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  • 1
    Electronic Resource
    Electronic Resource
    In vitro activity of combinations of beta-lactam antibiotics with beta-lactamase inhibitors against cephalosporinase-producing bacteria (1989)
    Springer
    European journal of clinical microbiology & infectious diseases 8 (1989), S. 783-788 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Combinations of different beta-lactam antibiotics, including cefotaxime, with three beta-lactamase inhibitors were tested against cephalosporinase producing bacterial strains. The most significant antagonism was obtained with a combination of clavulanic acid and cefotaxime, while almost no antagonism was observed with sulbactam and tazobactam. In strains belonging to five different species there was a correlation between the levels of cephalosporinase produced after exposure to different concentrations of inhibitors and the MICs of cefotaxime combined with the same concentrations of inhibitors. It is concluded that there is little likelihood of antagonism between beta-lactam antibiotics and sulbactam or tazobactam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185845
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Temporal Constraints on Hydrate-Controlled Methane Seepage off Svalbard (2014)
    AAAS (American Association for the Advancement of Science)
    In:  Science, 343 (6168). pp. 284-287.
    Details
    Publication Date: 2019-10-17
    Description: Methane hydrate is an icelike substance that is stable at high pressure and low temperature in continental margin sediments. Since the discovery of a large number of gas flares at the landward termination of the gas hydrate stability zone off Svalbard, there has been concern that warming bottom waters have started to dissociate large amounts of gas hydrate and that the resulting methane release may possibly accelerate global warming. Here, we can corroborate that hydrates play a role in the observed seepage of gas, but we present evidence that seepage off Svalbard has been ongoing for at least three thousand years and that seasonal fluctuations of 1-2°C in the bottom-water temperature cause periodic gas hydrate formation and dissociation, which focus seepage at the observed sites.
    Type: Article , PeerReviewed
    Format: text
    Format: audio
    Format: text
    DOI: 10.1126/science.1246298
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Water column methanotrophy controlled by a rapid oceanographic switch (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (5). pp. 378-382.
    Details
    Publication Date: 2020-11-23
    Description: Large amounts of the greenhouse gas methane are released from the seabed to the water column1, where it may be consumed by aerobic methanotrophic bacteria2. The size and activity of methanotrophic communities, which determine the amount of methane consumed in the water column, are thought to be mainly controlled by nutrient and redox dynamics3–7. Here, we report repeated measurements of methanotrophic activity and community size at methane seeps west of Svalbard, and relate them to physical water mass properties and modelled ocean currents. We show that cold bottom water, which contained a large number of aerobic methanotrophs, was displaced by warmer water with a considerably smaller methanotrophic community within days. Ocean current simulations using a global ocean/sea-ice model suggest that this water mass exchange is consistent with short-term variations in the meandering West Spitsbergen Current. We conclude that the shift from an offshore to a nearshore position of the current can rapidly and severely reduce methanotrophic activity in the water column. Strong fluctuating currents are common at many methane seep systems globally, and we suggest that they affect methane oxidation in the water column at other sites, too.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/ngeo2420
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Extensive release of methane from Arctic seabed west of Svalbard during summer 2014 does not influence the atmosphere (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 43 (9). pp. 4624-4631.
    Details
    Publication Date: 2020-10-16
    Description: We find that summer methane (CH4) release from seabed sediments west of Svalbard substantially increases CH4 concentrations in the ocean but has limited influence on the atmospheric CH4 levels. Our conclusion stems from complementary measurements at the seafloor, in the ocean, and in the atmosphere from land-based, ship and aircraft platforms during a summer campaign in 2014. We detected high concentrations of dissolved CH4 in the ocean above the seafloor with a sharp decrease above the pycnocline. Model approaches taking potential CH4 emissions from both dissolved and bubble-released CH4 from a larger region into account reveal a maximum flux compatible with the observed atmospheric CH4 mixing ratios of 2.4–3.8 nmol m−2 s−1. This is too low to have an impact on the atmospheric summer CH4 budget in the year 2014. Long-term ocean observatories may shed light on the complex variations of Arctic CH4 cycles throughout the year.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/2016GL068999
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The Lilliput effect in crinoids at the end of the Oceanic Anoxic Event 2: a case study from Poland (2016)
    Paleontological Society
    Details
    Publication Date: 2016-05-12
    Description: The Cretaceous Period (145–66 Ma) consisted of several oceanic anoxic events (120–80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes—e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
    Published by Paleontological Society
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    PAPER CURRENT
  • 6
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    Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates (2015)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2015-04-25
    Description: Biotic gas generation from the degradation of organic carbon in marine sediments supplies and maintains gas hydrates throughout the world’s oceans. In nascent, ultraslow-spreading ocean basins, methane generation can also be abiotic, occurring during the high-temperature (〉200 °C) serpentinization of ultramafic rocks. Here, we report on the evolution of a growing Arctic gas- and gas hydrate–charged sediment drift on oceanic crust in eastern Fram Strait, a tectonically controlled, deep-water gateway between the subpolar North Atlantic and Arctic Oceans. Ultraslow-spreading ridges between northwest Svalbard and northeast Greenland permit the sustained interaction of a mid-ocean ridge transform fault and developing sediment drift, on both young (〈10 Ma) and old (〉10 Ma) oceanic crust, since the late Miocene. Geophysical data image the gas-charged drift and crustal structure and constrain the timing of a major 30 km lateral displacement of the drift across the Molloy transform fault. We describe the buildup of a 2 m.y., long-lived gas hydrate– and free gas–charged drift system on young oceanic crust that may be fed and maintained by a dominantly abiotic methane source. Ultraslow-spreading, sedimented ridge flanks represent a previously unrecognized carbon reservoir for abiotic methane that could supply and maintain deep-water methane hydrate systems throughout the Arctic.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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    PAPER CURRENT
  • 7
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    Compositions of dissolved organic matter in the ice-covered waters above the Aurora hydrothermal vent system, Gakkel Ridge, Arctic Ocean (2022)
    In:  Biogeosciences
    Details
    Publication Date: 2022-05-25
    Description: Hydrothermal vents modify and displace subsurface dissolved organic matter (DOM) into the ocean. Once in the ocean, this DOM is transported together with elements, particles, dissolved gases and biomass along with the neutrally buoyant plume layer. Considering the number and extent of actively venting hydrothermal sites in the oceans, their contribution to the oceanic DOM pool may be substantial. Here, we investigate the dynamics of DOM in relation to hydrothermal venting and related processes at the as yet unexplored Aurora hydrothermal vent field within the ultraslow-spreading Gakkel Ridge in the Arctic Ocean at 82.9∘ N. We examined the vertical distribution of DOM composition from sea ice to deep waters at six hydrocast stations distal to the active vent and its neutrally buoyant plume layer. In comparison to background seawater, we found that the DOM in waters directly affected by the hydrothermal plume was molecularly less diverse and 5 %–10 % lower in number of molecular formulas associated with the molecular categories related to lipid and protein-like compounds. On the other hand, samples that were not directly affected by the plume were chemically more diverse and had a higher percentage of chemical formulas associated with the carbohydrate-like category. Our results suggest that hydrothermal processes at Aurora may influence the DOM distribution in the bathypelagic ocean by spreading more thermally and/or chemically induced compositions, while DOM compositions in epipelagic and mesopelagic layers are mainly governed by the microbial carbon pump dynamics and surface-ocean–sea-ice interactions.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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