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  • 1
    Book
    Book
    Late Quaternary variability of the Arabian Sea monsoon and oxygen minimum zone : = Laat Kwartaire variabiliteit van de moesson en de zuurstof minimum zone in de Arabische Zee (1997)
    Utrecht : Univ.
    Details Availability
    Keywords: Dissertation ; Report ; Hochschulschrift
    Type of Medium: Book
    Pages: 174 S , graph. Darst., Kt
    ISBN: 9057440121
    Series Statement: Geologica Ultraiectina 154
    Language: English
    Note: Includes bibliographical references , Zugl.: Utrecht, Univ., Diss., 1997
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  • 2
    Electronic Resource
    Electronic Resource
    Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary (2007)
    [s.l.] : Nature Publishing Group
    Nature 450 (2007), S. 1218-1221 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The start of the Palaeocene/Eocene thermal maximum—a period of exceptional global warming about 55 million years ago—is marked by a prominent negative carbon isotope excursion that reflects a massive input of 13C-depleted (‘light’) carbon to the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06400
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum (2006)
    [s.l.] : Nature Publishing Group
    Nature 441 (2006), S. 610-613 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Palaeocene/Eocene thermal maximum, ∼55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04668
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    Paper (German National Licenses)
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  • 4
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    Salinity control on Na incorporation into calcite tests of the planktonic foraminifera Trilobatus sacculifer – Evidence from culture experiments and surface sediments (2018)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 15 (20). pp. 5991-6018.
    Details
    Publication Date: 2021-03-18
    Description: The quantitative reconstruction of past seawater salinity has yet to be achieved and the search for a direct and independent salinity proxy is ongoing. Recent culture and field studies show a significant positive correlation of Na/Ca with salinity in benthic and planktonic foraminiferal calcite. For accurate paleoceanographic reconstructions, consistent and reliable calibrations are necessary, which are still missing. In order to assess the reliability of foraminiferal Na/Ca as a direct proxy for seawater salinity, this study presents electron microprobe Na/Ca data, measured on cultured specimens of Trilobatus sacculifer. The culture experiments were conducted over a wide salinity range of 26 to 45, while temperature was kept constant. To further understand potential controlling factors of Na incorporation, measurements were also performed on foraminifera cultured at various temperatures in the range of 19.5 °C to 29.5 °C under constant salinity conditions. Foraminiferal Na/Ca ratios positively correlate with seawater salinity (Na/Caforam = 0.97 + 0.115 ⋅ Salinity, R = 0.97, p 〈 0.005). Temperature on the other hand exhibits no statistically significant relationship with Na/Ca ratios indicating salinity to be the dominant factor controlling Na incorporation. The culturing results are corroborated by measurements on T. sacculifer from Caribbean and Gulf of Guinea surface sediments. In conclusion, planktonic foraminiferal Na/Ca can be applied as a reliable proxy for reconstructing sea surface salinities, albeit species-specific calibrations might be necessary.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-15-5991-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Ocean Acidification Reduces Growth and Calcification in a Marine Dinoflagellate (2013)
    Public Library of Science
    In:  PLoS ONE, 8 (6). e65987.
    Details
    Publication Date: 2014-04-22
    Description: Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1371/journal.pone.0065987
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  • 6
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    Incorporation of uranium in benthic foraminiferal calcite reflects seawater carbonate ion concentration (2013)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (1). pp. 102-111.
    Details
    Publication Date: 2013-10-28
    Description: The chemical and isotopic composition of foraminiferal shells (so-called proxies) reflects the physico-chemical properties of the seawater. In current day paleoclimate research, the reconstruction of past seawater carbonate system to infer atmospheric CO2 concentrations is one of the most pressing challenges and a variety of proxies have been investigated, such as foraminiferal U/Ca. Since in natural seawater and traditional CO2 perturbation experiments, the carbonate system parameters co-vary, it is not possible to determine the parameter of the carbonate system causing e.g. changes in U/Ca, complicating the use of the latter as a carbonate system proxy. We overcome this problem, by culturing the benthic foraminifer Ammonia sp. at a range of carbonate chemistry manipulation treatments. Shell U/Ca values were determined to test sensitivity of U incorporation to various parameters of the carbonate system. We argue that [CO32-] is the parameter affecting the U/Ca ratio and consequently, the partitioning coefficient for U in Ammonia sp DU. We can confirm the strong potential of foraminiferal U/Ca as a [CO32-] proxy.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1029/2012GC004330
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Anti-cyclonic eddy imprint on calcite geochemistry of several planktonic foraminiferal species in the Mozambique Channel (2014)
    Elsevier
    In:  Marine Micropaleontology, 113 . pp. 20-33.
    Details
    Publication Date: 2017-06-21
    Description: Highlights: • We coupled LA-ICP-MS Me/Ca single-chamber composition of four planktonic foraminifera with eddy induced hydrographic changes • The Mg/Ca-based temperature difference between N. dutertrei and G. scitula are likely to be an eddy proxy suitable for down-core application • Near-surface dwelling species inhabit well oxygenated surface waters and show lower test Mn/Ca values, compared to deeper dwelling species • Planktonic foraminifera Mn/Ca test values are in line with water column variability in dissolved Mn concentrations Hydrographic conditions in the Mozambique Channel are dominated by the passing of large anticyclonic eddies, propagating poleward into the upstream Agulhas area. Further south, these eddies have been found to control the shedding of Agulhas rings into the Atlantic ocean, thereby playing a key role in Indo-Atlantic Ocean exchange. The element composition of several planktonic foraminifera species collected from sediment trap samples, was compared to in situ water column data from the Mozambique Channel. Single-chamber trace element composition of these foraminifera reveals a close coupling with hydrographic changes induced by anticyclonic eddies. Obtained Mg/Ca values for the surface dwelling Globigerinoides ruber as well as the thermocline dwelling Neogloboquadrina dutertrei follow temperature changes and reduced temperature stratification during eddy conditions. At greater depth. Globorotalia scitula and Pulleniatina obliquiloculata record stable temperatures and thus respond to hydrographic changes with a deepening in habitat depth. Furthermore, test Mn/Ca values indicate a close relationship between water column oxygenation and Mn incorporation in these planktonic foraminiferal species
    Type: Article , PeerReviewed
    Format: other
    Format: other
    Format: text
    DOI: 10.1016/j.marmicro.2014.09.001
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Foraminiferal Mg/Ca increase in the Caribbean during the Pliocene: Western Atlantic Warm Pool formation, salinity influence, or diagenetic overprint? (2008)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 9 . Q01P23.
    Details
    Publication Date: 2018-03-07
    Description: We constructed a high-resolution Mg/Ca record on the planktonic foraminifer Globigerinoides sacculifer in order to explore the change in sea surface temperature (SST) due to the shoaling of the Isthmus of Panama as well as the impact of secondary factors like diagenesis and large salinity fluctuations. The study covers the latest Miocene and the early Pliocene (5.6–3.9 Ma) and was combined with δ18O to isolate changes in sea surface salinity (SSS). Before 4.5 Ma, SSTMg/Ca and SSS show moderate fluctuations, indicating a free exchange of surface ocean water masses between the Pacific and the Atlantic. The increase in δ18O after 4.5 Ma represents increasing salinities in the Caribbean due to the progressive closure of the Panamanian Gateway. The increase in Mg/Ca toward values of maximum 7 mmol/mol suggests that secondary influences have played a significant role. Evidence of crystalline overgrowths on the foraminiferal tests in correlation with aragonite, Sr/Ca, and productivity cyclicities indicates a diagenetic overprint on the foraminiferal tests. Laser ablation inductively coupled plasma–mass spectrometry analyses, however, do not show significantly increased Mg/Ca ratios in the crystalline overgrowths, and neither do calculations based on pore water data conclusively result in significantly elevated Mg/Ca ratios in the crystalline overgrowths. Alternatively, the elevated Mg/Ca ratios might have been caused by salinity as the δ18O record of Site 1000 has been interpreted to represent large fluctuations in SSS, and cultivating experiments have shown an increase in Mg/Ca with increasing salinity. We conclude that the Mg/Ca record 〈4.5 Ma can only reliably be considered for paleoceanographical purposes when the minimum values, not showing any evidence of secondary influences, are used, resulting in a warming of central Caribbean surface water masses after 4.5 Ma of ∼2°C.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2006GC001564
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  • 9
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    Orbitally forced Azolla blooms and Middle Eocene Arctic hydrology: Clues from palynology (2011)
    Geological Society of America (GSA)
    Details
    Publication Date: 2011-05-01
    Description: The high abundances and cyclic distribution of remains of the freshwater fern Azolla in early-Middle Eocene sediments from the Arctic Ocean have previously been related to episodic surface-water freshening, which was speculated to be orbitally modulated. Our integrated palynological and cyclostratigraphical analysis of the recovered Azolla interval in Integrated Ocean Drilling Program (IODP) core 302-M0004A-11X resulted in the recognition of two clear periodicities: a dominant [~]1.2 m cyclicity, which we relate to changes in obliquity ([~]40 k.y.), and a weaker [~]0.7 m cyclicity, which we link to precession ([~]21 k.y.). Cycles in the abundances of Azolla, cysts of freshwater-tolerant dinoflagellates, and swamp-vegetation pollen show covariability in the obliquity domain. This strong correlation suggests periods of enhanced rainfall and runoff during Azolla blooms, presumably linked to increased local summer temperatures during obliquity maxima. Larix and bisaccate conifer pollen covary at the precession frequency, with peak occurrences corresponding to precession minima, possibly as a result of enhanced continental runoff from a more remote source area and a stronger seasonal contrast. Following the sudden demise of Azolla ca. 48.1 Ma, runoff (cycles) continued to influence the central Arctic at decreased intensity. This and a concomitant decline in swamp-vegetation pollen suggest edaphically drier conditions on land and decreased runoff into the Arctic Ocean, causing salinity changes, which might have been fatal for Azolla. Moreover, a sea-level rise, inferred from overall decreasing total terrestrial palynomorph concentrations, possibly facilitated oceanic connections.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 10
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    Planktonic foraminiferal spine versus shell carbonate Na incorporation in relation to salinity (2019)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 16 (6). pp. 1147-1165.
    Details
    Publication Date: 2022-01-31
    Description: Sea surface salinity is one of the most important parameters to reconstruct in paleoclimatology, reflecting amongst others the hydrological cycle, paleo-density, ice volume, and regional and global circulation of water masses. Recent culture studies and a Red Sea field study revealed a significant positive relation between salinity and Na incorporation within benthic and planktonic foraminiferal shells. However, these studies reported varying partitioning of Na between and within the same species. The latter could be associated with ontogenetic variations, most likely spine loss. Varying Na concentrations were observed in different parts of foraminiferal shells, with especially spines and regions close to the primary organic sheet being enriched in Na. In this study, we unravel the Na composition of different components of the planktonic foraminiferal shell wall using Electron Probe Micro Analysis (EPMA) and solution-ICP-MS. A model is presented to interpret EPMA data for spines and spine bases to quantitatively assess differences in composition and contribution to whole shell Na/Ca signals. The same model can also be applied to other spatial inhomogeneities observed in foraminiferal shell chemistry, like elemental (e.g. Mg, Na, S) banding and/or hotspots. The relative contribution of shell calcite, organic linings, spines and spine bases to whole shell Na chemistry is considered quantitatively. This study shows that whereas the high Na areas may be susceptible to taphonomy, the Na chemistry of the shell itself seems relatively robust. Comparing both shell and spine Na/Ca values with salinity shows that shell chemistry records salinity, albeit with a very modest slope.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.5194/bg-16-1147-2019
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