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Interpretation of benthic foraminiferal stable isotopes in subtidal estuarine environments

Interpretation of benthic foraminiferal stable isotopes in subtidal estuarine environments

salinity on the basis of fossil assemblages. Results obtained in this study show clearly that in subtidal environments, high spatial and temporal variability of the en- vironmental parameters as well as benthic foraminiferal as- semblages seriously hamper the application of oxygen and carbon isotope geochemistry for environmental reconstruc- tions. In these extremely variable environments, timing of foraminiferal calcification has a profound impact on the δ 18 O of the shells. Here we show that different calcification peri- ods apply to different species, in different parts of the es- tuary. Although stable isotopes have been used in brackish marine environments to reconstruct paleosalinity over time scales varying from centuries (Thomas et al., 2000; Scheurle and Hebbeln, 2003) to thousands of years (Winn et al., 1998; Kim and Kennett, 1998; Polyak et al., 2003; Peros et al., 2007), it is obvious that the reconstructing salinity or tem- perature in these settings needs additional constraints from independent proxies (Polyak et al., 2003; Peros et al., 2007). Acknowledgements. This work is a contribution to the PaleoSalt
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Trophic ecology of Southern Ocean sea stars inferred from stable isotopes ratios of C and N

Trophic ecology of Southern Ocean sea stars inferred from stable isotopes ratios of C and N

Using stable isotopes in trophic ecology ● Stable isotope composition of an organism reflects stable isotope composition of its food ● Isotopic niche ↔ trophic niches ➞ estimation of trophic diversity, trophic plasticity and diet overlap with ellipse areas (SIBER

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Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems

Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems

2.2. Food web integrators δ 13 C may sometimes define an isotopic signature for seagrass, distinguishable from those of other primary producers. For example, in a Corsican seagrass bed, it is possible to assign an isotopic signature to the phyto- plankton (-23‰), to dominant macroalgae (-19‰) and to seagrass leaves (-9‰) (Dauby, 1989). These signatures of potential food sources, and the fact that the isotopic composition of an animal is strongly determined by the isotopic composition of its food, allow the use of isotopic ratios as food web integrators. On the other hand, δ 15 N offers the possibility of estimating the trophic level of organisms, because δ 15 N values generally increase with increasing trophic position (e.g. Hobson and Welsh, 1992) but this 15 N enrichment is variable; it varies between animal groups and is often diet-related (e.g. Mac Cutchan et al., 2003; Vanderklift and Ponsard, 2003). Stable isotopes (C, N, S) have been largely used to assess seagrass food webs in temperate meadows (e.g. Kharlamenko et al., 2001; Stephenson et al., 1986), in Mediterranean meadows (e.g. Dauby, 1989; Jennings et al., 1997; Lepoint et al., 2000; Pinnegar and Polunin, 2000; Vizzini and Mazzola, 2003), and in subtropical and tropical meadows (e.g. Fry, 1984; Kitting et al., 1984; Loneragan et al., 1997; Marguillier et al., 1998; Melville and Connolly, 2003; Moncrieff and Sullivan, 2001).
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Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes

Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes

Correspondence to: David Uhlig (david.uhlig@gfz-potsdam.de) Received: 30 November 2016 – Discussion started: 16 January 2017 Revised: 7 May 2017 – Accepted: 14 May 2017 – Published: 26 June 2017 Abstract. Plants and soil microbiota play an active role in rock weathering and potentially couple weathering at depth with erosion at the soil surface. The nature of this coupling is still unresolved because we lacked means to quantify the pas- sage of chemical elements from rock through higher plants. In a temperate forested landscape characterised by relatively fast ( ∼ 220 t km −2 yr −1 ) denudation and a kinetically lim- ited weathering regime of the Southern Sierra Critical Zone Observatory (SSCZO), California, we measured magnesium (Mg) stable isotopes that are sensitive indicators of Mg util- isation by biota. We find that Mg is highly bio-utilised: 50– 100 % of the Mg released by chemical weathering is taken up by forest trees. To estimate the tree uptake of other bio- utilised elements (K, Ca, P and Si) we compared the dis- solved fluxes of these elements and Mg in rivers with their solubilisation fluxes from rock (rock dissolution flux minus secondary mineral formation flux). We find a deficit in the dissolved fluxes throughout, which we attribute to the nutri- ent uptake by forest trees. Therefore both the Mg isotopes and the flux comparison suggest that a substantial part of the major element weathering flux is consumed by the tree biomass. The enrichment of 26 Mg over 24 Mg in tree trunks relative to leaves suggests that tree trunks account for a sub- stantial fraction of the net uptake of Mg. This isotopic and elemental compartment separation is prevented from obliter- ation (which would occur by Mg redissolution) by two po- tential effects. Either the mineral nutrients accumulate today in regrowing forest biomass after clear cutting, or they are exported in litter and coarse woody debris (CWD) such that they remain in “solid” biomass. Over pre-forest-management
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Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

residence times of soil water (Lee et al., 2007). Even if transpiration predominates under temperate climates and is considered to not fractionate water stable isotopes, evaporation from plant interception or from the upper soil leads to fractionation and enrichment in heavy isotopes (Braud et al., 2005, 2009b; Sprenger et al., 2016; Sutanto et al., 2012). Water recharging during a given season can therefore be identified in deep unsaturated zone profiles, and recharge rates can be obtained from the displacement between successive seasonal inputs (Gehrels et al., 1998; Małoszewski et al., 2006; Małoszewski and Zuber, 1993; McConville et al., 2001; Saxena, 1984). On the one hand, this simple peak-shift method is easily applied (Adomako et al., 2010), even if the isotopic compositions of precipitation are not available (Gehrels et al., 1998). On the other hand, numerical models, such as SiSPAT-Isotopes (Braud et al., 2005, 2009a), Soil-Litter-Iso (Haverd and Cuntz, 2010), or a modified version of HYDRUS-1D (Stumpp et al., 2009a, 2009b; Stumpp and Hendry, 2012), are increasingly being used to understand the dynamics of water stable isotopic composition in the unsaturated zone (Sprenger et al., 2015). Such level of model refinement is associated with a high data requirement that can only be achieved for specific study sites, but less for more numerous and less known sites at the regional scale where there is a lack of recharge rate estimations.
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Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

Dome C Figure 1. AMPS topography of Antarctica and location of selected stations. arrived at 500 hPa. They found that during snowy conditions in winter the travel time of five days was sufficient to identify the evaporation area at the sea surface. In summer, the tra- jectories were often positioned entirely above the continent and at greater height, thus not yielding information about moisture origin. However, the authors did not distinguish between clear-sky precipitation and synoptic precipitation, and the cloud observations had large uncertainties. Sode- mann and Stohl (2009) studied the seasonality of moisture sources for Antarctic precipitation using Lagrangian mois- ture source diagnostic. They traced water vapour transport backwards in time for 20 days to estimate the precipitation origin for Antarctica and found a source region for Dome Fuji at a mean latitude of 44 ◦ S. They state that their results are consistent with findings from GCM with tagged tracers. However, it is not trivial to understand the dynamics of the calculated transport. The shorter trajectories in the present study were cross-checked with the synoptic analysis. 2.3 Stable isotopes
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Evaluating methane oxidation efficiencies in experimental landfill biocovers by mass balance and carbon stable isotopes

Evaluating methane oxidation efficiencies in experimental landfill biocovers by mass balance and carbon stable isotopes

result from several causes. The most important one is possibly related to the fact that the most active zone for CH 4 oxidation in biocovers is located very near the surface, where O 2 availability is greater (Czepiel et al., 1996; Jones and Nedwell, 1993; Jugnia et al., 2008). In fact, as CH 4 migrates through the last stretch of the cover, a significant portion of it can still be oxidized. As a consequence, efficiencies calculated using stable isotope data from samples taken at 0.10 m can – at most – provide the lowest estimate possible for the actual efficiency of the system. Powelson et al. (2007) found that CH 4 oxidation efficiencies evaluated by stable isotopes averaged only
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Precipitation Water Stable Isotopes in the South Tibetan Plateau: Observations and Modeling

Precipitation Water Stable Isotopes in the South Tibetan Plateau: Observations and Modeling

This study shows the potential of Tibetan Plateau precipitation isotopic composition databases for testing the realism of the water cycle simulated by isotopic AGCMs and the importance of spatial resolution for re- alistic simulations. There is a strong need to maintain long-term observations at the monthly time frame, to improve the spatial coverage of the datasets, and to de- velop event-based studies that are necessary to better understand the exact processes at play, including, in the future, the parallel monitoring of water vapor isotopic composition. Our comparison with two AGCMs shows very large systematic biases in the AGCMs regarding both the regional climate and the properties of water stable isotopes in precipitation. The complex topographic features add to the difficulties in correctly simulating moisture advection from the lowlands to the Tibetan Plateau. Second-order isotopic data such as deuterium excess and oxygen 17 are expected to bring further con- straints on the water cycle, moisture origin, local recy- cling, and convective processes. However, models that can correctly capture these second-order tracers remain a future research effort due to the large biases in second- order isotopic data, which are probably linked to land surface, convection, and cloud representations. Nudging does not resolve these parameterization problems but helps to build a framework within which the synoptic- scale atmospheric dynamics is realistic.
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Use of C & N stable isotopes to evaluate interspecific trophic diversity among amphipods from Posidonia oceanica meadows

Use of C & N stable isotopes to evaluate interspecific trophic diversity among amphipods from Posidonia oceanica meadows

Use of C & N stable isotopes to evaluate interspecific Loïc Michel 1,* , Gilles Lepoint 2 , Fabienne Nyssen 1 , Sylvie Gobert 2 & Patrick Dauby 1 1 Laboratory of Systematics and Animal Diversity, MARE Centre, University of Liège, Liège, Belgium, 2 Laboratory of Oceanology, MARE Centre, University of Liège, Liège, Belgium * Corresponding author. E-mail : Loic.Michel@ulg.ac.be

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Artificial reefs do increase secondary biomass production: mechanisms evidenced by stable isotopes

Artificial reefs do increase secondary biomass production: mechanisms evidenced by stable isotopes

In their review regarding the ‘attraction vs. produc- tion’ debate, Brickhill et al. (2005) list some of the knowledge gaps in this topic. Most of them concern trophic relationships on ARs and the transfer of organic matter (OM) from producers to consumers. Brickhill et al. (2005) promote the use of chemical tracers such as carbon and nitrogen stable isotopes to link fish biomass with primary production on ARs, as numerous works demonstrate that this technique is well suited for studying marine food webs (e.g. Kang et al. 2008, Boecklen et al. 2011, Layman et al. 2012, Daigle et al. 2013). The isotopic ratios of a consumer are directly linked with those of its prey with a difference between them. This factor is relatively low for carbon (~1 ‰). Consequently, the carbon isotopic ratio of a consumer is close to those of the OM sources it is depending on, and is used to trace them. In contrast, the nitrogen frac- tionation factor is higher (theoretically 3 to 4 ‰ per trophic level) and the isotopic ratio of nitrogen is com- monly used as a proxy for trophic level (Post 2002). Sta- ble isotope ratios of the diet are integrated in the tissues of a consumer within several months. The cou- pled use of carbon and nitrogen isotopic ratios allows a better understanding of the trophic position of all or- ganisms invol ved in a food web, and gives an inte- grated view of the trophic functioning of an ecosystem. Through the ‘RECIFS PRADO’ program, 400 ARs were deployed in a 2 km 2 zone in the Bay of Marseille
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Applications of stable isotopes in environmental studies at the University of Liege

Applications of stable isotopes in environmental studies at the University of Liege

Applications of stable isotopes in environmental studies at the University of Liege Sturaro N 1 , Borges A V 2 , Das K 1 , Dauby P 3 , Gobert S 1 , Mascart T 1 , Michel L 1 , Remy F 1 and Lepoint G 1 1. Laboratory of Oceanology - MARE Centre - University of LIEGE - B6C - 4000 LIEGE - Sart Tilman - Belgium

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Different particle sources in a bivalve species of a coastal lagoon: evidence from stable isotopes, fatty acids, and compound-specific stable isotopes

Different particle sources in a bivalve species of a coastal lagoon: evidence from stable isotopes, fatty acids, and compound-specific stable isotopes

compound-specific stable isotopes Mathieu-Resuge Margaux 1, 4, * , Schaal Gauthier 1 , Kraffe Edouard 1 , Corvaisier Rudolph 1 , Lebeau Oanez 2 , Lluch-Cota Salvador E. 3 , Salgado García Rosa L. 3 , Kainz Martin J. 4 , Le Grand Fabienne 1

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Stable isotopes as descriptors of trophic niches

Stable isotopes as descriptors of trophic niches

Universidad de Los Llanos Ezequiel Zamora, UNELLEZ, Guanare, Apartado Postal 3310 Venezuela 4 Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut 06520-8106 USA Abstract. Stable isotope ratios (typically of carbon and nitrogen) provide one representation of an organism’s trophic niche and are widely used to examine aspects of food web structure. Yet stable isotopes have not been applied to quantitatively characterize community-wide aspects of trophic structure (i.e., at the level of an entire food web). We propose quantitative metrics that can be used to this end, drawing on similar approaches from ecomorphology research. For example, the convex hull area occupied by species in d 13 C– d 15 N niche space is a representation of the total extent of trophic diversity within a food web, whereas mean nearest neighbor distance among all species pairs is a measure of species packing within trophic niche space. To facilitate discussion of opportunities and limitations of the metrics, we provide empirical and conceptual examples drawn from Bahamian tidal creek food webs. These examples illustrate how this methodology can be used to quantify trophic diversity and trophic redundancy in food webs, as well as to link individual species to characteristics of the food web in which they are embedded. Building from extensive applications of stable isotope ratios by ecologists, the community-wide metrics may provide a new perspective on food web structure, function, and dynamics.
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Calcium stable isotopes place Devonian conodonts as first level consumers

Calcium stable isotopes place Devonian conodonts as first level consumers

In the present work, which is a pilot study, we use for the first time calcium (Ca) stable isotopes to infer the feeding habit of conodont animals. The first studies showing that trophic levels of animals, including fish, could be inferred from the Ca isotope compositions of their shell or inner skeleton lay back in the 2000’s (Skulan et al., 1997; Skulan and DePaolo, 1999; Clementz et al., 2003; DePaolo, 2004). These results were recently confirmed on modern and fossil elasmobranchs (Martin et al., 2015), a subclass of cartilaginous fish, including the sharks, rays and skates, and sawfish. Some authors have already measured the Ca isotope composition of conodonts but with the aim to reconstruct variations of the seawater composition (Hinojosa et al. 2012; Jost et al. 2014; Le Houedec
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Partitioning groundwater recharge between rainfall infiltration and irrigation return flows using stable isotopes: the Crau aquifer.

Partitioning groundwater recharge between rainfall infiltration and irrigation return flows using stable isotopes: the Crau aquifer.

computed in this study appears to be consistent, although slightly higher than the previously estimated values. Solving a groundwa- ter mass balance equation implies that the recharge estimate depends on the quantification of the discharge. As previously men- tioned, the choice of the aquifer limits can be a major source of error, especially for the main natural discharge on the southwest border presenting very low hydraulic gradients. Different esti- mates of the total uptakes and the upstream groundwater drainage could also partly explain these differences. But, despite a slight dis- crepancy regarding the absolute flux values, similar orders of mag- nitudes are obtained between these different studies for the respective proportions of natural recharge and irrigation return flow. Nevertheless, stable isotopes of water constitute a robust and independent geochemical tracer for partitioning groundwater recharges at the scale of the entire aquifer. In addition, the method proposed in this study also has the advantage of providing uncer- tainties characterizing, inter alia, time variations in the estimated flows.
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Calcium stable isotopes place Devonian conodonts as first level consumers

Calcium stable isotopes place Devonian conodonts as first level consumers

In the present work, which is a pilot study, we use for the first time calcium (Ca) stable isotopes to infer the feeding habit of conodont animals. The first studies showing that trophic levels of animals, including fish, could be inferred from the Ca isotope compositions of their shell or inner skeleton lay back in the 2000’s (Skulan et al., 1997; Skulan and DePaolo, 1999; Clementz et al., 2003; DePaolo, 2004). These results were recently confirmed on modern and fossil elasmobranchs (Martin et al., 2015), a subclass of cartilaginous fish, including the sharks, rays and skates, and sawfish. Some authors have already measured the Ca isotope composition of conodonts but with the aim to reconstruct variations of the seawater composition (Hinojosa et al. 2012; Jost et al. 2014; Le Houedec
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Tree-ring stable isotopes for regional discharge reconstruction in eastern Labrador and teleconnection with the Arctic Oscillation.

Tree-ring stable isotopes for regional discharge reconstruction in eastern Labrador and teleconnection with the Arctic Oscillation.

and river flows (Waterhouse et al. 2000 ; Wils et al. 2010 ). In the present study, Lab 32 and Lab 65 are located at 47 and 8 km, respectively, from the Churchill River, which dis- cards the direct influence of river moisture to trees invoked by Waterhouse et al. ( 2000 ). Moreover, under the known climatic conditions of the region, water availability is not a limiting factor for tree growth and could rather be a reducing factor for climate sensitivity of tree-ring width chronologies (Nishimura and Laroque 2011 ; Trindade et al. 2011b ). At Lab 32 and 65, tree-ring width series show inconsistent or non-significant correlations with climatic variables (data not show), while tree-ring isotope series significantly correlate with summer conditions. Those climatic conditions directly influence stomatal aperture of tree needles, photosynthesis and the distillation of cloud masses that regulate tree-ring δ 13 C and δ 18 O variations. Using tree-ring stable isotopes
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Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

Even if transpiration predominates under temperate climates and is considered to not fractionate water stable isotopes, evaporation from plant interception or from the upper soil leads to fractionation and enrichment in heavy isotopes (Braud et al., 2005, 2009b; Sprenger et al., 2016; Sutanto et al., 2012). Water recharging during a given season can therefore be identified in deep unsaturated zone profiles, and recharge rates can be obtained from the displacement between successive seasonal inputs (Gehrels et al., 1998; Małoszewski et al., 2006; Małoszewski and Zuber, 1993; McConville et al., 2001; Saxena, 1984). On the one hand, this simple peak-shift method is easily applied (Adomako et al., 2010), even if the isotopic compositions of precipitation are not available (Gehrels et al., 1998). On the other hand, numerical models, such as SiSPAT-Isotopes (Braud et al., 2005, 2009a), Soil-Litter-Iso (Haverd and Cuntz, 2010), or a modified version of HYDRUS-1D (Stumpp et al., 2009a, 2009b; Stumpp and Hendry, 2012), are increasingly being used to understand the dynamics of water stable isotopic composition in the unsaturated zone (Sprenger et al., 2015). Such level of model refinement is associated with a high data requirement that can only be achieved for specific study sites, but less for more numerous and less known sites at the regional scale where there is a lack of recharge rate estimations.
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Applications of stable isotopes in trophic ecology and ecotoxicology

Applications of stable isotopes in trophic ecology and ecotoxicology

Stable isotopes in Trophic ecology and Ecotoxicology - Pessac - September 2014 C ASE STUDY 2: TO ELUCIDATE CONTAMINATION PATHWAY OF AN ORGANOCHLORINE PESTICIDE Organochlorine pollution in tropical rivers (Guadeloupe): Role of ecological factors in

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Reconciling glacial Antarctic water stable isotopes with ice sheet topography and the isotopic paleothermometer

Reconciling glacial Antarctic water stable isotopes with ice sheet topography and the isotopic paleothermometer

For such isoGCM simulations of the climate of the last glacial maximum (LGM), major uncertainties in required boundary conditions are the prescribed sea surface temperature, sea ice extent and ice sheet topography, while orbital parameters and GHG are well known for the LGM period. Large uncer- tainties remain associated with the knowledge of glacial West Antarctic ice sheet topography, evidenced by the large spread of existing reconstructions 35 – 39 . Here, results of isoGCM simu- lations with prescribed different ice sheet reconstructions are compared with ice core data from West and East Antarctica. The deviation between simulated water stable isotopes and ice core records provides a constraint on the realism of LGM ice sheet reconstructions.
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