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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: Cobalt and copper distributions in the waters of Santa Monica Basin, California,
Description: The trace metals cobalt and copper are removed from the oceans interior by scavenging on to particle surfaces, but the mechanisms for removal of these two metals are probably quite different. Cobalt appears to be scavenged by manganese oxide particles, whereas organic compounds are the main carrier phase for copper. Remobilization of these metals in marine sediments therefore proceeds by different pathways. The differences in the pathways of remobilization are accentuated in oxygen-deficient environments: manganese oxide reduction is accelerated at low oxygen levels and organic carbon is preserved. Cobalt fluxes from sediments underlying oxygen-deficient waters should be enhanced and copper fluxes reduced. We report here measurements of the cobalt and copper distributions in the waters of an oxygen-deficient marine basin in the Southern California Bight. Cobalt concentrations near the bottom are raised four times above the background level, whereas copper concentrations show no increase. These measurements confirm features of existing models for the oceanic cycles of these metals., Cited By (since 1996):18, Oceanography, CODEN: NATUA, ,
Author: Johnson, Stout, Berelson, Sakamoto-Arnold
Date: 1988-01-01T00:00:00Z

Title: Chemical and biological interactions in the Rose Garden hydrothermal vent field, Galapagos spreading center,
Description: The concentrations of a suite of redox reactive chemicals were measured in the Rose Garden hydrothermal vent field of the Galapagos spreading center. Sulfide, silicate, oxygen and temperature distributions were measured in situ with a submersible chemical analyser. In addition, 15 chemical species were measured in discrete samples. Variability in the slope of the temperature-silicate plots indicates that heat is lost from these relatively low temperatures (<15°C) solutions by conduction to the solid phase. Consumption of oxygen, sulfide and nitrate from the hydrothermal solution as it flows past the vent animals is apparent from the distributions measured in situ and in the discrete samples. The fraction of sulfide and nitrate removed from the solution by consumption appears to have increased between 1979-1985. Sulfide and oxygen appear to be consumed under different conditions: sulfide is removed primarily from the warmest solutions, and oxygen is consumed only from the cold seawater. This separation may be driven primarily by the increased gradients of each chemical under these conditions. There is no evidence for the consumption of significant amounts of manganese(II) by the vent organisms. The analysis of other data sets from this vent field indicate no significant consumption of methane by the vent organisms, as well. © 1988., Cited By (since 1996):103, Oceanography, ,
Author: Johnson, Childress, Hessler, Sakamoto-Arnold, Beehler
Date: 1988-01-01T00:00:00Z

Title: The tail of the Storegga Slide: Insights from the geochemistry and sedimentology of the Norwegian Basin deposits
Description: Deposits within the floor of the Norwegian Basin were sampled to characterize the deposition from the Storegga Slide, the largest known Holocene-aged continental margin slope failure complex. A 29 to 67 cm thick veneer of variable-coloured, finely layered Holocene sediment caps a homogeneous, extremely well-sorted, poorly consolidated, very fine-grained, grey-coloured sediment section that is >20 m thick on the basin floor. This homogeneous unit is interpreted to represent the uppermost deposits generated by a gravity flow associated with the last major Storegga Slide event. Sediments analogous to the inferred source material of the slide deposits were collected from upslope on the Norwegian Margin. Sediments sampled within the basin are distinguishable from the purported source sediments, suggesting that size sorting has significantly altered this material along its flow path. Moreover, the very fine grain size (3·1 ± 0·3 μm) suggests that the >20 m thick homogeneous unit which was sampled settled from suspension after the turbulent flow was over. Although the turbulent phase of the gravity flow that moved material out into the basin may have been brief (days), significantly more time (years) is required for turbid sediments to settle and dewater and for the new sea floor to be colonized with a normal benthonic fauna. Pore water sulphate concentrations within the uppermost 20 m of the event deposit are higher than those normally found in sea water. Apparently the impact of microbial sulphate reduction over the last ca 8·1 cal ka bp since the re-deposition of these sediments has not been adequate to regenerate a typical sulphate gradient of decreasing concentration with sub-bottom depth. This observation suggests low rates of microbial reactions, which may be attributed to the refractory carbon composition in these re-deposited sediments. © 2010 The Authors. Journal compilation © 2010 International Association of Sedimentologists., Cited By (since 1996):1, Rocks & Cores
Author: Paull, Ussler III, Holbrook, Hill, Haflidason, Winters, Lorenson, Aiello, Johnson, Lundsten
Date: 2010-01-01T00:00:00Z

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: A model of the iron cycle in the ocean,
Description: The IRONEX II in situ fertilization experiment showed decisively that availability of iron limits the growth of phytoplankton in equatorial Pacific surface waters. High-nutrient low-chlorophyll (HNLC) surface waters, potentially iron limited, are also found in the North Pacific and the Southern Ocean. A model of seawater iron geochemistry has been incorporated into a global ocean circulation and carbon cycle model and tuned to match the observed ocean Fe distribution. The model reproduces the observed HNLC areas in the equatorial Pacific and Southern Ocean but predicts nutrient depletion in the North Pacific (a region of high dust fluxes from Asia). The model is based on the idea that the concentrations of organic iron-binding ligands in seawater control the subsurface Fe concentration and predicts that a majority (70-80%) of the global carbon export production can be sustained by upwelling of dissolved iron in seawater rather than by atmospheric deposition. The ocean iron cycle increases the efficiency of iron utilization in the biological pump, buffers new production against interannual fluctuations in iron deposition, and contributes several new intrinsic timescales to the ocean carbon cycle: several hundred years for the ocean iron concentration and perhaps several thousand for the concentration of ligand in the deep sea. Ocean recycling of Fe appears to play a major role in determining the strength of the biological pump in the ocean and the pCO2 of the atmosphere., Cited By (since 1996):117, , , Oceanography
Author: Archer, Johnson
Date: 2000-01-01T00:00:00Z

Title: Solenoid pumps for flow injection analysis,
Description: Methods employing flow injection analysis (FIA), particularly for in situ seawater techniques, would benefit from reduction in pump size and power requirement, longer maintenance intervals, and the ability to incorporate microprocessor control of each reagent and sample flow stream. In this work, the peristaltic pump of a conventional FIA system was replaced by three solenoid-driven diaphragm pumps with integral Viton check valves, and the system was tested by performing the simple nitrile analysis, which has well-defined FIA performance characteristics. Sixty injections per hour were possible with flow rates of 0.5 mL/min for reagents and sample. The coefficient of variation was 1% for 10μM NO2- concentrations, and the detection limit was less than 0.1μM NO2-. These values match the reported performance for this method using peristaltic pumps., , CODEN: IJCVE, ,
Author: Weeks, Johnson
Date: 1996-01-01T00:00:00Z

Title: Morphological, molecular, and in situ behavioral observations of the rare deep-sea anglerfish Chaunacops coloratus (Garman, 1899), order Lophiiformes, in the eastern North Pacific
Description: In situ observations and collections of Chaunacops coloratus (Garman, 1899) from seamounts in the eastern North Pacific Ocean lend new behavioral, morphological and molecular data to an under-sampled, deep-sea group of fishes in the order Lophiiformes. Seven observations were made at Davidson Seamount, 130. km southwest of Monterey, CA, and from the Taney Seamount chain, 290. km west of Moss Landing, CA, from depths ranging from 2313 to 3297. m. Specimens were collected at both locations. Morphometric and meristic analyses were performed to identify individuals to the species level. These observations of C. coloratus provide greater latitude and depth distributions in the eastern North Pacific Ocean than previously known. Detailed habitat information indicated the fish occurred near manganese-encrusted volcanic talus slopes, a highly rugose habitat. Video observations revealed possible ontogenetic color changes in which small fish were blue and large fish were red. Video recorded rapid, vertical swimming as an escape response and maneuvering, or walking, with pectoral and pelvic fins and esca deployment. Phylogenetic analyses used here verify what has been known since Garman first described C. coloratus in 1899, that Chaunax and Chaunacops are closely related; molecular tools complement previous knowledge and genetic information created has been submitted to GenBank for further use by the scientific community. © 2012 Elsevier Ltd.
Author: Lundsten, Johnson, Cailliet, DeVogelaere, Clague
Date: 2012-01-01T00:00:00Z

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: Continuous determination of nitrate concentrations in situ,
Description: A submersible chemical analyser (Scanner) was used to measure nitrate concentrations in situ to depths of nearly 2000 m. Nitrate anomalies with a vertical span of 5 m can be detected at lowering rates up to 40 m min-1. The nitrate concentrations measured in situ are in good agreement with hydrographic data collected by conventional means at the same location. The relative standard deviation of the analyses performed in situ is ±0.79%. The method can be easily extended to most other colorimetric analyses., Cited By (since 1996):9 Oceanography, ,
Author: Johnson, Sakamoto-Arnold, Beehler
Date: 1989-01-01T00:00:00Z

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: Larval settlement can explain the adult distribution of Mytilus californianus Conrad but not of M. galloprovincialis Lamarck or M. trossulus Gould in Moss Landing, central California,
Description: We investigated the spatial distribution of adult and newly settled mussels (Mytilus galloprovincialis Lamarck, Mytilus trossulus Gould and Mytilus californianus Conrad) on the shore at Moss Landing, California to test the hypothesis that adult distributions are a result of settlement patterns. Adult M. californianus were most abundant on a wave-exposed rocky jetty and adults of Blue mussels (M. trossulus and M. galloprovincialis) were more abundant inside the protected Moss Landing harbor. Using taxon-specific polymerase chain reactions, we monitored recruitment during continuous 1-2 week intervals on fibrous scrubbing pads for 12 months in 2002-2003. All mussel species settled in greatest numbers on the exposed jetty, and Blue mussels settled in greater numbers there than did M. californianus. Because Blue mussels settled abundantly where their adults were rare, post-settlement mortality appeared to be the strongest influence on adult distribution. In contrast, M. californianus settled mostly in their adult habitat., Cited By (since 1996):13, CODEN: JEMBA, ,
Author: Johnson, Geller
Date: 2006-01-01T00:00:00Z

Title: Organic matter diagenesis in the sediments of the San Pedro Shelf along a transect affected by sewage effluent,
Description: A study was conducted to examine the rate of organic matter degradation within the sediments adjacent to the Whites Point Los Angeles County sewage outfall system on the San Pedro Shelf. Benthic chamber deployments were made at three stations in a transect away from the outfall pipe during three cruise periods (October 1990, February and October 1991). The fluxes of phosphate, silicate and radon-222 showed the most significant difference (factor of 3) between stations proximal and distal to the sewage effluent outfall pipe; the fluxes of nitrate, ammonia, alkalinity and TCO2 showed some gradient (a factor of 1.5-2) and the uptake of oxygen showed no variability between sites. Carbon oxidation in these sediments is driven primarily by net oxygen consumption and secondarily by net sulfate reduction. Net sulfate reduction accounts for about 30% of the carbon oxidation near the outfall pipe and 10-15% at the distal sites. Measurements of radon-222 fluxes and radon emanation rates from sediments indicate that the intensity of bio-irrigation is greater by a factor of 2 at sites away from the outfall pipe, but also shows that bio-irrigation does take place at the site adjacent to the pipe. The total amount of particulate organic carbon (POC) oxidized in the sediments around the outfall is ∼2 × 107 g C/d. An estimate of carbon burial in this region is 4 × 107 g C/d. The outfall system could supply ∼3 × 107 g C/d of which 12-20% is estimated to have been deposited in the region. Hence, effluent-derived POC, although it may be a part of the total organic carbon pool undergoing diagenesis and burial on the sea floor, is not likely the only source of carbon to this system. Primary productivity in the surface ocean could supply 9-13 × 107 g C/d to the sea floor. A balanced carbon budget requires that half the primary production is exported to the sea floor, although this budget does not account for other sources of POC to the region. © 2002 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):13, CODEN: CSHRD, ,
Author: Berelson, Johnson, Coale, Li
Date: 2002-01-01T00:00:00Z

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: What controls dissolved iron concentrations in the world ocean?,
Description: Dissolved (<0.4 μm) iron has been measured in 354 samples at 30 stations in the North and South Pacific, Southern Ocean and North Atlantic by the Trace Metals Laboratory at Moss Landing Marine Laboratories. These stations are all more than 50 km from a continental margin. The global distribution of dissolved iron, which is derived from these profiles, is remarkable for several reasons. The dissolved iron profiles have a uniform shape with a nutrient-like profile at each station. Concentrations at the surface are all <0.2 nmol kg-1 and average 0.07 nmol kg-1. Below 500 m, the average concentration is 0.76 nmol kg-1. The largest value in the data set is 1.38 nmol kg-1. There is no inter-ocean fractionation, which is unique for an element with a nutrient-like profile. Published estimates of the iron residence time are on the order of 100 to 200 yr, indicative of rapid removal. Other elements with such short residence times are characterized by vertical profiles that decrease with depth and deep concentrations that decrease with age as water passes from the Atlantic to the Pacific. This is not the case for iron. The largest horizontal changes in dissolved iron are observed in gradients from the continental margin. There is only a factor of three difference between the minimum (0.4 nmol kg-1) and maximum (1.3 nmol kg-1) value in the data set at a depth near 750 m, where variability is at a maximum. The minimum concentrations are found at stations in the remote central Pacific and the maximum values occur at stations adjacent to the continental margin. The major source of iron in the deep sea is generally aeolian deposition. Integrated (surface to 500 m) concentrations of iron at each station are only weakly correlated with the aeolian iron deposition flux, however. This contrasts with other elements such as lead that also have strong atmospheric sources. These observations lead us to conclude that the nutrient-like profile is maintained by a mechanism that reduces the scavenging rate of dissolved iron at concentrations less than 0.6 nmol kg-1. This mechanism may be complexation by strong iron binding ligands, which have been found in both the Atlantic and Pacific at concentrations near 0.6 nM. This apparent solubility would act to diminish inter-ocean fractionation. It would allow a nutrient-like profile to develop before scavenging began to remove iron. In order to test the concept, we developed a numerical model to make quantitative predictions of dissolved iron concentrations from place to place. The dissolved iron source in the ocean interior is remineralization from sinking particulate organic matter. Scavenging removes dissolved iron only at concentrations greater than the apparent solubility. The only geographically variable parameter in the model is the export flux of carbon from the surface layer, which carries iron with it. The model generated dissolved iron profiles, based on measured or estimated values of the carbon export flux, are in remarkable agreement with the observed profiles at all stations from the North Atlantic through the Southern Ocean to the North Pacific., Cited By (since 1996):386, CODEN: MRCHB, Oceanography, , ,
Author: Johnson, Michael Gordon, Coale
Date: 1997-01-01T00:00:00Z

Title: Variable responses of temperate calcified and fleshy macroalgae to elevated pCO2 and warming
Description: Anthropogenic carbon dioxide (CO2) emissions simultaneously increase ocean temperatures and reduce ocean surface pH, a process termed ocean acidification (OA). OA is expected to negatively affect the growth and physiology of many calcified organisms, but the response of non-calcified (fleshy) organisms is less well understood. Rising temperatures and pCO2 can enhance photosynthetic rates (within tolerance limits). Therefore, warming may interact with OA to alter biological responses of macroalgae in complicated ways. Beyond thresholds of physiological tolerance, however, rising temperatures could further exacerbate negative responses to OA. Many studies have investigated the effects of OA or warming independently of each other, but few studies have quantified the interactive effects of OA and warming on marine organisms. We conducted four short-term independent factorial CO2 enrichment and warming experiments on six common species of calcified and fleshy macroalgae from southern California to investigate the independent and interactive effects of CO2 and warming on growth, carbonic anhydrase (CA) enzyme activity, pigment concentrations, and photosynthetic efficiency. There was no effect of elevated pCO2 on CA activity, pigment concentration, and photosynthetic efficiency in the macroalgal species studies.However,we found that calcareous algae suffered reduced growth rates under high pCO2 conditions alone, although the magnitude of the effect varied by species. Fleshy algae had mixed responses of growth rates to high pCO2, indicating that the effects of pCO2 enrichment are inconsistent across species. The combined effects of elevated pCO2 and warming had a significantly negative impact on growth for both fleshy and calcareous algae; calcareous algae experienced five times more weight loss than specimens in ambient control conditions and fleshy growth was reduced by 76%. Our results demonstrate the need to study the interactive effects of multiple stressors associated with global change on marine communities., http://icesjms.oxfordjournals.org/content/early/2015/09/25/icesjms.fsv168.abstract, Advanced view
Author: Kram, Price, Donham, Johnson, Kelly, Hamilton, Smith
Date: 2015-09-25T00:00:00Z

Title: An example crossover experiment for testing new vicarious calibration techniques for satellite ocean color radiometry,
Description: Vicarious calibration of ocean color satellites involves the use of accurate surface measurements of waterleaving radiance to update and improve the system calibration of ocean color satellite sensors. An experiment was performed to compare a free-fall technique with the established Marine Optical Buoy (MOBY) measurement. It was found in the laboratory that the radiance and irradiance instruments compared well within their estimated uncertainties for various spectral sources. The spectrally averaged differences between the National Institute of Standards and Technology (NIST) values for the sources and the instruments were<2.5% for the radiance sensors and<1.5% for the irradiance sensors. In the field, the sensors measuring the above-surface downwelling irradiance performed nearly as well as they had in the laboratory, with an average difference of<2%.While the water-leaving radiance L w calculated from each instrument agreed in almost all cases within the combined instrument uncertainties (approximately 7%), there was a relative bias between the two instrument classes/techniques that varied spectrally. The spectrally averaged (400-600 nm) difference between the two instrument classes/techniques was 3.1%. However, the spectral variation resulted in the freefall instruments being 0.2% lower at 450 nm and 5.9% higher at 550 nm. Based on the analysis of one matchup, the bias in L w was similar to that observed for L u(1 m) with both systems, indicating the difference did not come from propagating L u(1 m) to L w. © 2010 American Meteorological Society., Cited By (since 1996):6, Oceanography, CODEN: JAOTE, ,
Author: Voss, Mclean, Lewis, Johnson, Flora, Feinholz, Yarbrough, Trees, Twardowski, Clark
Date: 2010-01-01T00:00:00Z

Title: Biogeochemistry of hydrothermal vent mussel communities,
Description: Cited By (since 1996):64, Invertebrates, CODEN: DRORE, Continuous measurements of sulfide, silicate and temperature were made in situ from the submersible Alvin in the Rose Garden and New Vent hydrothermal fields of the Galapagos Spreading Center. Continuous measurements of temperature also were made for an 18 day period in the Rose Garden field. The results demonstrate several adaptations that appear to have contributed to the success of the vent mussel Bathymodiolus thermophilus in the Rose Garden. Dense clusters of B. thermophilus can disperse the hydrothermal fluids laterally for distances of several meters. This results in a large increase in the area of the redox transition zone, where both dissolved oxygen and hydrogen sulfide are available. As a result, the animal communities can grow to occupy areas that would not otherwise provide adequate reduced substrates. Measurements of the temperature demonstrate a distinct tidal periodicity. This periodicity will result in a large range of environmental conditions within the vent community. The mussel can tolerate these wide ranges in condition because of its ability to accept long periods of anoxia and to filter feed., ,
Author: Johnson, Childress, Beehler, Sakamoto
Date: 1994-01-01T00:00:00Z

Title: Organochlorines and other environmental contaminants in muscle tissues of sportfish collected from San Francisco Bay,
Description: Edible fish species were collected from 13 locations throughout San Francisco Bay, during the spring of 1994, for determination of contaminant levels in muscle tissue. Species collected included white croaker, surfperch, leopard and brown smoothhound sharks, striped bass, white sturgeon and halibut. 66 composite tissue samples were analysed for the presence of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, trace elements and dioxin/furans. The US EPA approach to assessing chemical contaminant data for fish tissue consumption was used for identifying the primary chemicals of concern. Six chemicals or chemical groups were found to exceed screening values (SVs) established using the US EPA approach. PCBs (as total Aroclors) exceeded the screening level of 3 ng g -1 in all 66 muscle tissue samples, with the greatest concentrations (638 ng g -1) found near San Francisco's industrial areas. Mercury was elevated (> 0.14 μg g -1) in 40 of 66 samples with the greatest concentrations (1.26 μg g -1) occurring in shark muscle tissues. Concentrations of the organochlorine pesticides dieldrin, total chlordane and total dichlorodiphenyltrichloroethane (DDT) exceeded screening levels in a number of samples. Dioxin/furans (as toxic equivalent concentrations (TEQ's)) were elevated (> 0.15 pg g -1) in 15 of the 19 samples analysed. Fish with high lipid content (croaker and surfperch) in their muscle tissue generally exhibited higher organic contaminant levels while fish with low lipid levels (halibut and shark) exhibited lower organic contaminant levels. Tissue samples taken from North Bay stations most often exhibited high levels of chemical contamination. The California Office of Health Hazard Assessment is currently evaluating the results of this study and has issued an interim Health Advisory concerning the human consumption of fish tissue from San Francisco Bay., Cited By (since 1996):61, CODEN: MPNBA, ,
Author: Fairey, Taberski, Lamerdin, Johnson, Clark, Downing, Newman, Petreas
Date: 1997-01-01T00:00:00Z

Title: IronEx-I, an in situ iron-enrichment experiment,
Description: An in situ iron-enrichment experiment near the Galapagos Islands was performed in October 1993. Here we report the theoretical and practical considerations of creating such a patch of iron-enriched surface water, as well as the strategies employed for the detection of the patch and the biological and chemical signals which developed, in an area dominated by advective processes. Physical and chemical models were used to predict the speciation, solubility, and the final concentration of iron in surface waters injected with acidic iron sulfate. A trial injection off the California coast in which 800 L of a 0.5 M FeSO4 were introduced into the ship's wake over a 1.5 km2 area, was used to test these predictions. Iron concentrations were determined continually onboard during the initial experiment as the ship steamed in transects through the enriched patch. The results indicate excellent spatial agreement with model predictions and final concentrations that were consistent with the chemical model. However, the use of a Cartesian coordinate system during rejection resulted in an extremely compressed, heterogeneous patch. Results from this preliminary experiment were then applied towards the development and implementation of the first open ocean iron enrichment experiment (IronEx I) near the Galapagos Islands in October 1993. The development and results of these methodologies are presented. In the IronEx I equatorial experiment, a Lagrangian coordinate system was established using a drogued buoy (equipped with GPS and packet radio) and the iron-enriched area (64 km2 containing 443 kg of Fe) was tagged with the inert chemical tracer sulfurhexafluoride (SF6). This strategy resulted in a fairly rectangular, homogeneous enriched patch initially detectable by both Fe and SF6 determination. Shipboard analysis and airborne observations confirmed good spatial agreement between the Lagrangian drifter and the biological and chemical signatures in the patch. Biological and chemical sampling of the enriched area showed an increase in chlorophyll, primary production, biomass and photosynthetic energy conversion efficiency relative to waters outside the patch, supporting the hypothesis that iron limits phytoplankton growth and biomass in a 'bottom up' manner in this area. The ability to create a coherent patch and track it over time led to this first open-ocean test of the iron hypothesis., Cited By (since 1996):42, CODEN: DSROE, ,
Author: Coale, Johnson, Fitzwater, Blain, Stanton, Coley
Date: 1998-01-01T00:00:00Z

Title: Aspects of the life histories of grass rockfish, Sebastes rastrelliger, and brown rockfish, S. auriculatus, from southern California,
Description: We collected data on age-length and length-weight relationships, age and length at first maturity, and spawning seasons of grass rockfish, Sebastes rastrelliger, and brown rockfish, S. auriculatus, off southern California. In addition, we also collected data on fecundity of grass rockfish. For both species, males and females grew at the same rates and von Bertalanffy age-length parameters for grass rockfish were l(∞)=51.3 cm, k=0.11, t0=-2.41 and for brown rockfish l(∞)=51.4 cm, k=0.16, t0=-0.55. Male and female grass rockfish matured at about the same length and age, between 22 and 28 cm and between 2 and 5 yr. There was also little difference between the sexes for brown rockfish; they matured between 19 and 32 cm and between 3 and 6 yr. Grass rockfish spawned from January to March, peaking during January; brown rockfish spawned from January to June (and perhaps August), also peaking in January. Fecundity of grass rockfish ranged from about 80,000-760,000 eggs., Cited By (since 1996):10, Fish and Fisheries, CODEN: FSYBA, ,
Author: Love, Johnson
Date: 1999-01-01T00:00:00Z

Title: Cadmium flux in Los Angeles/Long Beach harbours and at sites along the California continental margin,
Description: Fluxes of dissolved cadmium were measured in situ using benthic flux chambers at stations in Los Angeles/Long Beach harbour and at sites on the California continental margin. Cadmium fluxes ranged from -0.212 to 0.118 μmol m-2 d-1 indicating that Cd flux may either be into or out of sediments. Correlations between Cd flux and carbon oxidation rate and between carbon oxidation rate and sulfate reduction indicate that anaerobic microbial degradation was the major process controlling both the sign and the magnitude of cadmium fluxes at stations in Los Angeles and Long Beach harbours. A simple box model based on sediment fluxes and water column concentrations indicates cadmium has a residence time of 47 days within the Los Angeles/Long Beach harbour system, similar to the hydraulic residence time. Sedimentary flux is, therefore, sufficient to account for water column cadmium concentration in inner harbour areas, suggesting that the sediments are the dominant source and sink of cadmium in these areas of the harbour. Comparison of the cadmium: phosphate ratio for the Los Angeles/Long Beach harbour water column with those reported for the northeast Pacific suggests that distributions of Cd in the study area were elevated over expected values but appear to be dominated by natural physical and biogeochemical processes. © 2001 Academic Press., Cited By (since 1996):9, Oceanography, CODEN: ECSSD, ,
Author: Colbert, Coale, Berelson, Johnson
Date: 2001-01-01T00:00:00Z

Title: Direct ultraviolet spectrophotometric determination of total sulfide and iodide in natural waters,
Description: A technique is described that allows the determination of total dissolved sulfide in natural waters using direct ultraviolet detection of the HS- ion. The concentration of bisulfide is determined by measuring absorption from 214 to 300 nm and then deconvolution of the HS- spectra from the complex spectrum of natural fluids. A nonlinear least-squares fitting approach is used for the deconvolution. At a pH near 8, where >95% of total sulfide is present as HS-, the results are indistinguishable from total sulfide measured using the methylene blue method in a wide range of sample types and matrixes including freshwater from groundwater wells, marine hydrothermal vent fluids, and marine sediment porewaters. The method allows simultaneous determination of other UV-absorbing ions, including nitrate, bromide, and iodide, in samples with low total sulfide concentrations. Bisulfide concentrations can be determined in samples with low background absorption, such as well water and hydrothermal fluids, with a detection limit of <1 μM. The detection limit for bisulfide in sediment porewaters that have a high organic loading, which produces background absorbances of ∼0.5 A at 260 nm in a 1-cm cuvette, is 5 μM. The only chemical manipulation required is buffering acidic samples to pH > 7 and filtration of particulate-rich samples., Cited By (since 1996):36, Oceanography, CODEN: ANCHA, ,
Author: Guenther, Johnson, Coale
Date: 2001-01-01T00:00:00Z

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