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  • 1
    Book
    Book
    Zur Taxonomie von rezenten benthischen Foraminiferen aus dem Nansen Becken, Arktischer Ozean : = Taxonomic notes on recent benthic Foraminifera from Nansen Basin, Arctic Ocean (1992)
    Bremerhaven : Alfred-Wegener-Institut für Polar- und Meeresforschung
    Details Availability
    Keywords: Nordpolarmeer ; Benthos ; Foraminiferen ; Taxonomie ; Nansenbecken ; Foraminiferen
    Type of Medium: Book
    Pages: 137 S. , Ill., Kt.
    Series Statement: Berichte zur Polarforschung 112
    URL: https://www.gbv.de/dms/tib-ub-hannover/132544121.pdf
    DDC: 593.1/2/0916324
    RVK:
    RY 20075
    RVK:
    WP 1560
    Language: German
    Note: Text dt. mit engl. Zsfassung
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  • 2
    Book
    Book
    Benthische Foraminiferenfaunen als Wassermassen-, Produktions- und Eisdriftanzeiger im Arktischen Ozean : = Benthic foraminiferal assemblages in the Arctic Ocean, indicators for water mass distribution, productivity, and sea ice drift (1995)
    Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung
    Details Availability
    Keywords: Forschungsbericht ; Hochschulschrift ; Nordpolarmeer ; Benthos ; Foraminiferen ; Glaziologie
    Type of Medium: Book
    Pages: 227 S. , Ill., graph. Darst., Kt.
    Series Statement: Berichte zur Polarforschung 179
    URL: http://www.gbv.de/dms/bs/toc/190835729.pdf
    DDC: 579.4/417732
    RVK:
    RY 20075
    RVK:
    WI 4440
    Language: German
    Note: Literaturverz. S. 143 - 159 , Intermediärsprache: Englisch , Zugl.: Bremen, Univ. , Diss., 1995
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  • 3
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    Arctic megaslide at presumed rest (2016)
    Nature Research
    In:  Scientific Reports, 6 (38529).
    Details
    Publication Date: 2019-07-19
    Description: Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1038/srep38529
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Ballasting by cryogenic gypsum enhances carbon export in a Phaeocystis under-ice bloom (2018)
    Springer
    In:  EPIC3Scientific Reports, Springer, 8(7703)
    Details
    Publication Date: 2019-02-14
    Description: Mineral ballasting enhances carbon export from the surface to the deep ocean; however, little is known about the role of this process in the ice-covered Arctic Ocean. Here, we propose gypsum ballasting as a new mechanism that likely facilitated enhanced vertical carbon export from an under-ice phytoplankton bloom dominated by the haptophyte Phaeocystis. In the spring 2015 abundant gypsum crystals embedded in Phaeocystis aggregates were collected throughout the water column and on the sea floor at a depth below 2 km. Model predictions supported by isotopic signatures indicate that 2.7 g m−2 gypsum crystals were formed in sea ice at temperatures below −6.5°C and released into the water column during sea ice melting. Our finding indicates that sea ice derived (cryogenic) gypsum is stable enough to survive export to the deep ocean and serves as an effective ballast mineral. Our findings also suggest a potentially important and previously unknown role of Phaeocystis in deep carbon export due to cryogenic gypsum ballasting. The rapidly changing Arctic sea ice regime might favour this gypsum gravity chute with potential consequences for carbon export and food partitioning between pelagic and benthic ecosystems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Insight into deep-sea life - Cibicidoides pachyderma substrate and pH-dependent behaviour following disturbance (2018)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Deep-Sea Research Part I-Oceanographic Research Papers, PERGAMON-ELSEVIER SCIENCE LTD, 138, pp. 34-45, ISSN: 0967-0637
    Details
    Publication Date: 2019-02-15
    Description: Most palaeo-deep-water reconstructions are based on geochemical information stored in the calcareous shells of Cibicidoides species but hardly anything is known about their life cycle, population dynamics or ecology. The number of specimens of a single Cibicidoides species can locally be very limited and species may be lacking completely during certain intervals in the geological past. As a consequence, geochemical analyses are often carried out on lumped Cibicidoides spp. assuming that they share the same epizoic to epifaunal habitat and precipitated their shell in comparable offsets to surrounding bottom water mass properties. However, there is a growing body of evidence that particularly Cibicidoides pachyderma and its morphotypes C. mundulus and C. kullenbergi, may not be reliable bottom water recorders. We have recently developed aquaria that allowed, for the first time, observations of Cibicidoides pachyderma var. C. mundulus under in situ pressure and temperature. Experiments were carried out with and without artificial sediments to simulate soft sediments and rocks, respectively. Seawater was set to pH 8 and pH 7.4 to simulate more or less particulate carbon export or more or less ventilation of bottom water. Our experiments demonstrate that C. mundulus may opt for an epifaunal or an infaunal habitat depending on elapsed time following physical disturbance, pH, current activity, the availability of sediments and growth. The specimen's initial response following transfer from atmospheric pressure into the high-pressure aquaria was to immerse into the sediment or to cover more or less parts of the test with aggregated sediments or algae. However, within 24 h a strong rheotaxis became apparent and most specimens moved to sites of increased current activity under normal pH conditions (pH 8). Only few specimens remained in algae cysts or in the sediment in the pH-8 experiment. On the contrary, all specimens under pH 7.4 agglutinated a firm sediment cyst around their test and remained infaunal throughout the experimental period of three months. Independent of pH, growth was only observed in specimens that lived within an agglutinated cyst or infaunal. A solid thick cyst covered the specimens of the pH 7.4 experiment throughout the experiment and possibly restricted water exchange between the in-cyst water and the surrounding artificial bottom water mass. We suggest that a more fragile and possibly more porous sedimentary envelope may, at least temporally, have covered the infaunal specimens under pH 8 but no evidence for this was found upon termination of the experiment.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    The gypsum gravity chute to the Arctic abyss (2018)
    In:  EPIC3SCAR/IASC Open Science Conference & Open COMNAP Session, Davos, 2018-06-19-2018-06-23
    Details
    Publication Date: 2019-04-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
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    New observations of the distribution, morphology and dissolution dynamics of cryogenic gypsum in the Arctic Ocean (2020)
    European Geosciences Union
    In:  EPIC3The Cryosphere, European Geosciences Union, 14
    Details
    Publication Date: 2020-06-11
    Description: To date, observations on a single location indicate that cryogenic gypsum (Ca{SO4} *2H2O) may constitute an efficient but hitherto overlooked ballasting mineral enhancing the efficiency of the biological carbon pump in the Arctic Ocean. In June–July 2017 we sampled cryogenic gypsum under pack ice in the Nansen Basin north of Svalbard using a plankton net mounted on a remotely operated vehicle (ROVnet). Cryogenic gypsum crystals were present at all sampled stations, which suggested a persisting cryogenic gypsum release from melting sea ice throughout the investigated area. This was supported by a sea ice backtracking model, indicating that gypsum release was not related to a specific region of sea ice formation. The observed cryogenic gypsum crystals exhibited a large variability in morphology and size, with the largest crystals exceeding a length of 1 cm. Preservation, temperature and pressure laboratory studies revealed that gypsum dissolution rates accelerated with increasing temperature and pressure, ranging from 6%d-1 by mass in polar surface water (-0.5 °C) to 81%d-1 by mass in Atlantic Water (2.5°C at 65 bar). When testing the preservation of gypsum in formaldehyde-fixed samples, we observed immediate dissolution. Dissolution at warmer temperatures and through inappropriate preservation media may thus explain why cryogenic gypsum was not observed in scientific samples previously. Direct measurements of gypsum crystal sinking velocities ranged between 200 and 7000md-1, suggesting that gypsum-loaded marine aggregates could rapidly sink from the surface to abyssal depths, supporting the hypothesized potential of gypsum as a ballasting mineral in the Arctic Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 8
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    Planktonic foraminifera genomic variations reflect paleoceanographic changes in the Arctic: evidence from sedimentary ancient DNA (2020)
    Nature
    In:  EPIC3Scientific Reports, Nature, 10(1), ISSN: 2045-2322
    Details
    Publication Date: 2020-09-24
    Description: Deciphering the evolution of marine plankton is typically based on the study of microfossil groups. Cryptic speciation is common in these groups, and large intragenomic variations occur in ribosomal RNA genes of many morphospecies. In this study, we correlated the distribution of ribosomal amplicon sequence variants (ASVs) with paleoceanographic changes by analyzing the highthroughput sequence data assigned to Neogloboquadrina pachyderma in a 140,000-year-old sediment core from the Arctic Ocean. The sedimentary ancient DNA demonstrated the occurrence of various N. pachyderma ASVs whose occurrence and dominance varied through time. Most remarkable was the striking appearance of ASV18, which was nearly absent in older sediments but became dominant during the last glacial maximum and continues to persist today. Although the molecular ecology of planktonic foraminifera is still poorly known, the analysis of their intragenomic variations through time has the potential to provide new insight into the evolution of marine biodiversity and may lead to the development of new and important paleoceanographic proxies.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 9
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    Geochemical evidence of a floating Arctic ice sheet and underlying freshwater in the Arctic Mediterranean in glacial periods (2021)
    Copernicus
    In:  EPIC3Geochemical evidence of a floating Arctic ice sheet and underlying freshwater in the Arctic Mediterranean in glacial periods, EGU General Assembly 2021, Copernicus, pp. EGU21-12910
    Details
    Publication Date: 2021-05-01
    Description: Numerous studies have addressed the possible existence of large floating ice sheets in the glacial Arctic Ocean from theoretical, modelling, or seafloor morphology perspectives. Here, we add evidence from the sediment record that support the existence of such freshwater ice caps in certain intervals, and we discuss their implications for possible non-linear and rapid behaviour of such a system in the high latitudes. We present sedimentary activities of 230Th together with 234U/238U ratios, the concentrations of manganese, sulphur and calcium in the context of lithological information and records of microfossils and their isotope composition. New analyses (PS51/038, PS72/396) and a re-analysis of existing marine sediment records (PS1533, PS1235, PS2185, PS2200, amongst others) in view of the naturally occurring radionuclide 230Thex and, where available, 10Be from the Arctic Ocean and the Nordic Seas reveal the widespread occurrence of intervals with a specific geochemical signature. The pattern of these parameters in a pan-Arctic view can best be explained when assuming the repeated presence of freshwater in frozen and liquid form across large parts of the Arctic Ocean and the Nordic Seas. Based on the sedimentary evidence and known environmental constraints at the time, we develop a glacial scenario that explains how these ice sheets, together with eustatic sea-level changes, may have affected the past oceanography of the Arctic Ocean in a fundamental way that must have led to a drastic and non-linear response to external forcing. This concept offers a possibility to explain and to some extent reconcile contrasting age models for the Late Pleistocene in the Arctic Ocean. Our view, if adopted, offers a coherent dating approach across the Arctic Ocean and the Nordic Seas, linked to events outside the Arctic.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 10
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    Permanent ectoplasmic structures in deep-sea benthic Cibicides and Cibicidoides taxa – long-term observations at in situ pressure (2021)
    European Geoscience Union
    In:  EPIC3Biogeosciences, European Geoscience Union, 18(12), pp. 3903-3915, ISSN: 1726-4189
    Details
    Publication Date: 2021-07-04
    Description: Deep-sea Cibicidoides pachyderma (forma mundulus) and related Cibicidoides spp. were cultured at in situ pressure for 1–2 d, or 6 weeks to 3 months. During that period, fluorescence analyses following BCECF-AM (2′,7′-bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester) or calcein (bis[N,N-bis(carboxymethyl)aminomethyl]-fluorescein) labelling revealed a persisting cytoplasmic sheet or envelope surrounding the Cibicidoides tests. Thus, the Cibicidoides shell can be considered as an internal rather than an external cell structure. A couple of days to a week after being transferred into high-pressure aquaria and adjusted to a pressure of 115 bar, the foraminifera changed from a mobile to a more or less sessile living mode. During this quasi-sessile way of life, a series of comparably thick static ectoplasmic structures developed that were not resorbed or remodelled but, except for occasional further growth, remained unchanged throughout the experiments. Three different types of these permanent structures were observed. (a) Ectoplasmic “roots” were common in adult C. pachyderma, C. lobatulus, and C. wuellerstorfi specimens. In our experiments single ectoplasmic roots grew to a maximum of 700 times the individuals' shell diameter and were presumably used to anchor the specimen in an environment with strong currents. (b) Ectoplasmic “trees” describe rigid ectoplasmic structures directed into the aquarium's water body and were used by the foraminifera to climb up and down these ectoplasmic structures. Ectoplasmic trees have so far only been observed in C. pachyderma and enabled the tree-forming foraminifera to elevate itself above ground. (c) Ectoplasmic “twigs” were used to guide and hold the more delicate pseudopodial network when distributed into prevailing currents and were, in our experiments, also only developed in C. pachyderma specimens. Relocation of a specimen usually required it to tear apart and leave behind the rigid ectoplasmic structures and eventually also the envelope surrounding the test. Apparently, these rigid structures could not be resorbed or reused.
    Repository Name: EPIC Alfred Wegener Institut
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