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  • ASLO (Association for the Sciences of Limnology and Oceanography)  (1)
  • Vereinigung für Angewandte und Allgemeine Mikrobiologie
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    Vereinigung für Angewandte und Allgemeine Mikrobiologie
    Publication Date: 2014-10-13
    Description: Rivers represent a transition zone between terrestrial and aquatic environments, as well as a transition zone between methane rich and methane poor environments. Methane concentrations are generally higher in freshwater systems than in marine systems. The Elbe River is one of the crucial drainages into the North Sea and by this high amounts of methane are imported into the marine water column. Oxidation of methane by aerobic methanotrophic bacteria is the major biological sink. Six cruises from November 2013 until June 2014 were conducted along the salinity gradient from Hamburg towards Helgoland. Methane oxidation rate was measured with radiotracers and the abundance of methanotrophic bacteria was assessed via real-time PCR. A newly designed primer targeting the genomic sequence encoding the α-subunit of the functional pMMO enzyme in water column organisms was amplified and tested against the conventional primer set. At the marine stations the cell number was relatively stable with 3 x 104 cells per L, while in the Elbe cell numbers ranged between 103 – 106 cells per L. Environmental parameters (temperature, salinity, SPM) seemed to have no influence on the abundance. However the interaction between activity and abundance seemed to be more complex.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 2
    Publication Date: 2019-09-24
    Description: Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the seabed, the fate of this methane in the water column, and potential for its release to the atmosphere. We find that, at present, fluxes of dissolved methane are significantly moderated by anaerobic and aerobic oxidation of methane. If methane fluxes increase then a greater proportion of methane will be transported by advection or in the gas phase, which reduces the efficiency of the methanotrophic sink. Higher freshwater discharge to Arctic shelf seas may increase stratification and inhibit transfer of methane gas to surface waters, although there is some evidence that increased stratification may lead to warming of sub-pycnocline waters, increasing the potential for hydrate dissociation. Loss of sea-ice is likely to increase wind speeds and seaair exchange of methane will consequently increase. Studies of the distribution and cycling of methane beneath and within sea ice are limited, but it seems likely that the sea-air methane flux is higher during melting in seasonally ice-covered regions. Our review reveals that increased observations around especially the anaerobic and aerobic oxidation of methane, bubble transport, and the effects of ice cover, are required to fully understand the linkages and feedback pathways between climate warming and release of methane from marine sediments.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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