Search results

Title: Radiometric age validation of the yelloweye rockfish (Sebastes ruberrimus) from southeastern Alaska,
Description: The yelloweye rockfish (Sebastes ruberrimus), a dominant component of an important deep-water rockfish fishery of the Gulf of Alaska, is thought to be long-lived with an estimated longevity exceeding 100 years. For the purpose of monitoring stocks, age is routinely estimated by counting growth zones in otolith cross-sections using the break-and-burn technique; however, such age estimates for this species have remained unvalidated. To evaluate these age data, age estimations from the break-and-burn technique were corroborated by comparing results from transverse sectioning of otoliths. The agreement between the techniques was excellent and each technique had a very low coefficient of variation (3.6% and 4.5%). Radiometric age validation of these estimates was performed on the otolith core material (first three years of growth) of pooled age groups having an average estimated age of 27.4-101.4 years. Agreement was variable and somewhat subjective, but radiometric data support ages estimated from otolith growth zone counts. The strongest support for age that exceeds 100 years comes from the observation that as age derived from growth zones approached and exceeded 100 years, the sample ratios measured (210Pb:226Ra) approached equilibrium. The radiometric results of our study validate the estimates derived from growth zones and the age estimating procedures, which confirms that the longevity of yelloweye rockfish exceeds 100 years., Cited By (since 1996):22, CODEN: AJMFA, ,
Author: Andrews, Cailliet, Coale, Munk, Mahoney, O'Connell
Date: 2002-01-01T00:00:00Z

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: Geochemistry of barium in marine sediments,
Description: Variations in the accumulation rate of barium in marine sediments are thought to be indicative of variations in marine biological productivity through time. However, the use of Ba as a proxy for paleoproductivity is partly dependent upon its being preserved in the sediment record in a predictable or consistent fashion. Arguments in favor of high Ba preservation are partly based on the assumption that sediment porewaters are generally at saturation with respect to pure barite. The idea is that because nondetrital sedimentary Ba predominantly exists as barite, porewater saturation would promote burial. We present sediment porewater, sediment solid phase, and benthic incubation chamber data suggesting that solid-phase Ba preservation may be compromised in some geochemical settings. We propose that under suboxic diagenetic conditions, characterized by low bottom water oxygen and high organic carbon respiration rates, Ba preservation may be reduced. Independent of the mechanism, if this assertion is true, then it becomes important to know when the Ba record is unreliable. We present evidence demonstrating that the sedimentary accumulation of authigenic U may serve as a proxy for when the Ba record is unreliable. We then provide an example from the Southern Ocean during the last glacial period where high authigenic U concentrations coincide with high Pa:Th ratios and high accumulation rates of biogenic opal, but we find low accumulation rates of sedimentary Ba. Thus, for the study sites presented here during the last glacial, we conclude that Ba is an unreliable productivity proxy., Cited By (since 1996):163, ,
Author: McManus, Berelson, Klinkhammer, Johnson, Coale, Anderson, Kumar, Burdige, Hammond, Brumsack, McCorkle, Rushdi
Date: 1998-01-01T00:00:00Z

Title: Southern Ocean Iron Enrichment Experiment,
Description: The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide., Cited By (since 1996):316, Oceanography, CODEN: SCIEA, ,
Author: Coale, Johnson, Chavez, Buesseler, Barber, Brzezinski, Cochlan, Millero, Falkowski, Bauer, Wanninkhof, Kudela, Altabet, Hales, Takahashi, Landry, Bidigare, Wang, Chase, Strutton, Friederich, Gorbunov, Lance, Hilting, Hiscock, Demarest, Hiscock, Sullivan, Tanner, Gordon, Hunter, Elrod, Fitzwater, Jones, Tozzi, Koblizek, Roberts, Herndon, Brewster, Ladizinsky, Smith, Cooper, Timothy, Brown, Selph, Sheridan, Twining, Johnson
Date: 2004-01-01T00:00:00Z

Title: 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: Developing standards for dissolved iron in seawater
Description: Cited By (since 1996):114
Author: Johnson, Boyle, Bruland, Coale, Measures, Moffett, Aguilar-Islas, Barbeau, Bergquist, Bowie, Buck, Cai, Chase, Cullen, Doi, Elrod, Fitzwater, Gordon, King, Laan, Laglera-Baquer, Landing, Lohan, Mendez, Milne, Obata, Ossiander, Plant, Sarthou, Sedwick, Smith, Sohst, Tanner, Van den Berg, Wu
Date: 2007-01-01T00:00:00Z

Title: Lead speciation in surface waters of the eastern North Pacific,
Description: , , , Titrations using differential pulse anodic stripping voltammetry (DPASV) to detect electroactive lead were carried out on fresh seawater samples and on samples stored acidified to determine the extent of lead complexation in the eastern North Pacific. Results of these analyses on surface water samples indicate total dissolved lead concentrations between 17 and 49 pM. The inorganic or DPASV labile fraction is 30–50%. Titration with lead yielded data consistent with one class of organic ligand(s), present at low concentration (between 0.2 and 0.5 nM) with a mean value for a conditional stability constant with respect to inorganic lead of log K′cond=9.7. The presence of this ligand, together with the various inorganic ligands in seawater, gives rise to a concentration of free ionic lead of ∼ 0.4 pM., ,
Author: Capodaglio, Coale, Bruland
Date: 1990-01-01T00:00:00Z

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

Title: A switch from Si(OH)4 to NO- 3 depletion in the glacial Southern Ocean,
Description: Phytoplankton in the Antarctic deplete silicic acid (Si(OH)4) to a far greater extent than they do nitrate (NO3 -). This pattern can be reversed by the addition of iron which dramatically lowers diatom Si(OH)4:NO3 - uptake ratios. Higher iron supply during glacial times would thus drive the Antarctic towards NO3 - depletion with excess Si(OH)4 remaining in surface waters. New δ30Si and δ15N records from Antarctic sediments confirm diminished Si(OH)4 use and enhanced NO3 - depletion during the last three glaciations. The present low-Si(OH)4 water is transported northward to at least the subtropics. We postulate that the glacial high-Si(OH)4 water similarly may have been transported to the subtropics and beyond. This input of Si(OH)4 may have caused diatoms to displace coccolithophores at low latitudes, weakening the carbonate pump and increasing the depth of organic matter remineralization. These effects may have lowered glacial atmospheric pCO2 by as much as 60 ppm., Cited By (since 1996):108, CODEN: GPRLA, , , Oceanography, Antarctica
Author: Brzezinski, Pride, Franck, Sigman, Sarmiento, Matsumoto, Gruber, Rau, Coale
Date: 2002-01-01T00:00:00Z

Title: Toxic diatoms and domoic acid in natural and iron enriched waters of the oceanic Pacific
Description: Near-surface waters ranging from the Pacific subarctic (58°N) to the Southern Ocean (66°S) contain the neurotoxin domoic acid (DA), associated with the diatom Pseudo-nitzschia. Of the 35 stations sampled, including ones from historic iron fertilization experiments (SOFeX, IronEx II), we found Pseudo-nitzschia at 34 stations and DA measurable at 14 of the 26 stations analyzed for DA. Toxin ranged from 0.3 fg·cell -1 to 2 pg·cell -1, comparable with levels found in similar-sized cells from coastal waters. In the western subarctic, descent of intact Pseudo-nitzschia likely delivered significant amounts of toxin (up to 4 μg of DA·m -2·d -1) to underlying mesopelagic waters (150-500 m). By reexamining phytoplankton samples from SOFeX and IronEx II, we found substantial amounts of DA associated with Pseudo-nitzschia. Indeed, at SOFeX in the Antarctic Pacific, DA reached 220 ng·L -1, levels at which animal mortalities have occurred on continental shelves. Iron ocean fertilization also occurs naturally and may have promoted blooms of these ubiquitous algae over previous glacial cycles during deposition of ironrich aerosols. Thus, the neurotoxin DA occurs both in coastal and oceanic waters, and its concentration, associated with changes in Pseudo-nitzschia abundance, likely varies naturally with climate cycles, as well as with artificial iron fertilization. Given that iron fertilization in iron-depleted regions of the sea has been proposed to enhance phytoplankton growth and, thereby, both reduce atmospheric CO 2 and moderate ocean acidification in surface waters, consideration of the potentially serious ecosystem impacts associated with DA is prudent., Cited By (since 1996):9, CODEN: PNASA
Author: Silver, Bargu, Coale, Benitez-Nelson, Garcia, Roberts, Sekula-Wood, Bruland, Coale
Date: 2010-01-01T00:00:00Z

Title: Radiocarbon in otoliths of yelloweye rockfish (Sebasfes ruberrimus): A reference time series for the coastal waters of southeast Alaska,
Description: Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated 14C signal retained in fish otoliths can be used as a time-specific recorder of the 14C present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine 14C in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year's growth of 43 yelloweye rockfish otoliths plotted against estimated birth year produced a 14C time series (1940-1990) for these waters. The initial rise of 14C occurred in 1958 and 14C levels rose to peak values (60-70‰) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (-3.2‰). In addition, the 14C data confirmed the longevity of the yelloweye rockfish to a minimum of 44 years and strongly support higher age estimates. This 14C time series will be useful for the interpretation of 14C accreted in biological samples from these waters., Cited By (since 1996):24, CODEN: CJFSD, ,
Author: Kerr, Andrews, Frantz, Coale, Brown, Cailliet
Date: 2004-01-01T00:00:00Z

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

Title: Distribution and enrichment of trace metals in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana in the Gulf of Guinea
Description: We present results of a preliminary geochemical assessment of Cd, Pb, V, As, Ni, Cu, Zn, Mg, Al, K, Ca, and Fe in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana. Samples were taken along 4 regions G1, G2, G3 and G4 at approximately 25. m, 100. m, and 250. m, 500. m and 1000. m depths. Elemental compositions were assessed through the estimation of Al-normalized enrichment factors and geochemical accumulation indices, and the concentrations determined to produce any potential toxic effects to biota. Significant enrichment of the bottom sediments with Cd, Ni and As were observed at some locations with sediments showing signs of heavy pollution with As at region G4. Apart from Ni, V and As which were beyond threshold effects levels at most regions, all other metals were below probable effect levels. Both natural and anthropogenic processes controlled trace metal accumulation and distribution in the Ghanaian coastal environment. © 2015 Elsevier Ltd., Export Date: 28 September 2015
Author: Mahu, Nyarko, Hulme, Coale
Date: 2015-01-01T00:00:00Z

Title: Spatial and habitat-rased variations in total and methyl mercury concentrations in surficial sediments in the San Francisco Bay-Delta,
Description: Recent studies indicate significant amounts of mercury (Hg) are annually transported into the San Francisco Bay-Delta (Bay-Delta) as a result of historic gold and Hg mining activities. We examined temporal and spatial variation in concentrations of total Hg (HgT) and monomethylmercury (MMHg) in surficial sediments of various ecosystem types in the Bay-Delta. We sampled surficial sediments across the Bay-Delta system and found HgT sediment concentrations in the central Delta were generally 100-200 ng g -1 and increased westward through Suisun Bay to 250-350 ng g -1. MMHg concentrations in the central Delta were between 1 and 3 ng g-1, while those in sediments in the perimeter waterways and adjacent bays were less than 1 ng g-1. Six sites were monitored monthly for over a year to identify seasonal changes in Hg sediment concentrations. Hg T sediment concentrations ranged from 48 to 382 ng g-1 and varied as a function of location not season. However, MMHg concentrations varied seasonally, increasing from 1 ng g-1 during winter months to 6 ng g-1 during spring and summer. Transects conducted at three marshes in the central Delta revealed MMHg sediment concentrations of 4-8 ng g-1at the interior and 2 ng g-1 at the exterior of the marshes. Habitat type was a major factor controlling MMHg concentration and the MMHg to HgT ratio in sediments of the Bay-Delta. MMHg was significantly correlated to HgT (r2 = 0.49) in marsh sediments. © 2007 American Chemical Society., Cited By (since 1996):24, Oceanography, CODEN: ESTHA, ,
Author: Heim, Coale, Stephenson, Choe, Gill, Foe
Date: 2007-01-01T00:00:00Z

Title: A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean
Description: The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability., Cited By (since 1996):930, Oceanography
Author: Coale, Johnson, Fitzwater, Gordon, Tanner, Chavez, Ferioli, Sakamoto, Rogers, Millero, Steinberg, Nightingale, Cooper, Cochlan, Landry, Constantinou, Rollwagen, Trasvina, Kudela
Date: 1996-01-01T00:00:00Z

Title: Recent increase in atmospheric deposition of mercury to California aquatic systems inferred from a 300-year geochronological assessment of lake sediments,
Description: Age-dated sediment cores from 4 remote lakes across California were analyzed for total Hg (Hg T) concentration as a function of pre- and post-industrialization. Particle size, magnetic susceptibility and organic C and N, were measured to determine if the Hg concentration in sediment cores could be related to atmospheric deposition and/or watershed processes. Results indicate that (a) for each lake modern (1970-2004) Hg T lake sediment concentrations have increased by an average factor of 5 times more than historic (pre-1850) Hg T concentrations; (b) the ratio of modern to pre-industrial lake sediment Hg T for these lakes are higher than estimated for other locations where atmospheric deposition is presumed to be the main source of Hg; (c) 2 of the 4 studied lakes demonstrated significant relationships between Hg T concentrations and percentage organic material (r 2 = 0.68 and p < 0.01; r 2 = 0.67 and p < 0.01) whereas the other two indicated no significant relationship (r 2 = 0.05 and p = 0.51; r 2 = 0.12 and p = 0.36). © 2007 Elsevier Ltd. All rights reserved., Cited By (since 1996):13, CODEN: APPGE, ,
Author: Sanders, Coale, Gill, Andrews, Stephenson
Date: 2008-01-01T00:00:00Z

Title: Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon,
Description: Cited By (since 1996):26, , , ,
Author: Kerr, Andrews, Munk, Coale, Frantz, Cailliet, Brown
Date: 2005-01-01T00:00:00Z

Title: Appendix B: Blue Water Diving Equipment and Procedures Used at the University of California, Santa Cruz
Description: California Sea Grant College Program Publication, No. T-CSGCP-014
Author: Coale, Michaels, Pinto, Coale, Michaels, Pinto, Heine, Heine
Date: 1986-01-01T00:00:00Z

Title: Investigations of Δ14C, δ13C, and δ15N in vertebrae of white shark (Carcharodon carcharias) from the eastern North Pacific Ocean,
Description: The white shark, Carcharodon carcharias, has a complex life history that is characterized by large scale movements and a highly variable diet. Estimates of age and growth for the white shark from the eastern North Pacific Ocean indicate they have a slow growth rate and a relatively high longevity. Age, growth, and longevity estimates useful for stock assessment and fishery models, however, require some form of validation. By counting vertebral growth band pairs, ages can be estimated, but because not all sharks deposit annual growth bands and many are not easily discernable, it is necessary to validate growth band periodicity with an independent method. Radiocarbon (14C) age validation uses the discrete 14C signal produced from thermonuclear testing in the 1950s and 1960s that is retained in skeletal structures as a time-specific marker. Growth band pairs in vertebrae, estimated as annual and spanning the 1930s to 1990s, were analyzed for Δ14C and stable carbon and nitrogen isotopes (δ13C and δ15N). The aim of this study was to evaluate the utility of 14C age validation for a wide-ranging species with a complex life history and to use stable isotope measurements in vertebrae as a means of resolving complexity introduced into the 14C chronology by ontogenetic shifts in diet and habitat. Stable isotopes provided useful trophic position information; however, validation of age estimates was confounded by what may have been some combination of the dietary source of carbon to the vertebrae, large-scale movement patterns, and steep 14C gradients with depth in the eastern North Pacific Ocean., Cited By (since 1996):28, CODEN: EBFID, ,
Author: Kerr, Andrews, Cailliet, Brown, Coale
Date: 2006-01-01T00:00:00Z

Title: Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean,
Description: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km 2 in the open equatorial Pacific Ocean with iron. This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production. Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturaly enriched in iron. These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean., Cited By (since 1996):749, Oceanography, CODEN: NATUA, ,
Author: Martin, Coale, Johnson, Fitzwater, Gordon, Tanner, Hunter, Elrod, Nowicki, Coley, Barber, Lindley, Watson, Van Scoy, Law, Liddicoat, Ling, Stanton, Stockel, Collins, Anderson, Bidigare, Ondrusek, Latasa, Millero, Lee, Yao, Zhang, Friederich, Sakamoto, Chavez, Buck, Kolber, Greene, Falkowski, Chisholm, Hoge, Swift, Yungel, Turner, Nightingale, Hatton, Liss, Tindale
Date: 1994-01-01T00:00:00Z

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

Title: Copper, zinc, cadmium and lead in surface waters of lakes Erie and Ontario,
Description: Concentrations of Cu, Zn, Cd and Pb were determined from 16 stations in Lake Ontario and Lake Erie, using trace metal sampling and analytical technique developed for seawater analysis employing graphite furnace atomic absorption. While Cu concentrations are consistent with previously reported data for the Great Lakes, concentrations of Zn, Cd and Pb are one to two orders of magnitude below those previously reported. These new data, however, were substantiated by complementary measurements of these samples for Pb concentrations and isotopic compositions as determined by isotope dilution mass spectrometry in a concurrent study, and are consistent with measurements of these elements in oceanic surface waters. Using reported trace metal inputs, these current measurements yield estimates for the residence times of Cu, Zn, Cd and Pb in the Lake Ontario epilimnion of 950, 5, 9, and 4 days, respectively. Lake Erie residence times are similar, averaging 660, 23, 20 and 9 days for Cu, Zn, Cd and Pb respectively. These short residence times are qualified by the imprecision of the elemental input estimates., Cited By (since 1996):30, CODEN: STEVA, ,
Author: Coale, Flegal
Date: 1989-01-01T00:00:00Z

Title: Phytoplankton growth and biological response to iron and zinc addition in the Ross Sea and Antarctic Circumpolar Current along 170°W,
Description: Deckboard enrichment experiments were conducted during the US JGOFS Antarctic Environment Southern Ocean Process Study to determine the community response to added iron and zinc and their effect on phytoplankton growth. Seawater was collected into acid-cleaned 20-1 polycarbonate carboys and incubated with varying additions of iron and zinc. Cells representing individual taxa were counted before and after incubation. Chlorophyll a, particulate organic carbon, and particulate organic nitrogen were measured periodically throughout the experiments. Zinc is not a limiting factor on phytoplankton growth in both the Ross Sea and the Antarctic Circumpolar Current (ACC). The Ross Sea is less iron-stressed than the ACC, in particular at the southern site. However, iron addition largely increased phytoplankton growth and chlorophyll a in both regions. Community growth showed a stronger response to iron addition in high-silicate water than in low-silicate water. Dinoflagellates had the lowest abundance in both natural and iron-enriched seawaters. Prymnesiophytes and pennate diatoms were most sensitive to iron enrichment and were responsible for the bulk of the growth signal. In the high-silicate water of the ACC, Phaeocystis showed the strongest response to iron addition, increasing its abundance from <5% in natural seawater to ∼20% in 2.5 nM Fe-enriched water. Its maximum growth rate was 0.57 day-1 and the half-saturation constant was 0.27 nM, which were higher than most of the diatoms (0.2-0.4day-1 and 0.05-0.13 nM, respectively). © 2002 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):68, CODEN: DSROE, ,
Author: Coale, Wang, Tanner, Johnson
Date: 2003-01-01T00:00:00Z

Title: Effect of iron limitation on the cadmium to phosphorus ratio of natural phytoplankton assemblages from the Southern Ocean,
Description: There is considerable interest in the biogeochemical cycling of cadmium (Cd) and phosphate (PO 4) in surface waters, driven in part by the ongoing development of a paleonutrient proxy that utilizes Cd preserved in fossil planktonic foraminifera to determine past PO 4 utilization efficiencies in ocean surface waters. The present article reports the results of a field study into the effects of Fe limitation on the Cd:P composition of natural assemblages of marine phytoplankton in the Antarctic Zone of the Pacific sector of the Southern Ocean. Iron enrichment to shipboard incubation bottles led to increases in community growth rate and final biomass. After 10.7 d of incubation, the climax community was dominated by large diatoms of the genus Fragillariopsis, Pseudonitzschia, and Nitzschia. Direct measurements of phytoplankton metal : P ratios from controlled shipboard experiments indicate that Cd:P, Co:P, and Zn:P ratios decreased from control values with increasing initial dissolved Fe concentrations in the incubation bottles, by factors of ∼2-10 at highest Fe additions. We suggest that the effect of Fe limitation on resident diatoms is to decrease growth rate, leading to elevated cellular Cd content. The dissolved Cd:P ratio in iron-limited surface waters of the Southern Ocean may, therefore, respond to the supply of Fe to the resident phytoplankton community, which has implications for the developing paleonutrient proxy. We suggest that the biological uptake of Cd and P is independent of the dissolved Cd:PO 4 ratio. As a consequence, the results argue against the use of empirical Rayleigh fractionation models or models with fixed phytoplankton uptake ratios to account for regional variability in surface water dissolved Cd:PO 4., Cited By (since 1996):33, Oceanography, CODEN: LIOCA, ,
Author: Cullen, Chase, Coale, Fitzwater, Sherrell
Date: 2003-01-01T00:00:00Z

Title: What controls dissolved iron concentrations in the world ocean?: Authors' closing comments,
Description: , , , , ,
Author: Johnson, Michael Gordon, Coale
Date: 1997-01-01T00:00:00Z

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