists employing the technology at single locations. Here we examine their performance in a network context through comparison to discrete measurements of pH, using different configurations of the Honeywell DuraFET pH sensor deployed in six coastal settings by operators with a range of experience. Experience of the operator had the largest effect on performance. The average difference between discrete and ISFET pH was 0.005 pH units, but ranged from −0.030 to 0.083 among operators, with more experienced operators within ± 0.02 pH units of the discrete measurement. In addition, experienced operators achieved a narrower range of variance in difference between discrete bottle measurements and ISFET sensor readings compared to novice operators and novice operators had a higher proportion of data failing quality control screening. There were no statistically significant differences in data uncertainty associated with sensor manufacturer or deployment environment (pier-mounted, flowthrough system, and buoy-mounted). The variation we observed among operators highlights the necessity of best practices and training when instruments are to be used in a network where comparison across data streams is desired. However, while opportunities remain for improving the performance of the ISFET sensors when deployed by less experienced operators, the uncertainty associated with their deployment and validation was several-fold less than the observed natural temporal variability in pH, demonstrating the utility of these sensors in tracking local changes in acidification.
Author: McLaughlin, Dickson, Weisberg, Coale, Elrod, Hunter, Johnson, Kram, Kudela, Martz, Negrey, Passow, Shaughnessy, Smith, Tadesse, Washburn, Weis
Date: 2017-04-01T00:00:00Z