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  • 1
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    Springer
    In:  Norwell, Springer, vol. 6, no. 3, pp. 2-203, (ISBN: 3-540-26532-5, XVI + 208 p. 72 illus.)
    Publication Date: 2005
    Keywords: FractureT ; Seismology ; Geoelectrics ; Electromagnetic methods/phenomena ; Geothermics ; Non-linear effects ; Dynamic ; Earth ; system ; geophysics ; Inhomogeneity ; scaling
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  • 2
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    Cambridge University Press
    In:  Cambridge, UK, Cambridge University Press, vol. 10, no. 1, pp. 1-40, (ISBN 0-521-84678-1 (550 pp.))
    Publication Date: 2005
    Description: ... Overall, An Introduction to Programming with Mathematica is a useful and readable book that could serve as the text for a generic programming class, a supporting text for a class on programming for geoscientists, or an introduction for experienced geoscience programmers looking for an easily readable summary of Mathematica's programming language. Experienced Mathematica programmers may find it useful as a refresher. The book's principal drawbacks are the high price of Mathematica for those who do not already have the software (although a modestly priced student version is available) and, for geoscientists in particular, a lack of relevant example problems
    Keywords: Handbook of mathematics ; computer ; algebra ; software
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  • 3
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    Elsevier
    In:  Advances in Geophysics, ed.: Renata Dmowska, Warszawa, Elsevier, vol. 47, no. 7, pp. 65-111, pp. L21303, (ISBN: 0-12-018847-3)
    Publication Date: 2005
    Keywords: Fault zone ; Rock mechanics ; Friction ; Fracture ; Physical properties of rocks ; geometry
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  • 4
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    Elsevier
    In:  Advances in Geophysics, ed.: Renata Dmowska, Heidelberg, Elsevier, vol. 47, no. 8, pp. 1-64, pp. 1516, (ISBN: 0-12-018847-3)
    Publication Date: 2005
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Subduction zone ; USA
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  • 5
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    Springer
    In:  Amsterdam, Springer, vol. 1, pp. 225, (1-4020-3353-2)
    Publication Date: 2005
    Keywords: Tsunami(s) ; Earthquake risk ; Earthquake precursor: prediction research ; Review article ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Modelling ; NATHAZ ; measurement, ; tsunami ; model, ; data ; assimilation, ; data ; inversion, ; tsunami ; warning, ; tsunameters, ; forecast, ; hazard ; mitigation
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  • 6
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    Springer
    In:  New York, 390 pp., Springer, vol. 36, no. XVI:, pp. 1-14, (ISBN 3-211-23584-1)
    Publication Date: 2005
    Description: Motivation, Fundamentals of potential theory The gravity field of the earth, Gravity reduction, Heights The geometry of the earth, Gravity field outside the earth, Space methods Modern views on the determination of the figure of the earth Statistical methods in physical geodesy, Least-squares collocation Computational methods, References, Subject index
    Keywords: Textbook of geodesy ; Global Positioning System ; Geoid ; Gravimetry ; Potential ; Theory ; Reference ; Systems ; collocation ; geodetic ; satellite ; techniques ; heights
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  • 7
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    Springer
    In:  Berlin, Heidelberg, New York, Springer, vol. 4, no. 85, pp. 175, (ISBN 3-540-24988-5)
    Publication Date: 2005
    Keywords: Textbook of informatics ; Earthquake hazard ; Earthquake risk ; Tsunami(s) ; Proceedings of a conference ; INSPIRE ; OpenGIS ; GIS ; floods ; landslides ; storms ; geography ; Delft ; GFZ ; M ; 06.0234 ; 000303921
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  • 8
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    Springer
    In:  Basel, Switzerland, Springer, vol. 20, no. Publ. No. 12, pp. 23-40, (ISBN 1-4020-3326-5, VIII + 343 pp.)
    Publication Date: 2005
    Description: Twenty papers comprise a timely review of state-of-the-art tsunami research. Various approaches are taken to study tsunamis: field-surveys of recent tsunamis; analysis of tide-gauge records; numerical simulations of tsunami generation and propagation, tank experiments, and geological studies of tsunami deposits.
    Keywords: GFZ ; M ; 06.0379 ; 000304412
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  • 9
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    Springer
    In:  Professional Paper, Perspectives in Modern Seismology, Berlin, Springer, vol. 105, 223 pp., no. 231, pp. 13-30, (ISBN: 3-540-23712-7)
    Publication Date: 2005
    Keywords: Earthquake risk ; Site amplification ; Strong motions ; Earthquake engineering, engineering seismology ; Synthetic seismograms ; NOISE ; Nakamura ; Modelling ; Cologne ; DFNK ; Faecke ; Facke
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  • 10
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    Elsevier
    In:  Amsterdam, 652 pp., Elsevier, vol. 39, no. XVI:, pp. 227-235, (0-444-51955-6)
    Publication Date: 2005
    Keywords: Seismics (controlled source seismology) ; Applied geophysics ; Wave propagation ; plane ; spherical ; and ; cylindrical ; Waves ; in ; isotropic ; and ; transversely ; isotropic ; solids, ; liquid-solid ; models, ; and ; media ; with ; cylindrical ; inclusions ; (boreholes) ; Textbook of geophysics
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  • 11
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    Cambridge University Press
    In:  Cambridge, Cambridge University Press, vol. 7, no. Publ. No. 12, pp. 127, (ISBN: 0521839270, 520 p.)
    Publication Date: 2005
    Description: Fundamentals of Structural Geology provides a new framework for the investigation of geological structures by integrating field mapping and mechanical analysis. Assuming a basic knowledge of physical geology, introductory calculus and physics, it emphasizes the observational data, modern mapping technology, principles of continuum mechanics, and the mathematical and computational skills, necessary to quantitatively map, describe, model, and explain deformation in Earth's lithosphere. By starting from the fundamental conservation laws of mass and momentum, the constitutive laws of material behavior, and the kinematic relationships for strain and rate of deformation, the authors demonstrate the relevance of solid and fluid mechanics to structural geology. This book offers a modern quantitative approach to structural geology for advanced students and researchers in structural geology and tectonics. It is supported by a website hosting images from the book, additional colour images, student exercises and MATLAB scripts. Solutions to the exercises are available to instructors
    Keywords: Structural geology ; Textbook of geology ; MATLAB ; scripts ; Tectonics ; Lithosphere
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  • 12
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    Springer
    In:  Geo-Information for Disaster Management, Berlin, Heidelberg, New York, Springer, vol. 12, pp. 323-336, (ISBN 3-540-24988-5)
    Publication Date: 2005
    Keywords: Textbook of informatics ; Earthquake hazard ; Earthquake risk ; Tsunami(s) ; Proceedings of a conference ; Earthquake ; Indonesia ; Geodesy
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  • 13
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    Springer
    In:  Professional Paper, Perspectives in Modern Seismology, Dordrecht, Springer, vol. 65, no. 16, pp. 145-168, (ISBN 0080419208)
    Publication Date: 2005
    Keywords: paleo ; Seismicity ; Fault zone ; DSTF ; Seismology ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Bucharest ; Romania ; Earthquake risk
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  • 14
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    Springer
    In:  Bull., Polar Proj. OP-O3A4, Perspectives in Modern Seismology, London, Springer, vol. 201, no. XVI:, pp. 169-184, (ISBN: 3-540-23712-7)
    Publication Date: 2005
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Geodesy ; Finite Element Method ; Modelling ; Three dimensional ; Seismology ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Bucharest ; Romania ; Earthquake risk
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  • 15
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    Springer
    In:  Bull., Polar Proj. OP-O3A4, Perspectives in Modern Seismology, Dordrecht, Springer, vol. 20, no. 4, pp. 47-65, (ISBN 0080419208)
    Publication Date: 2005
    Keywords: Non-linear effects ; Seismology ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Bucharest ; Romania ; Earthquake risk
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  • 16
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    Springer
    In:  Bull., Open-File Rept., Perspectives in Modern Seismology, Arnsberg-Neheim, Springer, vol. 10, no. 87-17, pp. 69-94, (ISBN 0080419208)
    Publication Date: 2005
    Keywords: Plate tectonics ; hot ; spots ; GeodesyY ; Tomography ; Seismology ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Bucharest ; Romania
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  • 17
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    Springer
    In:  Professional Paper, Open-File Rept., Perspectives in Modern Seismology, Berlin, Springer, vol. 1, no. 16, pp. 1-12, (ISBN 0080419208)
    Publication Date: 2005
    Keywords: Review article ; Seismology ; Early warning systems (earthquakes, volcanic eruptions, tsunamis etc.) ; Bucharest ; Romania ; Earthquake risk
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  • 18
    Publication Date: 2021-06-04
    Description: Food supply is one of the main factors driving cold-water corals (CWC) distribution, which often concentrate on ridges where local near-bed turbulence/strong currents enhance food availability. However, efficiency in food capture is strongly dependent on current velocity. Moreover, seawater temperature may also affect feeding success, since polyp contraction or nematocyst function could be slower at temperatures below the natural thermal range of a species. The non-reef forming CWC Dendrophyllia cornigera occurs in areas at temperatures from 11 to 17 °C, but is apparently absent from most CWC reefs at temperatures constantly below 11 °C. This study thus aimed to assess if a reduction in feeding capacity may contribute to understand the absence of this CWC from strictly cold environments. The efficiency of D. cornigera to capture meso- and macrozooplankton was assessed under different flow speeds (2, 5 and 10 cm s − 1) and temperatures (8, 12, and 16 °C). Flow speeds did not significantly affect the capture of mesozooplankton, whereas capture of macrozooplankton was significantly enhanced with increasing flow speed. Both meso- and macrozooplankton captures were not significantly affected by temperature in D. cornigera. Overall, this CWC species is efficient in capturing zooplankton under a larger range of flow velocities than the widespread CWC Lophelia pertusa, whose capture efficiency significantly decreased from low to high flow speeds. Even if temperature does not directly affect the capture rates of D. cornigera, it may still influence the feeding capacity of this CWC since the capture rates at 8 °C were always in the lowest range of the observed values at each flow speed, and corals maintained at 8 °C required a much longer time to fully expand their polyps once they were placed in the incubation chambers, than corals maintained at 12 and 16 °C.
    Type: Article , PeerReviewed
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  • 19
    Publication Date: 2018-02-05
    Description: Recent work has shown that glaciers are a globally significant source of the micronutrient Fe to the ocean. Polar regions are particularly susceptible to climate change and have been subject to pronounced warming in the past few decades. In response to this warming, the volume of glacial meltwater runoff from Greenland has increased. This meltwater has a relatively high particulate and dissolved Fe content. Seasonal Fe limitation of marine ecosystems has been found in parts of the North Atlantic, so it has been proposed that increasing fluxes of Fe rich meltwater from Greenland to the North Atlantic could alleviate this Fe limitation and thereby increase marine primary production. However, here we use a synthesis of biogeochemical and physical oceanography studies to suggest that the physical circulation around Greenland does not favour direct export of dissolved or particulate Fe from inshore to offshore waters. The Fe budget in surface waters of the North Atlantic may therefore be insensitive to increasing meltwater fluxes from Greenland.
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  • 20
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    Springer
    In:  In: Evolution of Lightweight Structures. Biologically-inspired systems, 6 . Springer, Dordrecht, pp. 39-58.
    Publication Date: 2017-07-20
    Description: While the geometries of diatom frustules have been investigated in detail, the processes leading to their formation—morphogenesis and biomineralization—are not well understood. The study of organic templates, which are suspected to be important for biosilicification of diatoms, have been mainly investigated on the basis of diverse demineralization techniques. In contrast to naturally occurring dissolution of diatom cell walls in natural habitats, all experiments in vitro were based on chemical reagents including HF- or alkali-based techniques with addition of some additives as presented in this chapter. Mostly, the amino acids (serine, threonine, hydrohyproline) diverse proteinaceous materials (frustulins, pleuralins, silaffins, silacidins, circulins) as well as polyamines have been proposed to regulate biosilicification in vivo in diatoms. In this chapter, we review the biochemical pathways and potential functions of these chemical compounds and their roles in the biomineralization process. In addition, we demonstrate the presence of chitin and discuss its potential as scaffolding as well as a template material in siliceous cell walls of diatoms. The current findings show that a complex network of different organic components is responsible for the biomineralization of diatoms. Since both the organic network and the precipitated silica are integrated in the material which forms the diatom frustule, the material properties must differ from that of pure silica. As the material properties are a crucial factor for the defensive performance of the frustule and thus their survival, it is likely that organic templates for silicification play a role both for the development process and for the improvement of the material properties of the finished shells.
    Type: Book chapter , NonPeerReviewed
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  • 21
    Publication Date: 2018-02-05
    Description: Submarine groundwater discharge (SGD) is an important component of chemical fluxes in the coastal ocean. The composition of SGD is influenced by biogeochemical reactions that take place within the subterranean estuary (STE), the subsurface mixing zone of fresh and saline groundwaters. The STE is characterized by redox gradients that affect the speciation and mobility of redox-sensitive elements (RSEs). We examined the distributions and behavior of the RSEs Mo, U, V, and Cr within the larger redox framework of a shallow STE and evaluated the source-sink function of the STE for these elements. We found that the advection of water through the STE and the apparent respiration of organic matter drives the formation of a “classic” redox sequence typically observed in diffusion-dominated fine-grained sediments. High concentrations of dissolved organic matter (up to 2.9 mM) lead to extensive sulfide production (up to 1.8 mM) within 3 m of the surface. Both Mo and U are quantitatively removed as oxic surface waters mix into ferruginous and sulfidic zones. Molybdenum removal appears to occur where sulfide concentrations exceed ~ 11 μM, a previously reported threshold for quantitative formation of highly particle-reactive thiomolybdate species. Uranium removal apparently occurs via reduction and formation of insoluble phases or sorption to sediments. It is not clear how readily sequestered metals may be returned to solution, but SGD may be an important sink in the marine budget for both Mo and U. In contrast, both V and Cr show non-conservative addition across the salinity mixing gradient. Increases in pH appear to promote dissolution of V from minerals within the shallow aquifer, and mobilization may also be associated with dissolved organic matter. Chromium enrichment is associated with higher dissolved organic matter and is likely due to the formation of soluble Cr-organic complexes. Fluxes of these elements were constrained using SGD volume fluxes, determined using radium isotopes as well as direct discharge measurements by Lee-type seepage meters, and concentrations in directly-sampled seepage (Mo: − 0.21 to − 7.7 μmol m− 2 day− 1; U: − 0.02 to − 0.6 μmol m− 2 day− 1; V: 0.05 to 2.0 μmol m− 2 day− 1; Cr: 0.12 to 4.4 μmol m− 2 day− 1).
    Type: Article , PeerReviewed
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  • 22
    Publication Date: 2017-12-13
    Description: The Neoarchean-Paleoproterozoic Transvaal Supergroup in South Africa contains the well-preserved stromatolitic Campbellrand-Malmani carbonate platform, which was deposited in shallow seawater shortly before the 2.40–2.32 Ga Great Oxidation Event (GOE). This platform is composed of alternating stromatolitic carbonates and mudstones and is a prominent candidate for (isotope-) geochemical mapping to investigate the appearance of very small amounts of free oxygen that accumulated in shallow waters preceding the GOE. Mo isotopes in sedimentary archives are widely used as a proxy for redox-changes in modern and ancient environments and recent evidence suggests that oxy-molybdate (MoO42−) is directly transferred from ocean water to inorganic carbonates with negligible fractionation, thus reflecting oceanic Mo isotope signatures. In this study we analyzed major and trace element compositions as well as Mo isotopic compositions of carbonate and mudstone samples from the KMF-5 drill core. Geochemical indicators, such as Fe and Mn concentrations and Fe-to-Mn abundance ratios reveal the preservation of some geochemical indicators despite the widespread silicification and dolomitization of the platform. Heavy δ30Si values of silicified carbonates between 0.53 and 2.35‰ point to Si precipitation from surface water during early diagenesis rather than to a later hydrothermal overprint. This assessment is supported by the frequent observation of rip-up structures of silica (chert) layers within the entire sedimentary succession. The δ98Mo values of whole rock samples throughout the Malmani-Campbellrand platform range between −0.82 and +1.40‰, similar to values reported for deeper slope carbonates from the Griqualand West area, but variations are independent from lithology or depositional water depth. These large variations in δ98Mo values indicate molybdenum redox cycling and thus the presence of free oxygen in the atmosphere-ocean system at that time, in agreement with earlier Mo isotopic studies on Campbellrand carbonates and shales. A similar range in δ98Mo values for carbonates between +0.40 and +0.87‰, however, was also found on the hand specimen scale, indicating the danger of a sample bias on the Mo isotopic stratigraphy of this carbonate platform. Results of previously unpublished adsorption experiments of Mo on CaCO3 clearly indicate that the Mo inventory of Malmani-Campbellrand carbonates was not only influenced by primary adsorption from seawater, but to a much larger degree by secondary processes during early diagenesis, which also affected the Mo isotopic composition of the samples on a local scale. Our results indicate that Mo concentrations and isotopic compositions in ancient stromatolitic carbonates were subject to redox changes within microbial mats and within the soft sediment during early diagenesis and later lithification, and as such cannot be used to quantitatively reconstruct the amount of free atmospheric oxygen or its fluctuations through Earth's history. Nevertheless, we interpret our heavy Mo isotopic signatures from carbonates as a minimum value for Neoarchean seawater and reinforce the assumption that free atmospheric oxygen built up a heavy oceanic Mo reservoir at that time.
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  • 23
    Publication Date: 2020-11-02
    Description: Pteropods are important organisms in high-latitude ecosystems, and they are expected to severely suffer from climate change in the near future. In this study, sedimentation patterns of two pteropod species, the polar Limacina helicina and the subarctic boreal L. retroversa, are presented. Time series data received by moored sediment traps at the Long-Term Ecological Research (LTER) Observatory HAUSGARTEN in eastern Fram Strait were analyzed during the years 2008 to 2012. Results were derived from four different deployment depths (~200, 1,250, 2,400, and 2,550 m) at two different sites (79°N 04°20′E; 79°43′N 04°30′E). A species-specific sedimentation pattern was present at all depths and at both sites showing maximal flux rates during September/October for L. helicina and in November/December for L. retroversa. The polar L. helicina was outnumbered by L. retroversa (55–99 %) at both positions and at all depths supporting the recently observed trend toward the dominance of the subarctic boreal species. The largest decrease in pteropod abundance occurred within the mesopelagic zone (~200–1,250 m), indicating loss via microbial degradation and grazing. Pteropod carbonate (aragonite) amounted up to ~75 % of the total carbonate flux at 200 m and 2–13 % of the aragonite found in the shallow traps arrived at the deep sediment traps (~160 m above the seafloor), revealing the significance of pteropods in carbonate export at Fram Strait. Our results emphasize the relevance and the need for continuation of long-term studies to detect and trace changes in pteropod abundances and community composition and thus in the vertical transport of aragonite.
    Type: Article , PeerReviewed
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  • 24
    Publication Date: 2020-07-28
    Description: Carbohydrates on parasite surfaces have been shown to play an important role in host–parasite coevolution, mediating host non-self recognition and parasite camouflage. Parasites that switch hosts can change their surface molecules to remain undetected by the diverse immune systems of their different hosts. However, the question of individual variation in surface sugar composition and its relation to infectivity, virulence, immune evasion and growth of a parasite in its different hosts is as yet largely unexplored. We studied such fitness consequences of variation in surface sugars in a sympatric host–parasite system consisting of the cestode Schistocephalus solidus and its intermediate hosts, a copepod and the three-spined stickleback. Using lectins to analyse the sugar composition, we show that the tapeworm changes its surface according to the invertebrate or vertebrate host. Importantly, sugar composition seems to be genetically variable, as shown by differences among tapeworm sibships. These differences are related to variation in parasite fitness in its second intermediate host, i.e. infectivity and growth. Surface sugar composition may thus be a proximate correlate of the evolutionarily relevant variability in infectivity and virulence of parasites in different hosts.
    Type: Article , PeerReviewed
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  • 25
    Publication Date: 2017-03-24
    Description: The March 13th 1888 collapse of Ritter Island in Papua New Guinea is the largest known sector collapse of an island volcano in historical times. One single event removed most of the island and its western submarine flank, and produced a landslide deposit that extends at least 70 km from the headwall of the collapse scar. We have mapped and described the deposits of the debris avalanche left by the collapse using full-coverage multibeam bathymetry, side-scan sonar backscatter intensity mapping, chirp seismic-reflection profiles, TowCam photographs of the seafloor and samples from a single dredge. Applying concepts originally developed on the 1980 Mount St. Helens collapse landslide deposits, we find that the Ritter landslide deposits show three distinct morphological facies: large block debris avalanche, matrix-rich debris avalanche and distal debris flow facies. Restoring the island's land and submarine topography we obtained a volume of 4.2 km3 for the initial collapse, about 75% of which is now forming the large block facies at distances less than 12 km from the collapse scar. The matrix-rich facies volume is unknown, but large scale erosion of the marine sediment substrate yielded a minimum total volume of 6.4 km3 in the distal debris flow and/or turbidite deposits, highlighting the efficiency of substrate erosion during the later history of the landslide movement. Although studying submarine landslide deposits we can never have the same confidence that subaerial observations provide, our analysis shows that well-exposed submarine landslide deposits can be interpreted in a similar way to subaerial volcano collapse deposits, and that they can in turn be used to interpret older, incompletely exposed submarine landslide deposits. Studying the deposits from a facies perspective provides the basis for reconstructing the kinematics of a collapse event landslide; understanding the mechanisms involved in its movement and deposition; and so providing key inputs to tsunami models.
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  • 26
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    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 463 . pp. 125-134.
    Publication Date: 2017-12-14
    Description: The Mediterranean mid-littoral zone is inhabited by two sympatric chthamalid barnacles: Chthamalus stellatus and Euraphia depressa, C. stellatus extends from the high midtidal zone, above the algal belt, to the supra-littoral fringe, E. depressa is restricted to the uppermost intertidal levels in wave-beaten places and to cryptic habitats lower on the shore within the belt of C. stellatus. Previous studies have suggested that the reason for the fragmented distribution pattern of E. depressa is competitive displacement by the sympatric C. stellatus, following random settlement. This hypothesis is in agreement with the common model of zonation suggested by Connell that lower distribution limits are determined by biotic factors (competition and predation), while upper limits are set by physical factors. It is hard to test the validity of this model for this barnacle pair since the early ontogenetic stages of the species are morphologically indistinguishable, hindering our ability to understand distribution processes. Using 16S mtDNA as a genetic marker in a multiplex PCR system, cyprids and spats were individually identified. Settlement and recruitment rates were assessed using settlement plates, and the effect of post-settlement processes was tested with transplantation of settlers between zones. Results showed different strategies in each species: settlement of E. depressa was habitat-specific, while settlement of C. stellatus was random. Shifting individuals of C. stellatus to the high and cryptic zones resulted in high mortality; however, exposing juveniles of E. depressa that settled in artificially cryptic low shore habitat to C. stellatus presence had no effect on their survival. These finding do not agree with the formerly suggested hypothesis that zonation is mainly determined by post-settlement factors, and that the interspecies boundary is determined by interspecific competition, implying that competition model cannot be adapted to Mediterranean intertidal zonation and that other models, dominated by physical enforcement and pre-settlement recruitment-limiting factors, may prevail in this ecosystem.
    Type: Article , PeerReviewed
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  • 27
    Publication Date: 2017-12-13
    Description: We present whole rock 187Os/188Os data for the most mafic lavas along the Lesser Antilles arc (MgO = 5–17 wt.%) and for the subducting basalt and sediments. 187Os/188Os ratios vary from 0.127 to 0.202 in the arc lavas. Inverse correlations between 187Os/188Os and Os concentrations and between 187Os/188Os and indices of differentiation such as MgO suggests that assimilation, rather than source variation, is responsible for the range of Os isotopic variation observed. 87Sr/86Sr, La/Sm and Sr/Th are also modified by assimilation since they all correlate with 187Os/188Os. The assimilant is inferred to have a MORB-like 87Sr/86Sr with high Sr (〉700 ppm), low light on middle and heavy rare earth elements (L/M-HREE; La/Sm ∼2.5) and 187Os/188Os 〉 0.2. Such compositional features are likely to correspond to a plagioclase-rich early-arc cumulate. Given that assimilation affects lavas that were last stored at more than 5 kbar, assimilation must occur in the middle-lower crust. Only a high MgO picrite from Grenada escaped obvious assimilation (MgO = 17% wt.%) and could reflect mantle source composition. It has a very radiogenic 87Sr/86Sr (0.705) but a 187Os/188Os ratio that overlaps the mantle range (0.127). 187Os/188Os and 87Sr/88Sr ratios of the sediments and an altered basalt from the subducting slab vary from 0.18 to 3.52 and 0.708 to 0.714. We therefore suggest that, unlike Sr, no Os from the slab was transferred to the parental magmas. Os may be either retained in the mantle wedge or even returned to the deep mantle in the subducting slab.
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  • 28
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    Elsevier
    In:  Tectonophysics, 405 (1-4). pp. 121-140.
    Publication Date: 2019-04-29
    Description: The Hawaiian–Emperor Seamount chain records the motion of the Pacific Plate relative to the Hawaiian mantle hotspot for ~80 m.y. A notable feature of the chain is the pronounced bend at its middle. This bend had been widely credited to a change in plate motion, but recent research suggests a change in hotspot motion as an alternative. Existing paleomagnetic data from the Emperor Chain suggest that the hotspot moved south during the Late Cretaceous and Early Tertiary, but reached its current latitude by the age of the bend. Thus, data from area of the bend are important for understanding changes in plume latitude. In this study, we analyze the magnetic anomalies of five seamounts (Annei, Daikakuji-W, Daikakuji- E, Abbott, and Colahan) in the region of the bend. These particular seamounts were chosen because they have been recently surveyed to collect multibeam bathymetry and magnetic data positioned with GPS navigation. Inversions of the magnetic and bathymetric data were performed to determine the mean magnetization of each seamount and from these results, paleomagnetic poles and paleolatitudes were calculated. Three of the five seamounts have reversed magnetic polarities (two are normal) and four contain a small volume of magnetic polarity opposite to the main body, consistent with formation during the Early Cenozoic, a time of geomagnetic field reversals. Although magnetization inhomogene ties can degrade the accuracy of paleomagnetic poles calculated from such models, the seamounts give results consistent with one another and with other Pacific paleomagnetic data of approximately the same age. Seamount paleolatitudes range from 13.7 to 23.7, with an average of 19.4F7.4 (2j). These values are indistinguishable from the present-day paleolatitude of the Hawaiian hotspot. Together with other paleomagnetic and geologic evidence, these data imply that the Hawaiian hotspot has moved little in latitude during the past ~45 m.y.
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  • 29
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    Elsevier
    In:  In: Treatise on Geophysics. , ed. by Schubert, G. Elsevier, Amsterdam, pp. 277-305.
    Publication Date: 2017-12-04
    Description: Seismic anisotropy is common within the Earth's solid interior, in the crust, in the mantle, and in the inner core. Elastic anisotropy leads to direction-dependent wave velocities, shear-wave splitting, and polarization anomalies in both surface waves and body waves. We review the basic theory and the latest developments in modeling methods for seismic-wave propagation in anisotropic media. From mineral alignment to fine-layering effects and from mid-oceanic ridges and subduction zones to sutured continental terranes, we summarize the seismological observations that can be related to elastic anisotropy, the mechanisms proposed to explain it, and the geodynamic constraints that it offers.
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  • 30
    Publication Date: 2018-03-07
    Description: The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test, biasing any resulting paleoenvironmental reconstruction. The δ11B of planktic foraminiferal calcite is a promising ocean pH-proxy but the effect of diagenesis is still poorly known. Here we present new δ11B, δ13C, δ18O, Sr/Ca and B/Ca data from multiple species of planktic foraminifera from time-equivalent samples for two low latitude sites: clay-rich Tanzanian Drilling Project (TDP) Site 18 from the Indian Ocean containing well-preserved (‘glassy’) foraminifera and carbonate-rich Ocean Drilling Program (ODP) Site 865 from the central Pacific Ocean hosting recrystallized (‘frosty’) foraminifera. Our approach makes the assumption that environmental conditions were initially similar at both sites so most chemical differences are attributable to diagenesis. Planktic foraminiferal δ18O and δ13C records show offsets in both relative and absolute values between the two sites consistent with earlier findings that these isotopic ratios are strongly influenced by diagenetic alteration. Sr/Ca and B/Ca ratios in planktic foraminiferal calcite are also offset between the two sites but there is little change in the relative difference between surface and deep dwelling taxa. In contrast, δ11B values indicate no large differences between well-preserved and recrystallized foraminifera suggesting that despite extensive diagenetic alteration the δ11B of biogenic calcite appears robust, potentially indicative of a lack of free exchange of boron between pore fluids and the recrystallizing CaCO3. Our finding may remove one potential source of uncertainty in δ11B based pH reconstructions and provide us with greater confidence in our ability to reconstruct pH in the ancient oceans from at least some recrystallized foraminiferal calcite. However, further investigations should extend this approach to test the robustness of our findings across a range of taphonomies, ages and burial settings.
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  • 31
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    Springer
    In:  In: Marine Protists. , ed. by Ohtsuka, S., Suzaki, T., Horiguchi, T., Suzuki, N. and Not, F. Springer, Tokyo, pp. 179-222.
    Publication Date: 2018-03-23
    Description: Radiolaria are unicellular holoplanktonic protozoa with siliceous or strontium sulfate skeletons. Mainly studied by micropaleontologists because of their excellent fossil record, they are also key members of planktonic communities and play important roles in various oceanic ecosystems. This chapter presents an overview of the current knowledge on living Radiolaria (orders Acantharia, Collodaria, Nassellaria, Spumellaria and Taxopodia). Besides general considerations on Radiolaria as a whole, it focuses on the taxonomy, biology, and ecology of each radiolarian order. Finally this chapter provides insights on research perspectives to improve our knowledge of living radiolarians and their ecological role in marine ecosystems.
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  • 32
    Publication Date: 2016-12-05
    Description: Climate models are potentially useful tools for addressing human dispersals and demographic change. The Arabian Peninsula is becoming increasingly significant in the story of human dispersals out of Africa during the Late Pleistocene. Although characterised largely by arid environments today, emerging climate records indicate that the peninsula was wetter many times in the past, suggesting that the region may have been inhabited considerably more than hitherto thought. Explaining the origins and spatial distribution of increased rainfall is challenging because palaeoenvironmental research in the region is in an early developmental stage. We address environmental oscillations by assembling and analysing an ensemble of five global climate models (CCSM3, COSMOS, HadCM3, KCM, and NorESM). We focus on precipitation, as the variable is key for the development of lakes, rivers and savannas. The climate models generated here were compared with published palaeoenvironmental data such as palaeolakes, speleothems and alluvial fan records as a means of validation. All five models showed, to varying degrees, that the Arabia Peninsula was significantly wetter than today during the Last Interglacial (130 ka and 126/125 ka timeslices), and that the main source of increased rainfall was from the North African summer monsoon rather than the Indian Ocean monsoon or from Mediterranean climate patterns. Where available, 104 ka (MIS 5c), 56 ka (early MIS 3) and 21 ka (LGM) timeslices showed rainfall was present but not as extensive as during the Last Interglacial. The results favour the hypothesis that humans potentially moved out of Africa and into Arabia on multiple occasions during pluvial phases of the Late Pleistocene.
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  • 33
    Publication Date: 2020-07-30
    Description: The South Aegean Active Volcanic Arc consists of a chain of five volcanic centers, the most active of which is the Santorini Volcano. A local radio-linked seismological network is installed on the island consisting of five permanent and four temporary stations. The temporary stations have been in operation periodically during the period 1994–1996 and two of them were installed on adjacent islands. All stations are equipped with vertical-component short period seismometers. During the period 1994–2002 a significant number of earthquakes has been recorded, with local (duration) magnitudes, MD, up to 5.0 and focal depths varying between 0 km and 35 km. Two clusters of epicenters have been located in the broader area of the Santorini Volcano. The first cluster is located in the caldera of the volcano and is associated with the volcanic process in the Kameni Island. The second (larger) cluster is located near the northern edge of the Santorini Island at the Kolumbo Reef and is connected with the volcanic process at this reef. These clusters can be appropriately associated with the two main tectonic features (faults) in the area under study. The first one (N60°E direction) corresponds to the continuation of the Amorgos fault in the area, while the secondary tectonic line (EW direction) is probably related with the southern edge of a submarine graben, which is located between the islands Amorgos and Santorini. Using the data set of the best-located earthquakes, recorded during the period 1994–2002, an attempt has been made to derive an appropriate equivalent 1 –D earth model for the area under study, in order to improve the accuracy of the determined hypocenters, as well as to obtain a preliminary knowledge of the volcano structure.
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  • 34
    Publication Date: 2018-01-19
    Description: Integrated multi-trophic aquaculture (IMTA) is being explored on both economic and environmental grounds in many traditional aquaculture regions. To test a variety of suitable macroalgae species and management scenarios, a numerical model is developed to quantify the remediation of dissolved nutrients and production of macroalgae near a nutrient source. Differences in the morphological, physiological, and economic characteristics of different macroalgae species can provide flexibility when considering the cost and benefit of farming macroalgae. Results show that of the three species studied, Macrocystis pyrifera removed 75 % of dissolved inorganic nitrogen (DIN) input from a point source, while Porphyra umbilicalis and Ulva lactuca removed 5 %. Both M. pyrifera and P. umbilicalis have reduced bioremediation capacity at increasing flow rates. U. lactuca showed increased bioremediation potential as flow rate increased from low to moderate flows. Increasing the optical depth increased the bioremediation potential of M. pyrifera for moderate values of the light attenuation coefficient, whereas bioremediation was unaffected by optical depth for both U. lactuca and P. umbilicalis. Harvesting increased bioremediation capacity of all species by up to 25-fold dependent on the establishment phase and harvesting frequency. We conclude that the choice of macroalgae species greatly affects the success of IMTA and that both harvesting and farm arrangements can be used to greatly optimize bioremediation.
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  • 35
    Publication Date: 2017-05-09
    Description: Carbonates are widespread at methane and petroleum seeps and are often precipitated as consequence of an alkalinity increase due to the anaerobic oxidation of methane (AOM) or, less often reported, of higher hydrocarbons. These carbonates are taphonomic windows into Earth's history, because they excellently protect the in situ formed microbial signatures (e.g. lipid biomarkers) from diagenetic destruction. A complication for paleoreconstructions, however, is that seep carbonates also encapsulate variable amounts of allochthonous organic matter, sometimes even completely obscuring authigenic microbial signatures. Seep carbonates from the Holocene Black Sea, the Pleistocene Enza River and the Pliocene San Lorenzo (both Northern Apennines, Italy) provide hints to better understand (i) the importance of processes other than AOM for the formation of seep carbonates and (ii) the controls of allochthonous and autochthonous contribution of biomarkers to organic matter in seep carbonates. Biomarker distributions in different parts of a Black Sea carbonate clearly demonstrate that high allochthonous organic matter is entrapped if AOM carbonates are formed intrasedimentary, particularly if methane supply is relatively low and external organic matter input high. High allochthonous contributions were also found in the biomarker inventory of ancient seep carbonates from the Italian Northern Apennines (Enza River and San Lorenzo) pointing at their precipitation within the sediment. Specific and complex conditions were indicated from our data for the Enza River location. Carbonate facies and particularly biomarker compositions, with abundant signatures of sulfate reducing bacteria, suggest that sulfate reduction using alkaline, and eventually sulfate- and higher hydrocarbon-enriched fluids triggered the growth of these seep carbonates. Our and other data suggest that this process has to be more considered if interpreting seep settings, particularly where microbial processes rely on rising fluids from deep petroleum reservoirs.
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  • 36
    Publication Date: 2018-01-19
    Description: In the euxinic waters of the NW’ Black Sea shelf, tower-like carbonate build-ups up to several metres in height grow at sites of cold methane seepage. These structures are part of an unique microbial ecosystem that shows a considerable biodiversity and a remarkable degree of organization. The accretion of the build-ups is promoted by the growth of centimetre-sized, methane-filled spheres constructed by calcifying microbial mats. Progressive mineralization of these spheres involves the early precipitation of strongly luminescent high-Mg-calcite rich in iron sulphides, and closely interfingered aragonite phases that finally create the stable (mega-) thrombolithic fabric of the towers. Within the microbial mats, microorganisms occur in distinctive spatial arrangements. Major players among the microbial consortia are the archaea groups ANME-1 and ANME-2, Crenarchaeota, and sulphate-reducing bacteria (SRB) of the Desulfosarcina/Desulfobacterium group. The intracellular precipitation of iron sulphides (greigite) by some of these bacteria, growing in close association with ANME-2, suggests iron cycling as an additional biogeochemical pathway involved in the anaerobic oxidation of methane (AOM).
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  • 37
    Publication Date: 2018-01-19
    Description: Hydrothermal vents on mid-oceanic ridges are patchily distributed and host many taxa endemic to deep-sea chemosynthetic environments, whose dispersal may be constrained by geographical barriers. The aim of this study was to investigate the connectivity of three populations of the ‘scaly-foot gastropod’ (Chrysomallon squamiferum Chen et al., 2015), a species endemic to hydrothermal vents in the Indian Ocean, amongst two vent fields on the Central Indian Ridge (CIR) and Longqi field, the first sampled vent field on the Southwest Indian Ridge (SWIR). Connectivity and population structure across the two mid-oceanic ridges were investigated using a 489-bp fragment of the cytochrome oxidase c subunit I (COI) gene. Phylogeographical approaches used include measures of genetic differentiation (FST), reconstruction of parsimony haplotype network, mismatch analyses and neutrality tests. Relative migrants per generation were estimated between the fields. Significant differentiation (FST = 0.28–0.29, P 〈 0.001) was revealed between the vent field in SWIR and the two in CIR. Signatures were detected indicating recent bottleneck events followed by demographic expansion in all populations. Estimates of relative number of migrants were relatively low between the SWIR and CIR, compared with values between the CIR vent fields. The present study is the first to investigate connectivity between hydrothermal vents across two mid-ocean ridges in the Indian Ocean. The phylogeography revealed for C. squamiferum indicates low connectivity between SWIR and CIR vent populations, with implications for the future management of environmental impacts for seafloor mining at hydrothermal vents in the region, as proposed for Longqi.
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  • 38
    Publication Date: 2018-04-27
    Description: Highlights • We examine interplay between historical seismicity, mass failures and turbidites during sapropel S1 deposition; • We reconstruct chronology of earthquake triggered turbidites in the Ionian Sea during sapropel depostion; • We reconstruct the age of sapropel S1 in our core (6.0-10.2 kyr cal. BP) through Oxcal age modeling; • Turbidite emplacement time was deduced through age modeling. • We compiled a catalogue of mass flow events during several earthquake cycles. Abstract The recurrence of mass-flow units within sapropel S1, an organic carbon-rich lower Holocene marker bed in the Eastern Mediterranean Sea, was used to study the interplay between earthquakes and sedimentation along the seismically active Calabrian Arc (Ionian Sea). Nine turbidite beds interrupt anoxic conditions during the deposition of sapropel S1. Each of these turbidites is associated with sharp grain size and geochemical elemental anomalies (high Al and Si, low Ca and coarse-grained basal part marked by Zr peaks), and with displaced foraminiferal species from different bathymetric ranges. We used these proxies to identify turbidite beds also above and below the sapropel, where turbidite signature is less clear due to the absence of major color changes. Turbidite structure and composition, as well as comparison with historical seismoturbidites, suggest a seismic triggering for such mass flow events. The peculiar color, well-known composition, geochemistry and age of sapropel S1, make this unit a key bed within which turbidites may be considered a sort of sedimentary “bar code” recording high-energy events within the background pelagic sedimentation; deciphering this code will reconstruct paleo-seismicity in this well-defined stratigraphic interval. The pelagic units bracketing turbidite beds were radiometrically dated, and the age of the sapropel S1, deduced through age modeling, is between 6.0 and 10.2 kyr cal BP. The emplacement age of each turbidite was estimated considering the average time-interval between successive turbidite beds (from pelagic sediment thickness and sedimentation rate). Subsequently these ages were further refined through age modeling. In this way, we compiled a catalogue of mass flow events during sapropel S1 deposition, a time span long enough to include several earthquake cycles and allow reliable seismic and tsunami hazard assessment in this area.
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  • 39
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    Cambridge University Press
    In:  In: Climate Change Geoengineering Philosophical Perspectives, Legal Issues. Cambridge University Press, Cambridge, UK, pp. 242-262. ISBN 9781107502635
    Publication Date: 2019-09-23
    Description: Introduction. Today, most countries have accepted a 2 degrees Celsius temperature increase above preindustrial levels as the maximum tolerable limit for global warming. An exceedance probability of below 20 percent for this limit implies an emission budget of less than 250 GtC from 2000 until 2049, however, extrapolating from current global CO2 emissions, this budget will only last until 2024. This sobering math should wake us up to the reality that all options, including climate engineering, need to be considered to address climate change. Climate engineering options can be classified broadly into two categories: solar radiation management and carbon dioxide removal measures. Solar radiation management schemes seek to decrease the incoming solar radiation or to increase the reflection of incoming solar radiation. These approaches can generate fast climate responses, but do not immediately address the cause of the problem. Carbon dioxide removal measures seek to decrease atmospheric carbon concentrations by enhancing or substituting natural carbon sinks. The terrestrial carbon sink can be enhanced by means of forestation; the oceanic sink may, in some regions, be enhanced by means of fertilization, for example by artificially enhanced upwelling of macronutrients or by purposeful addition of the micronutrient iron; the mineral carbon sink can be enhanced by means of chemically accelerated weathering. Some analysts have expressed doubts about the potential of mitigating climate change by sink enhancement, because of concerns about whether carbon can be stored permanently. Nevertheless, terrestrial vegetation sinks have entered the Kyoto Protocol (KP) as offsets for anthropogenic greenhouse gas emissions, but ocean sinks have not.
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  • 40
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    Elsevier
    In:  Earth and Planetary Science Letters, 231 (1-2). pp. 53-72.
    Publication Date: 2017-05-02
    Description: We derive an estimate for the chemical composition of the depleted MORB mantle (DMM), the source reservoir to mid-ocean ridge basalts (MORBs), which represents at least 30% the mass of the whole silicate Earth. A database for the chemical and physical properties of abyssal peridotites has become robust and complete enough to truly access a reference DMM. Using trace element depletion trends from the abyssal peridotites, it is possible to construct a large part of DMM’s trace element pattern. Splicing this information with isotopic constraints (Sr–Nd–Pb–Hf) and canonical ratios (Ce/Pb, Nb/Ta, Nb/U, Ba/Rb, H2O/Ce, CO2/Nb and Cl/K), we can extend abundance estimates to all the incompatible elements including volatile content. The resulting trace element pattern for average DMM constrains parental MORB to be generated by 6% aggregated fractional melting, consistent with recent models for hydrous melting of the mantle [P.D. Asimow, J.E. Dixon, C.H. Langmuir, A hydrous melting and fractionation model for mid-ocean ridge basalts: application to the Mid-Atlantic Ridge near the Azores, Geochem. Geophys. Geosyst. 5 (2004) 10.1029/2003GC000568]. We show that DMM is roughly balanced by the continental crust and better balanced upon inclusion of ocean island basalt source and oceanic crust components. Compared to the primitive mantle, DMM has been depleted by 2–3% melt extraction and has only 15% the radiogenic heat production.
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  • 41
    Publication Date: 2020-07-30
    Description: To explore the transport of carbon into water masses from the surface ocean to depths of ∼1000 m∼1000 m in the southwest Pacific Ocean, we generated time series of radiocarbon (View the MathML sourceΔC14) from fish otoliths. Otoliths (carbonate earstones) from long-lived fish provide an indirect method to examine the “bomb pulse” of radiocarbon that originated in the 1950s and 1960s, allowing identification of changes to distributions of 14C that has entered and mixed within the ocean. We micro-sampled ocean perch (Helicolenus barathri ) otoliths, collected at ∼400–500 m∼400–500 m in the Tasman Sea, to obtain measurements of View the MathML sourceΔC14 for those depths. We compared our ocean perch View the MathML sourceΔC14 series to published otolith-based marine surface water View the MathML sourceΔC14 values (Australasian snapper (Chrysophrys auratus) and nannygai (Centroberyx affinis)) and to published deep-water values (800–1000 m; orange roughy (Hoplostethus atlanticus )) from the southwest Pacific to establish a mid-water View the MathML sourceΔC14 series. The otolith bomb 14C results from these different depths were consistent with previous water mass results in the upper 1500 m of the southwest Pacific Ocean (e.g. World Ocean Circulation Experiment and Geochemical Ocean Sections Study). A comparison between the initial View the MathML sourceΔC14 bomb pulse rise at 400–500 m suggested a ventilation lag of 5 to 10 yr, whereas a comparison of the surface and depths of 800–1000 m detailed a 10 to 20 yr lag in the time history of radiocarbon invasion at this depth. Pre-bomb reservoir ages derived from otolith 14C located in Tasman Sea thermocline waters were ∼530 yr∼530 yr, while reservoir ages estimated for Tasman Antarctic intermediate water were ∼730 yr∼730 yr.
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  • 42
    Publication Date: 2020-07-24
    Description: The present study is focused on the examination of the state of the recently activated Santorini VolcanicComplex (SVC) area, located in the Southern Aegean Sea. The seismic activity was investigated in detailand different methodologies have been applied to examine whether the SVC area approached an eruptivephase during the 2011–2012 seismic crisis period. The detailed spatiotemporal analysis for the broaderstudy area revealed two different seismic patterns: low seismic activity until 2010, mainly concentratedwithin the Anydros basin and close to the submarine volcano, Columbo, and activation during 2011 and2012 of two previously quiescent regions. The first is the Santorini Caldera, which had been active formore than one year, and the second is the area south of Christiana Islands, which was activated in January2012 with the occurrence of two major events of magnitude 5.1 and 5.2, respectively, followed by a largenumber of aftershocks.In this study, manual analysis and relocation of the 2011–2012 seismic crisis in the SVC was performed,in order to obtain a high-resolution image of the activated structures. The seismicity within the SantoriniCaldera, which is oriented approximately NE-SW, was rapidly diminished after the activation of theChristiana area. A large number of focal mechanisms were determined which mainly indicated strike-slip faulting inside the Caldera. Furthermore, the fault plane solutions of the major events in the areasouth of Christiana, derived by waveform modeling, also suggested similar type of faulting. This typediffers from the normal faults observed in the Anydros basin. However, the stress field in all cases isconsistently oriented in a NW-SE direction. Since the Santorini Volcano was seismically activated forthe first time after the 1950 eruption, changes of the physical properties of the medium were examinedusing different approaches to assess the state of the volcano. The shear-wave splitting analysis revealedthe existence of an anisotropic upper crust, while no significant temporal variations of the anisotropydirection were observed. The majority of the recorded events were classified as volcano-tectonic micro-earthquakes using spectral analysis. Nevertheless, certain cases of spasmodic bursts and LF events, whichcan be related to magma activity, have also been identified. A region of low Vsand high Vp/Vsratio hasbeen detected north of Nea Kammeni, at depths between 3 and 5 km, that is directly associated with themagmatic chamber inside the Caldera. The applied multi-method approach revealed that the SantoriniVolcano was activated, while the obtained results indicate that the Volcano did not reach a critical stateduring the 2011–2012 unrest period.
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  • 43
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    Springer
    In:  In: Cold-Water Corals and Ecosystems. , ed. by Freiwald , A. and Roberts , J. M. Erlangen Earth Conference Series . Springer, Berlin, pp. 731-744. ISBN 978-3-540-24136-2
    Publication Date: 2017-07-07
    Description: Colonial non-zooxanthellate corals from deep-water coral reefs, Lophelia pertusa and Madrepora oculata, produce large amounts of extracellular mucus (EMS). This mucus has various functions, e.g., an antifouling capability protecting the coral skeleton from attacks of endolithic and boring organisms. Both corals show thick epithecal and exothecal skeletal parts with a clear lamellar growth pattern. The formation of the epitheca is unclear. It is supposed that the EMS play a central role during the calcification process of the epithecal skeletal parts. Staining with the fluorochrome tetracycline has shown an enrichment of Ca2+ ions in the mucus. In order to investigate this hypothesis, the protein content of the mucus and the intracrystalline organic matter from newly formed epithecal aragonite of Madrepora oculata was determined via sodium dodecyl sulfate (SDS) gel electrophoresis. Identical band patterns within both substances could be detected, one around 45 kDa molecular weight and a cluster around 30–35 kDa molecular weight. The occurrence of identical protein patterns within the mucus and in the newly formed aragonite confirms the idea that the mucus plays an important role during the organomineralization of the coral epitheca.
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  • 44
    facet.materialart.
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    Springer
    In:  In: Cold-Water Corals and Ecosystems. , ed. by Freiwald, A. and Roberts, J. M. Erlangen Earth Conference Series . Springer, Berlin, pp. 771-805.
    Publication Date: 2017-07-07
    Description: The rate of discovery of reefs of the cold-water coral Lophelia pertusa (Linnaeus, 1758) has been remarkable, and attributable to the increased use of underwater video. These reefs form a major three-dimensional habitat in deeper waters where little other ‘cover’ for fish is available. They are common in the eastern North Atlantic, and occur at least in the western North Atlantic and off central Africa. There are also other non-reef records of Lophelia in the Atlantic, and in Indian and Pacific oceans. Thus, not only are these reefs a significant habitat on a local scale, but they may also provide an important habitat over a very wide geographic scale. The present study examined the association of fish species with Lophelia in the Northeast Atlantic, including the Trondheimsfjord and Sula Ridge in Norway, Kosterfjord in Sweden, Darwin Mounds west of Scotland, and Rockall Bank, Rockall Trough and Porcupine Seabight off Ireland. The fish fauna associated with a shipwreck west of Shetland was also studied. Data were collected from 11 study sites at 8 locations, using 52 hours of video and 15 reels of still photographs. Video and still photographs were collected from (1) manned submersible, (2) surface controlled remotely operated vehicle (ROV), (3) a towed “hopper” camera, (4) wide angle survey photography (WASP), (5) seabed high resolution imaging platform (SHRIMP), and (6) an in situ time-lapse camera “Bathysnap”. It was possible to identify 90 % of fish observed to species level and 6.5 % to genus or family level. Only 3.5 % of the fish were not identifiable. A guide to the fishes is given at http://www.ecoserve.ie/projects/aces/. Twenty-five species of fishes from 17 families were recorded over all the sites, of which 17 were of commercial importance and comprised 82 % of fish individuals observed. These commercial fish species contribute 90 % of commercial fish tonnage in the North Atlantic. The habitats sampled were comprised of 19 % reef, 20 % transitional zone (i.e. between living coral and debris zone), 25 % coral debris and 36 % off-reef seabed. Depth was the most significant parameter in influencing the fish associated with the reefs, both at the species and family level. There was a complete separation of sites above and below 400–600 m depth by multi-dimensional scaling (MDS) analysis. Less distinct assemblages of fish species were associated with each habitat. Fish species richness and abundance was greater on the reef than surrounding seabed. In fact, 92 % of species, and 80 % of individual fish were associated with the reef. The present data indicates that these reefs have a very important functional role in deep-water ecosystems as fish habitat.
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  • 45
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    Elsevier
    In:  Palaeogeography Palaeoclimatology Palaeoecology, 227 (1-3). pp. 31-47.
    Publication Date: 2017-06-30
    Description: Carbonates recovered from anoxic waters between 235 and 1555 m depth in the northwestern Black Sea were analyzed for lipid biomarkers and stable carbon isotopic compositions. In addition, a methane-seep-related microbial mat and a sample of surface sediment recovered from a non-seep site were studied for comparison. High concentrations of strongly 13C-depleted lipids attributed to bacteria and archaea mediating the anaerobic oxidation of methane (AOM) were found in all samples except for the sediment. Differences of the dominant AOM-performing communities between the carbonates indicated by specific lipid patterns appear to be caused by the respective biogeochemical settings. High proportions of ANME-2 consortia are found at sites of assumingly high partial pressures of methane while ANME-1 associations dominate at locations of moderate methane supply. In the sedimentary concretion, a complex mixture of biomarkers for terrestrial and planktonic organisms was found. Different molecular structures along with strong variations in the stable carbon isotopic compositions (δ13C = − 20.2‰ to − 94.3‰) allow for an estimation of the proportions of tetraether-bound biphytanes derived from planktonic Crenarchaeota and methanotrophic Euryarchaeota. Our data imply that the shape of AOM-derived carbonate precipitates in Black Sea environments is crucially influenced by the respective methane supply. Active AOM-driven chimney-like bioherms, similar to those previously observed on the Ukrainian shelf, might also develop in the deep euxinic zone at 1555 m water depths.
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  • 46
    Publication Date: 2018-02-05
    Description: Barnacles of the genus Galkinius occupy a large spectrum of host corals, making it one of the least host-specific genera within the Pyrgomatidae. Molecular analyses show that within the genus Galkinius there are highly supported clades, suggesting that the genus Galkinius is a complex of evolutionarily significant units (ESUs). The morphology of the opercular valves has been used as the basis for the separation of species of Galkinius. In this study, morphological variability was found both between specimens within ESUs extracted from different host species and between specimens extracted from the same colony. Identifications based on the opercular valves cannot therefore be assigned to different species despite being genetically distinguishable. It is proposed that in many cases the differences between valve morphology of different species of Galkinius are the outcome of ontogeny. Allometric growth of the valves has resulted in differences in the proportions of the parts of the valve.
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  • 47
    facet.materialart.
    Unknown
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 85 (3). pp. 519-522.
    Publication Date: 2020-07-16
    Description: The vertical distribution of the hydromedusa Aequorea forskalea was investigated using observations from the research submersible 'Jago' collected during 36 dives off the west coast of southern Africa during November 1997 and April 1999. The mean population depth of Aequorea? forskalea deepened with increasing sea surface temperature. We suggest that this behaviour enables individuals to avoid offshore advection, to minimize spatial overlap with other large medusae and to maintain their position over the middle of the shelf.
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  • 48
    Publication Date: 2018-02-05
    Description: Mature organisms often have to trade reproductive opportunities against the need to survive, especially in species with exaggerated, sexually selected traits. Life history theory predicts that old males with low residual reproductive value (RRV) would accept greater risk for current reproduction than their younger counterparts. Accordingly, we tested the prediction that, under predation risk, old males of the rock shrimp Rhynchocinetes typus pair with females faster and for a longer time than young males do. We exposed young and old dominant males (in the final ontogenetic stage, called “robustus”) to a female in the absence and presence of a predator. As predicted, older robustus males modified their mating behavior when exposed to a predator. However, in contrast to the prediction, they delayed female seizure under predation risk, possibly to carefully assess the actual threat before initiating female guarding. Once they had established the mate-guarding position, old robustus males did not interrupt it until the end of female spawning and, in the presence of predators, even guarded the female significantly longer than in predator-free treatments. In contrast, younger robustus males did not delay female seizure but abandoned the female repeatedly when a predator was present, suggesting that they perceived and responded to the predation risk. Our results suggest that older robustus males have the experience to assess threats before engaging in risky behaviors that bolster their reproductive success. Although consistent with the theory that low RRV individuals should accept greater reproductive risk, we suggest that old individuals do not recklessly engage in risky behaviors but rather cautiously evaluate the threats before investing in a potentially terminal reproductive event.
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  • 49
    Publication Date: 2017-12-12
    Description: The geologic framework controls on modern barrier island transgression and the relationship of these controls to subsurface structure, hydrology and island geomorphology are not well understood. Recent evidence suggests that alongshore variations in pre-Holocene geology of barrier islands modify nearshore hydrodynamic processes and sediment transport, ultimately affecting how barrier islands will respond to relative sea-level rise. Explorations of Holocene barrier island geology are usually based on cores to supplement bathymetric, onshore/offshore seismic and/or ground-penetrating radar (GPR) surveys. The advantages and limitations of these methods with respect to barrier island investigations are briefly described in this review. Alternative near-surface geophysical methods including electromagnetic induction (EMI) sensors are increasingly being used for coastal research because they are non-invasive, provide continuous subsurface information across a variety of sub-environments, and are capable of characterizing large areas in a short time. Although these EMI sensors have shown promise in coastal applications, a number of issues primarily related to subsurface hydrology need to be addressed to fully assess the limitations of this technique. This paper reviews the theory, methodology and applications of EMI in support of geologic framework studies with particular reference to barrier islands. Resolution of these issues will allow EMI sensors to complement and offer significant advantages over traditional methods in support of an improved understanding of large-scale barrier island evolution.
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  • 50
    Publication Date: 2017-09-08
    Description: Calcium isotope fractionation was measured on skeletal aragonite and calcite from different marine biota and on inorganic calcite. Precipitation temperatures ranged from 0 to 28°C. Calcium isotope fractionation shows a temperature dependence in accordance with previous observations: 1000 · ln(αcc) = −1.4 + 0.021 · T (°C) for calcite and 1000 · ln(αar) = −1.9 + 0.017 · T (°C) for aragonite. Within uncertainty the temperature slopes are identical for the two polymorphs. However, at all temperatures calcium isotopes are more fractionated in aragonite than in calcite. The offset in δ44/40Ca is about 0.6‰. The underlying mechanism for this offset may be related to the different coordination numbers and bond strengths of the calcium ions in calcite and aragonite crystals, or to different Ca reaction behavior at the solid-liquid interface. Recently, the observed temperature dependence of the Ca isotope fractionation was explained quantitatively by the temperature control on precipitation rates of calcium carbonates in an experimental setting (Lemarchand et al., 2004). We show that this mechanism can in principle also be applied to CaCO3 precipitation in natural environments in normal marine settings. Following this model, Ca isotope fractionation in marine Ca carbonates is primarily controlled by precipitation rates. On the other hand the larger Ca isotope fractionation of aragonite compared to calcite can not be explained by different precipitation rates. The rate control model of Ca isotope fractionation predicts a strong dependence of the Ca isotopic composition of carbonates on ambient CO32− concentration. While this model is in general accordance with our observations in marine carbonates, cultured specimens of the planktic foraminifer Orbulina universa show no dependence of Ca-isotope fractionation on the ambient CO32− concentration. The latter observation implies that the carbonate chemistry in the calcifying vesicles of the foraminifer is independent from the ambient carbonate ion concentration of the surrounding water.
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  • 51
    Publication Date: 2017-01-17
    Description: A new algorithmto retrieve characteristics (albedo and melt pond fraction) of summer ice in the Arctic fromoptical satellite data is described. In contrast to other algorithms this algorithm does not use a priori values of the spectral albedo of the sea-ice constituents (such asmelt ponds,white ice etc.). Instead, it is based on an analytical solution for the reflection from sea ice surface. The algorithm includes the correction of the sought-for ice and ponds characteristics with the iterative procedure based on the Newton–Raphson method. Also, it accounts for the bi-directional reflection from the ice/snow surface, which is particularly important for Arctic regions where the sun is low. The algorithm includes an original procedure for the atmospheric correction, as well. This algorithm is implemented as computer code called Melt Pond Detector (MPD). The input to the current version of the MPD algorithm is the MERIS Level 1B data, including the radiance coefficients at ten wavelengths and the solar and observation angles (zenith and azimuth). Also, specific parameters describing surface and atmospheric state can be set in a configuration input file. The software output is the map of the melt ponds area fraction and the spectral albedo of sea-ice in HDF5 format. The numerical verification shows that theMPD algorithm provides more accurate results for the light ponds than for the dark ones. The spectral albedo is retrieved with high accuracy for any type of ice and ponds.
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  • 52
    facet.materialart.
    Unknown
    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 472 . pp. 32-40.
    Publication Date: 2016-02-25
    Description: Highlights • Experimental stable isotope study on trophic plasticity in adult Macoma balthica. • Contrasts in isotope signatures attributed to hydrographical and biotic settings. • Changing signatures in transplanted clams show switch in feeding in new environment. Abstract Species show varying levels of plasticity regarding morphology, physiology and behaviour in relation to their immediate environment, and several trait characteristics are habitat-dependent. Determining when and how the environmental context changes trait expression is of key importance for understanding the role of individual species for ecosystem functioning. The tellinid clam Macoma balthica can vary its feeding behaviour, shifting between deposit- and suspension-feeding. In order to study the context-dependency of this trophic plasticity in adult clams, we conducted an experiment assessing food uptake by using stable isotope signatures (δ13C and δ15N). We transplanted individuals between and within two shallow bays differing in exposure (exposed–sheltered) and sediment characteristics. Our results show that isotope signatures of clams differed between the two habitats and that clams in the exposed site showed stable isotope values linked to a diet of suspended particulate organic material, while values of individuals in the sheltered site corresponded to an uptake of sediment-bound organic material. Clams transplanted between these two environmental settings were gradually showing differing isotopic signatures from clams at their original habitat, over time mirroring the changes in clams in the site to which they were transferred. The shift in carbon and nitrogen stable isotopes of the clams provides insights into the context-dependent intraspecific feeding plasticity of this zoobenthic key species. The causes for this shift were coupled to contrasts in the hydrodynamic and biotic setting, implying that feeding plasticity may explain adaptation of organisms to changes in their surroundings.
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  • 53
    facet.materialart.
    Unknown
    Elsevier
    In:  Advances in Ecological Research, 53 . pp. 97-160.
    Publication Date: 2016-03-08
    Description: Top-down trophic cascades are well known in many autotrophic systems, yet their role in heterotrophic food webs is less clear. We collated data from 78 investigations and applied meta-analysis to evaluate the strength of detrital trophic cascades in freshwater and terrestrial food webs. Predators exerted significant, indirect controls on detrital resources, in line with theoretical predictions, whereas this was not the case for omnivores, suggesting that detritivory prevailed over predation and disrupted trophic cascades. Significant relationships were observed for both types of consumer in terms of their responses to detrital quality: specifically, unimodal curves across C:N and N:P gradients were the best fits for predators, whilst cascade strength responses to detrital quality were saddle shaped. These insights suggest that while predatory strategy is determining cascades within detrital-based systems, resource quality has bottom-up role effects on predators and on preferential consumption by omnivores. As such, these environmental responses seem to mirror some provisioning and supporting services; our findings are discussed within conceptual frameworks related to ecological stoichiometry and ecosystem services.
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  • 54
    Publication Date: 2016-02-25
    Description: Highlights: • Reduced taxon-richness (96%, 151–6 taxa) leads to overall reduction in function. • Functional richness remained high (66% of tot.) even at the lowest taxon richness. • Analysis of changes in trait categories showed the importance of multifunctionality. • Number of taxa per trait category gives complementary information to the FD index. • Rare species did not express unique traits. Abstract: Alterations to ecosystem function due to reductions in species richness are predicted to increase as humans continue to affect the marine environment, especially in coastal areas, which serve as the interface between land and sea. The potential functional consequences due to reductions in species diversity have attracted considerable attention recently but little is known about the consequence of such loss in natural communities. We examined how the potential for function is affected by natural reductions in taxon richness using empirical (non-simulated) coastal marine benthic macrofaunal data from the Skagerrak-Baltic Sea region (N. Europe), where taxon richness decreases 25-fold, from 151 to 6 taxa. To estimate functional changes we defined multiple traits (10 traits and 51 categories) on which trait category richness, functional diversity (FD) and number of taxa per trait category were calculated. Our results show that decrease in taxon richness leads to an overall reduction in function but functional richness remains comparatively high even at the lowest level of taxon richness. Although the taxonomic reduction was sharp, up to 96% of total taxon richness, we identified both potential thresholds in functioning and subtler changes where function was maintained along the gradient. The functional changes were not only caused by reductions in taxa per trait category, some categories were maintained or even increased. Primarily, the reduction in species richness altered trait categories related to feeding, living and movement and thus potentially could have an effect on various ecosystem processes. This highlights the importance of recognising ecosystem multifunctionality, especially at low taxonomic richness. We also found that in this system rare species (singletons) did not stand for the functional complexities and changes. Our findings were consistent with theoretical and experimental predictions and suggest that a large proportion of the information about alterations of function is found in measures such as functional diversity and number of taxa per trait category.
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  • 55
    Publication Date: 2016-03-03
    Description: Highlights: • Rheological evolution of the rock is influenced by its original and evolving structure. • Strain localizes at boundary between domains of different assemblages (qtz-, fsp-rich). • Strain localizes in original and recrystallized/precipitated finer-grained phases. • Formation of interconnected meso- and microshear zones deformed by diffusion creep. • The rheology of studied example is controlled by Newtonian flow. Abstract: Deformation microstructures of a quartzo-feldspathic pegmatite deformed at mid-crustal levels allow the study of the dynamics of strain localization in polymineralic rocks. Strain localization results from (i) difference in grain sizes between phases, both original and obtained during fluid present reactions and (ii) initial compositional banding. Due to original difference in grain size stress concentrates in the initially finer-grained phases resulting in their intense grain size reduction via subgrain rotation recrystallization (SGR). When the grain size is sufficiently reduced through either deformation or interphase coupled dissolution–precipitation replacement of the coarse grained feldspar, aggregates start to deform by dominantly diffusion accommodated grain boundary sliding (GBS). Phase mixing inhibits grain growth and sustains a grain size allowing GBS. Consequently, discontinuous microscale shear zones form locally within initially coarse grained areas. At the same time difference in strain rate between feldspar-rich and quartz-rich domains needs to be accommodated at domain boundaries. This results in the formation of continuous mesoscale shear zones deformed by GBS. Once these are formed, deformation in the coarse grained parts is arrested and strain is mainly accommodated in the mesoscale shear zones resulting in “superplastic” behaviour consistent with diffusion creep.
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  • 56
    Publication Date: 2020-07-21
    Description: The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) is involved in a broad range of cellular processes including cell proliferation, apoptosis and inflammation. It is now also increasingly acknowledged as having a role to play in cognitive-related processes such as neurogenesis, synaptic plasticity and neural cell survival. Cognitive impairment represents a major debilitating feature of many neurodegenerative and psychiatric disorders, including Alzheimer's disease, mood disorders, schizophrenia and fragile X syndrome, as well as being a result of traumatic brain injury or cranial irradiation. Accordingly, GSK-3 has been identified as an important therapeutic target for cognitive impairment, and recent preclinical studies have yielded important evidence demonstrating that GSK-3 inhibitors may be useful therapeutic interventions for restoring cognitive function in some of these brain disorders. The current review summarises the role of GSK-3 as a regulator of cognitive-dependent functions, examines current preclinical and clinical evidence of the potential of GSK-3 inhibitors as therapeutic agents for cognitive impairments in neuropsychiatric disorders, and offers some insight into the current obstacles that are impeding the clinical use of selective GSK-3 inhibitors in the treatment of cognitive impairment.
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  • 57
    facet.materialart.
    Unknown
    Elsevier
    In:  Fish & Shellfish Immunology, 42 (2). pp. 363-366.
    Publication Date: 2017-01-05
    Description: Highlights: • β-glucan induces apoptosis in a time and concentration dependent manner. • ≥500 μg/ml induce apoptosis in pronephric cells in vitro. • Apoptosis is observed after 6 h of incubation. In previous studies an effect of β-glucan on apoptosis in fish was noted and in this investigation we determine the time and concentration dependency of this effect. Primary cell cultures of pronephric carp cells were incubated for 6, 24, 48 h with various concentrations ranging from 0 - 1000 μg/ml of MacroGard® β-glucan. Apoptosis was monitored via acridine orange staining. Results indicate a clear effect of time and concentration on the induction of apoptosis in vitro, with only concentration ≥ 500 μg/ml causing significantly higher percentages of apoptotic cells. Apoptosis was detected after 6 h. This concentration dependent effect has to be considered when studying apoptosis in relation to immunostimulation.
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  • 58
    Publication Date: 2019-09-23
    Description: Highlights: • Elemental C:N:P variations of organic matter are simulated at monitoring site BY15. • No N2 fixation needed to explain observed PO4PO4 and pCO2pCO2 levels after spring bloom. • Model features relevance of DOP production and remineralization for N2 fixation. • Model estimates of annual N2 fixation are View the MathML source297±24mmolNm-2a-1. • Model estimates of annual total production are View the MathML source14.16±0.71molCm-2a-1. Abstract: For most marine ecosystems the growth of diazotrophic cyanobacteria and the associated amount of nitrogen fixation are regulated by the availability of phosphorus. The intensity of summer blooms of nitrogen (N2) fixing algae in the Baltic Sea is assumed to be determinable from a surplus of dissolved inorganic phosphorus (DIP) that remains after the spring bloom has ended. But this surplus DIP concentration is observed to continuously decrease at times when no appreciable nitrogen fixation is measured. This peculiarity is currently discussed and has afforded different model interpretations for the Baltic Sea. In our study we propose a dynamical model solution that explains these observations with variations of the elemental carbon-to-nitrogen-to-phosphorus (C:N:P) ratio during distinct periods of organic matter production and remineralization. The biogeochemical model resolves seasonal C, N and P fluxes with depth at the Baltic Sea monitoring site BY15, based on three assumptions: (1) DIP is utilized by algae though not needed for immediate growth, (2) the uptake of dissolved inorganic nitrogen (DIN) is hampered when the algae׳s phosphorus (P) quota is low, and (3) carbon assimilation continues at times of nutrient depletion. Model results describe observed temporal variations of DIN, DIP and chlorophyll-a concentrations along with partial pressure of carbon dioxide (pCO2)(pCO2). In contrast to other model studies, our solution does not require N2 fixation to occur shortly after the spring bloom to explain DIP drawdown and pCO2pCO2 levels. Model estimates of annual N2 fixation are View the MathML source297±24mmolNm-2a-1. Estimates of total production are View the MathML source14200±700mmolCm-2a-1, View the MathML source1400±70mmolNm-2a-1, and View the MathML source114±5mmolPm-2a-1 for the upper 50 m. The models C, N and P fluxes disclose preferential remineralization of P and of organic N that was introduced via N2 fixation. Our results are in support of the idea that P uptake by phytoplankton during the spring bloom contributes to the consecutive availability of labile dissolved organic phosphorus (LDOP). The LDOP is retained within upper layers and its remineralization affects algal growth in summer, during periods of noticeable N2 fixation.
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  • 59
    Publication Date: 2019-02-27
    Description: Whilst Herpesviridae, which infect higher vertebrates, actively influence host immune responses to ensure viral replication, it is mostly unknown if Alloherpesviridae, which infect lower vertebrates, possess similar abilities. An important antiviral response is clearance of infected cells via apoptosis, which in mammals influences the outcome of infection. Here, we utilise common carp infected with CyHV-3 to determine the effect on the expression of genes encoding apoptosis-related proteins (p53, Caspase 9, Apaf-1, IAP, iNOS) in the pronephros, spleen and gills. The influence of CyHV-3 on CCB cells was also studied and compared to SVCV (a rhabdovirus) which induces apoptosis in carp cell lines. Although CyHV-3 induced iNOS expression in vivo, significant induction of the genetic apoptosis pathway was only seen in the pronephros. In vitro CyHV-3 did not induce apoptosis or apoptosis-related expression whilst SVCV did stimulate apoptosis. This suggests that CyHV-3 possesses mechanisms similar to herpesviruses of higher vertebrates to inhibit the antiviral apoptotic process.
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  • 60
    Publication Date: 2017-04-13
    Description: The European water framework directive and the marine strategy framework directive have the objective to establish at least ‘good’ ecological status in all European waters by 2015. Therefore a classification system has to be established in each European country, in order to assess their water bodies. For the German coastal waters of the Baltic Sea, a classification system for phytoplankton based on the abundance of Cyanophyceae and Chlorophyceae was already presented. This system has been successfully adapted in regions with low salinity levels (〈10 PSU). With this study, we present the results trying to develop a classification system for our German region of the Baltic Sea characterized by higher salinity (〉15 PSU). All present taxonomic groups, most common species and functional groups were tested. It could be shown that all tested correlations to nitrogen concentration as eutrophication descriptor are relatively week. Nevertheless, the biovolume of Cryptophyceae was found to be the most reliable phytoplankton composition indicator, which could serve as future assessment criterion. Furthermore, as proposed by some experts, the use of maximal dissolved winter nitrogen concentration as eutrophication descriptor might be an advantage over using the total nitrogen concentrations in summer.
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  • 61
    Publication Date: 2019-09-23
    Description: Highlights: • Different disturbance–diversity relationships in phytoplankton are still unresolved. • We modelled phytoplankton under different types of disturbance. • Diversity is increased by disturbance in comparison with a chemostat. • The disturbance–diversity relationship depends on the type of disturbance. • Disturbance increases the timescale of competitive exclusion. Abstract: The way in which disturbance shapes phytoplankton diversity is still subject to much debate. Various disturbance–diversity relationships have been proposed, with diversity increasing or decreasing with the intensity or frequency of disturbance, or peaking at intermediate levels. A key problem in this discussion is the use of different concepts of “disturbance”, which can encompass both positive and negative effects on phytoplankton. To investigate how different modes of disturbance affect phytoplankton diversity, we subject populations of modelled phytoplankton to different frequencies and intensities of three different disturbance modes: a positive, a negative and a combined positive and negative disturbance mode. A chemostat system, considered undisturbed, is used for comparison. We show that (1) disturbance increases phytoplankton coexistence, (2) the disturbance–diversity relationship depends on the type of disturbance and (3) the effect is transient and disturbances predominantly affect the timescale of competitive exclusion.
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  • 62
    Publication Date: 2019-09-23
    Description: The recrystallisation (dissolution–precipitation) of carbonate sediments has been successfully modelled to explain profiles of pore water Sr concentration and radiogenic Sr isotope composition at different locations of the global ocean. However, there have been few systematic studies trying to better understand the relative importance of factors influencing the variability of carbonate recrystallisation. Here we present results from a multi-component study of recrystallisation in sediments from the Integrated Ocean Drilling Program (IODP) Expedition 320/321 Pacific Equatorial Age Transect (PEAT), where sediments of similar initial composition have been subjected to different diagenetic histories. The PEAT sites investigated exhibit variable pore water Sr concentrations gradients with the largest gradients in the youngest sites. Radiogenic Sr isotopes suggest recrystallisation was relative rapid, consistent with modelling of other sediment columns, as the 87Sr/86Sr ratios are indistinguishable (within 2σ uncertainties) from contemporaneous seawater 87Sr/86Sr ratios. Bulk carbonate leachates and associated pore waters of Site U1336 have lower 87Sr/86Sr ratios than contemporaneous seawater in sediments older than 20.2 Ma most likely resulting from the upward diffusion of Sr from older recrystallised carbonates. It seems that recrystallisation at Site U1336 may still be on-going at depths below 102.5 rmcd (revised metres composite depth) suggesting a late phase of recrystallisation. Furthermore, the lower Sr/Ca ratios of bulk carbonates of Site U1336 compared to the other PEAT sites suggest more extensive diagenetic alteration as less Sr is incorporated into secondary calcite. Compared to the other PEAT sites, U1336 has an inferred greater thermal gradient and a higher carbonate content. The enhanced thermal gradient seems to have made these sediments more reactive and enhanced recrystallisation. In this study we investigate stable Sr isotopes from carbonate-rich deep sea sediments for the first time. Pore water δ88/86Sr increases with depth (from 0.428‰ to values reaching up to 0.700‰) at Site U1336 documenting an isotope fractionation process during recrystallisation. Secondary calcite preferentially incorporates the lighter Sr isotope (86Sr) leaving pore waters isotopically heavy. The δ88/86Sr values of the carbonates themselves show more uniform values with no detectable change with depth. Carbonates have a much higher Sr content and total Sr inventory than the pore waters meaning pore waters are much more sensitive to fractionation processes than the carbonates. The δ88/86Sr results indicate that pore water stable Sr isotopes have the potential to indicate the recrystallisation of carbonate sediments.
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  • 63
    facet.materialart.
    Unknown
    Elsevier
    In:  Precambrian Research, 259 . pp. 34-42.
    Publication Date: 2016-11-03
    Description: The southern part of the Baltic Shield hosts a series of mafic dykes and sills of Mesoproterozoic ages, including a ca. 1.53–1.46 Ga sheet-like gabbro-dolerite sills and the Salmi plateau-basalts from the Lake Ladoga region. Based on chiefly geochemical data, the region is conventionally interpreted as an intracratonic Ladoga rift (graben). We question the validity of this geodynamic interpretation by analyzing regional geophysical data (crustal structure, heat flow, Bouguer gravity anomalies, magnetic anomalies, and mantle Vs velocities). We provide a complete list of tectonic, magmatic, and geophysical characteristics typical of continental rifts in general and demonstrate that, except for magmatic and, perhaps, some gravity signature, the Lake Ladoga region lacks any other rift features. We also compare the geophysical data from the Lake Ladoga region with similar in age Midcontinent and Valday rifts, and provide alternative explanations for Mesoproterozoic geodynamic evolution of the southern Baltic Shield. We propose that Mesoproterozoic mafic intrusions in southern Fennoscandia may be associated with a complex deformation pattern during reconfiguration of (a part of) Nuna (Columbia) supercontinent, which led to magma intrusions as a series of mafic dykes along lithosphere weakness zones and ponding of small magma pockets within the cratonic lithosphere. Consequent magma cooling and its partial transition to eclogite facies could have led to the formation of a series of basement depressions, similar to intracratonic basins of North America, while spatially heterogeneous thermo-chemical subsidence, with phase transitions locally speeded by the presence of (subduction-related) fluids, could have produced a series of faults bounding graben-like structures.
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  • 64
    Publication Date: 2021-04-23
    Description: Some populations of brown seaweed species inhabit metal-polluted environments and can develop tolerance to metal stress, but the mechanisms by which this is accomplished are still to be elucidated. To address this, the responses of two strains of the model brown alga Ectocarpus siliculosus isolated from sites with different histories of metal contamination exposed to total copper (CuT) concentrations ranging between 0 and 2.4 μM for 10 days were investigated. The synthesis of the metal-chelator phytochelatin (PCs) and relative levels of transcripts encoding the enzymes γ-glutamylcysteine synthetase (γ-GCS), glutathione synthase (GS) and phytochelatin synthase (PCS) that participate in the PC biosynthetic pathway were measured, along with the effects on growth, and adsorption and uptake of Cu. Growth of strain LIA, from a pristine site in Scotland, was inhibited to a greater extent, and at lower concentrations, than that of Es524, isolated from a Cu-contaminated site in Chile. Concentrations of intra-cellular Cu were higher and the exchangeable fraction was lower in LIA than Es524, especially at the highest exposure levels. Total glutathione concentrations increased in both strains with Cu exposure, whereas total PCs levels were higher in Es524 than LIA; PC2 and PC3 were detected in Es524 but PC2 only was found in LIA. The greater production and levels of polymerisation of PCs in Es524 can be explained by the up-regulation of genes encoding for key enzymes involved in the synthesis of PCs. In Es524 there was an increase in the transcripts of γ-GCS, GS and PCS, particularly under high Cu exposure, whereas in LIA4 transcripts of γ-GCS1 increased only slightly, γ-GCS2 and GS decreased and PCS did not change. The consequences of higher intra-cellular concentrations of Cu, lower production of PCs, and lower expression of enzymes involved in GSH-PCs synthesis may be contributing to an induced oxidative stress condition in LIA, which explains, at least in part, the observed sensitivity of LIA to Cu. Therefore, responses to Cu exposure in E. siliculosus relate to the contamination histories of the locations from where the strains were isolated and differences in Cu exclusion and PCs production are in part responsible for the development of intra-specific resistance.
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  • 65
    Publication Date: 2015-01-22
    Description: An 1180-cm long core recovered from Lake Lyadhej-To (68°15′ N, 65°45′ E, 150 m a.s.l.) at the NW rim of the Polar Urals Mountains reflects the Holocene environmental history from ca. 11,000 cal. yr BP. Pollen assemblages from the diamicton (ca. 11,000–10,700 cal. yr BP) are dominated by Pre-Quaternary spores and redeposited Pinaceae pollen, pointing to a high terrestrial input. Turbid and nutrient-poor conditions existed in the lake ca. 10,700–10,550 cal. yr BP. The chironomid-inferred reconstructions suggest that mean July temperature increased rapidly from 10.0 to 11.8 °C during this period. Sparse, treeless vegetation dominated on the disturbed and denuded soils in the catchment area. A distinct dominance of planktonic diatoms ca. 10,500–8800 cal. yr BP points to the lowest lake-ice coverage, the longest growing season and the highest bioproductivity during the lake history. Birch forest with some shrub alder grew around the lake reflecting the warmest climate conditions during the Holocene. Mean July temperature was likely 11–13 °C and annual precipitation—400–500 mm. The period ca. 8800–5500 cal. yr BP is characterized by a gradual deterioration of environmental conditions in the lake and lake catchment. The pollen- and chironomid-inferred temperatures reflect a warm period (ca. 6500–6000 cal. BP) with a mean July temperature at least 1–2 °C higher than today. Birch forests disappeared from the lake vicinity after 6000 cal. yr BP. The vegetation in the Lyadhej-To region became similar to the modern one. Shrub (Betula nana, Salix) and herb tundra have dominated the lake catchment since ca. 5500 cal. yr BP. All proxies suggest rather harsh environmental conditions. Diatom assemblages reflect relatively short growing seasons and a longer persistence of lake-ice ca. 5500–2500 cal. yr BP. Pollen-based climate reconstructions suggest significant cooling between ca. 5500 and 3500 cal. yr BP with a mean July temperature 8–10 °C and annual precipitation—300–400 mm. The bioproductivity in the lake remained low after 2500 cal. yr BP, but biogeochemical proxies reflect a higher terrestrial influx. Changes in the diatom content may indicate warmer water temperatures and a reduced ice cover on the lake. However, chironomid-based reconstructions reflect a period with minimal temperatures during the lake history.
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  • 66
    Publication Date: 2015-01-22
    Description: Thermoterraces in syngenetic ice complexes are widespread along the erosion dominated Yakutia Arctic coast. Thermoterraces progressively record quantitative information about their existence, which may be used to determine the mean shore retreat rate during the time they are present. Initial measurements of four thermoterraces on the south coast of the Dmitry Laptev Strait were carried out by the authors in 2002 and shore retreat rates were calculated. Comparison of erosion rates obtained using thermoterrace dimensions and geodetic survey results with those determined using aerial photographs showed that erosion rate values obtained in these two ways are approximately of the same order.
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  • 67
    Publication Date: 2017-08-09
    Description: Hydrous CaMg-carbonate was synthesized at temperatures of 40 degrees, 60 degrees and 80 degrees C in the laboratory. This material has very similar mineralogical characteristics to natural disordered dolomite from the Coorong region in South Australia. Besides the dolomite variable amounts of amorphous carbonate are present in all samples. The oxygen isotope compositions of synthesized bulk carbonate samples (e.g., amorphous carbonate plus dolomite) plot significantly lower than the Northrop and Clayton (1966) dolomite-water equilibrium. Fractionated degassing of the samples, however, revealed relatively low oxygen isotope values for fast-reacting (using 100% H3PO4) amorphous carbonate. In contrast, slow-reacting dolomite has more positive oxygen isotope values, and calculated carbonate-water oxygen isotope fractionation values are close to strongest known dolomite-water oxygen isotope fractionation published earlier on. Variations of reaction/stabilization temperatures during synthesis gave evidence for dolomite formation from hypersaline solutions by a dissolution/reprecipitation process. It is likely that amorphous carbonate has been a problem in defining the dolomite-water fractionation in the past. Moreover, dolomite-associated amorphous carbonate contents probably led to incorrect speculations about lower oxygen isotope fractionation in a so-called protodolomite-water system. Copyright (c) 2005 Elsevier Ltd.
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  • 68
    facet.materialart.
    Unknown
    Elsevier
    In:  Sedimentary Geology, 175 . pp. 3-8.
    Publication Date: 2018-07-19
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  • 69
    facet.materialart.
    Unknown
    Elsevier
    In:  Earth and Planetary Science Letters, 237 (3-4). pp. 561-576.
    Publication Date: 2016-12-21
    Description: Rifted margins are commonly characterised by an extension discrepancy: the amount of extension measurable from the observed faulting is far less than that required to explain the crustal thinning. It is shown here that polyphase faulting may provide a simple explanation for this paradox, but can be very hard to recognise on seismic sections. However at the west Galicia rifted margin (the Galicia Interior Basin between the Galicia Bank and the mainland, and the deep Galicia margin to the west of the Galicia Bank), a combination of high quality depth images, seismic velocity information and stratigraphic control through ODP drilling and submersible sampling, provide complementary evidence for polyphase faulting. Berriasian–Hauterivian rifting in the Galicia Interior Basin occurred along two sets of faults: the first unroofed deep crustal rocks, evidenced by high seismic velocities close to top basement; the second cut and dismembered these early faults. Further rifting (up until the Aptian) then focussed west of the Galicia Bank, where two further phases of faulting can be inferred from the diachronous nature of seismostratigraphic units tilted within fault blocks. Removal of the latest phase of faulting aligns discontinuous reflections within the fault blocks into an anastomosing network of earlier faults; restoration along these brings the crust back to its early Hauterivian state, similar to the present structure of the Interior Basin.
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  • 70
    facet.materialart.
    Unknown
    Elsevier
    In:  Global and Planetary Change, 48 (1-3). pp. 187-207.
    Publication Date: 2017-09-13
    Description: Sediment core PS2458 from the Laptev Sea continental margin (983-m water depth) stems from a position close to the paleoriver mouth of Lena and Yana rivers. It was dated by AMS-14C and analyzed in high resolution for oxygen isotopes of planktic foraminifers. Except the uppermost 100 cm and possibly the lowermost meter of the 8-m-long core, the sediments were deposited during the last deglaciation (14.5–8.0 cal-ka). According to 210Pb data, the uppermost 100 cm represents only the last 200 years. Planktic foraminifers are present throughout the dated deglacial interval, with the exception of a short time after ca. 13 cal-ka. Taking into account the global “ice volume effect” on the oxygen isotopic composition of the foraminifers, the isotopic record is considered to reflect salinity changes which were influenced by variable freshwater runoff and a growing marine influence during the postglacial transgression of the Laptev Sea shelf. The most conspicuous feature in the isotopic record is an outstanding peak dated to ca. 13 cal-ka. It is proposed that it represents a rapid outburst of large amounts of freshwater, possibly from an ice-dammed lake in the hinterland. Possible correlations to the onset of the cool Younger Dryas event in the northern hemisphere are discussed.
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  • 71
    facet.materialart.
    Unknown
    Elsevier
    In:  Marine Chemistry, 94 (1-4). pp. 27-41.
    Publication Date: 2017-08-22
    Description: The persistence of the anthropogenic halogenated tracers, CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2FCClF2), carbon tetrachloride (CCl4) and methyl chloroform (CH3CCl3) in oxygen-depleted waters was investigated in the anoxic fjord Framvaren in southern Norway. A model for the ventilation of the water in the fjord was created based on tritium and CFC-12 profiles. The results suggest that CFC-12 is stable in this environment, although still affected by particulate scavenging, while the other four halocarbon species shows signs of significant removal in the oxic/anoxic interface. The first-order removal coefficients were calculated to be 0.35, 0.19, 1.23 and 0.31 year−1 for CFC-11, CFC-113, CCl4 and CH3CCl3, respectively. Significant downward flux of halogenated tracers by sinking organic matter is suggested by the model; the tracers are subsequently released to the water column by the remineralisation of the particles. This process acts as a sink of halogenated tracers in the surface waters, whereas it is a source for the deep waters. Our results points to bioaccumulation factors (BF) for the CFC tracers in the order of 4.4–5.4 (log BF), which is 100–600 times those previously reported. This might be of significance to near-shore, semi-enclosed, basins with a high flux of organic matter, but would still have little importance in open ocean basins.
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  • 72
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 52 (3-4). pp. 651-664.
    Publication Date: 2020-08-05
    Description: The development of a broad-scale array of about 3000 autonomous profiling floats, known as Argo, has been underway since 2000. This array will deliver up to 100,000 vertical profiles of temperature, salinity and other parameters from the surface to depths up to 2000 m. While floats are expected to give good measurements of temperature and pressure, salinity measurements sometimes show significant sensor drift with time or offsets. Unless a float is recovered before the battery fails, recalibrations cannot be performed and a remote calibration method is required. Such a quality control system has been set up for the North Atlantic to identify and correct salinity sensor drifts by using historical hydrographic data. An objective mapping method is used that takes the spatial and temporal variations in water mass properties into account. These scales aim to represent the hydrographic structure of the North Atlantic, which follow the large-scale contours of the potential vorticity. The float measurements of each profile are compared to the mapped salinities in potential conductivity space by weighted least-squares, giving one correction for each profile. It is assumed that any conductivity offset changes slowly over time, so that a linear fit of the profile based corrections over the float time series is done. The result is a set of calibrated salinity data with corresponding uncertainties.
    Type: Article , PeerReviewed
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  • 73
    Publication Date: 2019-01-24
    Description: The saltwater culture of a Penicillium chrysogenum strain isolated from the Mediterranean sponge Ircinia fasciculata yielded three new sorbicillin-derived compounds (1-3), whose structures were elucidated mainly by 2D NMR and mass spectrometry. Among them, sorbicillactones A (1) and B (2) are the first sorbicillinoid natural products that contain nitrogen. Compound 1 is anti-HIV active and it exhibits a strong cytotoxic activity against L5178y leukemic cells, combined with a relatively low toxicity to cervical carcinoma HeLa S3 cells and pheochromocytoma PC 12 cells. The absolute configurations of I and 2 were elucidated by quantum chemical calculation of circular dichroism (CD) spectra. Another compound isolated, sorbivinetone (3), might be an artifact derived from sorbicillinol (4) by Diels-Alder reaction with ethyl vinyl ether. Furthermore, the known sorbicillinoid fungal metabolites oxosorbicillinol (5), sorbicillin (6), and bisvertinolone (7) were identified, as well as the alkaloids meleagrine and roquefortine C. The biosynthetic origin of sorbicillactone A (1) from acetate, alanine, and methionine was investigated by feeding experiments with C-13-labeled precursors
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  • 74
    Publication Date: 2016-12-21
    Description: Dissolved Pb and Nd isotope ratios of seawater, as recorded by chemical marine precipitates such as hydrogenetic ferromanganese crusts, have been used as paleoenvironmental proxy tracers. For the North Pacific, however, all ferromanganese crusts studied so far have either been subject to phosphatization or hydrothermal influence in their old part, or only the young parts have been analyzed. Thus, the Pb and Nd isotope compositions of North Pacific deep waters prior to ∼20 Ma are not well constrained. We present new results for three ferromanganese crusts, one of which (CJ01) shows no phosphatization and is located far away from the EPR. Its age is inferred to be ∼75 Ma and thus provides for the first time an opportunity to trace the Nd and Pb isotope evolution of central North Pacific seawater back to the latest Cretaceous. The three crusts, no matter whether phosphatized or not, display very similar Pb and Nd isotope trends with age, suggesting no modification of the Pb and Nd isotope distribution by post-depositional phosphatization. Our data suggest that dissolved Pb in deep waters of the central North Pacific over the Cenozoic and latest Cretaceous has mainly been derived from eolian dust and only to a minor extent from weathering of island arcs. For Pb these trends broadly resemble the Pb isotope evolution of the eolian silicate dust fraction of core LL44-GPC3 in the central North Pacific. We suggest that the isotope evolution of dissolved Pb in central North Pacific seawater has been mainly controlled by Pb released from eolian dust from North America prior to 50 Ma and after 40 Ma from Asia. In contrast, the Nd isotope time series of the crusts are by no means similar to the Nd isotope evolution of the silicate dust fraction in core GPC3, suggesting a decoupling from the Pb and negligible contributions from dust to the dissolved Nd in the central North Pacific deep water. The rise of Nd isotope ratios of Pacific seawater during the Cenozoic has most likely been caused by the increasing volcanic activity and erosion of the volcanic arcs around the Pacific.
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  • 75
    Publication Date: 2016-12-21
    Description: The first detailed stratigraphic record from a deep-water carbonate mound in the Northeast Atlantic based on absolute datings (U/Th and AMS 14C) and stable oxygen isotope records reveals that its top sediment sequences are condensed by numerous hiatuses. According to stable isotope data, mainly sediments with an intermediate signal are preserved on the mound, while almost all fully glacial and interglacial sediments have either not been deposited or have been eroded later. The resulting hiatuses reduce the Late Pleistocene sediment accumulation at Propeller Mound to amounts smaller than the background sedimentation. The hiatuses most likely result due to the sweeping of the mound in turn with the re-establishment of vigour interglacial circulation patterns after sluggish current regimes during glacials. Thus, within the discussion if internal, fluid-driven or external environmentally driven processes control the evolution of such carbonate mounds, our findings for Propeller Mound clearly point to environmental forcing as the dominant mechanism shaping deep-water carbonate mounds in the NE Atlantic during the Late Pleistocene and Holocene
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  • 76
    Publication Date: 2017-08-22
    Description: We have compared 14 different sediment incubation chambers, most of them were used on bottom landers. Measurements of mixing time, pressure gradients at the bottom and Diffusive Boundary Layer thickness (DBL) were used to describe the hydrodynamic properties of the chambers and sediment–water solute fluxes of silicate (34 replicates) and oxygen (23 replicates) during three subsequently repeated incubation experiments on a homogenized, macrofauna-free sediment. The silicate fluxes ranged from 0.24 to 1.01 mmol m−2 day−1 and the oxygen fluxes from 9.3 to 22.6 mmol m−2 day−1. There was no statistically significant correlation between measured fluxes and the chamber design or between measured fluxes and hydrodynamic settings suggesting that type of chamber was not important in these flux measurements. For verification of sediment homogeneity, 61 samples of meiofauna were taken and identified to major taxa. In addition, 13 sediment cores were collected, sectioned into 5–10-mm slices and separated into pore water and solid phase. The pore water profiles of dissolved silicate were used to calculate diffusive fluxes of silicate. These fluxes ranged from 0.63 to 0.87 mmol m−2 day−1. All of the collected sediment parameters indicated that the sediment homogenization process had been satisfactorily accomplished. Hydrodynamic variations inside and between chambers are a reflection of the chamber design and the stirring device. In general, pump stirrers with diffusers give a more even distribution of bottom currents and DBL thicknesses than paddle wheel-type stirrers. Most chambers display no or low static differential pressures when the water is mixed at rates of normal use. Consequently, there is a low risk of creating stirrer induced pressure effects on the measured fluxes. Centrally placed stirrers are preferable to off-center placed stirrers which are more difficult to map and do not seem to give any hydrodynamic advantages. A vertically rotating stirrer gives about five times lower static differential pressures at the same stirring speed as the same stirrer mounted horizontally. If the aim is to simulate or mimic resuspension at high flow velocities, it cannot be satisfactorily done in a chamber using a horizontal (standing) rotating impeller (as is the case for most chambers in use) due to the creation of unnatural conditions, i.e. large static differential pressures and pre-mature resuspension at certain locations in the chamber.
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  • 77
    Publication Date: 2016-12-21
    Description: New 238U–230Th–226Ra and 231Pa–235U disequilibria data measured by TIMS are presented for ridge-centered MORB glasses dredged during the R/V Sonne 158 cruise at the Galápagos or Cocos-Nazca Spreading Center (GSC) between 86.0°W and 92.3°W. The application of U-series isotopes to the GSC region, situated a few hundred kilometres to the north of the Galápagos hotspot, allows assessment of fundamental questions related to the dynamics of plume–ridge interaction. These include (1) the relationship between long-lived source variations, U-series disequilibria and extent of differentiation, (2) partial melting during solid upwelling, and (3) the nature and rates of plume–ridge mass transfer. The along axis U-series disequilibria variation show gradational patterns that locally are correlated with geochemical and isotopic parameters such as La/Sm, Tb/Yb, 206Pb/204Pb and 143Nd/144Nd as well as major element compositions. The correlation of (230Th)/(238U) with radiogenic isotopes and Tb/Yb provides constraints on the plume source influence on the melting process, reflecting an increase in the amount of melting at depth in the presence of garnet or aluminous clinopyroxene. Moreover, the correlation between U-series signatures, radiogenic isotopes, incompatible element abundance and MgO content indicates a causative relationship between the melting of plume source materials and how these lavas differentiate at shallow depths. We speculate that this involves loss of alkalis from ascending melts to shallow peridotite and crustal gabbro, resulting in increased olivine fractionation from the magmas. The U-series data place stringent constraints on the timing of plume–ridge mass transfer and thus distinguish whether mass transfer occurs by movement of melts or solid mantle. Within the likely conditions proposed by the model of (Braun and Sohn [EPSL 213 (2003): 417–430] and with knowledge of (231Pa)/(235U) and (230Th)/(238U) observed in Galápagos Islands lavas [A. Saal, personal communication], we show that all 226Ra excess will be lost and the initial 231Pa and 230Th excesses will be largely decayed. Therefore, we conclude that the plume influence on the GSC lavas results from a solid mantle flow process instead of through migration of plume-derived melts to the ridge.
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  • 78
    facet.materialart.
    Unknown
    Springer
    In:  Helgoland Marine Research, 59 . pp. 71-83.
    Publication Date: 2018-05-28
    Description: Humans have interacted with the Wadden Sea since its origin 7,500 years ago. However, exploitation, habitat alteration and pollution have strongly increased since the Middle Ages, affecting abundance and distribution of many marine mammals, birds, fish, invertebrates and plants. Large whales and some large birds disappeared more than 500 years ago. Most small whales, seals, birds, large fish and oysters were severely reduced by the late 19th and early 20th centuries, leading to the collapse of several traditional fisheries. In the 20th century, conservation efforts have enabled some breeding birds and seals to recover. But other species declined further due to continuing exploitation, habitat destruction, pollution and eutrophication. Moreover, complex three-dimensional habitats such as oyster banks, Sabellaria reefs and subtidal eelgrass beds have been lost completely. In contrast, several opportunistic species such as gulls, polychaetes, green algae and exotic invaders increased during the 20th century. Taken together, multiple human impacts have caused dramatic losses of large predators and habitat-building species in the Wadden Sea over the last 500 years. Although still of high natural value and global importance, the Wadden Sea is a fundamentally changed ecosystem. On the other hand, reduced hunting pressure, increased habitat protection and reduced river pollution have enabled the recent recovery of several species and an increase in environmental quality. These successes, together with a historical vision of what was once possible, should guide current and future conservation, restoration and management efforts towards a more sustainable interaction between man and the sea.
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  • 79
    facet.materialart.
    Unknown
    Elsevier
    In:  Quaternary Science Reviews, 24 (16-17). pp. 1809-1820.
    Publication Date: 2016-09-16
    Description: A mechanism is advanced for explaining the Antarctic warm events from 90 to 30ka BP which involves meltwater-induced changes in the salinity gradient across the Antarctic Circumpolar Current (ACC) and consequent changes in the poleward heat transport by ocean eddies. Based on simple linear scale analysis, the mechanism is shown to yield warming in the Antarctic interior of roughly the magnitude seen in Antarctic ice-core records (∼2 °C) in response to ice discharges into the North Atlantic. Consistent with observations, the mechanism produces gradual Antarctic warming and cooling, as dictated by the time required for salinity anomalies to build up and dissipate across the ACC. The mechanism also allows the onset of warming or cooling to be tied to changes in Atlantic overturning, which is relevant here, not for influencing ocean heat transport directly, but for influencing the routing of meltwater from the North Atlantic into the Southern Ocean. The ideas presented here highlight the possibility that eddy processes in the ocean may play a first-order role in aspects of climate variability on millennial time scales.
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  • 80
    Publication Date: 2019-08-06
    Description: Todayrsquos Wadden Sea is a heavily human-altered ecosystem. Shaped by natural forces since its origin 7,500 years ago, humans gradually gained dominance in influencing ecosystem structure and functioning. Here, we reconstruct the timeline of human impacts and the history of ecological changes in the Wadden Sea. We then discuss the ecosystem and societal consequences of observed changes, and conclude with management implications. Human influences have intensified and multiplied over time. Large-scale habitat transformation over the last 1,000 years has eliminated diverse terrestrial, freshwater, brackish and marine habitats. Intensive exploitation of everything from oysters to whales has depleted most large predators and habitat-building species since medieval times. In the twentieth century, pollution, eutrophication, species invasions and, presumably, climate change have had marked impacts on the Wadden Sea flora and fauna. Yet habitat loss and overexploitation were the two main causes for the extinction or severe depletion of 144 species (~20% of total macrobiota). The loss of biodiversity, large predators, special habitats, filter and storage capacity, and degradation in water quality have led to a simplification and homogenisation of the food web structure and ecosystem functioning that has affected the Wadden Sea ecosystem and coastal societies alike. Recent conservation efforts have reversed some negative trends by enabling some birds and mammals to recover and by creating new economic options for society. The Wadden Sea history provides a unique long-term perspective on ecological change, new objectives for conservation, restoration and management, and an ecological baseline that allows us to envision a rich, productive and diverse Wadden Sea ecosystem and coastal society.
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  • 81
    Publication Date: 2016-12-21
    Type: Article , NonPeerReviewed
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  • 82
    facet.materialart.
    Unknown
    Elsevier
    In:  Global and Planetary Change, 45 (1-3). pp. 23-33.
    Publication Date: 2017-07-24
    Description: Today, the ocean is characterized by pools of warm tropical–subtropical water bounded poleward and at depth by cold water. In the tropics and subtropics, the warm waters are floored at depth by the thermocline–pycnocline, which crops out on the ocean surface between the subtropical and polar frontal systems that form the poleward boundary. It is along and between the frontal systems that the thermocline waters enter the ocean interior. These frontal systems form beneath the maxima of the zonal component of the westerly winds. Today, the location of the westerly winds is stabilized by the persistent high-pressure systems at the polar regions produced by the ice cover of the Antarctic and sea-ice cover of the Arctic. The paleobiogeographic distribution of plankton fossils indicates that, prior to the Oligocene, the subtropical and polar frontal systems were not persistent features. Recent climate model experiments show that without perennial ice cover in the polar regions a seasonal alternation between high and low atmospheric pressure systems can occur. These seasonal alternations would force major changes in the location and strength of the westerly winds, preventing the development of the well-defined frontal systems that characterize the Earth today. Without the subtropical and polar frontal systems, the thermocline would be less well developed and the pycnocline could be dominated by salinity differences. Evidence from ocean drilling suggests that the glaciation of East Antarctica began at the Eocene–Oligocene boundary, but took time to spread over the entire continent. The presence of calcareous nannoplankton in the Arctic basin prior to the Oligocene and their absence thereafter suggests that the ice cover of the Arctic Ocean also developed at the Eocene–Oligocene boundary. Both events appear to be related to the development of the modern oceanic structure, but it remains uncertain whether the ocean changed in response to the development of ice covered polar regions or vice versa.
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  • 83
    Publication Date: 2018-06-29
    Description: Macroalgae possess different defense mechanisms in response to herbivory. Some species produce anti-herbivore secondary metabolites, but production of these substances can be costly. Therefore, algae may produce defensive metabolites only in response to herbivory (inducible defense) or defend particular parts of the alga differentially (within-alga variation). In the present study, we examined whether two species of brown algae from the SE-Pacific show evidence of inducible chemical defense (non-polar compounds) or within-alga variation of defense, which we estimated in form of palatability of differently treated algae to amphipod grazers (with live algae and agar-based food containing non-polar algal extracts). In Glossophora kunthii (C. Agardh) J. Agardh, we observed an increase in palatability after algae were acclimated for 12 days without grazers. Subsequent addition of grazers for 12 days then resulted in a reduction of palatability indicating the existence of inducible defense. After removal of grazers for 12 days, these induced effects again disappeared. The reaction of G. kunthii was triggered even by the mere presence of grazers, which suggests that this alga can respond to waterborne cues by reducing palatability. Effects were only found for agar-based food containing non-polar extracts, but not for live algae, suggesting that some parts of the algae are undefended. Our second experiment on within-alga variation confirmed that only apical (growth region) and basal parts (near the holdfast region) of G. kunthii are defended against herbivores. For the second species, Macrocystis integrifolia Bory, the first experiment revealed no induction of defense, while the second experiment on within-alga variation showed that amphipods avoided basal parts and in particular stipes of M. integrifolia but only in live algae. Although both studied algal species differed substantially in their defensive strategies, their reaction was independent of the presence or absence of UV radiation. Thus, it appears that UV effects play only a minor role in anti-herbivore defense, which is in accordance with most previous studies.
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  • 84
    Publication Date: 2017-08-03
    Description: Offshore Ecuador, the Carnegie Ridge is a volcanic ridge with a carbonate sediment drape. During the SALIERI Cruise, multibeam bathymetry was collected across Carnegie Ridge with the Simrad EM120 of the R/V SONNE. The most conspicuous features discovered on the Carnegie Ridge are fields of circular closed depressions widely distributed along the mid-slope of the northern and southern flanks of the ridge between 1500 and 2600 m water depth. These circular depressions are 1–4 km wide and typically 100–400 m deep. Most are flat floored and some are so densely packed that they form a honeycomb pattern. The depressions were carved into the ridge sedimentary blanket, which consists of carbonate sediment and has been dated from upper Miocene to upper Pleistocene. Several hypotheses including pockmark origin, sediment creeping, paleo-topography of the volcanic basement, effects of subbottom currents, and both marine and subaerial karstic origins are discussed. We believe that underwater dissolution process merits the most serious consideration regarding the origin of the closed depression.
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  • 85
    facet.materialart.
    Unknown
    Elsevier
    In:  Global and Planetary Change, 48 (1-3). pp. 84-95.
    Publication Date: 2020-12-01
    Description: Historical data analyses show that the Lena River and its major tributaries experienced an extended low water period over 1936–1957 and high water periods over 1974–1983 and 1988–2001. Higher than normal river discharge and annual precipitation is particularly pronounced since the late 1960s due to large-scale changes in atmospheric circulation patterns. The trend in runoff observed in the Lena River basin increased by 10% from 1936 to 2001 due to extended wet periods during the second part of last century. The trend is weakened for the Vilui River basin since it experiences reservoir regulation, which causes additional water losses through reservoir filling and increased evaporation. Runoff regulation strongly affects the winter runoff regime of both the Vilui River and the lower reaches of the Lena River causing an increased winter discharge at the Lena river outlet station of approximately 33%.
    Type: Article , PeerReviewed
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  • 86
    Publication Date: 2015-01-30
    Description: A general overview of the processes taking place in the summer mixing zone of the fresh Yenisei River water with the marine waters of the Kara Sea is given in this study, with special emphasis on the interaction between bulk (total suspended matter), inorganic (Fe, Mn) and organic (suspended organic carbon, suspended nitrogen) proxies. Within the mixing zone, a zone of enhanced turbidity (maximum turbidity zone) was observed comparable to studies in other rivers. Flocculation of particles due to changes in salinity and hydrography cause this maximum turbidity zone, and resuspension additionally enhances the turbidity in the near-bottom layers. Organic matter behaves conservatively in the mixing zone in terms of its percentage of suspended matter. It, however, undergoes degradation as revealed by amino acid data. Inorganic, redox- and salinity-sensitive, proxies (Mn, Fe) behave non-conservatively. Dissolved iron is removed at low salinities (〈2) due to precipitation of iron oxyhydroxides and adsorption of manganese on suspended particles, enhancing the Mn/Al ratio of the suspended matter in the same zone. At higher salinities within the mixing zone, Fe/Al and Mn/Al ratios of the suspended particles are depleted due to resuspension of sediment with lower Fe/Al and Mn/Al ratios. Dissolved manganese concentrations are significantly higher in the near-bottom layers of the mixing zone due to release from the anoxic sediment. All things considered, the Yenisei River mixing zone shows patterns similar to other world's rivers.
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  • 87
    Publication Date: 2020-07-14
    Description: This study should clarify the importance of morphology and stability of the mandibular gnathobases for the diet of Antarctic copepod species. The gnathobase morphology of the dominant copepod species Calanoides acutus, Calanus propinquus, Ctenocalanus citer, Rhincalanus gigas, Metridia gerlachei, Stephos longipes, Microcalanus pygmaeus and Paraeuchaeta antarctica from the Southern Ocean was investigated in detail by means of a scanning electron microscope. The mandibular gnathobases of C. acutus, C. propinquus and C. citer have relatively short and compact teeth. These species feed mainly on diatoms and are able to crack the silicious diatom frustules with their mandibular gnathobases by directed pressure. In contrast the teeth of the mandibular gnathobases of P. antarctica are very long and pointed. The nutrition of this species consists predominantly of other smaller copepod species. The motile prey can be held by skewering, using the gnathobases, and then eventually minced. The mandibular gnathobases of P. antarctica have notably more small bristles than those of the other investigated copepod species. These bristles are probably associated with receptors and could serve to locate the prey. The morphology of the gnathobases of R. gigas and M. gerlachei is between that of P. antarctica on the one side and that of C. acutus, C. propinquus and C. citer on the other. Based on the morphology of its gnathobases the copepod species S. longipes, which has to date been found to feed primarily on phytoplankton, mainly ice algae, must also be considered a zooplankton feeder. The investigation showed that M. pygmaeus has gnathobases with surprisingly long and pointed teeth, indicating that this species very probably feeds both on phyto- and on zooplankton organisms. While the mandibular gnathobases of the males of C. propinquus, R. gigas, M. gerlachei and S. longipes have the same morphology as the females of the respective species, in the other four investigated copepod species the males have reduced (C. acutus, C. citer and M. pygmaeus) or completely missing mandibular gnathobases (P. antarctica). The teeth of the gnathobases of all studied species with the exception of M. gerlachei consist of a different material than the remaining parts of the gnathobases. This material seems to be silicate, which probably enhances the stability of the gnathobase teeth.
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  • 88
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 99 . pp. 10-22.
    Publication Date: 2019-07-10
    Description: Highlights: • Abyssal AUV-based microstructure measurements over rough topography. • Indications for hydraulic control downstream of a sill in a Mid-Atlantic Ridge valley. • Asymmetric distribution of dissipation rate and elevated density variability. Abstract: Diapycnal mixing in the deep ocean is known to be much stronger in the vicinity of rough topography of mid-ocean ridges than above abyssal plains. In this study a horizontally profiling microstructure probe attached to an autonomous underwater vehicle (AUV) is used to infer the spatial distribution of the dissipation rate of turbulent kinetic energy (ε ) in the central valley of the Mid-Atlantic Ridge. To the authors’ knowledge, this is the first successful realization of a horizontal, deep-ocean microstructure survey. More than 22 h of horizontal, near-bottom microstructure data from the Lucky Strike segment (37 °N) are presented. The study focuses on a channel with unidirectional sill overflow. Density was found to decrease along the channel following the mean northward flow of 3 to 8 cm/s. The magnitude of the rate of turbulent kinetic energy dissipation was distributed asymmetrically relative to the position of the sill. Elevated dissipation rates were present in a segment 1-4 km downstream (north) of the sill with peak values of 1⋅10−71⋅10−7 W/kg. Large flow speeds and elevated density finestructure were observed within this segment. Lowered hydrographic measurements indicated unstable stratification in the same region. The data indicate that hydraulic control is established at least temporarily. Inside the channel at wavelengths between 1 m and 250 m the slopes of AUV-inferred horizontal temperature gradient spectra were found to be consistent with turbulence in the inertial-convective subrange. Integrated temperature gradient variance in this wavelength interval is consistent with an ε2/3 dependence. The results illustrate that deep-reaching AUVs are a useful tool to study deep ocean turbulence over complex terrain where free-falling and lowered turbulence measurements are inefficient and time-consuming.
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  • 89
    Publication Date: 2020-01-01
    Description: The accumulation and transformation of organic matter during soil development is rarely investigated although such processes are relevant when discussing about carbon sequestration in soil. Here, we investigated soils under grassland and forest close to the North Sea that began its genesis under terrestrial conditions 30 years ago after dikes were closed. Organic C contents of up to 99 mg g−1 soil were found until 6 cm soil depth. The humus consisted mainly of the fraction lighter than 1.6 g cm−3 which refers to poorly degraded organic carbon. High microbial respiratory activity was determined with values between 1.57 and 1.17 μg CO2–C g−1 soil h−1 at 22 °C and 40 to 70% water-holding capacity for the grassland and forest topsoils, respectively. The microbial C to organic C ratio showed values up to 20 mg Cmic g−1 Corg. Although up to 2.69 kg C m−2 were estimated to be sequestered during 30 years, the microbial indicators showed intensive colonisation and high transformation rates under both forest and grassland which were higher than those determined in agricultural and forest topsoils in Northern Germany.
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  • 90
    Publication Date: 2015-02-11
    Description: A regional classification of shoreline segments along the Alaskan Beaufort Sea Coast was developed as the basis for quantifying coastal morphology, lithology, and carbon and mineral sediment fluxes. We delineated 48 mainland segments totaling 1,957 km, as well as 1,334 km of spits and islands. Mainland coasts were grouped into five broad classes: exposed bluffs (313 km), bays and inlets (235 km), lagoons with barrier islands (546 km), tapped basins (171 km) and deltas (691 km). Sediments are mostly silts and sands, with occasional gravel, and bank heights generally are low (2–4 m), especially for deltas (〈1 m). Mean annual erosion rates (MAER) by coastline type vary from 0.7 m/year (maximum 10.4 m/year) for lagoons to 2.4 m/year for exposed bluffs (maximum 16.7 m/year). MAERs are much higher in silty soils (3.2 m/year) than in sandy (1.2 m/year) to gravelly (−0.3 m/year) soils. Soil organic carbon along eroding shorelines (deltas excluded) range from 12 to 153 kg/m2 of bank surface down to the water line. We assume carbon flux out from depositional delta sediments is negligible. Across the entire Alaskan Beaufort Sea Coast, estimated annual carbon input from eroding shorelines ranges from –47 to 818 Mg/km/year (Metric tones/km/year) across the 48 segments, average 149 Mg/km/year (for 34 nondeltaic segments), and total 1.8×105 Mg/year. Annual mineral input from eroding shorelines ranges from −1,863 (accreting) to 15,752 Mg/km/year, average 2,743 Mg/km/year, and totals 3.3 ×106 Mg/year.
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  • 91
    Publication Date: 2015-11-25
    Description: Abyssal macrofaunal composition of 21 epibenthic sledge hauls from twelve stations taken in the Kuril–Kamchatka Trench (KKT) and at the adjacent abyssal plain, Northwest Pacific, is presented. Sampling with the fine meshed epibenthic sledge yielded higher abundances and species richness than was reported from previous expeditions from board of RV Vityaz. In total 84,651 invertebrates were sampled with RV Sonne between July and September of 2012 (31,854 invertebrates if standardised for 1000 m2 trawled distances) from 41 taxa of different taxonomic ranks (15 phyla, 28 classes, 7 orders) were sampled from a trawled area of 53,708 m² and have been analyzed. Few taxa were frequent and most taxa were rare in the samples, twelve taxa occurred with more than 1% frequency. Of these, the Polychaeta were most abundant followed by the benthic Copepoda and Isopoda. Total numbers of individuals varied between stations and were highest with 4238 individuals at station 2-10 close to the KKT in 4865 m depth and lowest with 374 individuals at station 6-11 in 5305 m depth. At this station also the lowest number of taxa occurred (18 taxa) while the highest number occurred with 31 taxa at station 3-9 in 4991 m depth. Numbers of individuals decreased with increasing depth between 4830 and 5780 m. Crustaceans of the superorder Peracarida were one of the dominating taxa with four orders occurring frequently in most samples. In total, Isopoda were most important and occurred with 59% of all peracarid orders sampled, followed by Amphipoda with 21%, Tanaidacea with 11%, Cumacea with 9%, and Mysidacea with 〈1%. The communities of the stations (and hauls) of the KKT abyssal area differ in terms of taxon composition from each other. A cluster analysis (nMDS) performed for all sampled stations revealed no clear pattern of community similarity between stations or hauls. All hauls close to the trench (2-9 and 2-10 close to the eastern slope of the KKT; and 3-9 and 4-3 at the western slope) were most different to the other hauls. Hauls 8-9 and 8-12 as well as 5-10 and 7-10 in the approximate centre of the overall research area were most similar (88% similarity). The non-isolated KKT area is characterized by higher abundances and higher benthic species richness than the geographically isolated and young deep-sea basin of the Sea of Japan.
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  • 92
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 111 . pp. 220-244.
    Publication Date: 2015-11-25
    Description: The isopod family Munnopsidae Lilljeborg, 1864 was the most diverse and species richest family among all macrobenthic organisms collected during the expedition KuramBio in the abyssal area off the Kuril–Kamchatka Trench (R.V. Sonne, 2012). The munnopsid genus Microcope Malyutina, 2008, represented by two species, was one of the most abundant and frequent isopod genera sampled at all stations. Microcope ovata ( Birstein, 1970), the only known Pacific species of Microcope to date, is redescribed based on the new collections, since the types of the species were lost. Descriptions of a new species from the KuramBio samples, Microcope stenopigussp. nov. and a new species from the opposite side of Pacific Ocean, from the southeastern Australian slope, Microcope justisp. nov., are presented herein. These findings increase the number of described species of Microcope to five and extended the geography of the genus from the previously known South Atlantic, Antarctic and the northwestern Pacific to the new localities from the southwestern Pacific. The depth range for the genus was also extended from 2014–7370 m, to 427–7370 m. A map of the distribution of the genus Microcope and a key to the described species of Microcope are provided.
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  • 93
    Publication Date: 2015-11-25
    Description: During the German–Russian expedition KuramBio (Kuril–Kamchatka Biodiversity Studies) from board of the RV Sonne to the Kuril–Kamchatka Trench and adjacent abyssal plain, benthic samples were taken by means of a camera-epibenthic sledge. Amongst one of the most diverse macrobenthic taxa, the Isopoda (Crustacea, Malacostraca), Ischnomesidae were the fifth most abundant isopod family in the Kuril–Kamchatka area and were sampled with 24 species from 5 genera in 21 hauls at 12 stations. Fortimesus occurs most frequently in the samples (36% of all Ischnomesidae sampled), followed by Stylomesus (26%), Heteromesus (23%), Ischnomesus (10%) and Gracilimesus (4%). Number of ischnomesid individuals is highest at station 10-12 with 35 specimens, followed by station 12-4 (30 ind.), station 6-12 (29 ind.), station 9-9 (28), and station 1-11 (24). At station 4-3 only 1 specimen was found. A key to all genera of Ischnomesidae is provided. Two new species from two genera: Stylomesus Wolff, 1956 and Fortimesus Kavanagh and Wilson, 2007 are described from the KuramBio material. Stylomesus malyutinae sp. nov. is distinguished by the smooth body surface, the shape of pleotelson and the length of uropods from other species of the genus from the Northwest Pacific Ocean. Fortimesus trispiculum sp. nov. is characterised by anterolateral projections of pereonites 1–3 which are forming an angle of about 45° with the longitudinal body axis decreasing in length from anterior to posterior.
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  • 94
    Publication Date: 2015-11-25
    Description: Individual wood fragments obtained from Agassiz trawl samples in the abyssal plain area off the Kuril–Kamchatka Trench were analysed for faunistic components. Out of seven pieces of wood collected, only five harboured fauna and each showed distinctively different colonization patterns. In total, 257 specimens, mainly belonging to the phyla Arthropoda, Nematoda, Mollusca and Annelida, were collected from the available pieces of wood. While wood-boring bivalves of the genus Xylophaga, generally seen as opportunists among wood-converting organisms, were present at nearly all stations, the overwhelming majority of taxa found were restricted to individual pieces of wood. A fresh piece of wood from a site opposite to the Tsugaru Strait, was the most heavily colonized. The presence of shallow or even putative fresh-water taxa beside truly deep-water components possibly suggests a recent sinking of that particular wood fragment and demonstrates the role of such ephemeral organic objects in deep-sea ecosystems as energy-rich feeding grounds and potential distributional stepping stones. Detailed studies of driftwood communities on single sunken wood fragments from deep oceans are limited. The present data not only demonstrate a tolerance of some taxa to changes in physical parameters, such as hydrostatic pressure, salinity and temperature, but also indicate a higher biodiversity on fresher wood pieces compared to wood which already underwent decomposition processes. It is, however, not clear whether the species diversity was linked to the type of wood, since exhaustive analyses on the wood pieces themselves were not conducted.
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  • 95
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 111 . pp. 376-388.
    Publication Date: 2015-11-25
    Description: During the German–Russian expedition KuramBio (Kuril–Kamchatka Biodiversity Studies) to the northwest Pacific Kuril–Kamchatka Trench and its adjacent abyssal plain, we found several kinds and sizes of plastic debris ranging from fishing nets and packaging to microplastic in the sediment of the deep-sea floor. Microplastics were ubiquitous in the smaller fractions of the box corer samples from every station from depths between 4869 and 5766 m. They were found on the abyssal plain and in the sediments of the trench slope on both sides. The amount of microplastics differed between the stations, with lowest concentration of 60 pieces per m2 and highest concentrations of more than 2000 pieces per m2. Around 75% of the microplastics (defined here as particles 〈1 mm) we isolated from the sediment samples were fibers. Other particles were paint chips or small cracked pieces of unknown origin. The Kuril–Kamchatka Trench area is known for its very rich marine fauna (Zenkevich, 1963). Yet we can only guess how these microplastics accumulated in the deep sea of the Kuril-Kamchatka Trench area and what consequences the microplastic itself and its adsorbed chemicals will have on this very special and rich deep-sea fauna. But we herewith present an evaluation of the different kinds of plastic debris we found, as a documentation of human impact into the deep sea of this region of the Northwest Pacific.
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  • 96
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 111 . pp. 26-33.
    Publication Date: 2015-12-01
    Description: During the German–Russian KuramBio (Kuril–Kamchatka Biodiversity Studies) expedition with the RV Sonne from July to September 2012, a 0.25 m2 box corer was used to sample the benthic fauna of the Kuril–Kamchatka area. 23 cores were deployed at 12 stations, and in total 36,648 individuals could be identified from a combined surface area of 5.75 m2. Total faunal densities ranged from 1024 to 16,592 ind. m−2, respectively, for the macrofauna from 436 to 3520 ind. m−2. The fauna was dominated by Nematoda (65%), even though this group and other meiofaunal taxa were only partially retained by the 300 µm screen that was used as the smallest screen for this study. The remaining part of the fauna was dominated by polychaetes (23%), followed by peracarid crustaceans (6%) and molluscs (3%). Most of the collected taxa occurred very patchily. Over 80% of the animals were extracted from the upper 2 centimeters of the sediment. Compared to other regions of the Pacific the density of the benthic fauna was unusually high. At the upper slope of the continental margin of the trench and at the southern part of the area the benthic fauna was most taxon rich. Station 3 from the continental slope of the trench was also most rich in terms of faunal density (total numbers of ind. m−2), followed by the station 11 and 12 from that the southernmost part of the abyss. Although the Kuril–Kamchatka area has been sampled on several expeditions during the last century, and some studies on the biomass of the benthic fauna have been published, this study offers the first quantitative community analysis of the benthic fauna in terms of abundance and taxon richness.
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  • 97
    Publication Date: 2020-11-23
    Description: A comparison of micropaleontological data on the distribution of the Cycladophora davisiana radiolarian species in the surface sediment layer and the Late Quaternary sediments from the Subarctic Pacific and Far East marginal seas allowed conclusions concerning the possible conditions and occurrence of intermediate waters during the last glacial maximum. We used the modern data on the C. davisiana species, which is a micropaleontological indicator of the cold oxygen-rich upper intermediate water mass, which is now forming only in the Sea of Okhotsk. The high amount of C. davisiana in sediments of the last glacial maximum may point to the possible formation and expansion of the ventilated intermediate water in the most part of the Subarctic paleo-Pacific: the Bering Sea, the Sea of Okhotsk, within the NW Gyre, and in the Gulf of Alaska.
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  • 98
    facet.materialart.
    Unknown
    Springer
    In:  Geo-Marine Letters, 25 (2-3). pp. 110-120.
    Publication Date: 2015-03-05
    Description: The results of permafrost and coastal dynamics investigations at four key sites on the shores of the Kara and Barents Seas are discussed. Three ACD key sites, Marre-Sale, Shpindler, and Kolguev, characterize areas with active thermal erosion; key site Cape Bolvansky is found on a relatively stable coast. It is found that the coastal retreat rate has spatial and temporal variability, which is typical of the entire Arctic coast. Coastal deposits on the Kara and Barents Seas have a low organic carbon content. Annual input of material into the Kara Sea resulting from coastal degradation reaches 35–40 million t, including about 7.5 million t of ice, 0.35 million t of organic carbon, and 0.3 million t of soluble salts.
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  • 99
    Publication Date: 2017-04-13
    Description: Highlights: • Distinct rare earth element profiles across southern boundary of Antarctic Circumpolar Current • Low particle concentrations and strong vertical exchange cause homogenous vertical profiles • Pronounced deepwater Ce anomalies reflect isolation from new continental sources to seawater The concentrations of rare earth elements (REEs) in seawater display systematic variations related to weathering inputs, particle scavenging and water mass histories. Here we investigate the REE concentrations of water column profiles in the Atlantic sector of the Southern Ocean, a key region of the global circulation and primary production. The data reveal a pronounced contrast between the vertical profiles in the Antarctic Circumpolar Current (ACC) and those to the south of the ACC in the Weddell Gyre (WG). The ACC profiles exhibit the typical increase of REE concentrations with water depth and a change in the shape of the profiles from near linear for the light REEs to more convex for the heavy REEs. In contrast, the WG profiles exhibit high REE concentrations throughout the water column with only the near surface samples showing slightly reduced concentrations indicative of particle scavenging. Seawater normalised REE patterns reveal the strong remineralisation signal in the ACC with the light REEs preferentially removed in surface waters and the mirror image pattern of their preferential release in deep waters. In the WG the patterns are relatively homogenous reflecting the prevalence of well-mixed Lower Circumpolar Deep Water (LCDW) that follows shoaling isopycnals in the region. In the WG particle scavenging of REEs is comparatively small and limited to the summer months by light limitation and winter sea ice cover. Considering the surface water depletion compared to LCDW and that the surface waters of the WG are replaced every few years, the removal rate is estimated to be on the order of 1 nmol m- 3 yr- 1 for La and Nd. The negative cerium anomalies observed in deep waters are some of the strongest found globally with only the deepest waters in parts of the Pacific having stronger anomalies. These deep waters have been isolated from fresh continental REE inputs during their long journey through the abyssal Indo-Pacific ocean and suggests that the high REE concentrations found in the ACC and WG reflect contributions from old deep waters.
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  • 100
    facet.materialart.
    Unknown
    Springer
    In:  Journal of Paleolimnology, 34 (3). pp. 363-376.
    Publication Date: 2015-04-02
    Description: Ostracode analysis was carried out on samples from ice-rich permafrost deposits obtained on the Bykovsky Peninsula (Laptev Sea). A composite profile was investigated that covers most of a 38-m thick permafrost sequence and corresponds to the last ca. 60 kyr of the Late Quaternary. The ostracode assemblages are similar to those known from European Quaternary lake deposits during cold stages. The ostracode habitats were small, shallow, cold, oligotrophic pools located in low centred ice wedge polygons or in small thermokarst depressions. In total, 15 taxa, representing 7 genera, were identified from 65 samples. The studied section is subdivided into six ostracode zones that correspond to Late Quaternary climatic and environmental stadial-interstadial variations established by other paleoenvironmental proxies: (1) cold and dry Zyrianian stadial (58–53 kyr BP); (2) warm and dry Karginian interstadial (48–34 kyr BP); (3) transition from the Karginian interstadial to the cold and dry Sartanian stadial (34–21 kyr BP); (4) transition from the Sartanian stadial to the warm and dry Late Pleistocene period, the Allerød (21–14 kyr BP); (5) transition from the Allerød to the warm and wet Middle Holocene (14–7 kyr BP); and (6) cool and wet Late Holocene (ca. 3 kyr BP). The abundance and diversity of the ostracodes will be used as an additional bioindicator for paleoenvironmental reconstructions of the Siberian Arctic.
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