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  • 1
    Electronic Resource
    Electronic Resource
    Solubility of cadmium and cobalt in a post-oxic or sub-oxic sediment suspension (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 611-622 
    Details
    ISSN: 1573-5117
    Keywords: cadmium ; cobalt ; sediment ; sulphide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A sediment sample with high organic matter and trace metal content was suspended in synthetic river water for four weeks under an inert gas atmosphere. Subsequently, the anaerobic suspension was reoxidized by bubbling air through it. The concentrations of dissolved oxygen, sulfide, ferrous iron, manganese, cadmium, cobalt and the pH-value were measured at close time intervals during the anaerobic incubation. The anaerobic suspension was a post-oxic or sub-oxic environment with oxygen and total sulfide concentrations less than 1 µmole 1−1. Concentrations of dissolved ferrous iron and manganese were 50–150 µmole 1−1 and 5–30 µmole 1−1, respectively. The total sulfide concentration was measured using a sensitive voltammetric technique, with a detection limit of 1 nmole 1−1. A sequential extraction procedure was applied to two sediment samples taken at the end of the anaerobic incubation and after one week of reoxidation. The extractions indicated that cadmium was bound in sulfide minerals under post-oxic conditions. Thermodynamic equilibrium calculations revealed that the concentrations of dissolved cobalt in the post-oxic suspension were limited by the precipitation of cobalt sulfide minerals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026249
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    Paper (German National Licenses)
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  • 2
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    Quantification of methane emission from bacterial mat sites at Quepos Slide offshore Costa Rica (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1817-1829.
    Details
    Publication Date: 2017-05-23
    Description: Seafloormethane emission from the Quepos Slide on the submarine segment of the Costa Rica fore-arc margin was estimated by extrapolating flux measurements from individual seeps to the total area covered by bacterial mats. This approach is based on the combination of detailed mapping to determine the abundance of seeps and the application of a numerical model to estimate the amount of benthic methane fluxes. Model results suggest that the majority of the studied seeps transport rather limited amount of methane (on average: *177 lmol cm-2 a-1) into the water column due to moderate upward advection, allowing for intense anaerobic oxidation of methane (AOM; on average: 53 % of the methane flux is consumed). Depth-integrated AOM rates (56–1,538 lmol CH4 cm-2 a-1) are comparable with values reported from other active seep sites. The overall amount of dissolved methane released into the water column from the entire area covered by bacterial mats on the Quepos Slide is estimated to be about 0.28 9 106 mol a-1. This conservative estimate which relies on rather accurate determinations of seafloor methane fluxes emphasizes the potential importance of submarine slides as sites of natural methane seepage; however, at present the global extent of methane seepage from submarine slides is largely unknown.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-012-0839-3
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Intercalibration of Bruevich's method to determine the total alkalinity in seawater (2008)
    Springer
    In:  Oceanology, 48 (3). pp. 438-443.
    Details
    Publication Date: 2017-02-01
    Description: In 2000, the Carbon Dioxide in the Ocean working group of the North Pacific Marine Science Organization (PICES) performed an international experiment on the intercalibration of the measurements of the total alkalinity in seawater using certified reference materials (CRM). Taking part in this experiment, Russian specialists presented the method by Bruevich. The results of the intercalibration showed that the alkalinity values obtained by Bruevich's method using modern burettes, an Na2CO3 reactant of high purity as a standard to ascertain the acid titre, and corrections for the acid density and for the weights of the acid and seawater samples in vacuum are in agreement with the standard within +/- 1 mu M/kg.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1134/S0001437008030168
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Hydrothermal activity at Hook Ridge in the Central Bransfield Basin, Antarctica (1999)
    Springer
    In:  Geo-Marine Letters, 18 (4). pp. 277-284.
    Details
    Publication Date: 2017-06-29
    Description: Hydrothermal activity in the Central Bransfield Basin revealed an active low-temperature vent field on top of a submarine volcanic structure. A temperature anomaly was detected and the sea floor showed various patches of white silica (opal-A) precipitate exposures and some yellow–brown Fe-oxyhydroxide crusts. Enriched dissolved methane concentrations were encountered. Sediment was near 24°C just after the grab came on deck. No dense population of chemosynthetically based macrofauna known from other hydrothermal venting areas was present, except for pogonophora. The observations suggest that the sedimented hydrothermal field at Hook Ridge is a low-temperature end-member branch from a deeper hydrothermal source.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s003670050080
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Fluid Venting Activity on the Costa Rica Margin: New Results from Authigenic Carbonates (2004)
    Springer
    In:  International Journal of Earth Sciences, 93 . pp. 596-611.
    Details
    Publication Date: 2019-09-23
    Description: Carbonate precipitates on mounds and along tectonic scarps off the Costa Rica margin are manifestations of subduction-induced dewatering. The long-term dewatering history is recorded in mineralogical, petrological and isotope signals of carbonates recovered from these sites. The carbonates are strongly depleted in δ13C (−11 to −53‰ PDB) and enriched in δ18O (+4 to +8‰ PDB). Thermogenic methane and biogenic methane were identified as sources of the carbon. Chemoherm carbonates and seepage-associated carbonates formed in a focused flow regime have lighter δ13C values, while others formed in a more diffusive flow regime have slightly enriched C isotope values. Three fluid components were inferred based on the calculation of equilibrium δ18O: clay dehydration water, gas hydrate water and seawater. Calculated equilibrium δ18O values of carbonates from different down-core depths as well as from different precipitation stages show that the δ18O of the precipitating fluid is progressively depleted with time. Dolostones showing a methane-C source and a well constrained O-isotope signature are thought to have formed at depth in the sediment and subsequently became exhumed. Glauconitic sandstones cemented by methane-derived carbonate provide evidence that fluid and solid material have been expelled by the mud volcano.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Geochemistry of gas hydrate accumulation offshore NE Sakhalin Island (the Sea of Okhotsk): results from the KOMEX-2002 cruise (2003)
    Springer
    In:  Geo-Marine Letters, 23 . pp. 278-288.
    Details
    Publication Date: 2017-05-22
    Description: Geochemical properties of gas hydrate accumulation associated with an active gas vent on the continental slope offshore northeast Sakhalin Island in the Sea of Okhotsk have been investigated. The pore water chemistry data suggest that the gas hydrates (GHs) were formed in an environment of upward-migrating fluid combined with a mechanism of pore water segregation. The upward infiltration of water enriched mainly by Cl− and K+ species appears to occur on the background of earlier diagenesis processes within the gas vent sediments. The GHs were formed from water with chlorinity ranging from 530 to 570 mM. The δ18O and δD of GH water varied from −1.4 to −1.8‰ and from −13 to −18‰, respectively, representing a mix of seawater and infiltrating fluid water. A complex interaction of pore water, water of ascending fluid and segregated pore water during hydrate formation is also supported by water content measurements and observed gas hydrate structure. The direction of segregated water is opposite to upward fluid migration. Decreasing activity of the gas vent is inferred by comparing the present top of the recovered hydrate layer with previous observations.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00367-003-0150-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    SUGAR (submarine gas hydrate reservoirs) (2009)
    Springer
    In:  Environmental Earth Sciences, 59 (2). pp. 485-487.
    Details
    Publication Date: 2018-09-12
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s12665-009-0235-x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Isotopic evidence (He, B, C) for deep fluid and mud mobilization from mud volcanoes in the Caucasus continental collision zone (Georgia, Russia) (2003)
    Springer
    In:  International Journal of Earth Sciences, 92 . pp. 407-425.
    Details
    Publication Date: 2018-05-30
    Description: The Caucasian orogenic wedge formed as a consequence of the closure of the Tethyan Ocean, and numerous fields of active mud volcanoes pepper the area adjacent to the Black and Caspian Seas. Stable isotope ratios of boron, helium, and carbon have been measured for gas, fluid and sediment samples from active mud volcanoes of Taman Peninsula and Georgia to estimate the sources and mobilization depths of the fluid phase and mud. Boron concentrations in mud volcano fluids were found to be 5–35× higher than seawater. Fluid isotope ratios vary between δ11B=22 and 39‰, while isotope ratios of the smectite- and illite-rich extruded mud are considerably depleted in heavy 11B (δ11B=−8 to +7‰). B contents of these muds are ~8× higher than modern marine sediments. This suggests that liquefaction prior to mud volcanism was accompanied by both B enrichment and isotope fractionation, most likely at an intermediate depth mud reservoir at 2–4 km. The hydrocarbon-generating source beds to the mud volcanoes are located at 7 to 〉10 km depth in the folded Maikop Formation and are of proposed Oligocene–Miocene age. The most likely mechanism is re-hydration of these shales by both hydrocarbons and a geochemically mature fluid from greater depth within the orogenic wedge. Such a deep fluid source is supported by our results from gas analyses, which imply an admixture of minor amounts (less than 1%vol) of 3He (Georgia), thermogenic 13C in methane as well as "ultraheavy" 13C in CO2 (both Taman and Georgia). The overall results attest active local flow of geochemically different fluids along deep-seated faults penetrating the two study areas in the Caucasian orogenic wedge, with the waters as well as the gases coming from below the Maikop Formation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-003-0326-y
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Biogeochemical feedbacks may amplify ongoing and future ocean deoxygenation: a case study from the Peruvian oxygen minimum zone (2022)
    Springer
    Details
    Publication Date: 2024-02-07
    Description: A new box model is employed to simulate the oxygen-dependent cycling of nutrients in the Peruvian oxygen minimum zone (OMZ). Model results and data for the present state of the OMZ indicate that dissolved iron is the limiting nutrient for primary production and is provided by the release of dissolved ferrous iron from shelf and slope sediments. Most of the removal of reactive nitrogen occurs by anaerobic oxidation of ammonium where ammonium is delivered by aerobic organic nitrogen degradation. Model experiments simulating the effects of ocean deoxygenation and warming show that the productivity of the Peruvian OMZ will increase due to the enhanced release of dissolved iron from shelf and slope sediments. A positive feedback loop rooted in the oxygen-dependent benthic iron release amplifies, both, the productivity rise and oxygen decline in ambient bottom waters. Hence, a 1% decline in oxygen supply reduces oxygen concentrations in sub-surface waters of the continental margin by 22%. The trend towards enhanced productivity and amplified deoxygenation will continue until further phytoplankton growth is limited by the loss of reactive nitrogen. Under nitrogen-limitation, the redox state of the OMZ is stabilized by negative feedbacks. A further increase in productivity and transition to sulfidic conditions is only possible if the rate of nitrogen fixation increases drastically under anoxic conditions. Such a transition would lead to a wide-spread accumulation of toxic sulfide with detrimental consequences for fishery yields in the Peruvian OMZ that currently provides a significant fraction of the global fish catch.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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