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  • ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  (2)
  • AGU (American Geophysical Union)  (2)
  • WILEY-BLACKWELL PUBLISHING  (2)
  • 1
    Publication Date: 2016-05-02
    Description: Stratospheric ozone depletion and emission of greenhouse gases lead to a trend of the southern annular mode (SAM) toward its high-index polarity. The positive phase of the SAM is characterized by stronger than usual westerly winds that induce changes in the physical carbon transport. Changes in the natural carbon budget of the upper 100 m of the Southern Ocean in response to a positive SAM phase are explored with a coupled ecosystem-general circulation model and regression analysis. Previously overlooked processes that are important for the upper ocean carbon budget during a positive SAM period are identified, namely, export production and downward transport of carbon north of the polar front (PF) as large as the upwelling in the south. The limiting micronutrient iron is brought into the surface layer by upwelling and stimulates phytoplankton growth and export production but only in summer. This leads to a drawdown of carbon and less summertime outgassing (or more uptake) of natural CO2. In winter, biological mechanisms are inactive, and the surface ocean equilibrates with the atmosphere by releasing CO2. In the annual mean, the upper ocean region south of the PF loses more carbon by additional export production than by the release of CO2 into the atmosphere, highlighting the role of the biological carbon pump in response to a positive SAM event.
    Type: Article , PeerReviewed
    Format: text
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  • 2
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    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 27 (1). pp. 11-20.
    Publication Date: 2016-05-02
    Description: We combined data sets of measured sedimentary calcium carbonate (CaCO3) and satellite-derived pelagic primary production to parameterize the relation between CaCO3 content on the Antarctic shelves and primary production in the overlying water column. CaCO3 content predicted in this way was in good agreement with the measured data. The parameterization was then used to chart CaCO3 content on the Antarctic shelves all around the Antarctic, using the satellite-derived primary production. The total inventory of CaCO3 in the bioturbated layer of Antarctic shelf sediments was estimated to be 0.5 Pg C. This quantity is comparable to the total CO2 uptake by the Southern Ocean in only one to a few years (dependent on the uptake estimate and area considered), indicating that the dissolution of these carbonates will neither delay ocean acidification in this area nor augment the Southern Ocean CO2 uptake capacity.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    WILEY-BLACKWELL PUBLISHING
    In:  EPIC3Journal of Phycology, WILEY-BLACKWELL PUBLISHING, 49, pp. 417-426, ISSN: 0022-3646
    Publication Date: 2019-07-17
    Description: Over the last four decades, different hypotheses of Ca2+ and dissolved inorganic carbon transport to the intracellular site of calcite precipitation have been put forth for Emiliania huxleyi (Lohmann) Hay & Mohler. The objective of this study was to assess these hypotheses by means of mathematical models. It is shown that a vesicle-based Ca2+ transport would require very high intravesicular Ca2+ concentrations, high vesicle fusion frequencies as well as a fast membrane recycling inside the cell. Furthermore, a kinetic model for the calcification compartment is presented that describes the internal chemical environment in terms of carbonate chemistry including calcite precipitation. Substrates for calcite precipitation are transported with different stoichiometries across the compartment membrane. As a result, the carbonate chemistry inside the compartment changes and hence influences the calcification rate. Moreover, the effect of carbonic anhydrase (CA) activity within the compartment is analyzed. One very promising model version is based on a Ca2+/H+ antiport, CO2 diffusion, and a CA inside the calcification compartment. Another promising model version is based on an import of Ca2+ and HCOÀ and an export of H+.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 4
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    ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
    In:  EPIC3Journal of Theoretical Biology, ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 364, pp. 305-315, ISSN: 0022-5193
    Publication Date: 2014-10-22
    Description: Coccolithophores play a crucial role in the marine carbon cycle and thus it is interesting to know how they will respond to climate change. After several decades of research the interplay between intracellular processes and the marine carbonate system is still not well understood. On the basis of experimental findings given in literature, a numerical cell model is developed that describes inorganic carbon fluxes between seawater and the intracellular sites of calcite precipitation and photosynthetic carbon fixation. The implemented cell model consists of four compartments, for each of which the carbonate system is resolved individually. The four compartments are connected to each other via H+, CO2, and View the MathML sourceHCO3− fluxes across the compartment-confining membranes. For CO2 accumulation around RubisCO, an energy-efficient carbon concentrating mechanism is proposed that relies on diffusive CO2 uptake. At low external CO2 concentrations and high light intensities, CO2 diffusion does not suffice to cover the carbon demand of photosynthesis and an additional uptake of external View the MathML sourceHCO3− becomes essential. The model is constrained by data of Emiliania huxleyi, the numerically most abundant coccolithophore species in the present-day ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 5
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    ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
    In:  EPIC3Journal of Theoretical Biology, ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 372, pp. 192-204, ISSN: 0022-5193
    Publication Date: 2015-04-22
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
    Publication Date: 2024-05-24
    Description: In the marine realm, microorganisms are responsible for the bulk of primary production, thereby sustaining marine life across all trophic levels. Longhurst provinces have distinct microbial fingerprints; however, little is known about how microbial diversity and primary productivity change at finer spatial scales. Here, we sampled the Atlantic Ocean from south to north (~50°S–50°N), every ~0.5° latitude. We conducted measurements of primary productivity, chlorophyll-a and relative abundance of 16S and 18S rRNA genes, alongside analyses of the physicochemical and hydrographic environment. We analysed the diversity of autotrophs, mixotrophs and heterotrophs, and noted distinct patterns among these guilds across provinces with high and low chlorophyll-a conditions. Eukaryotic autotrophs and prokaryotic heterotrophs showed a shared inter-province diversity pattern, distinct from the diversity pattern shared by mixotrophs, cyanobacteria and eukaryotic heterotrophs. Additionally, we calculated samplewise productivity-specific length scales, the potential horizontal displacement of microbial communities by surface currents to an intrinsic biological rate (here, specific primary productivity). This scale provides key context for our trophically disaggregated diversity analysis that we could relate to underlying oceanographic features. We integrate this element to provide more nuanced insights into the mosaic-like nature of microbial provincialism, linking diversity patterns to oceanographic transport through primary production.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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