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  • AGU (American Geophysical Union)  (4)
  • GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel  (4)
  • Nature Research  (2)
  • 1
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    Quantifying tidally-driven benthic oxygen exchange across permeable sediments: An aquatic eddy correlation study (2014)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 119 (10). pp. 6918-6932.
    Details
    Publication Date: 2018-02-26
    Description: Continental shelves are predominately (~70%) covered with permeable, sandy sediments. While identified as critical sites for intense oxygen, carbon, and nutrient turnover, constituent exchange across permeable sediments remains poorly quantified. The central North Sea largely consists of permeable sediments and has been identified as increasingly at risk for developing hypoxia. Therefore, we investigate the benthic O2 exchange across the permeable North Sea sediments using a combination of in situ microprofiles, a benthic chamber, and aquatic eddy correlation. Tidal bottom currents drive the variable sediment O2 penetration depth (from ~3 to 8 mm) and the concurrent turbulence-driven 25-fold variation in the benthic sediment O2 uptake. The O2 flux and variability were reproduced using a simple 1-D model linking the benthic turbulence to the sediment pore water exchange. The high O2 flux variability results from deeper sediment O2 penetration depths and increased O2 storage during high velocities, which is then utilized during low-flow periods. The study reveals that the benthic hydrodynamics, sediment permeability, and pore water redox oscillations are all intimately linked and crucial parameters determining the oxygen availability. These parameters must all be considered when evaluating mineralization pathways of organic matter and nutrients in permeable sediments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014JC010303
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Extensive nitrogen loss from permeable sediments off North-West Africa (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Biogeosciences, 121 (4). pp. 1144-1157.
    Details
    Publication Date: 2019-07-16
    Description: The upwelling area off North-West Africa is characterized by high export production, high nitrate and low oxygen concentration in bottom waters. The underlying sediment consists of sands that cover most of the continental shelf. Due to their permeability sands allow for fast advective pore water transport and can exhibit high rates of nitrogen (N) loss via denitrification as reported for anthropogenically eutrophied regions. However, N loss from sands underlying naturally eutrophied waters is not well studied, and in particular, N loss from the North-West African shelf is poorly constrained. During two research cruises in April/May 2010/2011, sediment was sampled along the North-West African shelf and volumetric denitrification rates were measured in sediment layers down to 8 cm depth using slurry incubations with 15N-labeled nitrate. Areal N loss was calculated by integrating volumetric rates down to the nitrate penetration depth derived from pore water profiles. Areal N loss was neither correlated with water depth nor with bottom water concentrations of nitrate and oxygen but was strongly dependent on sediment grain size and permeability. The derived empirical relation between benthic N loss and grains size suggests that pore water advection is an important regulating parameter for benthic denitrification in sands and further allowed extrapolating rates to an area of 53,000 km2 using detailed sediment maps. Denitrification from this region amounts to 995 kt yr-1 (average 3.6 mmol m-2 d-1) which is 4 times higher than previous estimates based on diffusive pore water transport. Sandy sediments cover 50-60% of the continental shelf and thus may contribute significantly to the global benthic N loss.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015JG003298
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Water column and sediment gas geochemistry (2012)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    In:  In: RV Celtic Explorer EUROFLEETS cruise report CE12010 - ECO2@NorthSea : 20.07. – 06.08.2012, Bremerhaven - Hamburg. , ed. by Linke, P. GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, pp. 8-27.
    Details
    Publication Date: 2014-02-20
    Type: Book chapter , NonPeerReviewed , info:eu-repo/semantics/bookPart
    DOI: 10.3289/GEOMAR_REP_NS_4_2012
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    OceanRep: Book chapter
  • 4
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    Gas release experiment (2012)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    In:  In: RV Celtic Explorer EUROFLEETS cruise report CE12010 - ECO2@NorthSea : 20.07. – 06.08.2012, Bremerhaven - Hamburg. , ed. by Linke, P. GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, pp. 28-32.
    Details
    Publication Date: 2014-02-20
    Type: Book chapter , NonPeerReviewed
    DOI: 10.3289/GEOMAR_REP_NS_4_2012
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    OceanRep: Book chapter
  • 5
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    2. Wochenbericht Alkor Expedition AL570 (2022)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    Details
    Publication Date: 2022-04-06
    Description: Alkor Expedition AL570, Kiel – Kiel, 22. März – 11. April 2022 ; MGF-Ostsee
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Weekly report
  • 6
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    1. Wochenbericht Alkor Expedition AL570 (2022)
    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    Details
    Publication Date: 2022-03-31
    Description: Alkor Expedition AL570, Kiel – Kiel, 22. März – 11. April 2022 ; MGF-Ostsee
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Weekly report
  • 7
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    Efficiency of benthic filter: Biological control of the emission of dissolved methane from sediments containing shallow gas hydrates at Hydrate Ridge (2006)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 20 (GB2019).
    Details
    Publication Date: 2018-03-16
    Description: In marine sedimentary environments, microbial methanotrophy represents an important sink for methane before it leaves the seafloor and enters the water column. Using benthic observatories in conjunction with numerical modeling of pore water gradients, we investigated seabed methane emission rates at cold seep sites with underlying gas hydrates at Hydrate Ridge, Cascadia margin. Measurements were conducted at three characteristic sites which have variable fluid flow and sulfide flux and sustain distinct chemosynthetic communities. In sediments covered with microbial mats of Beggiatoa, seabed methane efflux ranges from 1.9 to 11.5 mmol m−2 d−1. At these sites of relatively high advective flow, total oxygen uptake was very fast, yielding rates of up to 53.4 mmol m−2 d−1. In sediments populated by colonies with clams of the genus Calyptogena and characterized by low advective flow, seabed methane emission was 0.6 mmol m−2 d−1, whereas average total oxygen uptake amounted to only 3.7 mmol m−2 d−1. The efficiency of methane consumption at microbial mat and clam field sites was 66 and 83%, respectively. Our measurements indicate a high potential capacity of aerobic methane oxidation in the benthic boundary layer. This layer potentially restrains seabed methane emission when anaerobic methane oxidation in the sediment becomes saturated or when methane is bypassing the sediment matrix along fractures and channels.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2004GB002389
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Recycling and burial of biogenic silica in an open margin oxygen minimum zone (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11ºS and 12ºS. Each transect extends from the shelf to the upper slope (∼1000 m) and dissects the permanently anoxic waters between ∼200 – 500m water depth. BSi burial (2100 mmol m‐2 yr‐1) and recycling fluxes (3300 mmol m‐2 yr‐1) were highest on the shelf with mean preservation efficiencies (34±15%) that exceed the global mean of 10 – 20%. BSi preservation was highest on the inner shelf (up to 56%), decreasing to 7% and 12% under anoxic waters and below the OMZ, respectively. The data suggest that the main control on BSi preservation is the rate at which reactive BSi is transported away from undersaturated surface sediments by burial and bioturbation to the underlying saturated sediment layers where BSi dissolution is thermodynamically and/or kinetically inhibited. BSi burial across the entire Peruvian margin between 3ºS to 15ºS and down to 1000m water depth is estimated to be 0.1 – 0.2 Tmol yr‐1; equivalent to 2 – 7% of total burial on continental margins. Existing global data permit a simple relationship between BSi rain rate to the seafloor and the accumulation of unaltered BSi, giving the possibility to reconstruct rain rates and primary production from the sediment archive in addition to benthic Si turnover in global models.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Influence of methane seepage on isotopic signatures in living deep-sea benthic foraminifera, 79° N (2022)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Fossil benthic foraminifera are used to trace past methane release linked to climate change. However, it is still debated whether isotopic signatures of living foraminifera from methane-charged sediments reflect incorporation of methane-derived carbon. A deeper understanding of isotopic signatures of living benthic foraminifera from methane-rich environments will help to improve reconstructions of methane release in the past and better predict the impact of future climate warming on methane seepage. Here, we present isotopic signatures (δ13C and δ18O) of foraminiferal calcite together with biogeochemical data from Arctic seep environments from c. 1200 m water depth, Vestnesa Ridge, 79° N, Fram Strait. Lowest δ13C values were recorded in shells of Melonis barleeanus, − 5.2‰ in live specimens and − 6.5‰ in empty shells, from sediments dominated by aerobic (MOx) and anaerobic oxidation of methane (AOM), respectively. Our data indicate that foraminifera actively incorporate methane-derived carbon when living in sediments with moderate seepage activity, while in sediments with high seepage activity the poisonous sulfidic environment leads to death of the foraminifera and an overgrowth of their empty shells by methane-derived authigenic carbonates. We propose that the incorporation of methane-derived carbon in living foraminifera occurs via feeding on methanotrophic bacteria and/or incorporation of ambient dissolved inorganic carbon.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Coastal El Niño triggers rapid marine silicate alteration on the seafloor (2023)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Marine silicate alteration plays a key role in the global carbon and cation cycles, although the timeframe of this process in response to extreme weather events is poorly understood. Here we investigate surface sediments across the Peruvian margin before and after extreme rainfall and runoff (coastal El Niño) using Ge/Si ratios and laser-ablated solid and pore fluid Si isotopes (δ 30 Si). Pore fluids following the rainfall show elevated Ge/Si ratios (2.87 µmol mol −1 ) and δ 30 Si values (3.72‰), which we relate to rapid authigenic clay formation from reactive terrigenous minerals delivered by continental runoff. This study highlights the direct coupling of terrestrial erosion and associated marine sedimentary processes. We show that marine silicate alteration can be rapid and highly dynamic in response to local weather conditions, with a potential impact on marine alkalinity and CO 2 -cycling on short timescales of weeks to months, and thus element turnover on human time scales.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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