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  • 2020-2024  (11)
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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: 2023-02-08
    Description: In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics-namely production, consumption, and net emissions-is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climateactive trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
    Type: Article , PeerReviewed
    Format: text
    Format: video
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  • 3
    Publication Date: 2024-02-07
    Description: Anaerobic oxidation of ammonium (anammox) in oxygen minimum zones (OMZs) is a major pathway of oceanic nitrogen loss. Ammonium released from sinking particles has been suggested to fuel this process. During cruises to the Peruvian OMZ in April–June 2017 we found that anammox rates are strongly correlated with the volume of small particles (128–512 µm), even though anammox bacteria were not directly associated with particles. This suggests that the relationship between anammox rates and particles is related to the ammonium released from particles by remineralization. To investigate this, ammonium release from particles was modelled and theoretical encounters of free-living anammox bacteria with ammonium in the particle boundary layer were calculated. These results indicated that small sinking particles could be responsible for ~75% of ammonium release in anoxic waters and that free-living anammox bacteria frequently encounter ammonium in the vicinity of smaller particles. This indicates a so far underestimated role of abundant, slow-sinking small particles in controlling oceanic nutrient budgets, and furthermore implies that observations of the volume of small particles could be used to estimate N-loss across large areas.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2024-02-14
    Description: Subterranean estuaries are connective zones between inland aquifers and the open sea where terrestrial freshwater and circulating seawater mix and undergo major biogeochemical changes. They are biogeochemical reactors that modify groundwater chemistry prior to discharge into the sea. We propose that subterranean estuaries of high-energy beaches are particularly dynamic environments, where the effect of the dynamic boundary conditions propagates tens of meters into the subsurface, leading to strong spatio-temporal variability of geochemical conditions. We hypothesize that they form a unique habitat with an adapted microbial community unlike other typically more stable subsurface environments. So far, however, studies concerning subterranean estuaries of high-energy beaches have been rare and therefore their functioning, and their importance for coastal ecosystems, as well as for carbon, nutrient and trace element cycling, is little understood. We are addressing this knowledge gap within the interdisciplinary research project DynaDeep by studying the combined effect of surface (hydro- and morphodynamics) on subsurface processes (groundwater flow and transport, biogeochemical reactions, microbiology). A unique subterranean estuary observatory was established on the northern beach of the island of Spiekeroog facing the North Sea, serving as an exemplary high-energy research site and model system. It consists of fixed and permanent infrastructure such as a pole with measuring devices, multi-level groundwater wells and an electrode chain. This forms the base for autonomous measurements, regular repeated sampling, interdisciplinary field campaigns and experimental work, all of which are integrated via mathematical modelling to understand and quantify the functioning of the biogeochemical reactor. First results show that the DynaDeep observatory is collecting the intended spatially and temporally resolved morphological, sedimentological and biogeochemical data. Samples and data are further processed ex-situ and combined with experiments and modelling. Ultimately, DynaDeep aims at elucidating the global relevance of these common but overlooked environments.
    Type: Article , PeerReviewed
    Format: text
    Format: video
    Format: image
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  • 5
    Publication Date: 2023-12-15
    Description: We collected sediment cores from the Janssand intertidal sand flat in Germany in April 2016, August 2016, and February 2017. All measurements were made in laboratory experiments using NOx (nitrate + nitrite) microbiosensors and oxygen microelectrodes. Cores were kept at in situ temperatures with a simulated day/night cycle and regular flushing with site seawater to simulate natural porewater advection during periods of inundation. We determined the depth of maximum microphytobenthos photosynthetic activity from steady-state oxygen profiles. We then flushed site seawater down through the core to measure net NOx and oxygen consumption rates at that depth. We measured potential denitrification rates at high spatial resolution by flushing acetylene- and nitrate-amended site seawater down through the core and measuring the accumulation of nitrous oxide using a microelectrode. Finally, we applied a range of realistic downward advective flows of seawater into sediment, in both the light and the dark, in both the spring and summer. We measured the depth to which NOx and oxygen penetrated over the course of several hours under these steady flow conditions using NOx microbiosensors and oxygen microelectrodes. from our study site, NOx always reached the depths of maximum denitrification potential, regardless of light availability or season.
    Keywords: Denitrification; Microphytobenthos; nitrate uptake; permeable sediment; sand flat
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 6
    Publication Date: 2023-12-15
    Keywords: Calculated; Denitrification; DEPTH, sediment/rock; Microphytobenthos; Microprofiler; mpbvdnf_summer; N2O microsensors with acetylene block; nitrate uptake; Nitrogen denitrification rate; Nitrogen denitrification rate, standard deviation; permeable sediment; sand flat; SEDCO; Sediment corer
    Type: Dataset
    Format: text/tab-separated-values, 78 data points
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  • 7
    Publication Date: 2023-12-15
    Keywords: Core; Denitrification; Event label; Light; Microphytobenthos; mpbvdnf_spring; mpbvdnf_summer; nitrate uptake; Nitrogen oxide (nitrate + nitrite) consumption rate; NOx microbiosensor, static position; O2 microelectrode, static position; Oxygen consumption rate; permeable sediment; sand flat; Season; SEDCO; Sediment corer
    Type: Dataset
    Format: text/tab-separated-values, 40 data points
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  • 8
    Publication Date: 2023-12-15
    Keywords: Denitrification; Elapsed time; Event label; Flow rate; Light; Microphytobenthos; Microprofiler; Microprofiler time stamp; mpbvdnf_spring; mpbvdnf_summer; nitrate uptake; Nitrogen oxide (nitrate + nitrite) penetration depth; Oxygen penetration depth; permeable sediment; sand flat; Season; SEDCO; Sediment corer; Time to fill graduated cylinder
    Type: Dataset
    Format: text/tab-separated-values, 232 data points
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  • 9
    Publication Date: 2023-12-15
    Keywords: Calculated; Denitrification; DEPTH, sediment/rock; Microphytobenthos; Microprofiler; mpbvdnf_winter; N2O microsensors with acetylene block; nitrate uptake; Nitrogen denitrification rate; Nitrogen denitrification rate, standard deviation; permeable sediment; sand flat; SEDCO; Sediment corer
    Type: Dataset
    Format: text/tab-separated-values, 58 data points
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  • 10
    Publication Date: 2024-05-07
    Description: 85-day-long aerobic incubation of Yedoma permafrost soil from the Lena Delta into seawater from the eastern Kara Sea, at ~2°C in the dark. The setup is simulating the process of introduction of OC from eroding cost lines along the arctic cost and the resuspension in the shelf bottom waters via the later transport. Samples were incubated in a ratio of Yedoma 3mL to sea water 90 mL. Three treatments were set up 1) Yedoma+Sea water (untreated, 20 vials); 2) Yedoma+filtered Sea Water (0.2µm filter, 6 vials); 3) filtered Sea Water (0.2µm filter, 6 vials). Additionally, vials with pH and O₂ sensors were set up for each treatment: 1) 3 vials; 2) & 3) 2 vials each. Presented data include raw data of temperature, pH, oxygen concentrations, dissolved inorganic carbon concentrations (DIC) and radiocarbon signature (DI14), and sediment data (concentration and radiocarbon signature). Nutrients (NH₄, NO₂, NO₃, and PO₄), ions (Cl & SO₄), DIC, DI14C, total dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) are reported normalized to the water volume in the vials. Further, parameters of the carbonate system were calculated, in order to access CO₂ release and its age signature over the cause of the experiment (carbon budget).
    Keywords: Akademik Tryoshnikov; ArcticCentury; AT21; AT21_112-1; AWI Arctic Land Expedition; CAC19-Y; CTD/Rosette; CTD-RO; File content; incubation; Kara Sea; Laboratory experiment; Lena 2019; Lena Delta, Siberia; Office Open XML Workbook; permafost soil; RU-Land_2019_Lena; SOIL; Soil profile; Yedoma
    Type: Dataset
    Format: text/tab-separated-values, 12 data points
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