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  • 1
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    Resilience of benthic deep-sea fauna to mining activities (2017)
    Elsevier
    In:  Marine Environmental Research, 129 . pp. 76-101.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • Deep-sea mineral exploration and exploitation licenses have been issued recently. • Mining will modify the abiotic and biotic environment. • At directly mined sites, species are removed and cannot resist disturbance. • Recovery is highly variable in distinct ecosystems and among benthic taxa. • Community changes may persist over geological time-scales at directly mined sites. Abstract With increasing demand for mineral resources, extraction of polymetallic sulphides at hydrothermal vents, cobalt-rich ferromanganese crusts at seamounts, and polymetallic nodules on abyssal plains may be imminent. Here, we shortly introduce ecosystem characteristics of mining areas, report on recent mining developments, and identify potential stress and disturbances created by mining. We analyze species’ potential resistance to future mining and perform meta-analyses on population density and diversity recovery after disturbances most similar to mining: volcanic eruptions at vents, fisheries on seamounts, and experiments that mimic nodule mining on abyssal plains. We report wide variation in recovery rates among taxa, size, and mobility of fauna. While densities and diversities of some taxa can recover to or even exceed pre-disturbance levels, community composition remains affected after decades. The loss of hard substrata or alteration of substrata composition may cause substantial community shifts that persist over geological timescales at mined sites.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: other
    DOI: 10.1016/j.marenvres.2017.04.010
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    On the origin of multiple BSRs in the Danube deep-sea fan, Black Sea (2017)
    Elsevier
    In:  Earth and Planetary Science Letters, 462 . pp. 15-25.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • A stack of four BSRs were identified in levee deposits of the Danube deep-sea fan. • The multiple BSRs are not caused by overpressure compartments. • The multiple BSRs reflect stages of stable sealevel lowstands during glacial times. • Gas underneath the previous GHSZ does not start to migrate for thousands of years. Abstract High-resolution 2D seismic data reveal the character and distribution of up to four stacked bottom simulating reflectors (BSR) within the channel-levee systems of the Danube deep-sea fan. The theoretical base of the gas hydrate stability zone (GHSZ) calculated from regional geothermal gradients and salinity data is in agreement with the shallowest BSR. For the deeper BSRs, BSR formation due to overpressure compartments can be excluded because the necessary gas column would exceed the vertical distance between two overlying BSRs. We show instead that the deeper BSRs are likely paleo BSRs caused by a change in pressure and temperature conditions during different limnic phases of the Black Sea. This is supported by the observation that the BSRs correspond to paleo seafloor horizons located in a layer between a buried channel-levee system and the levee deposits of the Danube channel. The good match of the observed BSRs and the BSRs predicted from deposition of these sediment layers indicates that the multiple BSRs reflect stages of stable sealevel lowstands possibly during glacial times. The observation of sharp BSRs several 10,000 of years but possibly up to 300,000 yr after they have left the GHSZ demonstrates that either hydrate dissociation does not take place within this time frame or that only small amounts of gas are released that can be transported by diffusion. The gas underneath the previous GHSZ does not start to migrate for several thousands of years.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1016/j.epsl.2017.01.006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Response of anaerobic methanotrophs and benthic foraminifera on 20 years of methane emission from a gas blowout in the North Sea (2015)
    Elsevier
    In:  Marine and Petroleum Geology, 68 . pp. 731-742.
    Details
    Publication Date: 2017-04-11
    Description: Highlights • High abundance of active anaerobic methanotrophs in sediments of the blowout crater suggests adaptation to methane seepage within at most two decades. • Fast exchange processes in permeable surface sediments prevent sulfate depletion and probably methane-derived carbonate precipitation. • Methane seepage impacts isotopic and assemblage composition of benthic foraminifera. Abstract Methane emissions from marine sediments are partly controlled by microbial anaerobic oxidation of methane (AOM). AOM provides a long-term sink for carbon through precipitation of methane-derived authigenic carbonates (MDAC). Estimates on the adaptation time of this benthic methane filter as well as on the establishment of related processes and communities after an onset of methane seepage are rare. In the North Sea, considerable amounts of methane have been released since 20 years from a man-made gas blowout offering an ideal natural laboratory to study the effects of methane seepage on initially “pristine” sediment. Sediment cores were taken from the blowout crater and a reference site (50 m distance) in 2011 and 2012, respectively, to investigate porewater chemistry, the AOM community and activity, the presence of authigenic carbonates, and benthic foraminiferal assemblages. Potential AOM activity (up to 3060 nmol cm−3 sediment d−1 or 375 mmol m−2 d−1) was detected only in the blowout crater up to the maximum sampling depth of 18 cm. CARD-FISH analyzes suggest that monospecific ANME-2 aggregates were the only type of AOM organisms present, showing densities (up to 2.2*107 aggregates cm−3) similar to established methane seeps. No evidence for recent MDAC formation was found using stable isotope analyzes (δ13C and δ18O). In contrast, the carbon isotopic signature of methane was recorded by the epibenthic foraminifer Cibicides lobatulus (δ13C −0.66‰). Surprisingly, the foraminiferal assemblage in the blowout crater was dominated by Cibicides and other species commonly found in the Norwegian Channel and fjords, indicating that these organisms have responded sensitively to the specific environmental conditions at the blowout. The high activity and abundance of AOM organisms only at the blowout site suggests adaptation to a strong increase in methane flux in the order of at most two decades. High gas discharge dynamics in permeable surface sediments facilitate fast sulfate replenishing and stimulation of AOM. The accompanied prevention of total alkalinity build-up in the porewater thereby appears to inhibit the formation of substantial methane-derived authigenic carbonate at least within the given time window.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.marpetgeo.2015.07.012
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Microbial colonization and degradation of polyethylene and biodegradable plastic bags in temperate fine-grained organic-rich marine sediments (2016)
    Elsevier
    In:  Marine Pollution Bulletin, 103 (1-2). pp. 168-178.
    Details
    Publication Date: 2019-09-23
    Description: Highlights • Polypropylene and biodegradable plastic bags were incubated in marine sediments. • Bacterial colonization was highest on biodegradable plastic bags. • None of the two bag types showed signs of degradation after 98 days. • Marine sediments probably represent a long-term sink for both types of litter. Abstract To date, the longevity of plastic litter at the sea floor is poorly constrained. The present study compares colonization and biodegradation of plastic bags by aerobic and anaerobic benthic microbes in temperate fine-grained organic-rich marine sediments. Samples of polyethylene and biodegradable plastic carrier bags were incubated in natural oxic and anoxic sediments from Eckernförde Bay (Western Baltic Sea) for 98 days. Analyses included (1) microbial colonization rates on the bags, (2) examination of the surface structure, wettability, and chemistry, and (3) mass loss of the samples during incubation. On average, biodegradable plastic bags were colonized five times higher by aerobic and eight times higher by anaerobic microbes than polyethylene bags. Both types of bags showed no sign of biodegradation during this study. Therefore, marine sediment in temperate coastal zones may represent a long-term sink for plastic litter and also supposedly compostable material.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.marpolbul.2015.12.024
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    3-D numerical modelling of methane hydrate accumulations using PetroMod (2016)
    Elsevier
    In:  Marine and Petroleum Geology, 71 . pp. 288-295.
    Details
    Publication Date: 2019-09-23
    Description: Highlights • PetroMod is the 1st basin modelling software including methane hydrate simulation. • The Gas hydrate module includes physical, thermodynamic, and kinetic properties. • PetroMod simulates the evolution over time of the GHSZ. • PetroMod includes a kinetic for the organic matter degradation at low temperature. Abstract Within the German gas hydrate initiative SUGAR, a new 2-D/3-D module simulating the biogenic generation of methane from organic matter and the formation of gas hydrates has been developed and included in the petroleum systems modelling software package PetroMod®. Typically, PetroMod® simulates the thermogenic generation of multiple hydrocarbon components (oil and gas), their migration through geological strata, finally predicting oil and gas accumulations in suitable reservoir formations. We have extended PetroMod® to simulate gas hydrate accumulations in marine and permafrost environments by the implementation of algorithms describing (1) the physical, thermodynamic, and kinetic properties of gas hydrates; and (2) a kinetic continuum model for the microbially mediated, low temperature degradation of particulate organic carbon in sediments. Additionally, the temporal and spatial resolutions of PetroMod® were increased in order to simulate processes on time scales of hundreds of years and within decimetres of spatial extension. In order to validate the abilities of the new hydrate module, we present here results of a theoretical layer-cake model. The simulation runs predict the spatial distribution and evolution in time of the gas hydrate stability field, the generation and migration of thermogenic and biogenic methane gas, and its accumulation as gas hydrates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.marpetgeo.2015.12.019
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Quantification of methane emissions at abandoned gas wells in the Central North Sea (2015)
    Elsevier
    In:  Marine and Petroleum Geology, 68 . pp. 848-860.
    Details
    Publication Date: 2017-12-19
    Description: As a result of extensive hydrocarbon exploration, the North Sea hosts several thousand abandoned wells; many believed to be leaking methane. However, how much of this greenhouse gas is emitted into the water column and ultimately reaches the atmosphere is not known. Here, we investigate three abandoned wells at 81-93m water depth in the Norwegian sector of the North Sea, all of which show gas seepage into the bottom water. The isotopic signature of the emanating gas points towards a biogenic origin and hence to gas pockets in the sedimentary overburden above the gas reservoirs that the wells were drilled into. Video-analysis of the seeping gas bubbles and direct gas flow measurements resolved initial bubble sizes ranging between 3.2 and 7.4mm in diameter with a total seabed gas flow between 1 and 19 tons of CH4 per year per well. Estimated total annual seabed emissions from all three wells of ~24 tons are similar to the natural seepage rates at Tommeliten, suggesting that leaky abandoned wells represent a significant source of methane into North Sea bottom waters. However, the bubble-driven direct methane transport into the atmosphere was found to be negligible (〈2%) due to the small bubble sizes and the water depth at which they are released.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1016/j.marpetgeo.2015.07.030
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Seafloor integrity versus critical metal supply (2021)
    Elsevier | Cell Press
    Details
    Publication Date: 2023-10-06
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 8
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    Greenhouse gas emissions from marine decommissioned hydrocarbon wells: leakage detection, monitoring and mitigation strategies (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Highlights • Gas release from wells may counteract efforts to mitigate greenhouse gas emissions. • An approach for assessing methane release from marine decommissioned wells. • This gas release largely depends on the presence of shallow gas accumulations. • Methane release from hydrocarbon wells represents a major source in the North Sea. Abstract Hydrocarbon gas emissions from with decommissioned wells are an underreported source of greenhouse gas emissions in oil and gas provinces. The associated emissions may partly counteract efforts to mitigate greenhouse gas emissions from fossil fuel infrastructure. We have developed an approach for assessing methane leakage from marine decommissioned wells based on a combination of existing regional industrial seismic and newly acquired hydroacoustic water column imaging data from the Central North Sea. Here, we present hydroacoustic data which show that 28 out of 43 investigated wells release gas from the seafloor into the water column. This gas release largely depends on the presence of shallow gas accumulations and their distance to the wells. The released gas is likely primarily biogenic methane from shallow sources. In the upper 1,000 m below the seabed, gas migration is likely focused along drilling-induced fractures around the borehole or through non-sealing barriers. Combining available direct measurements for methane release from marine decommissioned wells with our leakage analysis suggests that gas release from investigated decommissioned hydrocarbon wells is a major source of methane in the North Sea (0.9-3.7 [95% confidence interval = 0.7-4.2] kt yr−1 of CH4 for 1,792 wells in the UK sector of the Central North Sea). This means hydrocarbon gas emissions associated with marine hydrocarbon wells are not significant for the global greenhouse gas budget, but have to be considered when compiling regional methane budgets.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: archive
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    New insights into geology and geochemistry of the Kerch seep area in the Black Sea (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Highlights • Combining porewater geochemistry, geochemical modeling and subsurface geophysical data in order to understand the fluid flow system of Kerch seep area. • This seep area is not in steady state. • Methane transport is in the form of gas bubbles not porewater advection. • High surface temperatures are the result of hydrate formation and not an indication for elevated geothermal gradients. • Modeling says this seep is young (〈500 years old). Abstract High-resolution 3D seismic data in combination with deep-towed sidescan sonar data and porewater analysis give insights into the seafloor expression and the plumbing system of the actively gas emitting Kerch seep area, which is located in the northeastern Black Sea in around 900 m water depth, i.e. well within the gas hydrate stability zone (GHSZ). Our analysis shows that the Kerch seep consists of three closely spaced but individual seeps above a paleo-channel-levee system of the Don Kuban deep-sea fan. We show that mounded seep morphology results from sediment up-doming due to gas overpressure. Each of the seeps hosts its own gas pocket underneath the domes which are fed with methane of predominantly microbial origin along narrow pipes through the GHSZ. Methane transport occurs dominantly in the form of gas bubbles decoupled from fluid advection. Elevated sediment temperatures of up to 0.3 °C above background values are most likely the result of gas hydrate formation within the uppermost 10 m of the sediment column. Compared to other seeps occurring within the GHSZ in the Black Sea overall only scarce gas indications are present in geoacoustic and geophysical data. Transport-reaction modeling suggests that the Kerch seep is a young seep far from steady state and probably not more than 500 years old.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Basin-scale estimates on petroleum components generation in the Western Black Sea basin based on 3-D numerical modelling (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Highlights • Total amount of generated biogenic methane is estimated at ~3100 Gt. • Total amount of generated thermogenic methane is estimated at ~1,560 Gt. • The Maykop formation is partially productive in the central basin and not yet fully productive towards the basin peripherals. A new numerical model reconstructing the depositional history (98–0 Ma) of the Western Black Sea sub-basin is presented. The model accounts for changing boundary conditions (i.e. water depth, bottom water temperature, heat flow evolution over time) and estimates the rates and total amounts of the in-situ biogenic methane generation and thermally-driven organic matter maturation in the source rocks. The overall thermogenic and biogenic gas generation predicted by the model is estimated at ~1560 Gt and ~3100 Gt, respectively.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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