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  • GEOMAR Catalogue / E-Books  (2)
  • Articles  (189)
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  • 1
    Keywords: Estuarine sediments Research ; Russia (Federation) ; Kara Sea ; Runoff Environmental aspects ; Russia (Federation) ; Kara Sea ; Seawater Organic compound content ; Marine ecology Russia (Federation) ; Kara Sea ; estuarine sediments ; runoff ; environmental aspects ; seawater, Organic compound content ; marine ecology ; Russia (Federation) ; Kara Sea ; Aufsatzsammlung ; Sibirien Nord ; Abflussregime ; Flusslandschaft ; Flusssystem ; Umweltfaktor ; Nordpolarmeer ; Karasee ; Fluss ; Mündung ; Unterlauf ; Fluviale Sedimentation ; Sibirien Nord ; Abflussregime ; Flusslandschaft ; Flusssystem ; Umweltfaktor ; Nordpolarmeer ; Karasee ; Fluss ; Mündung ; Unterlauf ; Fluviale Sedimentation
    Type of Medium: Book
    Pages: VII, 488 S , graph. Darst , 1 Beil. (Ber.-Bl.)
    Edition: 1. ed.
    ISBN: 0444513655
    Series Statement: Proceedings in marine science 6
    DDC: 551.461325
    Language: English
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  • 2
    Keywords: Copepoda Physiology ; Lipids Metabolism ; Hochschulschrift ; Forschungsbericht ; Antarktis ; Ökosystem ; Antarktis ; Ruderfußkrebse ; Lipidstoffwechselstörung
    Type of Medium: Book
    Pages: X, 135 S. , graph. Darst., Kt.
    Series Statement: Berichte zur Polarforschung 157
    DDC: 572/.5741534/09167
    RVK:
    RVK:
    Language: German
    Note: Zsfassung in dt. und engl. Sprache , Zugl.: Bremen, Univ., Diss., 1994
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  • 3
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The lipid and fatty acid compositions of microalgae were investigated in sea-ice and water samples from six different habitats of the Weddell Sea (Antarctica). All sea-ice samples and ice-associated water contained high algal biomass dominated by centric and pennate diatoms. Cells partially filled with oil droplets and resting spores were found. In the cells from the ice platelet layer triacylglycerols formed the largest component of the lipids. The fatty acid composition of sea-ice microalgae was dominated by the 16:1(n-7), 16:0, 18:1(n-9) and 20:5 (n-3) fatty acids. Except 18:1, they are typical for diatom fatty acids. These fatty acids were most abundant in pieces of first year ice with a brown colouration (“brown-ice”) and in the water column directly below sea-ice (sub-ice water). The small amounts of non-diatom acids, as 22:6 (n-3) and 18:4 (n-3), clearly showed that the sea-ice communities were not purely composed of diatoms. The most striking difference, in comparison to the general fatty acid composition of diatoms, was the high proportion of the 18:1 fatty acid in all samples, which might be caused by detrital material or lipid accumulation within cells and resting spores. In general, no clear adaptation of the fatty acid composition to the Antarctic and sea-ice environment was found. The fatty acid composition of the particulate matter from the water column was totally different from all other samples dominated by the saturated fatty acids 16:0 and 18:0.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2019-07-16
    Description: Sea surface temperature (SST) patterns in the northern North Atlantic, the Nordic seas, and the western Arctic Ocean (AO) were reconstructed across MIS 11c, a potential future climate analogue, using planktic foraminiferal abundances, alkenone-based Uk’37 and glycerol dialkyl glycerol tetraether (GDGT)-based TEX86 analyses, where possible. SSTforam reconstructions were supported by foraminiferal counts of small-sized fractions and rare foraminiferal species, stable oxygen isotope measurements on benthic and planktic foraminiferal species, and ice rafted debris (IRD) records. Additionally, the hydrogen isotopic (δD) compositions of long chain alkenones were determined to assess variations in paleo sea surface salinity in the North Atlantic. The preliminary alkenone δD data show that during MIS 11c salinity values in the North Atlantic were similar to Holocene values. In the North Atlantic our newly produced TEX86 –based SSTs range between 14 and 19 °C in agreement with summer SSTforam (13 and 18 °C) and alkenone SSTs (13 and 16 °C). However, the former showed higher fluctuations than SSTs based on foraminiferal abundances. In concordance with δ18O records TEX86 SSTs demonstrate notable variability in the middle of MIS 11c, between 400 and 410 ka, which we tentatively correlate with an intra-MIS 11c cold event occurring in the Arctic as we previously detected. This implies that MIC 11c climate was probably not as stable as it was believed before. SSTforam records imply that during MIS 11c parts of the AO experienced unusually warm, ice free conditions, whereas the Nordic seas remained rather cold, especially during the early phase of this period, as it is inferred from foraminiferal and alkenone SSTs. At the same time all our SST records show that the North Atlantic was 1-2°C warmer than present during MIS 11c. This pattern suggests that during MIS 11c the North Atlantic Current was deflected to the west, which intensified the subpolar gyre and that, therefore, less warm water was transported to the Nordic seas. Consequently, warm water transport from the Nordic seas to the Arctic was also reduced relative to the modern situation and proportionally more water entered the Arctic from the Pacific Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    In:  EPIC318th International Symposium on Polar Sciences (ISPS), Jeju Island, Repubic of Korea, 2012-05-22-2012-05-24
    Publication Date: 2019-07-16
    Description: Overall goal of our study of sediment material collected during RV Sonne Cruise 202 (INOPEX) in 2009 (Gersonde et al., Curise Report 2009), is the reconstruction of the short-term variability of sea-ice, sea-surface temperature (SST), primary productivity and terrigenous input in the subpolar North Pacific/Bering Sea and their relationship to global climate change, using organic-geochemical proxies (i.e. organic-geochemical bulk parameters and specific biomarkers such as: TOC, hydrogen indices; long-chain n-alkanes, sterols, alkenones; Uk37 and TEX86-Index; BIT-Index; HBIs, IP25, PIP25). In a first phase, these organic-geochemical proxies have been determined in surface sediments. The results show that the biomarker proxies reflect modern sea-ice and SST distributions as well as areas of increased primary productivity and increased input of terrigenous (organic) matter quite well. In a second phase of the project, the biomarkers have been determined in three selected sediment cores: Core SO202-18-6 (Umnak Plateau/Bering Sea; 60.127°N, 179.444°W; water depth 1105 m; core length 7.21 m; age interval 0 to 14 kyr.BP). Core SO202-07-6 (Detroit Seamount/western subpolar North Pacific; 51.272°N, 167.700°W; water depth 2340 m WD; core length 4.69 m; age interval MIS 1 to 3). Core SO202-27-6 (Patton Seamount/eastern subpolar North Pacific; 54.296°N, 149.600°W; water depth 2919 m; core length 2.91 m: age interval MIS 1 to 3). Here, we concentrate especially on the variability of sea-ice cover and sea-surface temperature, using the newly developed sea-ice proxy IP25 (Belt et al., 2007) and alkenone data, respectively, determined in the AMS14C-dated Core SO202-18-6. Based on these biomarker records, sea-ice cover and SST changed significantly in the northern Bering Sea during Deglacial-Holocene times. The Younger Dryas interval is characterized by extended sea-ice cover, coinciding with a drop in SST to 2-4°C. With the end of the Younger Dryas, between 460 and 420 cmbsf, sea-ice cover decreased with increasing SST. Between 420 and 120 cmbsf representing the early Holocene Thermal Maximum, IP25 is absent and maximum SST of about 6°C was reached. During the upper 120 cmbsf representing the late Holocene, IP25 occurred again and increased towards the top, paralleled by a decrease in SST of about 3°C. A very similar contemporaneous trend of increasing sea-ice cover during the late Holocene was recorded in the northern North Atlantic, paralleled by an advance of glaciers in Norway (Müller et al., 2009; 2012).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 6
    Publication Date: 2017-03-25
    Description: The recent dramatic decline of Arctic sea over the last decades and its controlling processes are still poorly understood. In order to distinguish between natural and anthropogenic processes controlling these changes in sea ice, we have to look back to the past beyond the times of direct measurements. For this purpose, we carried out a multi-proxy approach combining organic-geochemical data (bulk parameters: C/N, TOC, δ13Corg; biomarkers: IP25, sterols, GDGTs) with sedimentological data (core lithology, physical properties, IRD counting, XRF scanning) determined in sediments of Yermak Plateau Core PS92/039-2. This core is situated close to the modern summer ice edge and thus very sensitive for environmental changes. Based on magnetostratigraphy and correlations with dated sediment cores, this core represents the time span from MIS 6 to 1 (ca. 180,000 years) and allows the reconstruction of sea ice variability and related changes in oceanic circulation patterns and the Svalbard Barents Ice Sheet (SBIS) fluctuations during glacial/interglacial changes. As sea ice and phytoplankton biomarkers occur throughout the entire sedimentary section but show some strong variability, a more seasonal sea ice cover was probably predominant during the entire time interval, superimposed by a distinct short-term variability in extent. Significant fluctuations in most of our proxy records indicate highly variable sea ice conditions over the Yermak Plateau during MIS 6. Based on our biomarker data, the SBIS could not have reached the Yermak Plateau during MIS 6. During MIS 4 and 2, coevally elevated concentrations of the sea ice proxy IP25 and the biomarkers for phytoplankton productivity and terrigenous input point to a stationary ice margin above the core position at that time. Strengthened Atlantic Water inflow possibly coupled with katabatic winds from the protruding SBIS may have created this stable ice edge situation and the related sedimentary regime.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
    Publication Date: 2017-11-16
    Description: The Holocene is characterized by the late Holocene cooling trend as well as by internal short-term centennial fluctuations. Because Arctic sea ice acts as a significant component (amplifier) within the climate system, investigating its past long- and short-term variability and controlling processes is beneficial for future climate predictions. This study presents the first biomarker-based (IP25 and PIP25) sea ice reconstruction from the Kara Sea (core BP00-07/7), covering the last 8 ka. These biomarker proxies reflect conspicuous short-term sea ice variability during the last 6.5 ka that is identified unprecedentedly in the source region of Arctic sea ice by means of a direct sea ice indicator. Prominent peaks of extensive sea ice cover occurred at ~3, ~2, ~1.3 and ~0.3 ka. Spectral analysis of the IP25 record revealed ~400- and ~950-year cycles. These periodicities may be related to the Arctic/North Atlantic Oscillation, but probably also to internal climate system fluctuations. This demonstrates that sea ice belongs to a complex system that more likely depends on multiple internal forcing.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 8
    Publication Date: 2019-07-16
    Description: The coccolithophore Emiliania huxleyi is a microalga with biogeochemical and biotechnological relevance, due to its high abundance in the ocean and its ability to form intricate calcium carbonate structures. Depletion of macronutrients in oceanic waters is very common and will likely enhance with advancing climate change. We present the first comprehensive metabolome study analyzing the effect of phosphorus (P) and nitrogen (N) starvation on the diploid and haploid life-cycle stage, applying various metabolome analysis methods to gain new insights in intracellular mechanisms to cope with nutrient starvation. P-starvation led to an accumulation of many generic and especially N-rich metabolites, including lipids, osmolytes, and pigments. This suggests that P-starvation primarily arrests cell-cycling due to lacking P for nucleic acid synthesis, but that enzymatic functionality is widely preserved. Also, the de-epoxidation ratio of the xanthophyll cycle was upregulated in the diploid stage under P-starvation, indicating increased nonphotochemical quenching, a response typically observed under high light stress. In contrast, N-starvation resulted in a decrease of most central metabolites, also P-containing ones, especially in the diploid stage, indicating that most enzymatic functionality ceased. The two investigated nutrient starvation conditions caused significantly different responses, contrary to previous assumptions derived from transcriptomic studies. Data highlight that instantaneous biochemical flux is a more dominant driver of the metabolome than the transcriptomically rearranged pathway patterns. Due to the fundamental nature of the observed responses it may be speculated that microalgae with similar nutrient requirements can cope better with P-starvation than with N-starvation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2017-03-25
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
    Publication Date: 2017-03-25
    Description: One of the main characteristics of the Arctic Ocean is its seasonal to perennial sea-ice cover. Variations of sea-ice conditions affect the Earth’s albedo, primary production, rate of deep-water etc.. During the last decades, a drastic decrease in sea ice has been recorded, and the causes of which, i.e. natural vs. anthropogenic forcings, and their relevance within the global climate system, are subject of intense scientific and societal debate. In this context, records of past sea-ice conditions going beyond instrumental records are of major significance. These records may help to better understand the processes controlling natural sea-ice variability and to improve models for forecasts of future climatic conditions. During RV Polarstern Cruise PS92 in summer 2015, a 860 cm long sediment core (PS92/039-2) was re- covered from the eastern flank of Yermak Plateau north of the Svalbard archipelago (Peeken, 2015). Based on a preliminary age model, this sediment core probably represents the time interval from MIS 6 to MIS 1. This core, located close to the modern summer ice edge, has been selected for reconstruction of past Arctic sea-ice variability based on specific biomarkers. In this context, we have determined the ice-algae-derived sea-ice proxy IP25 (Belt et al., 2007), in combination with other biomarkers indicative for open-water conditions (cf., Müller et al., 2009, 2011). Furthermore, organic carbon fluxes were differentiated using specific biomarkers indicative for marine primary production (brassicasterol, dinosterol) and terrigenous input (campesterol, β-sitosterol). In this poster, preliminary results of our organic-geochemical and sedimentological investigations are presented. Distinct fluctuations of these biomarkers indicate several major, partly abrupt changes in sea-ice cover in the Yermak Plateau area during the late Quaternary. These changes are probably linked to changes in the inflow of Atlantic Water along the western coastline of Svalbard into the Arctic Ocean. Furthermore, the repetitive advance and retreat of the Svalbard Barents Sea Ice Sheet might have influenced the terrigenous input and the environmental setting north of Svalbard, as reflected in the sediment composition of Core PS92/039-2.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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