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  • 1
    Online Resource
    Online Resource
    WTZ Zentralasien: CARIMA - Natürliche vs. Anthropogene Steuerungsfaktoren spätquartärer Monsunvariabilität in Zentralasien aufgezeichnet in marinen Archiven; TP1.1 - Paläoproduktivität und Veränderungen des Kohlenstoff- und Stickstoffkreislaufs: Schlussbericht (2014)
    Hamburg : Inst. of Biogeochemistry and Marine Chemistry, Univ.
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: Online-Ressource (9 S., 74,89 KB)
    URL: https://edocs.tib.eu/files/e01fb15/837596025.pdf
    URL: https://doi.org/10.2314/GBV:837596025
    DOI: 10.2314/GBV:837596025
    Language: German
    Note: Förderkennzeichen BMBF 03G0806B. - Verbund-Nr. 01088026 , Engl. Berichtsbl. u.d.T.: CARIMA - Natural vs. anthropogenic controls of past monsoon variability in central Asia recorded in marine archives; TP1.1 - Palaeproductivity and changes of carbon- and nitrogen cycling , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Systemvoraussetzungen: Acrobat reader.
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  • 2
    Online Resource
    Online Resource
    BMBF-Verbundprojekt SO269 - SCOLIS-SONNE: Südchinesisches Meer - natürliches Laboratorium unter klimatischem und anthropogenem Stress ´; Vorhaben II: TP Stickstoffisotopie : Schlussbericht : Laufzeit des Vorhabens: 01.04.2019-31.08.2021 (2021)
    Hamburg : Universität Hamburg, Institut für Geologie
    Details Availability
    Keywords: Forschungsbericht ; Südchinesisches Meer ; Perlfluss ; Delta ; Megastadt ; Schadstoffbelastung ; Eutrophierung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (23 Seiten, 1,55 MB) , Illustrationen, Diagramme
    URL: https://doi.org/10.2314/KXP:1842481495
    DOI: 10.2314/KXP:1842481495
    Language: German , English
    Note: Förderkennzeichen BMBF 03G0269B , Verbundnummer 01184657 , Literaturverzeichnis: Seite 18-19 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Kurzfassungen: Deutsch, Englisch
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  • 3
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    Biogeochemical Regeneration of a Nodule Mining Disturbance Site: Trace Metals, DOC and Amino Acids in Deep-Sea Sediments and Pore Waters (2018)
    Frontiers
    In:  Frontiers in Marine Science, 5 . Art.Nr. 117.
    Details
    Publication Date: 2021-02-08
    Description: Increasing interest in deep-sea mineral resources, such as polymetallic nodules, calls for environmental research about possible impacts of mineral exploitation on the deep-sea ecosystem. So far, little geochemical comparisons of deep-sea sediments before and after mining induced disturbances have been made, and thus long-term environmental effects of deep-sea mining are unknown. Here we present geochemical data from sediment cores from an experimental disturbance area at 4,100 m water depth in the Peru Basin. The site was revisited in 2015, 26 years after a disturbance experiment mimicking nodule mining was carried out and compared to sites outside the experimental zone which served as a pre-disturbance reference. We investigated if signs of the disturbance are still visible in the solid phase and the pore water after 26 years or if pre-disturbance conditions have been re-established. Additionally, a new disturbance was created during the cruise and sampled 5 weeks later to compare short- and longer-term impacts. The particulate fraction and pore water were analyzed for major and trace elements to study element distribution and processes in the surface sediment. Pore water and bottom water samples were also analyzed for oxygen, nitrate, dissolved organic carbon, and dissolved amino acids, to examine organic matter degradation processes. The study area of about 11 km2 was found to be naturally more heterogeneous than expected, requiring an analysis of spatial variability before the disturbed and undisturbed sites can be compared. The disturbed sites exhibit various disturbance features: some surface sediments were mixed through, others had the top layer removed and some had additional material deposited on top. Pore water constituents have largely regained pre-disturbance gradients after 26 years. The solid phase, however, shows clear differences between disturbed and undisturbed sites in the top 20 cm so that the impact is still visible in the plowed tracks after 26 years. Especially the upper layer, usually rich in manganese-oxide and associated metals, such as Mo, Ni, Co, and Cu, shows substantial differences in metal distribution. Hence, it can be expected that disturbances from polymetallic nodule mining will have manifold and long-lasting impacts on the geochemistry of the underlying sediment.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3389/fmars.2018.00117
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Decreasing concentrations of dissolved oxygen in the ocean are considered one of the main threats to marine ecosystems as they jeopardize the growth of higher organisms. They also alter the marine nitrogen cycle, which is strongly bound to the carbon cycle and climate. While higher organisms in general start to suffer from oxygen concentrations 〈 ∼ 63 µM (hypoxia), the marine nitrogen cycle responds to oxygen concentration below a threshold of about 20 µM (microbial hypoxia), whereas anoxic processes dominate the nitrogen cycle at oxygen concentrations of 〈 ∼ 0.05 µM (functional anoxia). The Arabian Sea and the Bay of Bengal are home to approximately 21 % of the total volume of ocean waters revealing microbial hypoxia. While in the Arabian Sea this oxygen minimum zone (OMZ) is also functionally anoxic, the Bay of Bengal OMZ seems to be on the verge of becoming so. Even though there are a few isolated reports on the occurrence of anoxia prior to 1960, anoxic events have so far not been reported from the open northern Indian Ocean (i.e., other than on shelves) during the last 60 years. Maintenance of functional anoxia in the Arabian Sea OMZ with oxygen concentrations ranging between 〉 0 and ∼ 0.05 µM is highly extraordinary considering that the monsoon reverses the surface ocean circulation twice a year and turns vast areas of the Arabian Sea from an oligotrophic oceanic desert into one of the most productive regions of the oceans within a few weeks. Thus, the comparably low variability of oxygen concentration in the OMZ implies stable balances between the physical oxygen supply and the biological oxygen consumption, which includes negative feedback mechanisms such as reducing oxygen consumption at decreasing oxygen concentrations (e.g., reduced respiration). Lower biological oxygen consumption is also assumed to be responsible for a less intense OMZ in the Bay of Bengal. According to numerical model results, a decreasing physical oxygen supply via the inflow of water masses from the south intensified the Arabian Sea OMZ during the last 6000 years, whereas a reduced oxygen supply via the inflow of Persian Gulf Water from the north intensifies the OMZ today in response to global warming. The first is supported by data derived from the sedimentary records, and the latter concurs with observations of decreasing oxygen concentrations and a spreading of functional anoxia during the last decades in the Arabian Sea. In the Arabian Sea decreasing oxygen concentrations seem to have initiated a regime shift within the pelagic ecosystem structure, and this trend is also seen in benthic ecosystems. Consequences for biogeochemical cycles are as yet unknown, which, in addition to the poor representation of mesoscale features in global Earth system models, reduces the reliability of estimates of the future OMZ development in the northern Indian Ocean.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Evidence of parallel denitrification and nitrite oxidation in the ODZ of the Arabian Sea from paired stable isotopes of nitrate and nitrite (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-10-16
    Description: [1]  The Arabian Sea is a major oceanic nitrogen sink and its oxygen deficient zone extends from 150 m to 1200 m water depth. To identify the dominant transformation processes of reactive nitrogen and to quantify the amounts of nitrogen turned over in the different reactions of the nitrogen cycle, we use paired data on stable isotope ratios of nitrogen and oxygen in nitrate and nitrite measured at four near coastal and five open ocean stations in the Arabian Sea. We find significant nitrate reduction and denitrification between 100 m and 400 m in the open Arabian Sea, which are most intense in the eastern and northern part of the basin, and estimate that about 50% of initial nitrate is being reduced either to dinitrogen gas (denitrification) or to nitrite (nitrate reduction) in the core zone of denitrification. Nitrite accumulates in concentrations above 4 μM in the water column of the eastern and northern Arabian Sea. Large differences in isotopic ratios of nitrate and nitrite and a decoupling of their stable nitrogen and oxygen isotopes can be explained by the re-oxidation of nitrite. The observed decoupling of the paired isotopes may be due to the exchange of oxygen of nitrite with oxygen from ambient water. In agreement with model estimates from the literature, about 25 % of the nitrate initially reduced to nitrite is returned to the nitrate pool by nitrification in the upper and lower denitrification layer while 40 % is denitrified.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 6
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    What can we learn from amino acids about oceanic organic matter cycling and degradation? (2022)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-03-15
    Description: Amino acids (AAs) mainly bound in proteins are major constituents of living biomass and non-living organic material in the oceanic particulate and dissolved organic matter pool. Uptake and cycling by heterotrophic organisms lead to characteristic changes in AA composition so that AA-based biogeochemical indicators are often used to elucidate processes of organic matter cycling and degradation. We analyzed particulate AA in a large sample set collected in various oceanic regions covering sinking and suspended particles in the water column, sediment samples, and dissolved AA from water column and pore water samples. The aim of this study was to test and improve the use of AA-derived biogeochemical indicators as proxies for organic matter sources and degradation and to better understand particle dynamics and interaction between the dissolved and particulate organic matter pools. A principal component analysis (PCA) of all data delineates diverging AA compositions of sinking and suspended particles with increasing water depth. A new sinking particle and sediment degradation indicator (SDI) allows a fine-tuned classification of sinking particles and sediments with respect to the intensity of degradation, which is associated with changes of stable isotopic ratios of nitrogen (δ15N). This new indicator is furthermore sensitive to sedimentary redox conditions and can be used to detect past anoxic early diagenesis. A second indicator emerges from the AA spectra of suspended particulate matter (SPM) in the epipelagic and that of the meso- and bathypelagic ocean and is a residence time indicator (RTI). The characteristic changes in AA patterns from shallow to deep SPM are recapitulated in the AA spectra of the dissolved organic matter (DOM) pool, so that deep SPM is more similar to DOM than to any of the other organic matter pools. This implies that there is equilibration between finely dispersed SPM and DOM in the deep sea, which may be driven by microbial activity combined with annealing and fragmentation of gels. As these processes strongly depend on physico-chemical conditions in the deep ocean, changes in quality and degradability of DOM may strongly affect the relatively large pool of suspended and dissolved AA in the ocean that amounts to 15 Pg amino acid carbon (AAC) and 89 ± 29 Pg AAC, respectively.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Biogeochemical regeneration of a nodule mining disturbance site: Trace metals, DOC and amino acids in deep-sea sediments and pore waters (2018)
    In:  EPIC3Frontiers in Marine Science, 5(117)
    Details
    Publication Date: 2018-04-09
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 8
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    Sources of laminated sediments in the northeastern Arabian Sea off Pakistan and implications for sediment transport mechanisms during the late Holocene (2018)
    SAGE PUBLICATIONS LTD
    In:  EPIC3The Holocene, SAGE PUBLICATIONS LTD, ISSN: 0959-6836
    Details
    Publication Date: 2018-10-22
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Prospects for an Integrated German Indian Ocean Study (IGIOS): a contribution to IIOE-2. [presentation December 2015] (2017)
    GEOMAR | Hamburg, Germany
    Details
    Publication Date: 2021-05-19
    Description: Unpublished
    Keywords: IGIOS ; Integrated German Indian Ocean Study
    Repository Name: AquaDocs
    Type: Conference Material , Not Known
    Format: 12 slides
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  • 10
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    Coordinating sustained coastal and ocean observing efforts in Germany (2020)
    In:  EPIC3EGU General Assembly 2020: Sharing Geosciences Online, Online, 2020-05-04-2020-05-08
    Details
    Publication Date: 2020-05-17
    Description: Germany’s national ocean observing activities are carried out by multiple actors including governmental bodies, research institutions, and universities, and miss central coordination and governance. A particular strategic approach to coordinate and facilitate ocean research has formed in Germany under the umbrella of the German Marine Research Consortium (KDM). KDM aims at bringing together the marine science expertise of its member institutions and collectively presents them to policy makers, research funding organizations, and to the general public. Within KDM, several strategic groups (SGs), composed of national experts, have been established in order to strengthen different scientific and technological aspects of German Marine Research. Here we present the SG for sustained open ocean observing and the SG for sustained coastal observing. The coordination effort of the SG’s include (1) Representing German efforts in ocean observations, providing information about past, ongoing and planned activities and forwarding meta-information to data centers (e.g., JCOMMOPS), (2) Facilitating the integration of national observations into European and international observing programs (e.g. GCOS, GOOS, BluePlanet, GEOSS), (3) Supporting innovation in observing techniques and the development of scientific topics on observing strategies, (4) Developing strategies to expand and optimize national observing systems in consideration of the needs of stakeholders and conventions, (5) Contributing to agenda processes and roadmaps in science strategy and funding, and (6) Compiling recommendations for improved data collection and data handling, to better connect to the global data centers adhering to quality standards.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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