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  • Wiley  (9)
  • ASLO (Association for the Sciences of Limnology and Oceanography)  (3)
  • IFM-GEOMAR  (3)
  • 1
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    Relating sulfate and methane dynamics to geology: Accretionary prism offshore SW Taiwan (2013)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (7). pp. 2523-2545.
    Details
    Publication Date: 2018-02-28
    Description: Geochemical data (CH4, SO42−, I−, Cl−, particulate organic carbon (POC), δ13C-CH4, and δ13C-CO2) are presented from the upper 30 m of marine sediment on a tectonic submarine accretionary wedge offshore southwest Taiwan. The sampling stations covered three ridges (Tai-Nan, Yung-An, and Good Weather), each characterized by bottom simulating reflectors, acoustic turbidity, and different types of faulting and anticlines. Sulfate and iodide concentrations varied little from seawater-like values in the upper 1–3 m of sediment at all stations; a feature that is consistent with irrigation of seawater by gas bubbles rising through the soft surface sediments. Below this depth, sulfate was rapidly consumed within 5–10 m by anaerobic oxidation of methane (AOM) at the sulfate-methane transition. Carbon isotopic data imply a mainly biogenic methane source. A numerical transport-reaction model was used to identify the supply pathways of methane and estimate depth-integrated turnover rates at the three ridges. Methane gas ascending from deep layers, facilitated by thrusts and faults, was by far the dominant term in the methane budget at all sites. Differences in the proximity of the sampling sites to the faults and anticlines mainly accounted for the variability in gas fluxes and depth-integrated AOM rates. By comparison, methane produced in situ by POC degradation within the modeled sediment column was unimportant. This study demonstrates that the geochemical trends in the continental margins offshore SW Taiwan are closely related to the different geological settings.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/ggge.20168
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Towards a parameterization of global-scale organic carbon mineralization kinetics in surface marine sediments (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 29 . pp. 812-829.
    Details
    Publication Date: 2017-12-19
    Description: An empirical function is derived for predicting the rate-depth profile of particulate organic carbon (POC) degradation in surface marine sediments including the bioturbated layer. The rate takes the form of a power law analogous to the Middelburg function. The functional parameters were optimized by simulating measured benthic O2 and NO3− fluxes at 185 stations worldwide using a diagenetic model. The novelty of this work rests with the finding that the vertically-resolved POC degradation rate in the bioturbated zone can be determined using a simple function where the POC rain rate is the governing variable. Although imperfect, the model is able to fit 71 % of paired O2 and NO3− fluxes to within 50% of measured values. It further provides realistic geochemical concentration-depth profiles, NO3− penetration depths and apparent first-order POC mineralization rate constants. The model performs less well on the continental shelf due to the high heterogeneity there. When applied to globally resolved maps of rain rate, the model predicts a global denitrification rate of 182 ± 88 Tg yr−1 of N and a POC burial rate of 107 ± 52 Tg yr−1 of C with a mean carbon burial efficiency of 6.1%. These results are in very good agreement with published values. Our proposed function is conceptually simple, requires less parameterization than multi-G type models and is suitable for non-steady state applications. It provides a basis for more accurately simulating benthic nutrient fluxes and carbonate dissolution rates in Earth system models.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GB005087
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    SO 196 [SO196] - SUMSUN: Geochemische Untersuchungen der Porenwässer und Sedimente von CO2-Seeps : Abschlussbericht für das BMBF-Projekt: SUMSUN ; Berichtszeitraum: 01.01.2008 - 28.02.2009 (2009)
    IFM-GEOMAR
    In:  IFM-GEOMAR, Kiel, 14 pp.
    Details
    Publication Date: 2020-07-08
    Type: Report , NonPeerReviewed
    Format: text
    DOI: 10.2314/GBV:609534351
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    OceanRep: Report - other report
  • 4
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    The physicochemical habitat of Sclerolinum sp., at Hook Ridge hydrothermal vent, Bransfield Strait, Antarctica (2005)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 50 (2). pp. 598-606.
    Details
    Publication Date: 2019-09-23
    Description: At Hook Ridge hydrothermal vent, a new species of Sclerolinum (Monilifera, Siboglinidae) was found at a water depth of 1,045 m. On the basis of investigations of multicores and gravity cores, the species habitat is characterized. Sclerolinum does not occur in sediments that are most strongly influenced by hydrothermal fluids, probably because of high temperature (up to 49°C) and precipitation of siliceous crusts. About 800 individuals m-2 occur in sediments that are only weakly exposed to hydrothermal flow and have the following characteristics: 20°C (15 cm sediment depth) to 21.5°C (bottom water), 18-40 cm yr-1 advection rates, pH 5.5, 〈25 µmol L-1 methane, 〈170 µmol L-1 sulfide, and 〈0.0054 mol m-2 yr-1 sulfide flux. Comparison with geochemical data from other reducing sediments indicates that the two groups of Siboglinidae, Monilifera and Frenulata, occur in sediments with low sulfide concentration and flux. In contrast, sulfurbased chemosynthetic organisms that typically occur at hydrothermal vents and cold seeps (e.g., Vestimentifera, vesicomyid clams, and bacterial mats) occur in sediments with higher sulfide availability; threshold values are around 500 µmol L-1 sulfide and 0.1 mol m-2 yr-1 sulfide fluxes. We did not find typical hydrothermal vent species at Hook Ridge hydrothermal vent, which might be explained by the unfavorable physicochemical habitat: At sites inhabited by Sclerolinum, sulfide availability appears to be too low, whereas at sites with higher sulfide availability, the temperatures might be too high, siliceous crust precipitation could preclude their occurrence, or both.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lo.2005.50.2.0598
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    A revised global estimate of dissolved iron fluxes from marine sediments (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 29 (5). pp. 691-707.
    Details
    Publication Date: 2019-09-23
    Description: Literature data on benthic dissolved iron (DFe) fluxes (µmol m−2 d−1), bottom water oxygen concentrations (O2BW, μM), and sedimentary carbon oxidation rates (COX, mmol m−2 d−1) from water depths ranging from 80 to 3700 m were assembled. The data were analyzed with a diagenetic iron model to derive an empirical function for predicting benthic DFe fluxes: inline image where γ (= 170 µmol m−2 d−1) is the maximum flux for sediments at steady state located away from river mouths. This simple function unifies previous observations that COX and O2BW are important controls on DFe fluxes. Upscaling predicts a global DFe flux from continental margin sediments of 109 ± 55 Gmol yr−1, of which 72 Gmol yr−1 is contributed by the shelf (〈200 m) and 37 Gmol yr−1 by slope sediments (200–2000 m). The predicted deep-sea flux (〉2000 m) of 41 ± 21 Gmol yr−1 is unsupported by empirical data. Previous estimates of benthic DFe fluxes derived using global iron models are far lower (approximately 10–30 Gmol yr−1). This can be attributed to (i) inadequate treatment of the role of oxygen on benthic DFe fluxes and (ii) improper consideration of continental shelf processes due to coarse spatial resolution. Globally averaged DFe concentrations in surface waters simulated with the intermediate-complexity University of Victoria Earth System Climate Model were a factor of 2 higher with the new function. We conclude that (i) the DFe flux from marginal sediments has been underestimated in the marine iron cycle and (ii) iron scavenging in the water column is more intense than currently presumed.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/2014GB005017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    3-D basin-scale reconstruction of natural gas hydrate system of the Green Canyon, Gulf of Mexico (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 18 (5). pp. 1959-1985.
    Details
    Publication Date: 2020-02-06
    Description: Our study presents a basin-scale 3D modeling solution, quantifying and exploring gas hydrate accumulations in the marine environment around the Green Canyon (GC955) area, Gulf of Mexico. It is the first modeling study that considers the full complexity of gas hydrate formation in a natural geological system. Overall, it comprises a comprehensive basin re-construction, accounting for depositional and transient thermal history of the basin, source rock maturation, petroleum components generation, expulsion and migration, salt tectonics and associated multi-stage fault development. The resulting 3D gas hydrate distribution in the Green Canyon area is consistent with independent borehole observations. An important mechanism identified in this study and leading to high gas hydrate saturation (〉 80 vol. %) at the base of the gas hydrate stability zone (GHSZ), is the recycling of gas hydrate and free gas enhanced by high Neogene sedimentation rates in the region. Our model predicts the rapid development of secondary intra-salt mini-basins situated on top of the allochthonous salt deposits which leads to significant sediment subsidence and an ensuing dislocation of the lower GHSZ boundary. Consequently, large amounts of gas hydrates located in the deepest parts of the basin dissociate and the released free methane gas migrates upwards to recharge the GHSZ. In total, we have predicted the gas hydrate budget for the Green Canyon area that amounts to ∼3,256 Mt of gas hydrate which is equivalent to ∼340 Mt of carbon (∼7 x 1011 m3 of CH4 at STP conditions), and consists mostly of biogenic hydrates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017GC006876
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Benthic iron and phosphorus fluxes across the Peruvian oxigen minimum zone (2012)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 57 (3). pp. 851-867.
    Details
    Publication Date: 2019-09-23
    Description: Benthic fluxes of dissolved ferrous iron (Fe2+) and phosphate (TPO4) were quantified by in situ benthic chamber incubations and pore-water profiles along a depth transect (11°S, 80–1000 m) across the Peruvian oxygen minimum zone (OMZ). Bottom-water O2 levels were 〈 2 µmol L-1 down to 500-m water depth, and increased to ~40 µmol L-1 at 1000 m. Fe2+ fluxes were highest on the shallow shelf (maximum 316 mmol m-2 yr-1), moderate (15.4 mmol m-2 yr-1) between 250 m and 600 m, and negligible at deeper stations. In the persistent OMZ core, continuous reduction of Fe oxyhydroxides results in depletion of sedimentary Fe :Al ratios. TPO4 fluxes were high (maximum 292 mmol m-2 yr-1) throughout the shelf and the OMZ core in association with high organic carbon degradation rates. Ratios between organic carbon degradation and TPO4 flux indicate excess release of P over C when compared to Redfield stoichiometry. Most likely, this is caused by preferential P release from organic matter, dissolution of fish debris, and/or P release from microbial mat communities, while Fe oxyhydroxides can only be inferred as a major P source on the shallow shelf. The benthic fluxes presented here are among the highest reported from similar, oxygen-depleted environments and highlight the importance of sediments underlying anoxic water bodies as nutrient sources to the ocean. The shelf is particularly important as the periodic passage of coastal trapped waves and associated bottom-water oxygenation events can be expected to induce a transient biogeochemical environment with highly variable release of Fe2+ and TPO4.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lo.2012.57.3.0851
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Interaction of Oxygen and Marine Productivity (2005)
    IFM-GEOMAR
    In:  In: IFM-GEOMAR [Annual] Report 2002-2004 From the Seafloor to the Atmosphere - Marine Sciences at IFM-GEOMAR Kiel -. , ed. by Villwock, A. IFM-GEOMAR, Kiel, Germany, pp. 33-34.
    Details
    Publication Date: 2019-03-08
    Type: Book chapter , NonPeerReviewed
    Format: text
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    OceanRep: Book chapter
  • 9
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    Silicate weathering in anoxic marine sediments (2009)
    IFM-GEOMAR
    In:  IFM-GEOMAR Annual Report, 2008 . pp. 18-19.
    Details
    Publication Date: 2018-10-16
    Description: Weathering of silicate minerals is the major sink for atmospheric CO2 on geological time scales. It has commonly been assumed that this process is only occurring on land. New results, however, show that silicate minerals are also reactive within marine sediments. Most of the metabolic CO2 being produced in marine sediments enriched in organic matter is consumed by this reaction with major implications for the geological carbon cycle.
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 10
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    Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean (2020)
    AGU | Wiley
    Details
    Publication Date: 2023-02-08
    Description: We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in this region. Gas hydrates are present where a fracture network beneath the pockmark focusses migration of thermogenic hydrocarbons characterized by their C1/C2+ and stable isotopic compositions (δ2H‐CH4, δ13C‐CH4). Measured geothermal gradients (~80°C km‐1) and known formation temperatures (〉70°C) suggest that those hydrocarbons are formed at depths 〉800 mbsf. A combined analytical/modeling approach, including concentration and isotopic mass balances, reveals that pockmark sediments experience diffuse migration of thermogenic hydrocarbons. However, at sites without channeled flow this appears to be limited to depths 〉 ~50 mbsf. At all sites we document a contribution of microbial methanogenesis to the overall carbon cycle that includes a component of secondary carbonate reduction (CR) – i.e. reduction of dissolved inorganic carbon (DIC) generated by anaerobic oxidation of methane (AOM) in the uppermost methanogenic zone. AOM and CR rates are spatially variable within the pockmark and are highest at high‐flux sites. These reactions are revealed by δ13C‐DIC depletions at the sulfate‐methane interface at all sites. However, δ13C‐CH4 depletions are only observed at the low methane flux sites because changes in the isotopic composition of the overall methane pool are masked at high‐flux sites. 13C‐depletions of TOC suggest that at seeps sites, methane‐derived carbon is incorporated into de novo synthesized biomass.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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