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  • 1
    Online Resource
    Online Resource
    Bremen : MARUM - Zentrum für Marine Umweltwissenschaften, Fachbereich Geowissenschaften, Universität Bremen
    Keywords: Black Sea ; biogeochemistry ; paleoceanography ; microbiology ; polysaccharides ; greenhouse gases ; nitrification ; Forschungsbericht
    Description / Table of Contents: The R/V POSEIDON cruise POS539 took place in the northwestern basin of the Black Sea (42°30’N to 44°N and 29°E to 31°E). The overarching aim of the campaign was to obtain sediment and water samples, including suspended particle material, from the various redox zones of the Black Sea. The campaign lasted between November 6th and November 21st 2019 and the collected samples were taken in order to investigate the activity and physiology of microorganisms involved in the conversion of nitrogen compounds and degradation of organic carbon under various oxygen conditions. The main topics of the cruise were: (a) to quantify the contribution of archaeal nitrifiers to the nitrogen and carbon cycles, b) to measure the production and consumption of the powerful greenhouse gases CH4 and N2O, c) to record palaeoenvironmental changes in high resolution, and d) to describe the complexity and identity of biopolymers. For this, water and sediment samples were retrieved from 10 discrete shelf and slope stations. First, ‘deep water’ transect was conducted, which included three stations with water depths over 2000 m. The second perpendicular transect encompassed stations that gradually transitioned from the deep parts of the slope towards the shelf (ca. 80 m depth). Additionally, two stations were setup north and south of the shelf transect, respectively, for paleoceanographic studies. Throughout the cruise the weather conditions were overwhelmingly good, only towards the end of the campaign gusty winds of 7 Bft were recorded. The recorded oceanographic conditions were in agreement with the expected water properties at all stations. Station activities were completed on November 20th at 14:00 local board time. On November 21st at 10:30 local time, R/V POSEIDON reached the port of Varna, Bulgaria, thus concluding the POS539 expedition. Analyses and results from the samples and experiments will provide a basis for our understanding of the microbial control on the carbon and nitrogen cycle of the Black Sea.
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (34 Seiten)
    Series Statement: Berichte aus dem MARUM und dem Fachbereich Geowissenschaften der Universität Bremen No. 325
    DDC: 551.461
    Language: English
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  • 2
    Publication Date: 2021-05-26
    Description: Colonization of newly ice-free areas by marine benthic organisms intensifies burial of macroalgae detritus in Potter Cove coastal surface sediments (Western Antarctic Peninsula). Thus, fresh and labile macroalgal detritus serves as primary organic matter (OM) source for microbial degradation. Here, we investigated the effects on post-depositional microbial iron reduction in Potter Cove using sediment incubations amended with pulverized macroalgal detritus as OM source, acetate as primary product of OM degradation and lepidocrocite as reactive iron oxide to mimic in situ conditions. Humic substances analogue anthraquinone-2,6-disulfonic acid (AQDS) was also added to some treatments to simulate potential for electron shuttling. Microbial iron reduction was promoted by macroalgae and further enhanced by up to 30-folds with AQDS. Notably, while acetate amendment alone did not stimulate iron reduction, adding macroalgae alone did. Acetate, formate, lactate, butyrate and propionate were detected as fermentation products from macroalgae degradation. By combining 16S rRNA gene sequencing and RNA stable isotope probing, we reconstructed the potential microbial food chain from macroalgae degraders to iron reducers. Psychromonas, Marinifilum, Moritella, and Colwellia were detected as potential fermenters of macroalgae and fermentation products such as lactate. Members of class deltaproteobacteria including Sva1033, Desulfuromonas, and Desulfuromusa together with Arcobacter (former phylum Epsilonbacteraeota, now Campylobacterota) acted as dissimilatory iron reducers. Our findings demonstrate that increasing burial of macroalgal detritus in an Antarctic fjord affected by glacier retreat intensifies early diagenetic processes such as iron reduction. Under scenarios of global warming, the active microbial populations identified above will expand their environmental function, facilitate OM remineralisation, and contribute to an increased release of iron and CO2 from sediments. Such indirect consequences of glacial retreat are often overlooked but might, on a regional scale, be relevant for the assessment of future nutrient and carbon fluxes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Publication Date: 2020-12-04
    Description: Microorganisms in marine subsurface sediments substantially contribute to global biomass.Sediments warmer than 40°C account for roughly half the marine sediment volume, but theprocesses mediated by microbial populations in these hard-to-access environments are poorlyunderstood. We investigated microbial life in up to 1.2-kilometer-deep and up to 120°C hotsediments in the Nankai Trough subduction zone. Above 45°C, concentrations of vegetativecells drop two orders of magnitude and endospores become more than 6000 times more abundantthan vegetative cells. Methane is biologically produced and oxidized until sediments reach 80°to 85°C. In 100° to 120°C sediments, isotopic evidence and increased cell concentrationsdemonstrate the activity of acetate-degrading hyperthermophiles. Above 45°C, populated zonesalternate with zones up to 192 meters thick where microbes were undetectable
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2020-11-06
    Description: Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often characterized by co-burial of iron oxides with recalcitrant aromatic organic matter of terrigenous origin. Thus far, iron oxides are predicted to either impede organic matter degradation, aiding its preservation, or identified to enhance organic carbon oxidation via direct electron transfer. Here, we investigated the effect of various iron oxide phases with differing crystallinity (magnetite, hematite, and lepidocrocite) during microbial degradation of the aromatic model compound benzoate in methanic sediments. In slurry incubations with magnetite or hematite, concurrent iron reduction, and methanogenesis were stimulated during accelerated benzoate degradation with methanogenesis as the dominant electron sink. In contrast, with lepidocrocite, benzoate degradation, and methanogenesis were inhibited. These observations were reproducible in sediment-free enrichments, even after five successive transfers. Genes involved in the complete degradation of benzoate were identified in multiple metagenome assembled genomes. Four previously unknown benzoate degraders of the genera Thermincola (Peptococcaceae, Firmicutes), Dethiobacter (Syntrophomonadaceae, Firmicutes), Deltaproteobacteria bacteria SG8_13 (Desulfosarcinaceae, Deltaproteobacteria), and Melioribacter (Melioribacteraceae, Chlorobi) were identified from the marine sediment-derived enrichments. Scanning electron microscopy (SEM) and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) images showed the ability of microorganisms to colonize and concurrently reduce magnetite likely stimulated by the observed methanogenic benzoate degradation. These findings explain the possible contribution of organoclastic reduction of iron oxides to the elevated dissolved Fe2+ pool typically observed in methanic zones of rapidly accumulating coastal and continental margin sediments.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 5
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    American Association for the Advancement of Science
    In:  EPIC3Science advances, American Association for the Advancement of Science, 7(44), pp. eabg9739
    Publication Date: 2021-12-05
    Description: Elemental carbon exists in different structural forms including graphite, diamond, fullerenes, and amorphous carbon. In nature, these materials are produced through abiotic chemical processes under high temperature and pressure but are considered generally inaccessible to biochemical synthesis or breakdown. Here, we identified and characterized elemental carbon isolated from consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), which together carry out the anaerobic oxidation of methane (AOM). Two different AOM consortia, ANME-1a/HotSeep-1 and ANME-2a/c/Seep-SRB, produce a black material with similar characteristics to disordered graphite and amorphous carbon. Stable isotope probing studies revealed that the carbon is microbially generated during AOM. In addition, we found that select methanogens also produce amorphous carbon with similar characteristics to the carbon from AOM consortia. Biogenic amorphous carbon may serve as a conductive element to facilitate electron transfer, or redox active functional groups associated with the carbon could act as electron donors and acceptors.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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  • 6
    Publication Date: 2024-04-29
    Description: The Last Interglacial (~129,000–116,000 years ago) is the most recent geologic period with a warmer-than-present climate. Proxy-based temperature reconstructions from this interval can help contextualize natural climate variability in our currently warming world, especially if they can define changes on decadal timescales. Here, we established a ~4.800-year-long record of sea surface temperature (SST) variability from the eastern Mediterranean Sea at 1–4-year resolution by applying mass spectrometry imaging of long-chain alkenones to a finely laminated organic-matter-rich sapropel deposited during the Last Interglacial. We observe the highest amplitude of decadal variability in the early stage of sapropel deposition, plausibly due to reduced vertical mixing of the highly stratified water column. With the subsequent reorganization of oceanographic conditions in the later stage of sapropel deposition, when SST forcing resembled the modern situation, we observe that the maximum amplitude of reconstructed decadal variability did not exceed the range of the recent period of warming climate. The more gradual, centennial SST trends reveal that the maximal centennial scale SST increase in our Last Interglacial record is below the projected temperature warming in the twenty-first century.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 7
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    PANGAEA
    In:  MARUM - Center for Marine Environmental Sciences, University Bremen
    Publication Date: 2023-03-03
    Keywords: Center for Marine Environmental Sciences; DARCLIFE; DARCSEAS II; Deep subsurface Archaea: carbon cycle, life strategies, and role in sedimentary ecosystems; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; GeoB17305-3; IODP Method C (Blum, 1997); MARUM; MUC; MultiCorer; Porosity; POS450; POS450_581-3; Poseidon; Proposed International Geo Sample Number; Western Mediterranean Sea
    Type: Dataset
    Format: text/tab-separated-values, 36 data points
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  • 8
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    PANGAEA
    In:  MARUM - Center for Marine Environmental Sciences, University Bremen
    Publication Date: 2023-03-03
    Keywords: Center for Marine Environmental Sciences; DARCLIFE; DARCSEAS II; Deep subsurface Archaea: carbon cycle, life strategies, and role in sedimentary ecosystems; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; GC; GeoB17307-8; Gravity corer; IODP Method C (Blum, 1997); MARUM; Porosity; POS450; POS450_585-3; Poseidon; Proposed International Geo Sample Number; Western Mediterranean Sea
    Type: Dataset
    Format: text/tab-separated-values, 63 data points
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  • 9
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    PANGAEA
    In:  MARUM - Center for Marine Environmental Sciences, University Bremen
    Publication Date: 2023-03-03
    Keywords: Center for Marine Environmental Sciences; DARCLIFE; DARCSEAS II; Deep subsurface Archaea: carbon cycle, life strategies, and role in sedimentary ecosystems; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; GC; GeoB17306-2; Gravity corer; IODP Method C (Blum, 1997); MARUM; Porosity; POS450; POS450_586-1; Poseidon; Proposed International Geo Sample Number; Western Mediterranean Sea
    Type: Dataset
    Format: text/tab-separated-values, 106 data points
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  • 10
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    PANGAEA
    In:  MARUM - Center for Marine Environmental Sciences, University Bremen
    Publication Date: 2023-03-03
    Keywords: Center for Marine Environmental Sciences; DARCLIFE; DARCSEAS II; Deep subsurface Archaea: carbon cycle, life strategies, and role in sedimentary ecosystems; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; GeoB17308-1; IODP Method C (Blum, 1997); MARUM; MUC; MultiCorer; Porosity; POS450; POS450_584-1; Poseidon; Proposed International Geo Sample Number; Western Mediterranean Sea
    Type: Dataset
    Format: text/tab-separated-values, 32 data points
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