Stable Isotopes

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Calcareous nannofossils in the S-Atlantic during the Middle to Late Miocene: Coccolithophorid carbonate budgets, fine-fraction stable isotopes and their paleoceanographic implications

Calcareous nannofossils in the S-Atlantic during the Middle to Late Miocene: Coccolithophorid carbonate budgets, fine-fraction stable isotopes and their paleoceanographic implications

Coccolithophore production occurs nearly year-round in the tropics to subpolar regions, but it is punctuated by strong seasonal fluctuations due to changing availability of nutrients associated with seasonal upwelling and/or deep mixing of surface waters. In general, coccolithophore cell density in subtropical to polar regions is highest in early spring when the seasonal thermocline is weakly developed and the upper water column is relatively cool and rich in nutrients (e.g. Haidar and Thierstein, 2001). The flux of planktic foraminifers shows strong species-specific seasonal fluctuations (e.g. Deuser and Ross, 1989). G. sacculifer flux increases during the later half of the spring bloom period towards the summer, and reaches highest level in the fall between October and November (Deuser, 1987; Deuser and Ross, 1989). Therefore, the isotopic composition of Globigerinoides may represent hydrographic features of warmer, nutrient-poor post-spring bloom surface waters. Ennyu et al. (2002) suggest that polyspecific coccolith stable isotopes reflect surface-water hydrographic conditions during upwelling season or the period of vertical mixing (late winter-early spring) when the surface waters are enriched in nutrients, whereas Globigerinoides reflect the post- deep-mixing, relatively warmer (late spring to fall) stratified surface waters.
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Stable isotopes of water reveal differences in plant – soil water relationships across northern environments

Stable isotopes of water reveal differences in plant – soil water relationships across northern environments

We compared stable isotopes of water in plant stem (xylem) water and soil collected over a complete growing season from five well-known long-term study sites in north- ern/cold regions. These spanned a decreasing temperature gradient from Bruntland Burn (Scotland), Dorset (Canadian Shield), Dry Creek (USA), Krycklan (Sweden), to Wolf Creek (northern Canada). Xylem water was isotopically depleted compared to soil waters, most notably for deuterium. The degree to which potential soil water sources could explain the isotopic composition of xylem water was assessed quanti- tatively using overlapping polygons to enclose respective data sets when plotted in dual isotope space. At most sites isotopes in xylem water from angiosperms showed a strong overlap with soil water; this was not the case for gymnosperms. In most cases, xylem water composition on a given sampling day could be better explained if soil water composition was considered over longer antecedent periods spanning many months. Xylem water at most sites was usually most dissimilar to soil water in drier summer months, although sites differed in the sequence of change. Open ques- tions remain on why a significant proportion of isotopically depleted water in plant xylem cannot be explained by soil water sources, particularly for gymnosperms. It is recommended that future research focuses on the potential for fractionation to affect water uptake at the soil-root interface, both through effects of exchange between the vapour and liquid phases of soil water and the effects of mycorrhizal interactions. Additionally, in cold regions, evaporation and diffusion of xylem water in winter may be an important process.
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A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events

A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events

Our results from both cores provide evidence for coral responses to increased influence of different stressors and extreme events. The fact that both stable isotopes and extension rates in core CHI7 show a distinct baseline shift in the mid-1990s, which is not evident in growth data of core CHI5 from a different species, points to a major change in the physiology of coral CHI7 (P. strigosa). Recent studies have shown that in reef-building corals, some genotypes of endosymbiotic algae are more susceptible to heat stress than others, corals harboring these types are less resistant to temperature-induced bleaching 43 . A change to more heat-tolerant symbiont types after severe
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Pup vibrissae stable isotopes reveal geographic differences in adult female southern sea lion habitat use during gestation

Pup vibrissae stable isotopes reveal geographic differences in adult female southern sea lion habitat use during gestation

Here we use vibrissae stable isotopes to elucidate the habitat use of southern sea lions (SSL) ( Otaria flavescens). SSL experienced a precipitous decline at the Falkland Islands in the South Atlantic, with annual pup production falling from over 80,000 in the 1930s to less than 6,000 in the 1960s [ 15 ]. The population continued to decline into the mid 1990s and, although now increasing, it remains at less than 6% of the 1930s estimate [ 15 ]. Despite currently breeding at over 70 sites around the Falkland Islands (a similar breeding distribution as in the 1930s), cur- rent knowledge of SSL foraging ecology is principally derived from a single breeding colony, Big Shag Island (East Falkland). Data from biologging tags and stable isotopes showed that adult female SSL breeding at Big Shag Island forage in two discrete habitats, corresponding to inshore (coastal) and offshore waters (outer Patagonian Shelf) [ 16 ]. Adult female SSL that for- age offshore travel further, dive deeper and have characteristically lower δ 13 C and δ 15 N values compared to adult female SSL that forage inshore [ 16 ].
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Detection of Localized Hepatocellular Amino Acid Kinetics by using Mass Spectrometry Imaging of Stable Isotopes

Detection of Localized Hepatocellular Amino Acid Kinetics by using Mass Spectrometry Imaging of Stable Isotopes

softer matrix-assisted laser desorption ionization (MALDI). [5] It was demonstrated that rates of lipid synthesis are altered in different tumor cell subpopulations, thus highlighting the need to study localized synthesis kinetics in tumor metabo- lism. In addition, MALDI-MSI in combination with stable isotopes has been applied to study the formation of athero- sclerotic plaques [6] and the nitrogen cycle within plants. [7]

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Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems

Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems

The number of protons in an element (equal to the atomic number ‘Z’) is constant, but the number of neutrons (the neutron number ‘Nn’) may vary. Isotopes of a given element differ from one another owing to the number of neutrons they contain. This variation in neutron number does not affect the gross chemical properties of the element. The mass of an element (the sum of Z 1 Nn) is the superscripted number to the left of the element designation (Kendall and Caldwell, 1998). Thus, for N with an atomic number of 7, the stable isotopes have mass numbers of 14 ( 14 N with seven neutrons) and 15 ( 15 N with eight neutrons). These N isotopes occur naturally in the environment (Sharp, 2007). In air, the natural abundance of 15 N is constant with a 15 N/ 14 N ratio equal to 1/272 or 0.3676% (Junk and Svec, 1958).
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Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen

Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen

be attributed to their life span and behavior in the sec- ond intermediate host. In contrast to fast growing acan- thocephalans larval nematodes can live in the host for many months over different seasons before being trans- mitted to a definitive host. However, after molting into fourth-stage larva (L4) in the fish host they exhibit much lower metabolic rates than the actively growing and re- producing acanthocephalans. Therefore, changes in host food composition and feeding activity and an associated isotopic shift have most probably no such strong influ- ence on the composition of stable isotopes in nematodes as observed for the acanthocephalans.
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Nitrogen cycling in the southern North Sea - Assessment by stable isotopes

Nitrogen cycling in the southern North Sea - Assessment by stable isotopes

Estuaries have a prominent role in regulating material fluxes from land to sea (Crossland 2005), and the capacity of estuaries for reducing riverine nutrient loads to continental shelf seas has been appreciated as one of the most valuable functions of all global ecosystems (Costanza et al. 1997). According to current understanding of reactive nitrogen transport from land to sea, the estuaries of major rivers are thought to be sites of massive nitrate losses (Brion et al. 2004; Seitzinger et al. 2006), removing up to fifty per cent of reactive nitrogen(OsparCom 2000). In spite of its salient relevance as natural attenuation mechanism combating eutrophication of coastal seas and the intrinsic economic relevance of this specific ecosystem service, the cycling of nitrogen in contemporary estuaries is still subject to open questions. Most older studies are based on tidal input and output, which are prone to a large degree of uncertainty, or are based on mass fluxes alone, which is problematic when sources (e.g., nitrification) and sinks (assimilation and burial, denitrification) may be balanced. A few newer studies suggest that estuarine removal of reactive nitrogen may be significantly overrated, with estimates of removal efficiency ranging from ~5% in the Humber estuary (Jickells et al. 2000) to ~20% in the Rowley estuary (Tobias et al. 2003). More than concentration data alone, measurements of stable isotopes in reactive nitrogen species provide a powerful tool to assess internal turnover and sources in estuaries (Middelburg and Nieuwenhuize 2001; Sebilo et al. 2006). The combined use of δ 15 N-NO
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Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatty acids

Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatty acids

of heavy nitrogen (d 15 N) and carbon (d 13 C) ( Hyodo, 2015 ). d 15 N increases predictably when one organism consumes another, thus indicating whether species are at the top or bottom of the food web ( Heethoff & Scheu, 2016 ). d 13 C could be used to distinguish between main carbon sources at the bottom of the food web because C 3 , C 4 and CAM plants have different signatures ( O’Leary, 1988 ; Gannes, Del Rio & Koch, 1998 ). SIA provides time-representative clues about trophic position, but limited information on specific food sources or feeding behaviors. For instance, if two species feed exclusively on primary consumers, they will have similar d 15 N, regardless of what prey items they actually consume, or whether the food is obtained through predation or scavenging. As such, stable isotope signatures are not suitable to calculate niche breadth or overlap, or to be analyzed as species-resources interaction networks.
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Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests

Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests

While the thermocline temperature record of core GeoB 17419-1 suggests that the thermocline off PNG is affected by obliquity-driven climate variations of the southern hemisphere mid-lat[r]

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Biogeochemistry of sulfur in forest ecosystems with special focus on investigation of sulfur stable isotopes / eingereicht von Ing. Bc. Ondřej Hanousek

Biogeochemistry of sulfur in forest ecosystems with special focus on investigation of sulfur stable isotopes / eingereicht von Ing. Bc. Ondřej Hanousek

The argon ICP used in ICP-OES and quadrupole mass spectrometer (MS) used e.g. as a detector in gas chromatography were coupled to become ICP-MS for the first time in 1980 [61]. Some modifications had to be made to enable the ICP working with the grounded mass spectrometer. Since then, ICP was coupled with sector field or time-of-flight mass spectrometers and developments in sample introduction, ion transmission rate, dynamic detection range or interference removal efficiency have been made. The removal / reduction of interferences is highly relevant when analyzing S by ICP-MS. The ions generated in the ICP are detected according to their mass-to-charge (m/z) ratio. As the m/z of the most abundant S isotopes, 32 S and 34 S, corresponds – among others – to the m/z of
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Cadmium, copper and zinc stable isotopes as analytical tool to trace sources and processes in agricultural systems

Cadmium, copper and zinc stable isotopes as analytical tool to trace sources and processes in agricultural systems

Furthermore, stable metal isotopes of the soil and all inputs and outputs were (Cd) and will be (Cu & Zn) determined. Cd mass balances showed losses for wheat cultivation (-0.01 to -0.35 g ha -1 y -1 ) and accumulations for barley cultivation (0.18 to 0.71 g ha -1 y -1 ). Isotopic ratios in wheat (? 114/110 Cd straw-grain = -0.34 to -0.38‰) and barley plants (-0.44 to -0.82‰) revealed that uptake and retranslocation of Cd in the plants is driven by physiological processes to reduce toxic Cd impacts. Cu and Zn mass balances showed that manure application is by far the most important Cu (146-340 g ha -1 y -1 ) and Zn (947-1’742 g ha -1 y -1 ) input. Inputs with bulk deposition and through parent material weathering were by 1-2 orders of magnitude smaller. Beside the Cu and Zn budgets, stable isotope data (not yet analysed) will be presented and discussed to assess the biogeochemical processes and redistribution of (anthropogenic) Cu and Zn in agricultural systems.
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Modelling Stable Isotopes in the Eemian and Holocene Hydrological Cycles

Modelling Stable Isotopes in the Eemian and Holocene Hydrological Cycles

One of the main goals of paleoclimatology is answering the question whether the air tem- perature during a given period and in a given region was different from today. However, this question can neither be answered without knowledge about the seasonal distribution of temperature nor without knowledge about the seasonal distribution of the accumula- tion/preservation rate of the archive that is to be analysed by the palaeoclimatologist. Among the great variety of proxies for past climate variables there is only a small num- ber of archives that preserve seasonal climate signals. Some of these (e.g. corals of the genus porites, speleothems, and -for the recent past- ice cores) are able to record stable oxygen or hydrogen isotope signals, containing direct information about the paleo-hydrology on seasonal time scales. Furthermore, the isotopic composition of a climate archive can give valuable information about past temperature, amount of precipitation or wind regime.
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Novel methodological approaches in loess research – interrogating biomarkers and compound-specific stable isotopes

Novel methodological approaches in loess research – interrogating biomarkers and compound-specific stable isotopes

We discuss the potential of (i) n-alkanes as plant leaf wax-derived biomarkers for reconstructing vegetation history, (ii) amino acid racemization and glycerol dialkyl gly[r]

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Magnesium stable isotopes as a proxy for biogeochemical processes in terrestrial environment

Magnesium stable isotopes as a proxy for biogeochemical processes in terrestrial environment

I Magnesium (Mg) is the fourth most abundant element in the Earth and plays a significant role in biological activities. Processes involved in Mg cycle can fractionate Mg stabl[r]

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Stable isotopes in loess-paleosol-sequences from the Carpathian Basin : methodological challenges and paleoenvironmental implications

Stable isotopes in loess-paleosol-sequences from the Carpathian Basin : methodological challenges and paleoenvironmental implications

Germany; 3 Institute of Geography, Technical University of Dresden, Germany; 4 Organic Geochemistry Group, MARUM-Center for Marine Environmental Sciences and Department of Geosciences[r]

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Stable water isotopes in the global water cycle: Atmospheric model simulations and application to proxy data

Stable water isotopes in the global water cycle: Atmospheric model simulations and application to proxy data

In the second part of this thesis, the spatial distribution of hydrogen isotopes in Africa during three important past climate periods - the Last Glacial Maximum (LGM, 21 ka), Heinrich Stadial-1 (HS1, 16-18 ka) and the mid-Holocene (6 ka) - was investigated. Tropical African climate is closely related to the Inter-Tropical Convergence Zone (ITCZ) and the tropical rainbelt, the intensity and location of which supposedly varied with the climate-changes in the high latitudes ( Gasse , 2000 ) and the sea-surface temperature (SST) variations in the Northern Atlantic and Indian Ocean ( deMenocal et al. , 2000 ). Stable isotopes of hydrogen derived from plant leaf waxes have been used as a proxy to reconstruct the past climates over Africa, as the hydrogen isotopic composition of meteoric water and relative humidity influence the δD wax ( Sauer et al. , 2001 ; Collins et al. , 2013 ). In turn, in the monsoon domains, the ratio of isotopes in precipitation is mostly related to the amount of precipitation ( Risi et al. , 2008a ). Accordingly, the results suggest that enhanced convection and an increased summer precipitation led to more negative values of δD precip in North West Africa during the
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Isoscalar Dipole Excitation in Tin Isotopes

Isoscalar Dipole Excitation in Tin Isotopes

For a more precise description of collective and single particle excitation in nuclei, more advanced models and potentials have been developed. Potentials have been de- signed from first principles, for example the (pionless) effective field theory [SH00], or phenomenological interactions such as the Gogny-force [BGG91]. For the models the shell model is an example, in which the excitation energies and states are calculated. Also on the experimental side modes of excitation have been discovered and are stud- ied, e.g., collective modes. One of these is the Giant Dipole Resonance (GDR). This excitation mode splits into an isovector and isoscalar part and is located well above the particle separation energy. These modes can be pictured as a vibration of the protons and neutrons out-of-phase and in-phase, respectively, see for exam- ple [AN13, PVKC07a]. On the low-energy tail located between excitation energy of 5 and 11 MeV, another excitation mode was discovered, see for example [SAZ13], the low-energy dipole excitation, also referred to as soft-dipole mode or as pygmy dipole resonance. This mode appears for nuclei with an asymmetric proton-to-neutron ratio and its nature is still under debate. Nevertheless, to understand this mode, its isoscalar and isovector nature is explored. Many efforts are undertaken to investigate this mode with different probes as a function of the asymmetric proton-to-neutron ratio, see chap- ter 2. As such, the tin isotopes have been selected as they provide 10 stable isotopes and have a closed proton shell 1 (Z = 50).
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Gutenberg Open Science: Variation of stable silicon isotopes: Analytical developments and applications in Precambrian geochemistry

Gutenberg Open Science: Variation of stable silicon isotopes: Analytical developments and applications in Precambrian geochemistry

A common procedure for the short-term drift correction of the effects of instrumental mass bias are internal and external normalization, which describe an isotopic normalization by a ratio of either the same or a different element, respectively. However, internal normalization cannot be used in general for stable isotope ratio measurements, because it eliminates both instrumental and natural mass fractionations. A further technique, the double spike technique is inapplicable for silicon isotopes, as well, since the technique can only be applied to elements with four stable isotopes (Albarède and Beard, 2004), e.g. typically Fe isotopes. All procedures have in common that they employ either a linear, power or exponential law correction to overcome the mass bias. The choice among these laws will depend on which law best reproduces the true isotopic composition. Detailed studies of corrections schemes have shown that the power law and particularly the exponential law are preferable for the correction of larger mass fractionation effects (Russell et al., 1978; Wasserburg et al., 1981; Hart and Zindler, 1989). The basic principal of external normalization is that a solution is spiked with an external element, with a known (or constant) isotopic composition, with a molar mass as close as possible to the studied element. The mass bias measured for the element of known isotopic composition can be used to correct the measured isotopic composition of the analyte and determine its true unknown isotopic composition. Cardinal et al. (2003) showed that in case of silicon isotopes, Mg can be used as an external element (the reference standard SRM 980). The Mg concentration is adjusted to allow an intensity ratio Si:Mg ~ 1:1. Si isotope ratios are then corrected employing the exponential mass bias law with a fractionation factor (ƒ Mg ) determined from the analyzed 25 Mg/ 24 Mg ratio:
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Gutenberg Open Science: Exploring physical processes related to past climate proxies: lake sediments and stable water isotopes

Gutenberg Open Science: Exploring physical processes related to past climate proxies: lake sediments and stable water isotopes

deuterium excess. This finding contradicts results from other models. Although requiring con- firmation by isotope data from different regions and longer time scales, this weak correlation might be of major importance for the reconstruction of moisture source temperatures from ice core data. Second, the Lagrangian source diagnostic is combined with a Craig-Gordon frac- tionation parameterization for the identified evaporation events in order to simulate the isotope ratios at Rehovot. In this way, the Craig-Gordon model can be directly evaluated with atmo- spheric isotope data, and better constraints for uncertain model parameters can be obtained. A comparison of the simulated deuterium excess with the measurements reveals that a much better agreement can be achieved using a wind speed independent formulation of the non-equilibrium fractionation factor instead of the classical parameterization introduced by Merlivat and Jouzel, which is widely applied in isotope GCMs. Finally, the first steps of the implementation of water isotope physics in the limited-area COSMO model are described, and an approach is outlined that allows to compare simulated isotope ratios to measurements in an event-based manner by using a water tagging technique. Several case studies are performed, again focusing on iso- tope fractionation during water evaporation from the sea. The good agreement between model results and measurements at Rehovot demonstrates the applicability of the approach. Because the model can be run with high, potentially cloud-resolving spatial resolution, and because it contains sophisticated parameterizations of many atmospheric processes, a complete implemen- tation of isotope physics will allow detailed, process-oriented studies of the complex variability of stable isotopes in atmospheric waters in future research.
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