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  • PANGAEA  (41)
  • Wiley  (5)
  • Kiel : Ozean der Zukunft, Die Kieler Meereswissenschaften  (2)
  • Nature Publishing Group  (2)
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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Book
    Pages: [16] S. , zahlr. Ill..
    Series Statement: Kinder- und Schüleruni Kiel : für Schülerinnen und Schüler von 12 bis 16 Jahren 2010.10,20
    Language: German
    Note: Auch als elektronisches Dokument vorhanden
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  • 2
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressouce (PDF-Datein : 16 S., 1 MB) , zahlr. Ill..
    Series Statement: Kinder- und Schüleruni Kiel : für Schülerinnen und Schüler von 12 bis 16 Jahren 2010.10,20
    Language: German
    Note: Auch als gedr. Ausg. vorhanden
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  • 3
    Publication Date: 2019-09-23
    Description: Prokaryote communities were investigated on the seasonally stratified Alaska Beaufort Shelf (ABS). Water and sediment directly underlying water with origin in the Arctic, Pacific or Atlantic oceans were analyzed by pyrosequencing and length heterogeneity-PCR in conjunction with physicochemical and geographic distance data to determine what features structure ABS microbiomes. Distinct bacterial communities were evident in all water masses. Alphaproteobacteria explained similarity in Arctic surface water and Pacific derived water. Deltaproteobacteria were abundant in Atlantic origin water and drove similarity among samples. Most archaeal sequences in water were related to unclassified marine Euryarchaeota. Sediment communities influenced by Pacific and Atlantic water were distinct from each other and pelagic communities. Firmicutes and Chloroflexi were abundant in sediment, although their distribution varied in Atlantic and Pacific influenced sites. Thermoprotei dominated archaea in Pacific influenced sediments and Methanomicrobia dominated in methane-containing Atlantic influenced sediments. Length heterogeneity-PCR data from this study were analyzed with data from methane-containing sediments in other regions. Pacific influenced ABS sediments clustered with Pacific sites from New Zealand and Chilean coastal margins. Atlantic influenced ABS sediments formed another distinct cluster. Density and salinity were significant structuring features on pelagic communities. Porosity co-varied with benthic community structure across sites and methane did not. This study indicates that the origin of water overlying sediments shapes benthic communities locally and globally and that hydrography exerts greater influence on microbial community structure than the availability of methane.
    Type: Article , PeerReviewed
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  • 4
    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
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  • 5
    Publication Date: 2017-06-27
    Description: Anaerobic methane-oxidizing microbial communities in sediments at cold methane seeps are important factors in controlling methane emission to the ocean and atmosphere. Here, we investigated the distribution and carbon isotopic signature of specific biomarkers derived from anaerobic methanotrophic archaea (ANME groups) and sulphate-reducing bacteria (SRB) responsible for the anaerobic oxidation of methane (AOM) at different cold seep provinces of Hydrate Ridge, Cascadia margin. The special focus was on their relation to in situ cell abundances and methane turnover. In general, maxima in biomarker abundances and minima in carbon isotope signatures correlated with maxima in AOM and sulphate reduction as well as with consortium biomass. We found ANME-2a/DSS aggregates associated with high abundances of sn-2,3-di-O-isoprenoidal glycerol ethers (archaeol, sn-2-hydroxyarchaeol) and specific bacterial fatty acids (C16:1ω5c, cyC17:0ω5,6) as well as with high methane fluxes (Beggiatoa site). The low to medium flux site (Calyptogena field) was dominated by ANME-2c/DSS aggregates and contained less of both compound classes but more of AOM-related glycerol dialkyl glycerol tetraethers (GDGTs). ANME-1 archaea dominated deeper sediment horizons at the Calyptogena field where sn-1,2-di-O-alkyl glycerol ethers (DAGEs), archaeol, methyl-branched fatty acids (ai-C15:0, i-C16:0, ai-C17:0), and diagnostic GDGTs were prevailing. AOM-specific bacterial and archaeal biomarkers in these sediment strata generally revealed very similar δ13C-values of around −100. In ANME-2-dominated sediment sections, archaeal biomarkers were even more 13C-depleted (down to −120), whereas bacterial biomarkers were found to be likewise 13C-depleted as in ANME-1-dominated sediment layers (δ13C: −100). The zero flux site (Acharax field), containing only a few numbers of ANME-2/DSS aggregates, however, provided no specific biomarker pattern. Deeper sediment sections (below 20 cm sediment depth) from Beggiatoa covered areas which included solid layers of methane gas hydrates contained ANME-2/DSS typical biomarkers showing subsurface peaks combined with negative shifts in carbon isotopic compositions. The maxima were detected just above the hydrate layers, indicating that methane stored in the hydrates may be available for the microbial community. The observed variations in biomarker abundances and 13C-depletions are indicative of multiple environmental and physiological factors selecting for different AOM consortia (ANME-2a/DSS, ANME-2c/DSS, ANME-1) along horizontal and vertical gradients of cold seep settings.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2023-02-08
    Description: A site at the gas hydrate stability limit was investigated offshore northwestern Svalbard to study methane transport in sediment. The site was characterized by chemosynthetic communities (sulfur bacteria mats, tubeworms) and gas venting. Sediments were sampled with in‐situ porewater collectors and by gravity coring followed by analyses of porewater constituents, sediment and carbonate geochemistry, and microbial activity, taxonomy, and lipid biomarkers. Sulfide and alkalinity concentrations showed concentration maxima in near‐surface sediments at the bacterial mat and deeper maxima at the gas vent site. Sediments at the periphery of the chemosynthetic field were characterized by two sulfate‐methane transition zones (SMTZ) at ~204 and 45 cm depth, where activity maxima of microbial anaerobic oxidation of methane (AOM) with sulfate were found. Amplicon sequencing and lipid biomarker indicate that AOM at the SMTZs was mediated by ANME‐1 archaea. A 1D numerical transport reaction model suggests that the deeper SMTZ‐1 formed on centennial scale by vertical advection of methane, while the shallower SMTZ‐2 could only be reproduced by non‐vertical methane injections starting on decadal scale. Model results were supported by age distribution of authigenic carbonates, showing youngest carbonates within SMTZ‐2. We propose that non‐vertical methane injection was induced by increasing blockage of vertical transport or formation of sediment fractures. Our study further suggests that the methanotrophic response to the non‐vertical methane injection was commensurate with new methane supply. This finding provides new information about for the response time and efficiency of the benthic methane filter in environments with fluctuating methane transport.
    Type: Article , PeerReviewed
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    Format: video
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  • 7
    Publication Date: 2024-02-07
    Description: Carbonates that exhibit obvious diagenetic alteration are usually excluded as archives in palaeoenvironmental studies. However, the potential impact of microbial alteration during early diagenesis is still poorly explored. To investigate the sensitivity of sulphur concentration, distribution, oxidation state and isotopic composition in marine aragonite to microbial alteration, Arctica islandica bivalves and Porites sp. corals were experimentally exposed to anaerobic microbial activity. The anoxic incubation media included a benthic bacterial strain Shewanella sediminis and a natural anoxic sediment slurry with a natural microbial community of unknown species. Combined fluorescence microscopy and synchrotron‐based analysis of the sulphur distribution and oxidation state enabled a comparison of organic matter and sulphur content in the two materials. Results revealed a higher proportion of reduced sulphur species and locally stronger fluorescence within the pristine bivalve shell compared to the pristine coral skeleton. Within the pristine bivalve specimen, reduced sulphur was enriched in layers along the inner shell margin. After incubation in the anoxic sediment slurry, this region revealed rust‐brown staining and a patchy S2‐ distribution pattern rather than S2‐‐layers. Another effect on sulphur distribution was rust‐brown coloured fibres along one growth line, revealing a locally higher proportion of sulphur. The δ34S value of carbonate‐associated sulphate remained largely unaffected by both incubation media, but a lower δ34S value of water‐soluble sulphate reflected the degradation of insoluble organic matter by microbes in both experiments. No significant alteration was detected in the coral samples exposed to microbial alteration. The data clearly identified a distinct sensitivity of organically bound sulphur in biogenic aragonite to microbial alteration even when “traditional” geochemical proxies such as δ18OCARB or δ13CCARB in the carbonate didn’t show any effect. Differences in the intensity of microbial alteration documented are likely due to inherent variations in the concentration and nature of original organic compositions in the samples.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2024-05-02
    Description: Bacterial sulfate reduction (SR) is often determined by radiotracer techniques using 35S‐labeled sulfate. In environments featuring simultaneous sulfide oxidation, SR can be underestimated due to re‐oxidation of 35S‐sulfide. Recycling of 35S‐tracer is expected to be high in sediment with low concentrations of pore‐water sulfide and high abundance of giant filamentous sulfur‐oxidizing bacteria (GFSOB). Here, we applied a sulfide‐spiking method, originally developed for water samples, to sediments along a shelf‐slope transect (72, 128, 243, 752 m water depth) traversing the Peruvian oxygen minimum zone. Sediment spiked with unlabeled sulfide prior to 35S‐sulfate injection to prevent radiotracer recycling was compared to unspiked sediment. At stations characterized by low natural sulfide and abundant GFSOB (128 and 243 m), the method revealed 1–3 times higher SR rates in spiked sediment. Spiking had no effect on SR in sediment with high natural sulfide despite presence of GFSOB (72 m). Bioturbated sediment devoid of GFSOB (752 m) showed elevated SR in spiked samples, likely from artificial introduction of sulfidic conditions. Sulfide oxidation rates at the 128 and 243 m station, derived from the difference in SR between spiked and unspiked sediment, approximated rates of dissimilatory nitrate reduction to ammonium by GFSOB. Gross SR contributed considerably to benthic dissolved inorganic carbon fluxes at the three shallowest station, confirming that SR is an important process for benthic carbon respirations within the oxygen minimum zone. We recommend to further explore the spiking method to capture SR in sediment featuring low sulfide concentrations and high sulfur cycling by GFSOB.
    Type: Article , PeerReviewed
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  • 9
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    PANGAEA
    In:  Supplement to: Steinle, Lea; Graves, Carolyn; Treude, Tina; Ferre, Benedicte; Biastoch, Arne; Bussmann, Ingeborg; Berndt, Christian; Krastel, Sebastian; James, Rachael H; Behrens, Erik; Böning, Claus W; Greinert, Jens; Sapart, Célia-Julia; Scheinert, Markus; Sommer, Stefan; Lehmann, Moritz F; Niemann, Helge (2015): Water column methanotrophy controlled by a rapid oceanographic switch. Nature Geoscience, 8(5), 378–382, https://doi.org/10.1038/ngeo2420
    Publication Date: 2023-03-03
    Description: Large amounts of the greenhouse gas methane are released from the seabed to the water column where it may be consumed by aerobic methanotrophic bacteria. This microbial filter is consequently the last marine sink for methane before its liberation to the atmosphere. The size and activity of methanotrophic communities, which determine the capacity of the water column methane filter, are thought to be mainly controlled by nutrient and redox dynamics, but little is known about the effects of ocean currents. Here, we report measurements of methanotrophic activity and biomass (CARD-FISH) at methane seeps west of Svalbard, and related them to physical water mass properties (CTD) and modelled current dynamics. We show that cold bottom water containing a large number of aerobic methanotrophs was rapidly displaced by warmer water with a considerably smaller methanotrophic community. This water mass exchange, caused by short-term variations of the West Spitsbergen Current, constitutes a rapid oceanographic switch severely reducing methanotrophic activity in the water column. Strong and fluctuating currents are widespread oceanographic features common at many methane seep systems and are thus likely to globally affect methane oxidation in the ocean water column.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 10
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    PANGAEA
    In:  Supplement to: Berndt, Christian; Feseker, Tomas; Treude, Tina; Krastel, Sebastian; Liebetrau, Volker; Niemann, Helge; Bertics, Victoria J; Dumke, Ines; Dünnbier, Karolin; Ferre, Benedicte; Graves, Carolyn; Gross, Felix; Hissmann, Karen; Hühnerbach, Veit; Krause, Stefan; Lieser, Kathrin; Schauer, Jürgen; Steinle, Lea (2014): Temporal constraints on hydrate-controlled methane seepage off Svalbard. Published Online January 2 2014, Science, https://doi.org/10.1126/science.1246298
    Publication Date: 2023-03-03
    Description: Methane hydrate is an ice-like 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.
    Keywords: Center for Marine Environmental Sciences; GEOMAR; Helmholtz Centre for Ocean Research Kiel; MARUM
    Type: Dataset
    Format: application/zip, 29 datasets
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