Abstract Cold seep environments such as sediments above outcropping hydrate at Hydrate Ridge (Cascadia margin off Oregon) are characterized by methane venting, high sulfide fluxes caused by the anaerobic oxidation of methane, and the presence of chemosynthetic communities. Recent investigations showed that another characteristic feature of cold seeps is the occurrence of methanotrophic archaea, which can be identified by specific biomarker lipids and 16S rDNA analysis. This investigation deals with the diversity and distribution of sulfate-reducing bacteria, some of which are directly involved in the anaerobic oxidation of methane as syntrophic partners of the methanotrophic archaea. The composition and activity of the microbial communities at methane vented and nonvented sediments are compared by quantitative methods including total cell counts, fluorescence in situ hybridization (FISH), bacterial production, enzyme activity, and sulfate reduction rates. Bacteria involved in the degradation of particulate organic carbon (POC) are as active and diverse as at other productive margin sites of similar water depths. The availability of methane supports a two orders of magnitude higher microbial biomass (up to 9.6 2 10 10 cells cm m 3 ) and sulfate reduction rates (up to 8 w mol cm m 3 d m 1 ) in hydrate-bearing sediments, as well as a high bacterial diversity, especially in the group of i -proteobacteria including members of the branches Desulfosarcina/Desulfococcus , Desulforhopalus , Desulfobulbus , and Desulfocapsa . Most of the diversity of sulfate-reducing bacteria in hydrate-bearing sediments comprises seep-endemic clades, which share only low similarities with previously cultured bacteria. Keywords: Anaerobic Oxidation Of Methane Sulfate Reduction Sulfate-reducing Bacteria Bacterial Production Extracellular Enzymes Syntrophic Consortia Bacterial Diversity Gas Hydrate Hydrate Ridge Cascadia Margin
The Arctic Svalbard Archipelago hosts the world’s northernmost cold-water ‘carbonate factories’ thriving here despite of presumably unfavourable environmental conditions and extreme seasonality. Two contrasting sites of intense biogenic carbonate production, the rhodolith beds in Mosselbukta in the North of the archipelago and the barnacle-mollusc dominated carbonate sediments accumulating in the strong hydrodynamic regime of the Bjørnøy-Banken south of Spitsbergen, were the targets of the RV Maria S. Merian cruise 55 in June 2016. By integrating data from physical oceanography, marine biology, and marine geology, the present contribution characterises the environmental setting and biosedimentary dynamics of these two polar carbonate factories. Repetitive CTD profiling in concert with autonomous temperature/salinity loggers on a long-term settlement platform identified spatiotemporal patterns in the involved Atlantic and Polar water masses, whereas short-term deployments of a lander revealed fluctuations of environmental variables in the rhodolith beds in Mosselbukta and at same depth (46 m) at Bjørnøy-Banken. At both sites, dissolved inorganic nutrients in the water column were found depleted (except for elevated ammonium concentrations) and show an overall increase in concentration and N:P ratios towards deeper waters. This indicates that a recycling system was fuelling primary production after the phytoplankton spring bloom at the time of sampling in June 2016. Accordingly, oxygen levels were found elevated and carbon dioxide concentrations (pCO2) markedly reduced, on average only half the expected equilibrium values. Backed up by seawater stable carbon and oxygen isotope signatures, this is interpreted as an effect of limited air-sea gas exchange during seasonal ice cover in combination with a boost in community photosynthesis during the spring phytoplankton bloom. The observed trends are enhanced by the onset of rhodophyte photosynthesis in the rhodolith beds during the polar day upon retreat of sea-ice. Potential adverse effects of ocean acidification on the local calcifier community are thus predicted to be seasonally buffered by the marked drop in pCO2 during the phase of sea-ice cover and spring plankton bloom, but this effect will diminish should the seasonal sea-ice formation continue to decline. (Abstract truncated here - please see comments for our arrangement of excess word count)
Vom 26. Juli bis zum 14. August sind Wissenschaftler vom IFM-GEOMAR auf dem irischen Forschungsschiff Celtic Explorer in der Nordsee unterwegs. Die Expedition CE 0913 unter Fahrtleitung von Dr. Peter Linke findet im Rahmen des Projekts „Fluid- und Gasaustritte in der sudlichen deutschen Nordsee“ in Zusammenarbeit mit der Christian-Albrechts-Universitat zu Kiel, dem Bundesamt fur Seeschifffahrt und Hydrographie und Wintershall statt und dient der Auffindung von Fluid- und Gasaustritten. Die Art und Weise des Austritts und die chemische und isotopische Zusammensetzung der austretenden Gase sollen genauer analysiert werden. Dabei kommen der Tiefseeroboter ROV KIEL 6000, Vibrocorers und Landersysteme zum Einsatz.
CELTIC EXPLORER CE 0913: 2. Wochenbericht (10.‐14.08.2009)
Sonne 191/2
Die Sonne Expedition SO191/2 New Vents (Wellington-Wellington) unter der Fahrtleitung von Dr. Peter Linke (IFM-GEOMAR) fand vom 03.02.-25.02.07 statt.
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