Range Of δ13C Values Research Articles

СТАБИЛЬНЫЕ ИЗОТОПЫ O, H, C В ПОДЗЕМНЫХ ВОДАХ НЕФТЕГАЗОНОСНЫХ ОТЛОЖЕНИЙ СЕВЕРНЫХ РАЙОНОВ ЗАПАДНО-СИБИРСКОГО ОСАДОЧНОГО БАССЕЙНА

The water isotopic composition of petroleum deposits of the Arctic sector of West Siberia was first studied in the paper. The obtained values of isotopic oxygen shifts relative to the global meteor water line (GMWL) from 2 to 9‰ indicate the ancient sedimentation origin of most samples. The primary enrichment of waters with the heavy isotope 18O due to evaporation in warm climatic conditions was subsequently further enhanced by their isotopic exchange with oxygen-containing rocks. The migration hypothesis of light isotopes of water into the overlying water-bearing horizons during the formation of condensatogenic waters is proposed, the influence of moisture burial duration on its isotopic composition is shown. The isotopic concentration characteristic of DIC is very broad and covers the range of δ13C values (from –51.8 to +21.8 ‰) and the carbon dioxide content in waters (from 0.17 to 38.6 mmol/dm3). The content of DIC in waters is primarily associated with the availability of carbon-containing substance to waters and bacteria directly involved in its processing. The isotopic composition of DIC varies non-linearly and indicates a variety of competing processes of formation and isotopic exchange of carbon dioxide with the environment. The pattern suggesting the homogenization of isotopic composition of carbon dioxide in ground waters to values close to the average values of air CO2, taking into account the fractionation coefficients is found. The revealed effect may indicate the closure of carbon cycle in the “air CO2 – organic matter – DIC” system.

Infancy, childhood, and puberty on the Silk Road revealed with isotopic analysis of incremental dentine

Childhood is a unique phase in human life history, in which newborns are breastfed and weaned, and are progressively familiarized to adult diets. By investigating dietary changes from infancy to adolescence, valuable information regarding past cultural behaviors and aspects of human lives can be explored and elucidated. Here, in conjunction with published isotopic results of serial dentine (n = 21) from Yingpan Man, new δ13C and δ15N results are obtained from 172 samples of incremental dentine from 8 teeth of 8 individuals of the Yingpan cemetery, located in Xinjiang, China. The δ13C values range from – 18.2 to – 14.6‰ with a mean ± SD value of – 16.3 ± 0.9‰, and the δ15N results range between 13.4 and 19.9‰ with a mean ± SD value of 16.0 ± 1.4‰. This indicates that the childhood diets were mixtures of C3 and C4 dietary resources and were clearly influenced by breastfeeding and weaning practices. In particular, the findings indicate that there were significant inter-individual differences in terms of the timing and duration of breastfeeding and weaning practices as well as childhood dietary practices at Yingpan. For instance, three individuals were exclusively breastfed after birth, while, two individuals and Yingpan Man were not. In addition, the post-weaning diets of most Yingpan individuals were relatively stable, but one individual and Yingpan Man displayed clear evidence of increased consumption of C4 foods, likely millet, during late and post-weaning periods. Further, 7 individuals had unique dietary changes between 9 to 14 years old. Potential factors related to this are presented from the perspective of changes in social roles that might be caused by their early participation in the social division of labor or puberty and marriage.

The Stable Carbon Isotope Composition of Pinus yunnanensis Pollen and Leaf in Northwestern Yunnan, China

The basis for the δ13C values of plant tissues used to infer past ecological environments is their relationships with modern ecological conditions. A total of 71 pairs of pollen and leaf samples were collected from Pinus yunnanensis, an endemic species of the Yunnan plateau, in northwestern Yunnan, China. Their carbon isotopic composition was examined to investigate the two tissues’ difference of stable carbon isotopes, possible factors affecting their δ13C values, and their distinctiveness within Pinus and Pinaceae. Our study showed that pollen δ13C values range from −32.92 to −26.34‰ with an average of −30.88‰, whereas leaf δ13C values vary between −33.79 and −28.96‰ with an average value of −31.2‰, suggesting an isotope fractionation between the two tissues. A statistically significant negative correlation between the pollen δ13C values and altitudes of the sampling sites as well as no significant correlation between the leaf δ13C values and altitudes suggested that pollen may be more sensitive to some climatic parameters than leaf. A comparison of the pollen and leaf δ13C values from Pinus yunnanensis with the available data from other Pinus species and other genus species of Pinaceae indicated that the pollen and leaf δ13C values of Pinus yunnanensis are the lowest, partially due to the effects of water availability.

Spatial distribution, driving factors and health risks of fine particle-bound polycyclic aromatic hydrocarbons (PAHs) from indoors and outdoors in Hefei, China

Atmospheric particulate matter, especially in urban and industrial environments, can act as a source of different organic pollutants that can pose significant health impacts to residents. However, the pollution status and transport mechanisms of fine particle-bound polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor environments are uncertain. This study aimed to determine the spatial distribution and morphological characteristics of fine particle-bound PAHs and analyze the factors (source contributions and backward trajectories) that influence their concentrations. The results showed that mean concentrations of 16 PAHs were higher in indoor dust as compared to outdoor dust. In addition, the lowest concentrations of the 16 PAHs were found on the 11-20th floor, with smoking households > nonsmoking households (except Nap, Acy, and Ace). The 2–3 ring PAHs were more prominent in households with cooking activities. The particle size distribution showed that most of the particles were <62 μm in diameter, indicating that the indoor particles were smaller in size. Furthermore, the range of δ13C values in the outdoor dust (−30.17 ~ −28.63 ‰) samples was significantly lower than in indoor dust (−28.29 ~ −22.53 ‰). The results based on diagnostic ratios, positive matrix factorization (PMF) analysis and backward trajectory model analysis suggested that the sources of PAHs in indoor and outdoor dust were mixed, originated both locally and from neighboring provinces transported over long distances, especially concentrated in the Yangtze River Delta area. Finally, carcinogenic risk values for indoor dust were greater than those for outdoor dust. Therefore, it is recommended that local governments and industries with high PAH emissions should implement proper protocols to monitor and minimize the pollution levels of PAHs in the urban industrial environment in order to mitigate their health risks.

Estuarine food web structure and relative importance of organic matter sources for fish in a highly connected Northeastern Brazil ecotone

The lack of knowledge about highly anthropised tropical ecosystems poses a problem for their conservation. Using carbon and nitrogen stable isotopes, we studied the food web structure of the estuarine ecotone of the Santa Cruz Channel (SCC), which constitutes a critical habitat for many socio-economically important species in northeast Brazil. Therefore, we assessed the spatial (estuary/coast) and seasonal (dry/rainy) isotopic variation of basal food sources, invertebrates and fishes. We also used Bayesian mixing models to trace the origin (estuary vs coast) of the organic matter sources supporting SCC fishes food webs according to their feeding habits. We found a wide range of δ13C and δ15N values for basal sources, invertebrates, and fish in coastal and estuarine environments, but isotopic compositions showed greater variability in the estuary. This illustrated the heterogeneity of primary producers and sources in estuaries, intensified by SCC morphology, as both accesses to the sea provide strong mixing between riverine and marine inputs. Additionally, we found differences between fish isotope compositions according to their guilds. Coastal basal sources significantly support zoobenthivorous, piscivorous and zooplanktivorous fish estuarine food webs. Conversely, detritivores are supported by enriched sources of organic matter, especially during the dry season, which may be derived from terrestrial inputs. As contaminated land-based inputs can affect food webs and coastal fisheries, developing a management plan that includes all interconnected habitats is necessary.

Variabilities of δ13C and carbonaceous components in ambient PM2.5 in Northeast India: Insights into sources and atmospheric processes

A year-long sampling campaign of ambient PM2.5 (particulate matter with aerodynamic diameter ≤2.5 mm) at a regional station in the North-Eastern Region (NER) of India was performed to understand the sources and formation of carbonaceous aerosols. Mass concentration, carbon fractions (organic and elemental carbon), and stable carbon isotope ratio (δ13C) of PM2.5 were measured and studied along with cluster analysis and Potential Source Contribution Function (PSCF) modelling. PM2.5 mass concentration was observed to be highest during winter and post-monsoon seasons when the meteorological conditions were relatively stable compared to other seasons. Organic carbon (OC) concentration was more than two times higher in the post-monsoon and winter seasons than in the pre-monsoon and monsoon seasons. Air mass back trajectory cluster analysis showed the dominance of local and regional air masses during winter and post-monsoon periods. In contrast, long-range transported air masses influenced the background site in pre-monsoon and monsoon. Air mass data and PSCF analysis indicated that aerosols during winter and post-monsoon are dominated by freshly generated emissions from local sources along with the influence from regional transport of polluted aerosols. On the contrary, the long-range transported air masses containing aged aerosols were dominant during pre-monsoon. No significant variability was observed in the range of δ13C values (−28.2‰ to −26.4‰) during the sampled seasons. The δ13C of aerosols indicates major sources to be combustion of biomass/biofuels (C3 plant origin), biogenic aerosols, and secondary aerosols. The δ13C variability and cluster/PSCF modelling suggest that aged aerosols (along with enhanced photo-oxidation derived secondary aerosols) influenced the final δ13C during the pre-monsoon. On the other hand, lower δ13C in winter and post-monsoon is attributed to the freshly emitted aerosols from biomass/biofuels.

Kinetic isotope effect in siderite growth: Implications for the origin of banded iron formation siderite

The widespread occurrence of siderite (FeCO3) at Earth's modern surface and in sedimentary rocks has led to its frequent use as a tool for palaeoenvironmental reconstruction. Isotopic studies of siderite associated with Archaean-Palaeoproterozoic banded iron formations show negative δ13C values, which coupled with δ56Fe values, have been considered to support an important role of dissimilatory iron reduction (DIR) in the genesis of iron formations.Facies-specific analyses show that texturally and petrographically syndepositional and/or early diagenetic, finely laminated microsparitic (≤10 µm in diameter) siderite exhibits δ13C between −3 and −7‰. This siderite δ13C range can be interpreted in three ways: (1) precipitation of siderite from dissolved inorganic carbon (DIC) produced by DIR coupled to partial oxidation of organic carbon with δ13C < −25‰, (2) precipitation from a mixed hydrothermal-seawater fluid bearing mantle-derived DIC with δ13C ≅ −6.5‰, and (3) precipitation from seawater-derived DIC and expression of a kinetic isotope effect (KIE) associated with siderite growth.We present the carbon isotopic composition of siderite formed in abiotic seeded growth experiments over a wide range of solution siderite saturation at 25 °C and 1 bar. With a complete set of chemical kinetic data, we develop and apply a model of disequilibrium siderite precipitation to constrain the carbon KIE as a function of growth rate. Sampling of model parameters from distributions that represent uncertainty in the parameter values, we find best-fit values of equilibrium and kinetic fractionation factors: 103lnαeq = −0.2 and 103lnαf = −14.9.These constraints allow us to assess the origins of δ13C values in microsparitic siderite in iron formations. For example, a moderate level of siderite supersaturation (e.g., Ωsid = 100) in the hydrothermal-seawater mixing fluids (source of dissolved iron) would have induced a carbon KIE of ∼−8‰ in fluid-buffered early diagenetic siderite growth; a range that encompasses essentially all negative δ13C values reported from microsparitic siderite in Campbellrand-Kuruman iron formations, Transvaal Supergroup, South Africa. We suggest that a straightforward, abiotic explanation for the range of δ13C values in microsparitic siderite in Archaean-Palaeoproterozoic banded iron formations is pulsed deposition of iron-rich sediments associated with intense hydrothermal activity. Specifically, the siderite-δ13C range is well explained by a partial expression of carbon KIE associated with siderite growth from supersaturated solutions, and from a bottom-water DIC reservoir with near-zero δ13C values (seawater with a possible contribution of mantle carbon).

Biogeochemistry and trophic structure of a cold seep ecosystem, offshore Krishna-Godavari basin (east coast of India)

Active cold seep sites associated with shallow gas hydrates were recently reported from Krishna-Godavari (K-G) basin, off east coast of India. Benthic fauna including chemosymbiotic bivalves (genera Bathymodiolus, Acharax, Conchocele), polychaetes (genus Sclerolinum), and heterotrophs (gastropods: Provannidae family; squat lobster: Munidopsidae/Galatheidae; Goose barnacle: genus Neolepas; Brittle star: genus Amphiodia) were sampled from the cold seep locations. Here, we present the first δ13C and δ15N data sets of the soft tissues extracted from the organisms along with the sediment pore fluid composition. The isotope ratios of the soft tissues provide a glimpse of the potential food sources for the cold seep organisms and the trophic structure of the ecosystem. The δ13C values suggest the dependence of the Bathymodiolus on methanotrophic symbionts, whereas Acharax, Conchocele, and Sclerolinum show the tell-tale signature of the thiotrophic pathways. In contrast, the heterotrophic benthic fauna shows a wide range of δ13C values, a signature of a variety of carbon sources. The δ15N values of the studied organisms also show a broad range (−1 to +9 ‰) indicating variable food sources as well as variable nitrogen assimilation pathways followed by various symbionts.

Retrospective stable isotopes of vertebrae reveal sexual ontogenetic patterns and trophic ecology in oceanic whitetip shark, Carcharhinus longimanus.

There is a common phenomenon in nature whereby some animals have differences in their ontogenetic changes in dietary preferences between sexes, especially apex predators. These reflect changes in the needs of development during their lifetimes. Apex predators potentially have diverse dietary niches and a large impact on the trophic dynamics within ecosystems. However, the difference in life history between males and females often leads to increased difficulty in management and conservation. In this study, 25 oceanic whitetip sharks, Carcharhinus longimanus, were collected from the central and eastern tropical Pacific. Retrospective stable isotope analysis of vertebrae was used to evaluate the potential ontogenetic differences in feeding habits and niche width between sexes. Results showed that C. longimanus had a wide range of δ13C values (−18.1 to −12.3‰) and δ15N values (8.9–14.8‰). However, males and females had similar trophic positions with large niche overlap at similar growth stages. Both sexes had increasing δ13C values but relatively constant δ15N values along the vertebrae. These results indicated that male and female C. longimanus may share similar feeding strategies and movement patterns. The results presented in this study enhance our understanding of sexual ontogenetic patterns and ecological role of C. longimanus and highlighted the applicability of vertebrae for characterizing shark life‐history traits.

Paleodiet reconstruction of human and animal bones at the Dalujiao cemetery in Early Iron Age Xinjiang, China

AbstractLong before the East–West “Silk Road” appeared, cultural communication as well as exchanges of materials and technologies had existed between different populations across the Eurasian Steppe. Xinjiang, located at a crossroads of the East and the West, is particularly important for exploring human interactions. The present paper contributes to this end from a stable isotopic perspective. Carbon and nitrogen stable isotope analysis were applied to 51 human and four animal bone remains collected from three types of tombs—namely, the earthen vertical tomb‐pit, earthen vertical tomb‐pit with second‐tier ledge, and earthen vertical tomb‐pit with side chamber—excavated from the Dalujiao cemetery, dated to the Early Iron Age (542 BCE–59 CE), in Xinjiang of northwest China. The δ13C (mean: −18.6 ‰) and δ15N (mean: 7.5‰) results of the faunal remains suggest that the two herbivore species (horse and sheep) were fed mainly by C3 terrestrial plants. By contrast, the human bone specimens differ in δ13C values (from −16.0‰ to −11.6‰, with a mean of −14.1‰ ± 1.1‰, n = 51). People buried in vertical tomb‐pits show a narrow range of δ13C values, an indication that they consumed quite stable sources of food. In contrast, those buried in vertical tomb‐pits with a second‐tier ledge or with a side chamber consumed more diverse foods and probably adopted different subsistence strategies. Taking into consideration both isotopic results and types of tombs, we propose that at least three groups of populations with diverse dietary and subsistence strategies are identifiable at the Dalujiao cemetery. Our study reveals not only human diets and subsistence patterns in the study area but also interactions among different populations prior to the rise of “Silk Road.”

Active Degassing of Deeply Sourced Fluids in Central Europe: New Evidences From a Geochemical Study in Serbia

AbstractWe report on the results of an extensive geochemical survey of fluids released in the Vardar zone (central‐western Serbia), a mega‐suture zone at the boundary between Eurasia and Africa plates. Thirty‐one bubbling gas samples are investigated for their chemical and isotopic compositions (He, C, Ar) and cluster into three distinct groups (CO2‐dominated, N2‐dominated, and CH4‐dominated) based on the dominant gas species. The measured He isotope ratios range from 0.08 to 1.19 Ra (where Ra is the atmospheric ratio), and reveal for the first time the presence of a minor (&lt;20%) but detectable regional mantle‐derived component in Serbia. δ13C values range from −20.2‰ to −0.1‰ (versus PDB), with the more negative compositions observed in N2‐dominated samples. The carbon‐helium relationship indicates that these negative δ13C compositions could be due to isotopic fractionation processes during CO2 dissolution into groundwater. In contrast, CO2‐rich samples reflect mixing between crustal and mantle‐derived CO2. Our estimated mantle‐derived He flux (9.0 × 109 atoms m−2 s−1) is up to 2 orders of magnitude higher than the typical fluxes in stable continental areas, suggesting a structural/tectonic setting favoring the migration of deep‐mantle fluids through the crust.

Middle Jurassic–Lower Cretaceous glendonites from the eastern Barents Shelf as a tool for paleoenvironmental and paleoclimatic reconstructions

Glendonites are carbonate pseudomorphs after ikaite which use as indicators of near-freezing temperatures. We describe the first glendonites of Middle–Late Jurassic to Early Cretaceous age from the Barents Shelf, including the first glendonites of Late Barremian–Early Aptian age ever discovered on Earth and provide the detailed mineralogical-geochemical and isotopic studies. Mesozoic glendonites are well-known across the Arctic realm, however the ikaite-calcite transformation and implication of glendonite findings are still debatable. Pseudomorphs are mainly composed of calcite. Cathodoluminescence and scanning electron microscopy studies reveal three types (I-III) of calcite: type I - elongated, rounded and irregular calcite; type II - blocky, fibrous and needle-like calcite/siderite; type III - blocky calcite in pores. Elemental analyses distinguish geochemical differences between the calcite types: type I comprises pure CaCO3; type II calcite contains Mg and P (in all studied samples), Fe (Bajocian–Callovian), S (Middle Volgian) or Sr (Upper Barremian–Lower Aptian); type III calcite is depleted in Mg, P and Fe. Concentrations of Mn, Fe, Sr and calculated Mn/Ca, Fe/Ca and Sr/Ca ratios are suggestive of diagenetic alteration. Bulk δ18O values range from −5.39 to −1.71‰ VPDB, supporting overprinting of primary values during burial diagenesis, while bulk δ13C values range from −33.3 to −22.6‰ VPDB, providing the influence of organic matter on ikaite-glendonite formation. However, 87Sr/86Sr values range from 0.7070 to 0.7110, mainly corresponding to Jurassic–Cretaceous seawater. Rare-earth elements characterize porewater REE-patterns, with slight middle REE-enrichment and depletion in light and heavy REE. Weak positive and negative Ce anomalies indicate fluctiating from anoxic to oxic conditions during ikaite-glendonite formation. Our new biostratigraphic data refine the ages of glendonite-bearing horizons in the Barents Shelf region, allowing a more definitive correlation with coeval glendonite occurrences across the Arctic realm and with global climatic changes during the Jurassic–Cretaceous.

Eco-engineered mangroves provide complex but functionally divergent niches for estuarine species compared to natural mangroves

There is growing demand for novel coastal protection approaches that also provide co-benefits such as enhanced biodiversity. Rock-fillets, which are used to stabilise eroding banks in estuaries, can be colonised by mangroves, and may provide habitat for estuarine fauna. However, it is unknown whether hybrid mangrove/rock-fillet habitats are functionally equivalent to natural mangroves, for estuarine fauna. To determine whether hybrid mangrove habitats are functionally equivalent to natural mangroves, we used δ13C and δ15N stable isotope analyses to describe the isotopic niche space and overlap of estuarine species in these two habitats across three estuaries in NSW, Australia. Using a Bayesian standard ellipse analysis of isotopic niche area, over half the 12 species observed had larger isotopic niche areas in natural mangroves compared to hybrid habitats, however there were no clear patterns for species between habitats. Natural mangroves and hybrid rock-fillet habitats were isotopically distinct for all species sampled (low proportional overlap, 0–19%) suggesting they are not, at present, wholistically functionally equivalent. Estuarine communities from the two habitat types, however, had similar isotopic niches. Hybrid communities displayed a broader range of δ13C values compared to natural mangroves, suggesting mangrove/rock-fillet habitats have a more diverse range of basal food sources. These findings demonstrate the potential for defence solutions to provide unique co-benefits by supporting food webs, but also that natural habitats provide unique ecosystem services that should be protected and rehabilitated where possible. Future modelling and monitoring of habitat utilisation and species performance could provide further insight into the co-benefits and trade-offs of hybrid habitats.

Organic Matter Compositions and Loadings in River Sediments From Humid Tropical Volcanic Luzon Island of the Philippines

AbstractTropical rivers deliver ∼60% of particulate organic carbon to the world ocean. However, compositions and loadings of sedimentary organic matter (OM) from tropical small mountainous rivers are largely unknown. Here, we provide an initial constrain on sources of sedimentary OM from 28 fluvial systems across Luzon in the Philippines by measuring total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C) and radiocarbon activity of TOC (expressed as fraction modern—Fm), as well as grain size and mineral surface area (SA) of sediments. Results indicate that sediments in Luzon rivers contain both contemporary and 14C‐depleted OM (Fm: 0.71–1.06, mean 0.97 ± 0.07) with a wide range of δ13C values (−28.3‰ to −17.7‰, −24.9 ± 2.2‰). This is attributed to the OM sources originated from modern surface soil and 14C‐depleted subsoil and deep soil vegetated by C3 and C4 plants, with mean fraction of C3 plant at 80% ± 11%. Minor input from bedrock may also contribute to the 14C‐depleted OM in sediments, accounting for 6% ± 6%. Sediments in most rivers are featured by low OC loadings (OC/SA ratio &lt; 0.4 mg C m−2), owing either to a less OM input or intensive OM degradation. The estimated yields of particulate OC from Luzon vary between 3.2 and 3.7 t km−2 yr−1, which is higher than most tropical large rivers.

Stable Isotopes Reveal the Dominant Species to Have the Widest Trophic Niche of Three Syntopic Microtus Voles

Simple SummaryDiets and the trophic positions of animals are fundamental issues in their ecology. We analysed the isotopic niches (as a proxy for trophic niches) of common (Microtus arvalis), field (M. agrestis), and root (M. oeconomus) voles co-occurring in orchards, berry plantations, and nearby meadows using isotopic (δ15N and δ13C) compositions from hair samples. We tested if the niche of the dominant common vole was widest, whether its width was related to the presence of other Microtus species, and whether there were intraspecific differences in average δ13C and δ15N stable isotope values. The obtained results showed relative stability in the trophic niche across the vegetative period. The isotopic niche of the common vole was the widest, exceeding the other two Microtus species by 1.6–3 times. Co-occurring vole species were separated according to δ13C (i.e., used different plants as main food), but they maintained similarity according to δ15N distribution. The effect of animal age and gender on the width of the trophic niche was strongest in root vole, which is a species that has spread across the country in the last 70 years. These results give new insights into the trophic ecology small herbivores, showing the impact of species co-occurrence.Diets and trophic positions of co-occurring animals are fundamental issues in their ecology, and these issues in syntopic rodents have been studied insufficiently. Using carbon (δ13C) and nitrogen (δ15N) stable isotope ratios from hair samples, we analysed the trophic niches of common (Microtus arvalis), field (M. agrestis), and root (M. oeconomus) voles co-occurring in orchards, berry plantations, and nearby meadows (as control habitat to orchards and plantations). We tested if the niche of the dominant common vole was the widest, whether its width depended on the presence of other vole species, and whether there were intraspecific differences. Results suggest stability in the trophic niches of all three Microtus species, as season explained only 2% of the variance. The widest trophic niche was a characteristic of the dominant common vole, the range of δ13C values exceeding the other two species by 1.6, the range of δ15N values exceeding the other two species by 1.9, and the total area of niche exceeding that of the other voles by 2.3–3 times. In the meadows and apple orchards, co-occurring vole species were separated according to δ13C (highest values in the dominant common vole), but they maintained similar δ15N values. Results give new insights into the trophic ecology small herbivores, showing the impact of species co-occurrence.

Triple oxygen and clumped isotopes in modern soil carbonate along an aridity gradient in the Serengeti, Tanzania

The isotopic composition of paleosol carbonates is used extensively to reconstruct past vegetation, climate, and altimetry, but poor constraints on soil evaporation and temperature have limited the utility of oxygen isotopes in the studies. Recent advances in carbonate clumped isotope thermometry (TΔ47) allow for independent controls on temperature, but the influence of evaporation remains unresolved. However, the sensitivity of 18O-17O-16O distributions to kinetic fractionation makes it possible to use triple oxygen isotopes (Δ′17O) to track evaporation in water. Recent work shows the sensitivity of Δ′17O to evaporation in lakes and lacustrine carbonates, but little is known about variation of Δ′17O in soil carbonates and their potential to track evaporation. For this study, we sampled soils across an aridity gradient in the Serengeti, Tanzania to evaluate how soil carbonate Δ′17O tracks soil water evaporation. Modern soil carbonates were collected from 11 sites across a transect of the Serengeti Ecosystem where mean annual precipitation and aridity index range from 499 to 846 mm yr−1 and 0.33 to 0.55, respectively. δ13C values range from −2.7 to 1.8‰ and reflect C4 dominated grasslands, whereas δ18O values of soil carbonates vary by ∼8‰ along a gradient in aridity. TΔ47 from these soil carbonates average 23°C (1σ± 4°C), which does not vary significantly across sites or with depth, likely due to minimal annual variation in temperature at the equator. Using these temperatures for each carbonate, reconstructed δ18O values of soil water are up to 6‰ higher than δ18O values of local precipitation and springs, indicating considerable soil water evaporation. The Δ′17O values of these soil carbonates range from −162 to −106 per meg and decrease as both aridity and δ18O values increase. Our results support the hypothesis that soil water evaporation drives the variance in δ18O and Δ′17O of soil carbonate in arid climates, demonstrating the potential for soil carbonate Δ′17O to track paleoaridity and constrain interpretations of paleosol carbonate δ18O records.

Seeing the forest for the trees-and the grasses: revisiting the evidence for grazer-maintained grasslands in Madagascar's Central Highlands.

Seeing the forest for the trees-and the grasses: revisiting the evidence for grazer-maintained grasslands in Madagascar's Central Highlands.

Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil.

We used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (δ13C) and nitrogen (δ15N) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of δ15N (fishes: 6.49–14.94‰; sources: 2.58–6.79‰) and δ13C values (fishes: -23.86 to -13.71‰; sources: -24.32 to -13.53‰), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were determined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high δ15N values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population parameters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery.

Isotopic Traceability (13C and 18O) of Greek Olive Oil.

In recent years, isotopic analysis has been proven a valuable tool for the determination of the origin of various materials. In this article, we studied the 18O and 13C isotopic values of 210 olive oil samples that were originated from different regions in Greece in order to verify how these values are affected by the climate regime. We observed that the δ18O isotopic values range from 19.2 ‰ to 25.2 ‰ and the δ13C values range from −32.7 ‰ to −28.3 ‰. These differences between the olive oils’ isotopic values depended on the regional temperature, the meteoric water, and the distance from the sea. Furthermore, we studied the 13C isotopic values of biophenolic extracts, and we observed that they have same capability to differentiate the geographic origin. Finally, we compared the isotopic values of Greek olive oils with samples from Italy, and we concluded that there is a great dependence of oxygen isotopes on the climatic characteristics of the different geographical areas.

Isotopic Ecology in Modern and Holocene Populations of Pampas Deer (Ozotoceros bezoarticus) from Eastern Central Argentina. Implications for Conservation Biology and Ecological Models of Hunter-gatherer Subsistence

ABSTRACT The Pampas deer (Ozotoceros bezoarticus) is an endangered ungulate from South American. The following paper presents the first investigation on the isotopic ecology (δ13Ccollagen; δ15Ncollagen) of modern populations of Pampas deer. The information obtained is compared with new δ13C and δ15N data of Pampas deer bones recovered from archaeological sites in the Central Pampean Dunefields (Inland Pampa phytogeographic area) and with previously published archeofaunistic isotope data for sites from eastern central Argentina. The range of δ13C values of Pampas deer is broad, ranging from a diet dominated by C3 plants to a mixed diet of C3 and C4 plants. The δ15N values mainly show distinct signals between the Atlantic coast and the interior. The diet breadth of the Pampas deer suggests a high adaptability to different environments, a crucial factor for conservation programs of this species. The δ13C values of the Inland Pampa do not show great differences between the Middle Holocene, Late Holocene and today. Adaptation strategies of the Pampas deer to the environmental changes during the Holocene were not associated with a modification of their feeding habits, but rather with social and demographic strategies. These variations in ecology conditioned the predictability of this prey for hunter-gatherers.