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  • 2010-2014  (35)
  • 1990-1994  (30)
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  • 1
    Online Resource
    Online Resource
    The expedition of the research vessel "Polarstern" to the Antarctic in 2009 (ANT-XXV/3 - LOHAFEX) (2010)
    Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung
    Details Availability
    Description / Table of Contents: Wissenschaftliche Fragestellung : Fahrtabschnitt ANT-XXV/3 war ein gemeinsames indisch-deutsches Eisendüngungs-Experiment, dessen Kosten von beiden Seiten zu etwa gleichen Teilen getragen wurden. LOHAFEX (Loha ist das Hindi-Wort für Eisen) war das dritte derartige Experiment, das von der Polarstern durchgeführt wurde und den Aufbau und Niedergang einer Phytoplankton-Blüte untersuchte. Die Blüte wurde durch Eisensulphat-Düngung im Kern eines mesoskaligen Wirbels entlang der Polarfront hervorgerufen...Eisendüngungs-Experimente sind das Äquivalent zu Störungs-Experimenten, die von allen wissenschaftlichen Disziplinen durchgeführt werden, um Struktur und Funktion ANT-XXV/3 4 von Systemen zu untersuchen, die zu komplex sind, um sie durch die bloße Beobachtung zu entschlüsseln. Das übergeordnete Ziel dieser interdisziplinären Fahrt war also, unser Verständnis darüber zu fördern, wie Ökosysteme im offenen Ozean funktionieren und wie sich die Organismen des Planktons untereinander und ihre Umgebung beeinflussen und dadurch biogeochemische Kreisläufe und das Absinken von partikulärem Material in die Tiefsee antreiben. Künstliche Eisendüngung simuliert natürliche Prozesse, durch die Eisen in eisenlimitierte, landferne Meeresgebiete eingebracht wird...Ein Hauptziel der Fahrt war es, das Schicksal der Eisen gedüngten Blüten-Biomasse in einem produktiven Gebiet des ACC zu untersuchen: wird deren Biomasse in der Oberflächenschicht von Bakterien und Zooplankton in CO2 zurückverwandelt, oder sinkt zumindest ein Teil davon ab, und entfernt damit CO2 aus der Atmosphäre und lagert es in die Tiefsee ein. Die Antwort auf diese Frage ist für das Verständnis der vergangenen Klimakreisläufe von Bedeutung, aber auch für die Umsetzbarkeit der Anwendung von künstlicher Eisendüngung des ACC als Technik die globale Erwärmung abzuschwächen.
    Type of Medium: Online Resource
    Pages: Online-Ressource
    Series Statement: Berichte zur Polar- und Meeresforschung 613
    URL: http://hdl.handle.net/10013/epic.35169
    URL: http://hdl.handle.net/10013/epic.35169.d001
    Language: English
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  • 2
    Online Resource
    Online Resource
    Die Struktur mariner pelagischer Systeme : Ansätze zu einer Synthese von physikoçhemischen und biologischen Betrachtungsweisen (1985-)
    Kiel
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Edition: 2021
    Language: German , English
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  • 3
    Electronic Resource
    Electronic Resource
    Patterns of production and sedimentation in the boreal and polar Northeast Atlantic (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 10 (1991), S. 0 
    Details
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Pelagic systems are potentially capable of retaining and recycling all autochthonous organic material, although some losses due to sinking particles inevitably occur. Relating processes in the surface layers quantitatively to vertical particle flux is difficult because only a small percentage of the total production is lost annually via sinking in the open ocean. Further, only a few types of particles contribute to this flux and only a smalt proportion of these may actually reach greater depths.Measurements of vertical flux with sediment traps revealed seasonal and regional patterns also within the northwestern Atlantic and indicate imbalances between particle formation and degradation. The classical pattern of spring bloom sedimentation followed by reduced loss rates has been found in shelf and shallow water regions such as the Norwegian Coastal Current and fjords and is also encountered in the Barents Sea. In the Norwegian Sea. however, the seasonal pattern appears different as the seasonal maximum has been observed during late summer/autumn.The physical environment determines nutrient availability and hence the particles potentially available for sedimentation. The relationship between phyto- and zooplankton governs vertical flux seasonality, and zooplankters with different life cycles and feeding strategies further modify the principle patterns. Herbivores with life-cycle strategies involving overwintering of large biomass and predictable seasonal appearance (copepods, cuphausiids) will have a different impact than opportunistic organisms with very low overwintering biomass, for example salps and ptcropods. The latter exhibit much greater intcrannual biomass variation and may thus contribute to intcrannual variability of the vertical flux. Shelf systems of similar latitude arc generally comparable with respect to their flux patterns and also share similarities with marginal ice zones. Open ocean systems as the Norwegian Sea, however, exhibit different patterns which are similar to the subarctic Pacific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-8369.1991.tb00647.x
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Phytoplankton growth and CO 2 (1993)
    [s.l.] : Nature Publishing Group
    Nature 363 (1993), S. 678-679 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] RIEBESELL ET AL. REPLY - Turpin makes two important points pertinent to the question of CO2 limitation of phyto-plankton growth. With respect to his first comment, we agree that inorganic carbon use by the common marine di-atom species needs to be rigorously tested. With the exception of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/363678c0
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Mirror-script and left-handedness (1992)
    [s.l.] : Nature Publishing Group
    Nature 355 (1992), S. 118-119 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-Leonardo da Vinci's famous sketches are accompanied by illegible notes which, viewed in a mirror, turn out to be neatly written Roman script. Reading and writing mirror script is very difficult for most people, so why did Leonardo go to the trouble? As a code, it is much too easy to crack, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/355118b0
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    Paper (German National Licenses)
    Fulltext
  • 6
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    Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX (2013)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 27 (3). pp. 871-881.
    Details
    Publication Date: 2018-03-19
    Description: A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yield (FV/FM) increased from 0.33 to ≥0.40. Silicic acid (〈2 µmol L−1) limited diatoms, which contributed 〈10% of phytoplankton biomass. Copepods exerted high grazing pressure. This is the first study of particle flux out of an artificially fertilized bloom with very low diatom biomass. Net community production (NCP) inside the patch, estimated from O2:Ar ratios, averaged 21 mmol POC m−2 d−1, probably ±20%. 234Th profiles implied constant export of ~6.3 mmol POC m−2 d−1 in the patch, similar to unfertilized waters. The difference between NCP and 234Th-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 m. Neutrally buoyant sediment traps at 200 and 450 m inside and outside the patch caught mostly 〈1.1 mmol POC m−2 d−1, predominantly of fecal origin; flux did not increase upon fertilization. Our data thus indicate intense flux attenuation between 100 and 200 m, and probably between the mixed layer and 100 m. We attribute the lack of fertilization-induced export to silicon limitation of diatoms and reprocessing of sinking particles by detritus feeders. Our data are consistent with the view that nitrate-rich but silicate-deficient waters are not poised for enhanced particle export upon iron addition.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/gbc.20077
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Deep carbon export from a Southern Ocean iron-fertilized diatom bloom (2012)
    Nature Publishing Group
    In:  Nature, 487 (7407). pp. 313-319.
    Details
    Publication Date: 2019-09-23
    Description: Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    DOI: 10.1038/nature11229
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Observation of manganese deposits in the Southern Ocean during the R/V Polarstern ANT-IX/3 and ANT-IX/4 expeditions (1992)
    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Details
    Publication Date: 2023-08-28
    Description: On a previous R/V Polarstern cruise ANT-VIII/5 (1989/90), a deep-sea area in the central Weddell Sea was investigated along geophysical and bathymetrical transects. As a result, a seamount-like structure, the informally named "Polarstern Seamount", was detected. This seamount was one of the sampling areas during the ANT-IX/3 leg. Attempts were made to retrieve glaciomarine and hemipelagic sediments, which in this area were expected not to be so strongly affected by bottom currents as are the sediments in the deeper surroundings seas. The seafloor on top of the Polarstern Searnount revealed to be densely covered with Mn encrusted dropstones, as observed by the underwater video-recording obtained from a camera installed at the multi box corer (MG), as well as in the retrieved sediments.
    Keywords: Agulhas Basin; ANT-IX/3; ANT-IX/4; AWI_Paleo; Comment; Deposit type; DEPTH, sediment/rock; Description; Elevation of event; Event label; Gravity corer (Kiel type); Identification; KL; Latitude of event; Longitude of event; Maud Rise; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Piston corer (BGR type); Polarstern; Polarstern Kuppe; Position; PS18; PS18/145; PS18/147; PS18/225; PS18/238; PS2003-2; PS2005-1; PS2070-1; PS2082-1; Quantity of deposit; Sediment type; Size; SL; Substrate type; Visual description
    Type: Dataset
    Format: text/tab-separated-values, 50 data points
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    DATA PANGAEA
  • 9
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    Net community production, Thorium-234 activity and particle flux during the Southern Ocean iron fertilization experiment LOHAFEX (2013)
    PANGAEA
    In:  Supplement to: Martin, Patrick; Rutgers van der Loeff, Michiel M; Cassar, Nicolas; Vandromme, Pieter; d'Ovidio, Francesco; Stemmann, Lars; Rengarajan, Ramabadran; Soares, Melena; González, Humberto E; Ebersbach, Friederike; Lampitt, Richard Stephen; Sanders, Richard J; Barnett, Bruce A; Smetacek, Victor; Naqvi, Syed Wajih Ahmad (2013): Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX. Global Biogeochemical Cycles, 27(3), 871-881, https://doi.org/10.1002/gbc.20077
    Details
    Publication Date: 2023-11-09
    Description: A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km**2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yield (FV/FM) increased from 0.33 to 〉0.40. Silicic acid (〈2 µmol/L) limited diatoms, which contributed 〈10% of phytoplankton biomass. Copepods exerted high grazing pressure. This is the first study of particle flux out of an artificially fertilized bloom with very low diatom biomass. Net community production (NCP) inside the patch, estimated from O2:Ar ratios, averaged 21 mmol POC/m**2/d, probably ±20%. 234Th profiles implied constant export of ~6.3 mmol POC/m**2/d in the patch, similar to unfertilized waters. The difference between NCP and 234Th-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 m. Neutrally buoyant sediment traps at 200 and 450 m inside and outside the patch caught mostly 〈1.1 mmol POC/m**2/d, predominantly of fecal origin; flux did not increase upon fertilization. Our data thus indicate intense flux attenuation between 100 and 200 m, and probably between the mixed layer and 100 m. We attribute the lack of fertilization-induced export to silicon limitation of diatoms and reprocessing of sinking particles by detritus feeders. Our data are consistent with the view that nitrate-rich but silicate-deficient waters are not poised for enhanced particle export upon iron addition.
    Keywords: AWI_MarGeoChem; Marine Geochemistry @ AWI
    Type: Dataset
    Format: application/zip, 7 datasets
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    DATA PANGAEA
  • 10
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    Net community production estimates from underway O2:Ar measurement during POLARSTERN cruise ANT-XXV/3 (LOHAFEX) (2013)
    PANGAEA
    Details
    Publication Date: 2023-11-09
    Keywords: ANT-XXV/3; AWI_MarGeoChem; Comment; CT; DATE/TIME; DEPTH, water; LATITUDE; LONGITUDE; Marine Geochemistry @ AWI; Net community production of oxygen; Polarstern; PS73/3-track; PS73 LOHAFEX; South Atlantic Ocean; Underway cruise track measurements
    Type: Dataset
    Format: text/tab-separated-values, 62614 data points
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    DATA PANGAEA
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