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Precise and accurate quantification of Ag and platinum group elements in marine, estuarine and riverine waters is challenging due to the complex matrices and ultra-low concentrations in the pmol kg− 1 and fmol kg− 1 range. A methodological approach has been developed for the analysis of Ag and Pt in seawater based on the extraction of their anionic chloro-complexes utilizing the strong anion exchange resin Dowex™ 1-× 8 in an off-line matrix separation and pre-concentration approach prior to determination by ICP-SFMS. The method allows simultaneous processing of four 100 mL samples at a flow rate of up to 2 mL min− 1 in an ultra-clean manifold. Enrichment factors of 40 could be achieved with elution into 2.5 g of a mixture of HNO3 /HCl, yielding adequately low detection limits to obtain open ocean profiles. Quantification was performed by matrix-matched calibration and internal standardization. To validate the accuracy of this approach, isotope dilution analysis was also used. The applicability of the method was demonstrated on a suite of reference samples and depth profiles collected during the 2009 2nd U.S. GEOTRACES Intercalibration cruise in the eastern North Pacific.

Distributions of iron and nitrate in the central California Current System upwelling regime (cCCS) from 34 to 41°N were determined during cruises in May 2010 and August 2011. High spatial and temporal resolution data for dissolved Fe and NO 3 − (nitrate+nitrite) in the cCCS from this study greatly expands upon previous studies that were narrower in scope (e.g., focused on just the Monterey Bay region). Shelf sediments from mid-shelf mud belts in this region provide the dominant source of Fe, and there are areas in the cCCS where insufficient Fe is upwelled to accompany elevated levels of other macronutrients (nitrate, phosphate, silicate) to fuel extensive diatom blooms. Surface dissolved Fe concentrations were related to continental shelf width and upwelling strength, and surface Fe concentrations tended to be lower in the late summer than early spring. We present extensive benthic boundary layer (BBL) dissolved and leachable particulate Fe data from both seasons in the mid-shelf region along the central California coast. Leachable particulate Fe concentrations were strongly related to the width of the mid-shelf mud belts (i.e., the continental shelf between the 50 and 90 m isobaths). Dissolved Fe concentrations in the BBL over the mid-shelf were generally highest in wide mud belt areas as well as in areas with very low dissolved oxygen concentrations but did not show a clear seasonal trend. Evidence for probable Fe limitation in upwelled waters was found by using surface dissolved Fe: NO 3 − ratios and the estimated specific growth rate of coastal diatoms based on either Fe or NO 3 − concentrations. Several coastal upwelling regions with only moderate to narrow continental shelves (Pt. Arena to Cape Mendocino and the Big Sur Coast) exhibited evidence for Fe limitation in both the spring and summer upwelling seasons.

Surface transects and vertical profiles of macronutrients, dissolved iron (D-Fe), and dissolved manganese (D-Mn) were investigated during August 2003 in the southeastern Bering Sea. We observed iron-limited, HNLC surface waters in the deep basin of the Bering Sea (15–20 μmol/kg nitrate, ∼0.07 nmol/kg D-Fe, and ⩽1.0 nmol/kg D-Mn); nitrate-limited, iron-replete surface waters over the shelf (

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes., National Science Foundation (U.S.) (OCE-0608600), National Science Foundation (U.S.) (OCE-0938349), National Science Foundation (U.S.) (OCE-1243377)

We compare the relative contribution of large phytoplankton (.5 and .10 mm) to uptake rates of carbon (C), nitrate (NO ), and dissolved silicon (Si) and uptake ratios of Si : NO and Si : C in Monterey Bay, California (a 2 2 3 3 high-iron region) with three low-iron regions in the eastern tropical Pacific: the Costa Rica upwelling dome, Humboldt current, and Peru upwelling. We also demonstrate the effect of iron enrichment on the above parameters in the latter three regions. In Monterey Bay waters, the .5-mm size fraction accounted on average for the majority of particulate organic C and was responsible for 92% of total C uptake, 81% of total NO uptake, and 98% of total 2 3 Si uptake. In contrast, in low-iron eastern tropical Pacific waters, the .5-mm size fraction accounted for less than half of the particulate organic C and was responsible for a substantially smaller proportion of total C and NO 2 3 uptake: 27‐43% for C and 34‐59% for NO . Iron enrichment experiments in the eastern tropical Pacific resulted 2 3 in much higher NO , C, and Si uptake rates, although increases were restricted to cells in the .5-mm size fraction. 2 3 Si : NO and Si : C uptake ratios decreased after iron addition at most locations, and decreases were a direct result 2 3 of lower Si : NO and Si : C uptake ratios in the .5-mm size fraction. Our results suggest that iron availability is a 2 3 major factor regulating primary production, new production, Si uptake, and Si : NO and Si : C uptake ratios in the 2 3 larger phytoplankton size classes in high-nitrate, low-chlorophyll (HNLC) regions in the eastern tropical Pacific.

Surface water transects and vertical profiles for dissolved iron, macronutrients, chlorophyll a (Chl a), and hydrographic data were obtained in the Peru upwelling regime during August and September 2000. The supply of the micronutrient iron, relative to that of the macronutrients nitrate, phosphate and silicic acid, is shown to play a critical role in allowing extensive diatom blooms to develop in the Peru upwelling system. The extremely high-chlorophyll bbrown waters of PeruQ (with Chl a concentrations between 20 and 45 Ag/l) result from massive diatom blooms with maximal photochemical efficiencies (Fv/Fm N0.6) occurring in the iron-rich upwelling region observed over the broad continental shelf off northern and central Peru. The source of the upwelled water in this region is the nutrient-rich subsurface countercurrent in contact with the organicrich shelf sediments. This subsurface shelf water is suboxic and has extremely high concentrations of dissolved Fe (N50 nM) in the near-bottom waters. In marked contrast, relatively low-chlorophyll bblue watersQ (Chl a b2 Ag/l) with low concentrations of dissolved Fe (b0.1 nM) and high unutilized macronutrient concentrations are observed in the coastal upwelled waters along the southern coast of Peru and in the offshore regions of the Peru Current. Southern Peru is a region without a wide shelf to serve as a source of iron and, as a result, dissolved Fe concentrations in the near-bottom suboxic waters of this region are an order-ofmagnitude lower than observed off northern and central Peru. In addition, the offshore Peru Current is a broad, Fe-limited, highnitrate, lower than expected chlorophyll region extending hundreds of kilometers offshore into the northeast region of the South Pacific subtropical gyre and northwestward into the South Equatorial Pacific. D 2004 Elsevier B.V. All rights reserved.

We investigated phytoplankton Fe limitation using shipboard incubation experiments in the high-nutrient South American eastern boundary current regime. Low ambient Fe concentrations (;0.1 nM) in water collected from the Humboldt and Peru Currents were supplemented with a range of added Fe levels up to 2.5 nM. Phytoplankton chlorophyll a, photosystem II photosynthetic efficiency, and nitrate and phosphate drawdown increased in proportion to the amount of Fe added. The Humboldt Current algal community after Fe additions included colonial and flagellated Phaeocystis globosa and large pennate diatoms, whereas the Peru Upwelling assemblage was dominated by coccolithophorids and small pennate diatoms. Apparent half-saturation constants for growth of the two communities were 0.17 nM Fe (Humboldt Current) and 0.26 nM Fe (Peru Upwelling). Net molar dissolved Si(OH)4 : NO drawdown ratios were low in both experiments (;0.2‐0.7), but net particulate silica to nitrogen production 2 3 ratios were higher. Fe limitation decreased net NO : PO utilization ratios in the Humboldt Current incubation to 2 32 34 well below Redfield values. Phytoplankton community sinking rates were decreased by Fe additions in the Peru Upwelling, suggesting potential Fe effects on carbon export. Our results confirm that primary producers in the Peru Upwelling/Humboldt Current system can be limited by Fe, but the biological and biogeochemical consequences of Fe limitation differ from Fe-limited California coastal upwelling waters that have been previously studied.

The supply of iron, relative to that of the macronutrients nitrate, phosphate, and silicic acid, plays a critical role in allowing extensive diatom blooms to develop in coastal upwelling regimes. The presence or absence of a broad continental shelf influences the supply of iron. The iron input to central California upwelling waters varies spatially and can be characterized by two end-member regimes. One end member, which includes Monterey Bay and extending north to Pt. Reyes, is an iron-replete regime where upwelling occurs over a relatively broad continental shelf that results in waters with high concentrations of dissolved and particulate iron ( .10 nM) entrained together with high concentrations of nitrate and silicic acid. In these iron-replete regions, extensive blooms of large diatoms deplete macronutrient concentrations, which results in correspondingly high chlorophyll a concentrations. The other end member, located to the south of Monterey Bay off the Big Sur coast, is an iron-deplete regime where upwelling is focused offshore of a narrow continental shelf. Upwelled waters in the Big Sur region are characterized by low dissolved and particulate iron concentrations (,1 nM), together with high concentrations of nitrate and silicic acid. Extremely low iron concentrations, unused nitrate and silicic acid, and a low abundance of large diatoms characterize surface waters in these iron-deplete regions, and thus represent coastal upwelling, high-nutrient, low-chlorophyll systems limited by the micronutrient iron.

Iron (Fe) is an essential element for the biochemical and physiological functioning of terrestrial and oceanic organisms, including phytoplankton, which are responsible for the primary productivity in the world's oceans. However, due to the low solubility of Fe in seawater, phytoplankton are often limited by their inability to incorporate enough Fe to allow for optimal growth rates in regions with dissolved Fe concentrations below 1 nM. It has been postulated that certain phytoplankton may produce compounds to facilitate the uptake of Fe from seawater to overcome this limitation. Dissolved Fe in the oceans is overwhelmingly complexed (>99%) by strong organic ligands that may control the uptake of Fe by microbiota; however, the identity, origin, and chemical characteristics of these organic chelates are largely unknown. Although it has been implied that some components of natural Fe-binding ligands are siderophores, no direct analyses of such compounds from natural seawater have been conducted. Here, we present a simple solid-phase extraction technique employing Biobeads SM-2 and Amberlite XAD-16 resins for concentrating naturally occurring dissolved iron-binding compounds from large volumes (>200 l) of seawater. Additionally, we report on the first successful determination of molecular weight size classes and preliminary iron-binding functional group characterization within those size classes for isolates collected from the surface and below the photic zone (150 m) in the central California coastal upwelling system. Electrochemical analyses using competitive ligand equilibration/adsorptive cathodic stripping voltammetry (CLE-ACSV) showed that isolated compounds had conditional Fe-binding affinities (with respect to inorganic iron—Fe′) of K FeL,Fe′ cond =10 11.5 –10 11.9 M −1 , similar to purified marine siderophores produced in laboratory cultures and to the ambient Fe-binding ligands observed in seawater. In addition, 63% of the extracted compounds from surface-collected samples fall within the defined size range of siderophores (300–1000 Da). Hydroxamate or catecholate Fe-binding functional groups were present in each compound for which Fe binding was detected. These results illustrate that the functional groups previously shown to be present in marine and terrestrial siderophores extracted and purified from laboratory cultures are also present in the natural marine environment. These data provide evidence that a significant fraction of the organic Fe-binding compounds we collected contain Fe-binding functional groups consistent with biologically produced siderophores. These results provide further insight into characteristics of the Fe-binding ligands that are thought to be important in controlling the biological availability of Fe in the oceans.

The bioactive metals Fe, Mn, Cu, Zn and Ni in Narragansett Bay, RI, were partitioned into soluble, colloidal and particulate size fractions using a combination of conventional and cross-flow filtrations. Particulate samples (0.2–8.0 μm; >8 μm) were chemically fractionated into acetic-acid reactive and non-reactive metals. Conventional “dissolved” samples ( Mn>Zn>Cu>Ni with concentrations in the 0.2–0.8 μm fraction being generally higher than in the >8.0 μm fraction. The acid leachable fraction of the particulate phase increased from ∼32%–80% in the order Fe 8.0 μm) being generally less labile than small particulates (0.2–8.0 μm). The colloidal phase represented an average 4%–96% of the “dissolved” metals, ranging in importance from Fe (96%)>Cu (44%)>Ni (25%)>Zn (7%)>Mn (4%). Although generally small, the colloidal fraction of Zn and Mn was highest in a region of the bay where biomass typically is high. Changes in soluble and colloidal fractions along a transect through the bay indicate that a significant proportion of Fe, Cu and Ni were transferred from “dissolved” to particulate size fractions via colloid aggregation. Predicting colloidal metal concentrations from measurements of particulate mass ( C p ) and literature values of colloid metal partition coefficients ( K c ) underestimated the measured concentrations by 5–50×. Acetic acid leachable metal concentrations in the small particle (0.2–8 μm) phase correlated well with metal concentrations in the larger (8 kDa–0.2 μm) colloid fraction ( r =0.91–0.99). In contrast, metals in the smaller colloid fraction (1–8 kDa) were for the most part independent of any measured parameters. Metals were not distributed equally between colloidal size classes; colloidal Zn was associated with larger colloids (>90%), Fe and Ni were associated primarily with larger colloids (∼70–85%) but also with the smaller colloid fraction, while ≳70% of colloidal Cu was associated with smaller colloids. The non-uniform distribution of metals within colloidal size classes indicates that metal:colloid associations are regulated by specific interactions. These findings suggest that it is inappropriate to employ single, non-specific sorbing metal tracers (e.g. Th) to delimit the pathways and kinetics of bioactive metal interactions with marine colloids.

Depth profiles for a series of redox-sensitive elements were determined in the productive eastern boundary of the tropical North Pacific. Suboxic conditions (regions with dissolved oxygen concentrations < 5 pmol kg-' and evidence of nitrate reduction) was observed at depths between 140 and 600 m. The behavior of a suite of trace (51 pM) redox-sensitive species such as oxidized and reduced forms of iodine, manganese, chromium, selenium, and iron was examined, in order to better characterize redox conditions within such suboxic zones. Iodate was completely reduced to iodide, and leachable particulate manganese was completely reduced to dissolved manganese between the depths of 140 and 600 m. In contrast, no more than 30% of the chromate, selenate, and selenite were reduced, while there was no evidence of leachable particulate iron being reduced. The resulting distributions of trace redox elements in these suboxic waters are influenced both by the extent that they are reduced and by the particular biogeochemical characteristics of their oxidized and reduced species. 0 1997 Elsevier Science Ltd. All rights reserved

Dissolved trace element (copper, nickel, cadmium, zinc, cobalt, and iron) concentrations were measured in surface water samples collected from 27 stations in the San Francisco Bay and Sacramento—San Joaquin Delta during April, August and December of 1989. The trace element distributions were relatively similar for all three sampling periods, and evidenced two distinct biogeochemical regimes within the estuarine system. The two regimes were comprised of relatively typical trace element gradients in the northern reach and anthropogenically perturbed gradients in the southern reach of the estuary. These dichotomous trace element distributions were consistent with previous reports on the distributions of nutrients and some other constituents within the estuary. In the northern reach, trace element and dissolved phosphate concentrations were non-conservative. Simple estuarine mixing models indicated substantial internal sources of dissolved copper (46–150%), nickel (250–500%) and cadmium (630–780%) relative to riverine inputs in April and August, and sizable internal sinks for dissolved cobalt (> 99%) and iron (> 70%) during the same periods. Dissolved zinc fluxes varied temporally, with a relatively large (135%) internal source in April and a relatively small (29%) internal sink in August. Concentrations of many trace elements (copper, nickel, cadmium, zinc, and cobalt) in the southern reach were anomalously high relative to concentrations at comparable salinities in the northern reach. Mass balance calculations indicated that those excesses were primarily due to anthropogenic inputs (waste-water discharges and urban runoff) and diagenetic remobilization from benthic sediments. The magnitude of these excesses was amplified by the long hydraulic residence time of dissolved constituents within the South Bay. The influence of other factors was evident throughout the system. Notably, upwelling appeared to elevate substantially dissolved cadmium concentrations at the mouth of the estuary and authigenic flocculation appeared to dominate the cycling of dissolved iron in both the northern and southern reaches of the system. Biological scavenging, geochemical scavenging and diagenic remobilization were also found to be important in different parts of the estuary. Additional complementary information is required to quantify accurately these processes.

[1] Factors influencing concentrations of nitrate, silicic acid, dissolved Fe, and dissolved Mn in the near-field Columbia River plume were examined during late spring and summer from 2004 to 2006 as part of the River Influences on Shelf Ecosystems program. Under upwelling-active phases, cold, high-nitrate coastal seawater was entrained in the plume, and nitrate concentrations of 16–19 μM were observed with as much as 90% from a coastal seawater origin. Under downwelling-relaxation phases, warm, nutrient-depleted coastal seawater was entrained forming a near-field plume with nitrate concentrations of 2.5–6 μM, with the river as the only source. Elevated silicic acid in the river is the dominant source, with concentrations of 60–80 μM in the near-field plume. During upwelling-active phases, high concentrations of dissolved Fe (as high as 40 nM) in the cold, low-oxygen, nutrient-rich coastal seawater were entrained to form a near-field plume with 15–20 nM dissolved Fe. During downwelling-relaxation phases, dissolved Fe in the intruding underlying warm coastal seawater was 1–3 nM, producing plume concentrations of 2–13 nM, with higher concentrations during the high river flow of May 2006. Dissolved Mn in the near-field plume covaried markedly as a function of increased tidal flushing in the estuary. The use of CORIE (pilot environmental observation and forecasting system for the Columbia River) time series conductivity-temperature-depth data within the estuary, along with data presented in this study, allows extrapolation of the near-field plume chemistry throughout the spring and summer seasons to provide insight into this important source of nutrients to the coastal waters in this region.

Human autoantibodies which bind to red blood cells and cause agglutination in the cold, collectively comprise the cold agglutinins: a subset of these antibodies with specificity for the Ii carbohydrate antigen on the red cell surface bears cross-reacting idiotypic determinants. A monoclonal antibody has been raised which specifically inhibits the cold agglutination reaction, and has been used to probe normal lymphoid cell populations for the presence of B cells expressing the same idiotope. Although such cells comprise only 1-2% of the lymphoid cells in the tonsil, it has been possible to isolate them in good yield and purity using the antibody and magnetic beads. Released cells were infected with the Epstein-Barr (EB) virus and an idiotope-bearing line established. The IgM secreted by the line was found to agglutinate red cells in the cold indicating that cold agglutinin-producing cells were among this idiotope-positive population. The immunophenotype of the line, and the agglutinating power of the secreted IgM, have been compared with a similarly immortalized idiotope-bearing line established from neoplastic B cells of a patient with frank cold agglutination disease.

Spatial gradients of silver concentrations in the surface waters of San Francisco Bay reveal substantial anthropogenic perturbations of the biogeochemical cycle of the element throughout the estuarine system. The most pronounced perturbations are in the south bay, where dissolved (