Search results

Title: In situ chemical mapping of dissolved iron and manganese in hydrothermal plumes,
Description: Hydrothermal vents along mid-ocean ridges are an important source of elements such as lithium, silicon, manganese and iron to the world's oceans. The venting produces both episodic and steady-state hydrothermal plumes with unique thermochemical signatures in the mid-water column. The particulate phases in these plumes (predominantly iron oxides and hydroxides) also scavenge phosphorus, vanadium, arsenic, lead, polonium and several rare-earth elements from sea water. Thus, on a global scale, hydrothermal plumes are both a source for some elements and a sink for others. Ultimately, the particulate metals precipitated from plumes form extensive regions of metalliferous sediments over the crests and flanks of mid-ocean ridges. Although the metalliferous sediment coverage is vast and well documented, only a tiny fraction of the vents responsible for these sediments have been located (Fig. 1a). To date, both the number and location of hydrothermal vents and the detailed distribution of chemical constituents within the resultant plumes are poorly understood because of under-sampling of the mid-ocean ridges and the overlying waters. Here we present the results of high-resolution mapping of the chemical and thermal characteristics of hydrothermal plumes in near real time using a novel submersible chemical analyser (Scanner) and a conductivity/temperature/depth/transmissometer instrument package (CTDT). We show that the kinetics of iron oxidation in the plume can be used to constrain estimates of the plume's age, and that variation in the ratio of manganese content to excess heat can be explained by the mixing of several different vent fluids., Cited By (since 1996):31, CODEN: NATUA, ,
Author: Coale, Chin, Massoth, Johnson, Baker
Date: 1991-01-01T00:00:00Z

Title: Sediment-water exchange of total mercury and monomethyl mercury in the San Francisco Bay-Delta,
Description: Five field trips were conducted in the San Francisco Bay-Delta between May 2000 and October 2001 to investigate the sediment-water exchange of total mercury (Hg) and monomethyl mercury (MMHg). Solid-phase Hg averaged ∼1 nmol g -1 and did not show any variability with depth or time or among sites. In contrast, solid-phase MMHg showed considerable vertical, temporal, and spatial variability (0.4-66 pmol g -1), with the highest values occurring at a peat-rich environment in May 2001, suggesting that MMHg production was largely controlled by temporal factors and habitat type. In pore water, both Hg and MMHg concentrations were generally elevated near the sediment-water interface during warm months. Sediment-water exchange flux of MMHg, determined with benthic chamber deployments, ranged from -92 to 850 pmol m -2 d -1, with higher values occurring in May. In most cases, diffusional fluxes of Hg and MMHg, estimated with the use of interfacial concentration gradients, constituted only a minor portion of the measured fluxes, suggesting the importance of advective processes on sediment-water exchange. Surface-water transect and time series studies conducted in Franks Tract support the commonly held belief that wetland and marsh regions are major sources for MMHg within the Delta. The integrated sediment-water fluxes of Hg and MMHg in the study area were estimated to be 130 and 6 mmol d -1, respectively, and the benthic input was as important a source of Hg and MMHg as the riverine input within the Delta during low-flow months., Cited By (since 1996):63, Rocks and Cores, Oceanography, CODEN: LIOCA, ,
Author: Choe, Gill, Lehman, Han, Heim, Coale
Date: 2004-01-01T00:00:00Z

Title: Benthic manganese fluxes along the Oregon-California continental shelf and slope
Description: Here we examine the factors that influence the manganese (Mn) benthic flux from eastern North Pacific marine sediments, with a primary emphasis on continental shelf locations off Oregon and California and studies that involve the use of in situ benthic chambers. Typical shelf-to-shallow margin (<~350m) sites have benthic Mn efflux rates that average ~8±5μmolm-2d-1. In contrast, for the Eel River continental shelf region the benthic Mn efflux can be an order of magnitude higher than other shelf settings with benthic effluxes exceeding ~50μmolm-2d-1. Based on prior work and some new results, continental margin and slope sites (350-~4000m) have benthic Mn efflux rates that average ~1±1μmolm-2d-1. The combination of the benthic flux and Mn solid-phase data, indicate that for the continental shelf off the Umpqua and Eel Rivers, approximately 15±10% of the total Mn that is delivered to the seafloor is remobilized. The compiled data set shows that the benthic Mn efflux co-varies with the organic carbon oxidation rate with a Mn to organic carbon oxidation (Cox) ratio of ~0.8mmol Mn mol-1. Although this ratio can be as high as ~5 for some Eel River sites, the generally close correspondence between Mn and organic carbon implies that the organic carbon oxidation rate exerts some primary control over the rate of the Mn efflux. The amount of organic carbon oxidized by Mn-oxides, however, represents a small fraction (i.e., generally <1%) of the total organic carbon oxidized in these seafloor sediments. © 2012 Elsevier Ltd., Cited By (since 1996):5, Oceanography, CODEN: CSHRD
Author: McManus, Berelson, Severmann, Johnson, Hammond, Roy, Coale
Date: 2012-01-01T00:00:00Z

Title: Isotopic tracers of lead contamination in the Great Lakes,
Description: , , , Fluxes of lead to the Great Lakes are dominated by atmospheric depositions of industrial lead, which account for ~ 64% of the lead inputs to Lake Ontario and >90% of the inputs to Lake Superior. It has recently been demonstrated that lead aerosols in the Great Lakes region may be identified by the contrasting 206Pb/207Pb ratios of industrial leads from the United States (1.221 ±0.009) and Canada (1.151 ±0.010). Here we show that those ratios may also be used to identify and trace industrial lead inputs to the Great Lakes. These corroborate spatial gradients in lead concentrations in surface waters, which range from 290 pmol kg−1 in Hamilton Harbour to <10 pmol kg−1 in the central waters of Lake Ontario. The latter concentrations and corresponding residence-time estimates, which are both an order of magnitude lower than previously reported, indicate that lead is rapidly scavenged in the epilimnion during periods of high primary productivity. We find that industrial lead from Canada and the United States are the two principal sources of lead contamination in the Great Lakes., ,
Author: Flegal, Nriagu, Niemeyer, Coale
Date: 1989-01-01T00:00:00Z

Title: Assessing mercury exposure and biomarkers in largemouth bass (Micropterus Salmoides) from a contaminated river system in California
Description: We evaluated mercury (Hg) exposure and two biomarkers, metallothionein (MT) gene expression and histopathological alterations in a wild fish species, largemouth bass (Micropterus salmoides), collected from the Sacramento-San Joaquin Delta, CA, a region polluted with Hg from historic mining activities. Hg is highly toxic and can disrupt multiple physiological systems in vertebrate species, including the immune system. Total mercury (THg) concentration in muscle tissue ranged from 0.12 to 0.98 ppm (wet weight) and was not related to body condition (r 2 = 0.005, p = 0.555). Using linear regression analysis, we found a positive relationship between MT gene expression (as determined using quantitative polymerase chain reaction) and copper, zinc, manganese, aluminum, and nickel (decreased to one variable by way of principal component analysis) (r 2 = 0.379, p = 0.044), a negative relationship with selenium (r 2 = 0.487, p = 0.017), and a weak, negative relationship with THg concentrations (r 2 = 0.337, p = 0.061). Juvenile largemouth bass collected from Hg-contaminated areas displayed histopathological features of immunosuppression compared with those collected from less contaminated areas as evidenced by significantly lower macrophage density in kidney and liver tissue (p = 0.018 and 0.020, respectively), greater trematode density in liver tissue (p = 0.014), and a greater number of adult trematodes. Our results suggest that largemouth bass may be experiencing sublethal effects from chronic Hg exposure. Furthermore, our findings illustrate the utility of examining multiple sublethal markers of effect to assess the impacts of contaminant exposure on physiological function in wild species. © 2012 Springer Science+Business Media New York., Fish and Fisheries, CODEN: AECTC
Author: Gehringer, Finkelstein, Coale, Stephenson, Geller
Date: 2013-01-01T00:00:00Z

Title: Trace metals and nitrogenous nutrition of Antarctic phytoplankton: Experimental observations in the Ross Sea,
Description: As part of the US JGOFS Antarctic Environment Southern Ocean Process Study (AESOPS), shipboard incubation experiments were conducted to investigate the effects of iron and zinc addition on ammonium (NH4+) and nitrate (NO3-) uptake by natural assemblages of Antarctic phytoplankton. Samples were collected from the Ross Sea during austral summer (January-February, 1997) within the mixed layer at two stations: a continental shelf station - Orca, and a high NO3-, low chlorophyll (HNLC) station located further offshore - Blue. Twenty-liter bottle incubations were sampled repeatedly during an 8-day period at Orca, and a 13-day period at Blue for short-term 15N-tracer uptake experiments. Ambient concentrations of NO3- were elevated at both locations. Biomass, measured as chlorophyll a (chl a), was relatively high at Orca (chl a = 2.31 μgl-1), whereas true HNLC conditions were observed at Blue (chl a = 0.52 μgl-1). All Fe enrichments produced an acceleration in NO3- decline, and accumulation in biomass. Chl a increased 2-3-fold at Orca and 4-5-fold at Blue; these increases were directly correlated with increasing Fe enrichment. Unambiguous responses to zinc addition were not evident at Blue, whereas increased total biomass accumulation and nitrate drawdown were observed at Orca. Rates of biomass (particulate nitrogen) specific NO3--uptake in the Fe-enriched samples were up to 2-fold greater than un-enriched controls at both sites. There were no significant changes in specific uptake rates of NH4+ at the HNLC site, and only a 30-40% increase at Orca with the highest Fe enrichments. These results clearly indicate that Fe additions resulted in faster rates of NO3- consumption per unit phytoplankton biomass at both sites. The N-uptake response to zinc enrichment was not as evident as with Fe, presumably due in part to the relatively high dissolved concentrations of zinc (ambient concentrations = ca. 2 nM). However, during the later sampling periods, zinc addition resulted in a 40% increase in the specific uptake rates of NO3- but not NH4+, whereas the specific uptake rates of NO3- and NH4+ increased by 4-16% and 18-49%, respectively, at Orca. Absolute uptake rates of NO3-- and NH4+ (corrected for isotopic dilution) were 4-5 and 2-3 times greater, respectively, than the controls at Blue, whereas at Orca both NO3-- and NH4+-uptake rates doubled as a result of Fe enrichment. Post-incubation, size-fractionation uptake experiments demonstrated that the higher rates of nitrogen uptake were primarily due to larger phytoplankton (> 5 μm). The f-ratio [f = NO3--uptake/(NO3- + NH4+-uptake)] increased from ca. 0.7 to 0.8 as a result of Fe enrichment at the HNLC site, but declined from an average of 0.84 to 0.52-0.69 in both the controls and the Fe-amended samples collected further onshore at Orca. This decrease may be due to the inhibition of NO3--uptake by elevated NH4+ concentrations resulting from increased heterotrophic remineralization within the carboys over time. Based on the apparent half-saturation constant (Ks) of 0.09 nM Fe estimated for community planktonic NO3--uptake, the availability of dissolved Fe (ambient concentration = 0.03-0.04 nM) limits the uptake of NO3- by phytoplankton at the HNLC and continental shelf regions of the western Ross Sea during austral summer. © 2002 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):24, Antarctica, CODEN: DSROE, ,
Author: Cochlan, Bronk, Coale
Date: 2002-01-01T00:00:00Z

Title: Effects of iron, manganese, copper, and zinc enrichments on productivity and biomass in the subarctic Pacific,
Description: Natural plankton populations from subarctic Pacific surface waters were incubated in 7-d experiments with added concentrations of Fe, Mn, Cu, and Zn. Small additions of metals (0.89 nM Fe, 1.8 nM Mn, 3.9 nM Cu, and 0.75 nM Zn) were used to simulate natural perturbations in metal concentrations potentially experienced by marine plankton. Although the controls indicated little growth, increases in phytoplankton productivity, Chl a, and cell densities were dramatic after addition of 0.89 nM Fe, indicating that it may limit the rates of algal production in these waters. Similar increases were observed in experiments with 3.9 nM Cu added. The Cu effect is attributed to a decrease in the grazing activities of the microzooplankton (ciliates) and increases in the rates of production. Mn enrichment had its greatest effect on diatom biomass, whereas Zn enrichment had its greatest effect on other autofluorescent organisms. Natural systems may be affected as follows: natural levels of Fe and Cu may influence phytoplankton productivity and trophic structure in open-ocean, high-nutrient, low-biomass systems; rates of net production are not limited by one micronutrient alone. -from Author, , , ,
Author: Coale
Date: 1991-01-01T00:00:00Z

Title: Copper complexation in the Northeast Pacific,
Description: Copper titrations were conducted at sea with differential pulse anodic stripping voltammetry to examine the degree to which copper was associated with organic ligands. Greater than 99.7% of the total dissolved copper in surface waters of the central Northeast Pacific shallower than 200 m was estimated to be associated with strong organic complexes. Below 200 m, increasing proportions of inorganic or labile copper species were observed. At middepths (1000 m), about 50-70% of the total dissolved copper was in the organically complexed form. Whereas total copper varies by a factor of only three from the surface to middepths (0.6-1.8 nM), copper complexation gives rise to extremely low cupric ion activities in surface waters ({Cu2+} = 1.4 × 10-4 M) and higher values at middepth ({Cu2+} = 10-11 M) -a variation of three orders of magnitude., Cited By (since 1996):208 Oceanography, ,
Author: Coale, Bruland
Date: 1988-01-01T00:00:00Z

Title: Spectrophotometric determination of dissolved manganese in natural waters with 1-(2-pyridylazo)-2-naphthol: Application to analysis in situ in hydrothermal plumes,
Description: A spectrophotometric method using the complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN) was developed for the determination of dissolved manganese in seawater. A detection limit of approximately 22 nM was obtained when the analyses were performed in situ with a submersible chemical analyzer (Scanner). Color formation was rapid (less than 1 s), which permitted the technique to be used in flow injection and continuous flow systems. An investigation of possible interferences revealed that the only significant interferent to manganese determinations in seawater (hydrothermal plumes) was iron. The iron-specific chelating agent desferrioxamine B was used to mask this interference. Temperature and pressure did not adversely affect the sensitivity of the technique, which made it amenable to applications in situ to depths of 3000 m. This method was tested by measuring dissolved manganese concentrations in situ in submarine hydrothermal plumes using a Scanner. Scanner deployments over the Juan de Fuca Ridge produced the first near real time analyses of manganese from a hydrothermal plume environment. Estuarine samples have also been successfully analyzed in the laboratory and the results confirmed by an independent method. © 1992., Cited By (since 1996):22, Oceanography, CODEN: MRCHB, ,
Author: Chin, Johnson, Coale
Date: 1992-01-01T00:00:00Z

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: 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: 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: Biological response to iron fertilization in the eastern equatorial Pacific (IronEx II). I. Microplankton community abundances and biomass,
Description: During the IronEx II experiment in the eastern equatorial Pacific (May to June 1995), the response of the microplankton community to mesoscale iron fertilization was followed using a combination of marker-pigment, microscopical and flow cytometric techniques. Phytoplankton standing stock bloomed dramatically over a period of 6 d following 3 iron additions of 2 and 1 nM, respectively. Carbon biomass in the patch increased by a factor of 4, chlorophyll a by about a factor of 16 and diatoms by > 70-fold relative to contemporaneous levels in the ambient community. The bloom then plateaued sharply and remained at a more or less constant level for 4 d, despite the addition of more iron (1 nM) and physiological indices (low C:chl a ratio and elevated photochemical quantum efficiency) suggesting that the cells were healthy and growing rapidly. Relatively large pennate diatoms (Nitzschia spp., median length 20 to 24 μm) dominated the patch bloom, with smaller pennate species and centric diatoms declining in relative importance. Heterotrophic bacteria increased at a slow rate (0.08 d -1) for > 10 d during the experiment, as did heterotrophic nanoflagellates. There were also indications of enhanced cell size, cellular pigment content and possibly growth rates of small phytoplankton. Nonetheless, little difference was observed between the ambient community and the peak patch bloom with respect to the size composition of auto- and heterotrophic populations < 10 μm in cell size. The relative constancy of the smaller size fractions, the sharp curtailment of net growth of the bloom after 6 d, and > 3-fold increase in large heterotrophic dinoflagellates and ciliates suggest that protistan grazers may have played an active role in controlling the phytoplankton response to increased iron availability., , , ,
Author: Landry, Ondrusek, Tanner, Brown, Constantinou, Bidigare, Coale, Fitzwater
Date: 2000-01-01T00:00:00Z

Title: 234Th:238U disequilibria within the California Current
Description: Profiles of dissolved and particulate 234Th were determined at several stations within the California Current. Modeling of the disequilibria between the 234Th and 23aU within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging (TP varies from 6 to 50 days), the particle residence time (TP varies from 2 to 20 days), and the particulate 234Th flux exiting the surface layer. The model-derived, first-order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production. Particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present. Model-derived particulate 234Th fluxes are in good agreement with direct measurements by sediment traps.
Author: Coale, Bruland
Date: 1985-01-01T00:00:00Z

Title: Multidrug efflux transporters limit accumulation of inorganic, but not organic, mercury in sea urchin embryos,
Description: Mercuric compounds are persistent global pollutants that accumulate in marine organisms and in humans who consume them. While the chemical cycles and speciation of mercury intheoceansarerelativelywelldescribed, thecellularmechanisms that govern which forms of mercury accumulate in cells and why they persist are less understood. In this study we examined the role of multidrug efflux transport in the differential accumulation of inorganic (HgCl2) and organic (CH3HgCl) mercury inseaurchin (Strongylocentrotus purpuratus) embryos. We found that inhibition of MRP/ABCC-type transporters increases intracellular accumulation of inorganic mercury but had no effect on accumulation of organic mercury. Similarly, pharmacological inhibition of metal conjugating enzymes by ligands GST/GSH significantly increases this antimitotic potency of inorganic mercury, but had no effect on the potency of organic mercury. Our results point to MRP-mediated elimination of inorganic mercury conjugates as a cellular basis for differences in the accumulation and potency of the two major forms of mercury found in marine environments. © 2009 American Chemical Society., Cited By (since 1996):9, CODEN: ESTHA, ,
Author: Bošnjak, Uhlinger, Heim, Smital, Franekić-Čolić, Coale, Epel, Hamdoun
Date: 2009-01-01T00:00:00Z

Title: A time series of benthic flux measurements from Monterey Bay, CA,
Description: In situ incubation chamber measurements of benthic nutrient recycling rates were made on the Monterey Bay shelf at 100m during various years and seasons. Variability in nutrient (Si, PO 4 2+, NH 3, NO 3 -) and trace metal (Mn, Fe (II), Cu) fluxes correlate with variability in the amount of organic carbon oxidized on the sea floor. Patterns of primary productivity show a mid-year maxima, consistent with the timing of increased rates of benthic C org and opal recycling. High rates of C org rain to the shelf promote nitrate consumption at a rate that equals or exceeds ammonia efflux. Low rates of C org rain promote greater efflux of DIN; thus these margin sediments provide a negative feedback to local productivity cycles. The efflux of iron (II) from shelf sediments is sufficient to support > 100% of new production, yet Fe flux is positively correlated with C org recycling which lags the maximum in new production. On account of this time lag, diagenetically recycled Fe is not likely a micro-nutrient trigger of new production, but could serve as a positive feedback. Bio-irrigation rates are seasonally variable by 30% but maximal during the maximum productivity months. © 2003 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):65, CODEN: CSHRD, , , Oceanography
Author: Berelson, McManus, Coale, Johnson, Burdige, Kilgore, Colodner, Chavez, Kudela, Boucher
Date: 2003-01-01T00:00:00Z

Title: SeaWiFS satellite ocean color data from the Southern Ocean,
Description: SeaWiFS estimates of surface chlorophyll. concentrations are reported for the region of the U.S. JGOFS study in the Southern Ocean (∼ 170 °W, 60 °S). Elevated chlorophyll was observed at the Southern Ocean fronts, near the edge of the seasonal ice sheet, and above the Pacific-Antarctic Ridge. The elevated chlorophyll levels associated with the Pacific-Antarctic Ridge are surprising since even the crest of the ridge is at depths > 2000 m. This elevated phytoplankton biomass is likely the result of mesoscale physical-biological interactions where the Antarctic Circumpolar Current (ACC) encounters the ridge. Four cruises surveyed this region between October 1997 and March 1998, as part of the U.S. JGOFS. Satellite-derived chlorophyll concentrations were compared with in situ extracted chlorophyll measurements from these cruises. There was good agreement (r 2 of 0.72, from a linear regression of shipboard vs. satellite chlorophyll), although SeaWiFS underestimated chlorophyll concentrations relative to the ship data. Copyright 1999 by the American Geophysical Union., Cited By (since 1996):83, CODEN: GPRLA, ,
Author: Moore, Abbott, Richman, Smith, Cowles, Coale, Gardner, Barber
Date: 1999-01-01T00:00:00Z

Title: Phosphorus regeneration in continental margin sediments,
Description: Benthic incubation chambers have been deployed in a variety of geochemical environments along the California Continental Margin. These include both high and low oxygen environments and sites where the rate of organic matter oxidation on the seafloor (Cox) ranges from < 1 mmol m-2 day-1 to more than 7 mmol m-2 day-1 through a depth range of 100-3500 m. This range in the rate of organic matter oxidation along with variations in the concentration of bottom water oxygen allow us to elucidate the diagenetic conditions under which P regeneration may be decoupled from organic matter cycling. Under conditions where bottom water oxygen concentration is low (<50 μM), and the rate of organic matter oxidation is also low (< 1 mmol m-2 day-1), P regeneration may be less than that expected from the decay of organic debris and, in some cases, there is a flux of phosphate into the sediments. At stations where bottom water oxygen is low, and the degradation rate of organic material is greater than 1 mmol m-2 day-1, phosphate may be released at a rate exceeding the production expected from the oxidation of organic matter. At stations having high bottom water oxygen concentrations, rates of organic matter decomposition < ∼7 mmol m-2 day-1, and where benthic irrigation is not significant, P regeneration is consistent with that expected from the decomposition of organic debris. In addition, our data indicate that high benthic iron fluxes are observed in regions exhibiting a decoupling between organic matter and phosphate, whereas low to zero iron fluxes are observed in regions where P regeneration is either consistent with or less than that expected from the decomposition of organic material. These results support previous work suggesting a coupling between iron cycling and phosphate cycling in suboxic environments. Data presented here show that this coupling may result in either preferential phosphate burial or release relative to organic material in suboxic environments. Copyright © 1997 Elsevier Science Ltd., Cited By (since 1996):105, ,
Author: Mcmanus, Berelson, Coale, Johnson, Kilgore
Date: 1997-01-01T00:00:00Z

Title: Mesoscale iron enrichment experiments 1993-2005,
Description: Since the mid-1980s, our understanding of nutrient limitation of oceanic primary production has radically changed. Mesoscale iron addition experiments (FeAXs) have unequivocally shown that iron supply limits production in one-third of the world ocean, where surface macronutrient concentrations are perennially high. The findings of these 12 FeAXs also reveal that iron supply exerts controls on the dynamics of plankton blooms, which in turn affect the biogeochemical cycles of carbon, nitrogen, silicon, and sulfur and ultimately influence the Earth climate system. However, extrapolation of the key results of FeAXs to regional and seasonal scales in some cases is limited because of differing modes of iron supply in FeAXs and in the modern and paleo-oceans. New research directions include quantification of the coupling of oceanic iron and carbon biogeochemistry., Cited By (since 1996):367, CODEN: SCIEA, ,
Author: Boyd, Jickells, Law, Blain, Boyle, Buesseler, Coale, Cullen, De Baar, Follows, Harvey, Lancelot, Levasseur, Owens, Pollard, Rivkin, Sarmiento, Schoemann, Smetacek, Takeda, Tsuda, Turner, Watson
Date: 2007-01-01T00:00:00Z

$Diagenetic fractionation of Ge and Si in reducing sediments$

Title: Diagenetic fractionation of Ge and Si in reducing sediments,
Description: The average Ge/Si ratio in the ocean is determined by the budgets for each of these elements. Previous budget formulations have assumed that the only important sink for both elements is burial as opal, based on studies of the Si cycle and the close oceanic coupling observed between inorganic Ge and Si distributions. However, these budgets implied two paradoxes: (1) hydrothermal flow through ocean ridges is smaller than predicted by other tracers, and (2) the lower Ge/Si ratio of opal deposited during glacial times compared to that deposited during interglacial times required enhanced weathering during cooler, drier climates. Both paradoxes could be resolved if a significant sedimentary sink for Ge other than opal burial could be identified, and the objective of this study was to search for one. Two pore water profiles collected in Equatorial Pacific sediments show that Ge and Si behave similarly in the upper 10 cm of sediment, indicating no evidence for a significant non-opal sink for Ge in oxic sediments. By contrast, profiles in several cores from the California Margin demonstrate that in reducing sediments, Ge diagenesis is poorly coupled to Si diagenesis: significant Ge removal is evident, both downcore and sometimes in the near-surface. Benthic flux chamber measurements at three continental slope stations, all with an oxic layer less than 1 cm thick and large iron gradients in near-surface pore waters, showed that 55 ± 9% of the Ge released by opal dissolution is sequestered. However, at two locations with anoxic sediments but little pore water Fe+2 in the upper 2 cm, flux measurements indicated little fractionation from the oceanic ratio during diagnesis, implicating the importance of iron for fractionating Ge from Si during diagenesis. If the Ge sequestration observed in the iron-rich CA margin sediments is typical of all slope sediments (using a depth range of 200-1000 m), then the Ge sink is sufficient to bring the hydrothermal budget based on Ge into concurrence with that based on other tracers. The temporal variation in oceanic Ge/Si could be explained if Ge and Si inputs remain constant and the effective diagenetic fractionation of Ge increases by a factor of 2-3 during glacial times. Increased fractionation would require that glacial periods are characterized by increased opal dissolution in iron-rich reducing sediments; this could be caused by (1) thinning of the oxygenated sediment layer in response to decreased bottom water oxygen concentrations or increased rain of organics to the sea floor, (2) increased rain of iron-rich detrital sediments in areas receiving high opal rain, (3) increased rain of opal to sediments in margin areas. If the oceanic Ge/Si ratio reflects increased rain of diatom opal or organic carbon in margin areas during glacial periods, it may indicate an increase in the efficiency of the biological pump for CO2 during glacial times. Copyright (C) 2000 Elsevier Science Ltd., Cited By (since 1996):38, Oceanography, ,
Author: Hammond, McManus, Berelson, Meredith, Klinkhammer, Coale
Date: 2000-01-01T00:00:00Z

Title: Labyrinth of doom: a device to minimize the "swimmer' component in sediment trap collections,
Description: The device consists of a series of funnels which concentrate passively sinking material into a central collection tube, whereas swimmers are distributed randomly between the inner and outer collection tubes., , ,
Author: Coale
Date: 1990-01-01T00:00:00Z

Title: Synthesis of iron fertilization experiments: From the iron age in the age of enlightenment,
Description: Comparison of eight iron experiments shows that maximum Chl a, the maximum DIC removal, and the overall DIC/Fe efficiency all scale inversely with depth of the wind mixed layer (WML) defining the light environment. Moreover, lateral patch dilution, sea surface irradiance, temperature, and grazing play additional roles. The Southern Ocean experiments were most influenced by very deep WMLs. In contrast, light conditions were most favorable during SEEDS and SERIES as well as during IronEx-2. The two extreme experiments, EisenEx and SEEDS, can be linked via EisenEx bottle incubations with shallower simulated WML depth. Large diatoms always benefit the most from Fe addition, where a remarkably small group of thriving diatom species is dominated by universal response of Pseudo-nitzschia spp. Significant response of these moderate (10-30 μm), medium (30-60 μm), and large (>60 μm) diatoms is consistent with growth physiology determined for single species in natural seawater. The minimum level of "dissolved" Fe (filtrate < 0.2 μm) maintained during an experiment determines the dominant diatom size class. However, this is further complicated by continuous transfer of original truly dissolved reduced Fe(II) into the colloidal pool, which may constitute some 75% of the "dissolved" pool. Depth integration of carbon inventory changes partly compensates the adverse effects of a deep WML due to its greater integration depths, decreasing the differences in responses between the eight experiments. About half of depth-integrated overall primary productivity is reflected in a decrease of DIC. The overall C/Fe efficiency of DIC uptake is DIC/Fe ∼ 5600 for all eight experiments. The increase of particulate organic carbon is about a quarter of the primary production, suggesting food web losses for the other three quarters. Replenishment of DIC by air/sea exchange tends to be a minor few percent of primary CO2 fixation but will continue well after observations have stopped. Export of carbon into deeper waters is difficult to assess and is until now firmly proven and quite modest in only two experiments. Copyright 2005 by the American Geophysical Union., Cited By (since 1996):271, Oceanography, Art. No.: C09S16, , , Downloaded from: http://onlinelibrary.wiley.com/doi/10.1029/2004JC002601/pdf (16 June 2014).
Author: de Baar, Boyd, Coale, Landry, Tsuda, Assmy, Bakker, Bozec, Barber, Brzezinski, Buesseler, Boyé, Croot, Gervais, Gorbunov, Harrison, Hiscock, Laan, Lancelot, Law, Levasseur, Marchetti, Millero, Nishioka, Nojiri, van Oijen, Riebesell, Rijkenberg, Saito, Takeda, Timmermans, Veldhuis, Waite, Wong
Date: 2005-01-01T00:00:00Z

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: 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: The Galapagos iron experiments: Preface,
Description: , , , , ,
Author: Coale
Date: 1998-01-01T00:00:00Z

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