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The measurement of bulk tissue nitrogen (δ15N) and carbon isotope values (δ13C) chronologically along biologically inert tissues sampled from offspring can provide a longitudinal record of their mothers’ foraging habits. This study tested the important assumption that mother–offspring stable isotope values are positively and linearly correlated. In addition, any change in the mother–offspring bulk tissues and individual amino acids that occurred during gestation was investigated. Whiskers sampled from southern elephant seal pups (Mirounga leonina) and temporally overlapping whiskers from their mothers were analyzed. This included n = 1895 chronologically subsampled whisker segments for bulk tissue δ15N and δ13C in total and n = 20 whisker segments for amino acid δ15N values, sampled from recently weaned pups (n = 17), juvenile southern elephant seals (SES)

Significance Dietary habits, especially meat consumption, represent a key aspect in the behavior and evolution of fossil hominin species. Here, we explore zinc (Zn) isotope ratios in tooth enamel of fossil mammals. We show discrimination between different trophic levels and demonstrate that Zn isotopes could prove useful in paleodietary studies of fossil hominin, or other mammalian species, to assess their consumption of animal versus plant resources. We also demonstrate the high preservation potential of pristine diet-related Zn isotope ratios, even under tropical conditions with poor collagen preservation, such as the studied depositional context in Southeast Asia. However, assessing the preservation of original δ66Zn values is required for each fossil site as diagenesis may vary across and even within taphonomic settings., Stable carbon and nitrogen isotope ratios of collagen from bone and dentin have frequently been used for dietary reconstruction, but this method is limited by protein preservation. Isotopes of the trace element zinc (Zn) in bioapatite constitute a promising proxy to infer dietary information from extant and extinct vertebrates. The 66Zn/64Zn ratio (expressed as δ66Zn value) shows an enrichment of the heavy isotope in mammals along each trophic step. However, preservation of diet-related δ66Zn values in fossil teeth has not been assessed yet. Here, we analyzed enamel of fossil teeth from the Late Pleistocene (38.4–13.5 ka) mammalian assemblage of the Tam Hay Marklot (THM) cave in northeastern Laos, to reconstruct the food web and assess the preservation of original δ66Zn values. Distinct enamel δ66Zn values of the fossil taxa (δ66Zncarnivore < δ66Znomnivore < δ66Znherbivore) according to their expected feeding habits were observed, with a trophic carnivore-herbivore spacing of +0.60‰ and omnivores having intermediate values. Zn and trace element concentration profiles similar to those of modern teeth also indicate minimal impact of diagenesis on the enamel. While further work is needed to explore preservation for settings with different taphonomic conditions, the diet-related δ66Zn values in fossil enamel from THM cave suggest an excellent long-term preservation potential, even under tropical conditions that are well known to be adverse for collagen preservation. Zinc isotopes could thus provide a new tool to assess the diet of fossil hominins and associated fauna, as well as trophic relationships in past food webs.

Atrazine is a frequently detected groundwater contaminant. It can be microbially degraded by oxidative dealkylation or by hydrolytic dechlorination. Compound-specific isotope analysis is a powerful tool to assess its transformation. In previous work, carbon and nitrogen isotope effects were found to reflect these different transformation pathways. However, chlorine isotope fractionation could be a particularly sensitive indicator of natural transformation since chlorine isotope effects are fully represented in the molecular average while carbon and nitrogen isotope effects are diluted by non-reacting atoms. Therefore, this study explored chlorine isotope effects during atrazine hydrolysis with Arthrobacter aurescens TC1 and oxidative dealkylation with Rhodococcus sp. NI86/21. Dual element isotope slopes of chlorine vs. carbon isotope fractionation (?ArthroCl/C = 1.7 +/- 0.9 vs. ?RhodoCl/C = 0.6 +/- 0.1) and chlorine vs. nitrogen isotope fractionation (?ArthroCl/N = -1.2 +/- 0.7 vs. ?RhodoCl/N = 0.4 +/- 0.2) provided reliable indicators of different pathways. Observed chlorine isotope effects in oxidative dealkylation (epsilon(Cl) = -4.3 +/- 1.8 parts per thousand) were surprisingly large, whereas in hydrolysis (epsilon(Cl) = -1.4 +/- 0.6 parts per thousand) they were small, indicating that C-Cl bond cleavage was not the rate-determining step. This demonstrates the importance of constraining expected isotope effects of new elements before using the approach in the field. Overall, the triple element isotope information brought forward here enables a more reliable identification of atrazine sources and degradation pathways.

Human-induced eutrophication has altered ecological processes in aquatic ecosystems. Detection of ecological changes is a prerequisite for protecting ecosystems from degradation. In this study, nitrogen stable isotopes (δ15N) in fish are evaluated as indicators of environmental changes in south Florida wetlands. Stable nitrogen isotope (δ15N) data of select fish species and water quality collected from the Florida Everglades between the 1990s and 2000s were used to assess the relationship between total phosphorus concentrations and δ15N ratios. The δ15N ratios in nine of ten select fish species increase significantly as total phosphorus concentration in the surface water increases. There were significant relationships between total nitrogen concentration in the surface water and δ15N ratios in several fish species. The pattern of changes in δ15N ratios along nutrient gradients suggests that increased eutrophication is recorded as the δ15N ratios in fish. The lack of human wastewater loading, the dominance in agricultural runoff and the high TN:TP ratio suggest that phosphorus is the limiting factor driving ecosystem productivity and the changes of δ15N ratios in fish. Results from this analysis demonstrate that δ15N ratios in fish integrate biotic responses to eutrophic process over time and could be a robust indicator for early ecological changes.

The economic motivation for adulteration and mislabeling of origin is significant as edible bird’s nest (EBN) rank amongst the world’s most expensive animal products for food and traditional medicinal uses. The aim of this study is to determine the geographical origin of Malaysian Edible Bird’s Nest by using bio element fingerprinting techniques using carbon, nitrogen and sulphur (CNS) isotopes in order to avoid product fraud, and to guarantee product quality and safety. The samples used were authentic processed EBNs from different states in Malaysia and supplied by Ministry of Health, Malaysia. The ground EBN samples were analyzed using Elemental Analyzer Isotope Ratio Mass Spectrometer (EA-IRMS) system. The EBN measured δ13C values cover a range of -26.99‰ to -23.80‰ and the δ15N values cover a range of 5.05‰ to 8.06‰. The carbon isotope values are typical of Calvin (C3) plant sources. The nitrogen isotope values show that the swifts feed on relatively small primary consumer insects. This is also evidenced by the substantial overlap of δ15N values from the different locations. From the analysis, a statistically significant correlation does exist between the δ13C and δ15N values for the EBNs. The EBN measured δ34S values covered a range of +1.9‰ to +14.3‰ with a mean value of +7.8‰. Higher δ34S values were observed for EBN produced in the state of Sarawak compared to the EBN produced in the other states of Kelantan, Malacca, Negeri Sembilan, Perak and Selangor. Stable carbon, nitrogen and sulphur isotope analysis of Malaysian EBNs has shown potential for distinguishing between the various states in which they are produced, based on preliminary data. Using additional stable isotope data such as that derived from hydrogen and/or oxygen and combining trace element profiling would likely improve the reliability of the determination of geographical origin and classification rates.

The climatological impacts on biogeochemical processes in the polar North Atlantic remain poorly understood, as there exist both biological and physical mechanisms that drive nutrient availability ...

Carbon and nitrogen stable isotope compositions (δ13C and δ15N) of organic matter (OM) and total organic carbon to total nitrogen ratio (Corg/TN) in a sediment core collected in Sagua estuary (Cuba), were investigated to elucidate the origin of the Sedimentary OM (SOM) and changes in its main sources, over the last 100 years. Results showed almost constant values in the elemental and isotope composition of SOM from 1908 to 1970 with an abrupt change after 1970. From 1970 to 2005, δ13C increased from -21.2 up to -19.3 ‰, while δ15N declined from 1.5 to values close to 0 ‰. The output of the mass-balance model for the identification of OM sources indicated that δ13C and Corg/TN values are generally influenced by marine Particulate OM (POM) sources. Between 1900 and 1970, the main OM source in sediments was marine POM (>85 %), with freshwater POM contributing ca. 15%. Since 1970, the establishment of the Alacranes Dam determined drastic environmental changes influencing the OM sources in the area. Mixing models pointed to seagrasses (79 %) as the main contributors to SOM in the first period, while since 1973 onward, the contribution of human-derived sources such as fertilizers and urban discharges became greater. This information can provide baseline data for the environmental management of the Sagua watershed.

We present stable carbon and nitrogen isotope analyses of animal and human bones from south-eastern Poland, dated to the Neolithic and the Bronze Ages. The analyses are discussed against the background of archaeobotanical data from the studied sites from Miechow and Mozgawa. The mean values of δ13C and δ15N obtained from wheat grains from south-eastern Poland were used to model human palaeodiet. Our results show high levels of plant proteins in the diet, taking into account crop grain enriched in heavy nitrogen instead of the δ15N values for plants estimated from herbivore collagen. Dental abrasion analyses suggests the contribution of a highly abrasive food component in the diet (e.g. from plants). As the number of samples was limited and there were no statistically significant differences between chronological and gender groups, we conclude that despite some small differences in carbon isotopic composition between genders, Miechow site societies were egalitarian in this respect. Despite the presence of millet in the studied area in the Bronze Age no evidence of C4 plant consumption was noted in the δ13C of human and animal bones.

International audience; Carbon (delta C-13) and nitrogen (delta N-15) stable isotope analyses are used in marine ecology to study trophic relationships and migrations of species since they reflect dietary sources consumed which may vary geographically. However, better estimations of isotope incorporation rates and trophic discrimination factors (TDF) under controlled conditions are required. Moreover, variability of isotope incorporation rates and TDF among and within populations has been poorly described, especially in fish scales, whereas the use of non-lethal method is becoming a standard. This study aimed to experimentally assess whether carbon and nitrogen isotope incorporation rates (lambda C and lambda N, respectively) and TDF of scales vary in the European sea bass (Dicentrarchus labrax) among (1) Atlantic, West Mediterranean and East Mediterranean populations, (2) sexes and (3) individuals. Fish were reared under controlled conditions and switched from a diet 1 to a diet 2 with different delta C-13 and delta N-15 values. Scales were sampled repeatedly on 16 fish within the three populations, from the day of diet change (day 0) to the end of the experiment (day 217). Isotope incorporation rates of scales and TDF were determined using a time-dependent model. Isotopic carbon and nitrogen half-lives (t(50)C and t(50)N) were similar among the three populations but males had significantly lower t(50)C and t(50)N than females (29 +/- 2 and 35 +/- 2 days vs. 53 +/- 7 and 80 +/- 11 days, respectively). Females had higher growth rates but lower catabolic rates than males. Variability of lambda C . and lambda N was large within sexes: t(50)C ranged from 17 to 159 days and t(50)N ranged from 18 to 342 days among individuals. Thus, variability between sexes and among individuals must be considered to avoid misinterpretation in field-based studies. For the 48 fish, TDF were 4.91 +/- 0.03 and 2.46 +/- 0.06 parts per thousand for carbon and nitrogen, respectively, and similar between sexes and among populations. Besides, TDF varied among individuals from 2.95 to 5.59 parts per thousand and from 0.93 to 3.55 parts per thousand for carbon and nitrogen, respectively. Empirical mixing models were run to estimate how different TDF influenced estimation of the contributions of food sources to diet of their consumer. The output differed considerably when using TDF from fish literature or those estimated herein, which confirms that a tissue-specific TDF must be used to avoid misinterpretation in field-based studies. Individual variation in TDF did not, however, influence estimation of the contributions of food sources, confirming that scales are a valid tissue for non-lethal sampling.

The isotopic composition of baleen whales' epidermis structural layers can give information about dietary change over time. This study investigated if epidermis layers integrated isotopic values that record physiological changes from gestation to lactation. Epidermis tissues (n = 43) were collected from free ranging lactating female gray whale and calves during the beginning of three breeding seasons. Modelling of δ13C and δ15N values show intra- and inter-individual differences based on epidermal layers, age class and year of sampling. The isotopic composition of mother-calf pairs is correlated, and the estimates of the maximum mother-to-calf isotopic difference was ~1.4‰ for δ13C and between 1 and 1.5‰ for δ15N values. Change in δ15N values among epidermal layers in calves was associated with the transition from fetus to consumption of maternal milk. It is here proposed when lactation influences calf epidermis, δ15N values decrease consistently from the outermost to the innermost layer. However, if a calf was born only few days before collection, epidermis integrates more variable δ15N patterns because gestation still affects the isotopic composition of the layers. The possibility of calculating mother-to-calf nitrogen isotope fractionation, and the regularity of changes between calf layer δ15N values, allowed results of an isotopic clock model to predict the age of each calf when sampled with its mother. This model has the potential to be a straightforward method to estimate the beginning of lactation, therefore calf birth date when direct observations are not feasible. The non-lethal remote collection of epidermis appears to be an effective tool for the study of the physiology of reproduction of baleen whales. The parallel study of the three epidermal structural layers highlighted the importance of considering the unique mother-calf pair physiological status at the time of sampling time when stable isotope results are interpreted.

Rationale Carbonised plant remains are analysed for reconstruction of past climates and agricultural regimes. Several recent studies have used C4 plants to address related questions, and correlations between modern C4 plant δ13 C values and rainfall have been found. The millets were important food crops in prehistoric Eurasia, yet little is known about causes of isotopic variation within millet species. Previous research has shown there to be significant isotopic variation between millet accessions. Here we compare isotope ratios from plants grown under different watering regimes. This allows for a consideration of whether or not Setaria italica is a good proxy for environmental reconstruction. Methods We compare stable isotope ratios of Setaria italica plants grown in a controlled environment chamber with different watering regimes. We compare the carbon isotope ratios of leaves and grains, and the nitrogen isotope ratios of grains, from 12 accessions of Setaria italica. Results We find significant isotopic variability between watering regimes. Carbon isotope ratios are positively correlated with water availability, and on average vary by 1.9‰ and 1.7‰ for leaves and grains, respectively. Grain nitrogen isotope ratios also vary with watering regime; however, the highest isotope ratios are found with the 130-mL watering regime. Conclusions The carbon isotope ratios of Setaria italica are strongly correlated with water availability. However, the correlation is the opposite to that seen in studies of C3 plants. The difference in isotopic ratio due to watering regime is comparable with that seen between different accessions; thus distinguishing between changing varieties of Setaria italica and changing climate is problematic. In terms of grain nitrogen isotope ratios, the highest δ15 N values were not associated with the lowest watering regime. Again, δ15 N variation is comparable with that which would be expected from an aridity effect or a manuring effect, and thus distinguishing between these factors is probably problematic.

Southern elephant seal (SES) and Antarctic fur seal (AFS) are short Southern Ocean food web top predators and are spatial and temporal trend bioindicators of Antarctic Hg bioavailability. Hg, stable isotope composition (δ 13C and δ 15N) and trophic position (TP) regarding sex were determined using lanugo samples from Antarctic pinnipeds pups (SES n = 35 and AFS n = 11). Hg concentrations in over 50% of the SES pups (mean 5.9 ± 3.1 mg kg−1 dry wt.) are compatible with those found to cause neurologic damage to polar bears in the Arctic. No significant differences regarding sexes for SES or AFS are found based on mean Hg concentrations normalized by body weight. δ 15N values and TPs are similar among both species, indicating that gestating SES and AFS mothers feed at the same trophic level. Significantly different δ 13C values were found, indicating distinct feeding grounds for mothers belonging to both species when pup lanugo is formed in utero; while SES females like to feed in Antarctic waters, AFS females remain in sub-Antarctic waters. The differences in Hg and δ 13C observed for both species reflect not only contrasting feeding habits and anthropogenic Hg inputs, but also maternal foraging strategies.

Black carbon (BC), characterized by high aromaticity and stability, has been recognized as a substantial fraction of the carbon pool in soil and sediment. The effect of BC on the particulate organic carbon (POC) pool in lake water, which is an important medium of carbon transmission and transformation, has not been thoroughly studied. The investigations of BC composition and distribution, POC, polycyclic aromatic hydrocarbons (PAHs), and stable carbon and nitrogen isotopes were conducted in a eutrophic urban lake, Taihu Lake, which is the third largest freshwater lake in China. The results indicate that the BC is composed of 55 ± 12% char and 45 ± 12% soot and accounted for 12 ± 6% of POC (the maximum value is 31%). The comparatively high levels of BC and char are distributed in the northern Taihu Lake, especially in Meiliang Bay (0.72 ± 0.38 mg L-1 and 0.45 ± 0.24 mg L-1). The distribution of soot presents a declining trend from the lakeshore to the central lake, particularly in the northern, western, and southern lakes. Source apportionment results from positive matrix factorization of PAHs suggest that consumption of fossil fuel (79 ± 20%) is the dominant source of BC, which agrees with the low ratio of char/soot (1.41 ± 0.71) and relatively depleted δ13C. The covariation of BC and PAHs and terrestrial dissolved organic carbon indicate that the effect of terrestrial input significantly regulates the distribution of BC in Taihu Lake, which is reflected in the high BC value along the lakeshore.

The stable carbon (δ13C) and nitrogen (δ15N) isotope composition of human bone collagen is increasingly used to investigate past mobility and subsistence strategies. This study presents a compilation of 1298 carbon and nitrogen isotope analyses of archaeological human bone collagen from the British Isles spanning much of the Holocene, along with a compilation of 4148 analyses of modern and ancient isotope analyses from the major marine and terrestrial dietary resources from the same region. We convert ancient human stable isotope data to modern diet equivalent (MDE) values for humans, and convert the isotope composition of ancient dietary items to modern tissue equivalent (MTE) isotope values. These conversions enable a direct comparison of ancient and modern datasets. Results for food groups (plants, grain, herbivores, omnivores, shellfish, freshwater fish and marine fish) show a remarkably broad range of δ13CMTE values from ∼-36 to −7‰ and δ15NMTE values from ∼-2 to +21‰ and we provide estimates for each food type that can be used in dietary reconstruction in the absence of site-specific data. We further show that there is no significant change in terrestrial stable isotope baseline values over the Holocene, with observed variability in baseline values due to local eco-physiological, edaphic and microclimatic factors. The range of values expressed in the human sample set from the beginning of the Iron Age is relatively tightly clustered with 50% of all human modern diet equivalent results falling within a ∼2‰ range in δ13CMDE values (−25.5 to −27.5‰) and a ∼3.5‰ range in δ15NMDE values from (+4‰ to +8‰). From the Iron Age to post-medieval times there is a consistent progressive shift to higher δ13CMDE and δ15NMDE values at the population level. This shift likely reflects a combination of successive innovations associated with food production, preservation and transport that enabled a broader cross-section of the population of the British Isles to incorporate a higher proportion of animal, and particularly marine protein, into their diets.

Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (δ15N-NOx) emitted from biomass burning, the lack of data on δ15N-NOx values associated with biomass burning in China limits the use of this parameter in identifying and quantifying the sources of atmospheric nitrate (NO3-) and NOx. The results showed that the δ15N-NOx values of open burning and rural cooking stoves in China ranged from -3.7‰ to 3.1‰ and -11.9‰ to 1.5‰, respectively. The δ15N values of nine biomass fuel sources (δ15N-biomass) ranged from 0.1‰ to 4.1‰. Significant linear relationships between the δ15N-biomass values and δ15N-NOx values of open burning (δ15N-NOx = 1.1δ15N-biomass - 2.7; r2 = 0.63; p

Ammonium (NH4+) is a well-known alkaline species for haze formation and possesses potential impacts on human health and biological diversity. To date, regional source apportionments of NH4+ have been poorly understood in Northern China Plain (NCP). In this study, daily PM2.5 samples were synchronously collected in eight cities over the NCP region. In addition to water-soluble ions, the nitrogen isotopic composition of NH4+ (δ15N–NH4+) was also analyzed. The average concentrations of NH4+, a targeted species, varied from 0.9 μg/m³ to 42.5 μg/m³. Note that the significant enhancements of NH4+ coincided with increasing PM2.5 masses, suggesting that NH4+ was one of the contributing species for haze formation. The δ15N–NH4+averaged 12.4 ± 6.9‰ and the average δ15N–NH3 were further calculated to be −9.0 ± 6.7‰ over the NCP region. Both δ15N–NH4+ and δ15N–NH3 showed negative correlations with PM2.5 mass and there were no obvious differences among those 8 cities. Combining air-mass backward trajectories and quantifying contributions of potential sources, we pointed out that non-agricultural sources (fossil fuel related and NH3 slip) were dominant sources (totally contributed 42%–85%) not only on extreme haze phase but also on haze accumulation/dissipation phase in all 8 cities of NCP region in winter, the heating season in North China. However, the contribution of fossil fuel related source reduced to only 20%–35% while livestock breeding source rose to about 15%–32% and NH3 slip source kept contributing about 30% on the extreme haze phase. Thus, we considered that volatilization-related agricultural sources (especially livestock breeding) could discharge considerable NH3 to form SIA-led haze event in urban cities of the NCP region, even though non-agricultural sources were the foremost sources.

Free amino acids (FAAs) are particularly interesting because they play an important role in the atmosphere, but their origins are not well understood. This study measured the concentrations of FAAs and water-soluble ions as well as δ15N values of Glycine (Gly) in total suspended particle (TSP) samples collected at Nanchang in 2017. The correlation of total FAAs concentrations with meteorological conditions and atmospheric oxidants showed that secondary formation processes could be an important contribution sources for FAAs in the atmosphere. Moreover, the concentrations of FAAs in aerosols may be affected by the wind directions and the regions where air mass passed. The correlations of FAAs with water-soluble ions and PMF analysis indicated that the concentration of FAAs in Nanchang aerosols was influenced by agricultural activities and dust sources, mixture of natural origins and biomass burning and mixture of secondary formation process and biomass burning. Interestingly, we also found that coal combustion and vehicle emission are not the sources for atmospheric FAAs. Based on δ15N values of free Gly, a Bayesian model was performed to obtain the individual fractional contributions of free Gly from major sources (natural and biomass burning sources) to aerosol Gly. Subsequently, applying fractional contributions of free Gly from biomass burning obtained by Bayesian model to the analysis result of PMF, the overestimated of the contribution of secondary formation processes and natural sources to atmospheric FAAs concentration caused by biomass burning source could be excluded. Our findings suggest that combining δ15N values of free Gly and PMF analysis could provide further information on the sources of atmospheric FAAs.

The equilibrium sediment exchange process is defined as instantaneous deposition of suspended sediment to the streambed countered by equal erosion of sediment from the streambed. Equilibrium exchange has rarely been included in sediment transport studies but is needed when the sediment continuum is used to investigate the earth’s critical zone. Numerical modeling in the watershed uplands and stream corridor simulates sediment yield and sediment source partitioning for the Upper South Elkhorn watershed in Kentucky, USA. We simulate equilibrium exchange when upland-derived sediment simultaneously deposits to the streambed while streambed sediments erode. Sediment fingerprinting with stable carbon isotopes allowed constraint of the process in a gently rolling watershed. Carbon isotopes work well to partition upland sediment versus streambed sediment because sediment deposited in the streambed accrues a unique autotrophic, i.e., algal, fingerprint. Stable nitrogen isotopes do not work well to partition the sources in this study because the nitrogen isotope fingerprint of algae falls in the middle of the nitrogen isotope fingerprint of upland sediment. The source of sediment depends on flow intensity for the gently rolling watershed. Streambed sediments dominate the fluvial load for low and moderate events, while upland sediments become increasingly important during high flows and extreme events. We used sediment fingerprinting results to calibrate the equilibrium sediment exchange rate in the watershed sediment transport model. Our sediment fingerprinting and modeling evidence suggest equilibrium sediment exchange is a substantial process occurring in the system studied. The process does not change the sediment load or streambed sediment storage but does impact the quality of sediment residing in the streambed. Therefore, we suggest equilibrium sediment exchange should be considered when the sediment continuum is used to investigate the critical zone. We conclude the paper by outlining future research priorities for coupling sediment fingerprinting with watershed modeling.

The paper presents first nitrogen isotope analyses in shungites sampled from the core material of boreholes and from adits in the Onega region, Russia. The samples represent all varieties of the rocks, both stratified and migrated, with concentrations of reduced carbon ranging from a few percent to almost 100%. Analyses were carried out on a mass spectrometric complex (designed at the Open University), with the simultaneous measurements of the isotopic composition and concentrations of nitrogen and carbon using the step oxidation technique. It was determined that nitrogen is released mostly when the carbon is oxidized. The individual samples differ from one another in nitrogen isotopic composition and the nitrogen/carbon ratio, which indicates that these samples contain three distinct organic components of biological origin. Variations in δ15N and C/N that correspond to mixing of organic matter of the three types have been also observed during stepped oxidation. One of them has a relatively low C/N of approximately 200 and contains isotopically light nitrogen (δ15N up to –10‰). This component is thought to be primary, produced when the shungite rocks have been formed in a biological cycle involving reduced nitrogen species and formation of chemoautolithotrophic organisms, similar to what nowadays takes places in hydrothermal systems related to volcanic activity in spreading zones in the seafloor. Another component of the organic matter, with a relatively high δ15N from 0 to +3‰ and C/N of approximately 1000, was likely derived from the primary one in the course of diagenesis and metamorphism, due to nitrogen losses, resulted in heavier isotopic composition of the residual nitrogen. Finally, during post metamorphism time, the shungites have been contaminated with organic matter brought by meteoric waters. This organic matter had a relatively high δ15N of approximately +10‰ and the lowest C/N < 50. The different oxidation temperatures of the three organic components explain the reason for the variations in δ15N and C/N during step combustion of the material.

In the Antarctic Zone of the Southern Ocean, the coupled observations of elevated diatom‐bound 15N/14N (δ15Ndb) and reduced export production during the ice ages indicates more complete nitrate (NO3−) consumption. This evidence points to an ice age decline in gross NO3− supply from the deep ocean to the surface wind‐mixed layer, which may help to explain the reduced CO2 levels of the ice age atmosphere. We use a seasonally resolved, two‐layer model of the N isotopes in the Antarctic Zone upper ocean to quantify the ice age decline in gross NO3− supply implied by the data. When model parameters are varied to reflect reduced gross NO3− supply, the concentration of wintertime upper ocean NO3− is lowered, but with a much weaker increase in NO3− δ15N than predicted by analytical models such as the Rayleigh and steady state models. Physical mixing is the dominant cause, with a modest contribution from foodweb dynamics. As a result, the observed δ15Ndb rise of ~3‰–4‰ must be explained mostly by a greater summertime increase in NO3− δ15N during the ice ages. The high degree of NO3− consumption required to generate this summertime δ15N rise indicates a >80% reduction in gross NO3− supply. Half or more of the modern gross NO3− supply is from wind‐forced Antarctic upwelling that drives the upper cell of Southern Ocean overturning. Thus, the decrease in NO3− supply cannot be achieved solely by a decline in vertical mixing or wintertime convection; rather, it requires an ice age weakening of the upper cell.

Floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes. Here, we generated carbon and nitrogen isotope profiles for soil organic matter (SOM) in the Weinan loess-paleosol section in order to investigate changes in floral communities on the Chinese Loess Plateau (CLP) and their relationship to climate variation since 75 ka. δ13CSOM at Weinan ranges from −23.6 to −18.0‰ and δ15NSOM ranges from +3.4 to +5.5‰. Modeling based on the δ13CSOM record suggests that the proportion of C4 plants (%C4) has varied from lower during cold intervals (with minima of 24–32% at 73.1 ka, 20.9 ka (LGM), and 0.6 ka) to higher during warm intervals (with maxima of 62–64% at 53.0 ka and 8.2 ka). The δ13CSOM and δ15NSOM profiles are strongly correlated (r = +0.82; p(α)

In this paper, we report the stable carbon and nitrogen isotope analysis results of wild (n = 15) and domestic (n = 21) animal samples from the Proezzhaia I site, a fortified Medieval settlement in Trans-Baikal, Siberia. Additionally, we analyzed five modern freshwater fish samples from the Shilka River, which flows immediately north of the site. Together, these samples provide the first dietary stable isotope data for the entire Trans-Baikal region. Our results reveal a C3 plant dominated diet for all animal taxa sampled, but with a possible minor inclusion of C4 plant material in the diets of some cattle (Bos sp.) and horses (Equus sp.). We infer this C4 plant was likely a type of millet, the remains of which were identified at a contemporaneous site upriver. Additionally, these results indicate that some cattle and horses consumed plant material grown in 15N-enriched soil, which suggests several distinct animal management practices, or may indicate a trade in or movement of animals from an area with a different nitrogen isotope baseline.

Nitrogen (N) isotope ratio (δ15N) of soil extractable NO−3 plays a pivotal role in the study of N biogeochemical circulation in ecosystems. However, the NO−3 concentration and its isotope composition of soil samples are unstable, making sample storage critical for preserving the N isotope composition of extracted soil NO−3. Nevertheless, studies on the appropriate selection of storage methods after soil sampling are scarce. In this study, we compared two commonly used methods for storing soil samples and investigated the stability of N isotopes of soil NO−3. The results demonstrated that no significant changes in the NO−3 concentration and δ15N value occurred in the samples stored at –18 °C. However, the soil NO−3 concentration markedly increased, and NO−3 δ15N value significantly changed after air-drying storage. Meanwhile, we also found that NO−3 and its δ15N were well preserved in the filtered soil extracts after 1 month. In contrast, the NO−3 concentration gradually decreased and the 15N in NO−3 was gradually enriched in the bactericidal agent-containing soil mixture solution during the storage period. Overall, our results indicated that N isotopes of NO−3 could be effectively preserved in frozen-stored soil samples or filtered soil extracts. For field investigations conducted in remote areas and continued for a long-time period (and lacking a refrigerant supply), soil extraction/filtration using a CaSO4-saturated solution may be a superior preparation and storage method for analyzing N isotopes of soil NO−3.

Tree-ring studies using increment cores have increasingly measured elemental (N) and isotopic (δ15N) nitrogen values to evaluate environmental changes in the nitrogen cycle. The paucity of nitrogen in wood has constrained tree-ring analyses to annual resolution. Based on 77 rings and 310 sub-rings, we provide evidence for substantial intra-annual variability in N and δ15N values in the heartwood of 11 geographically widely separated, old growth Sitka spruce [Picea sitchensis (Bong.) Carrière] trees from coastal British Columbia. The range of N and δ15N values within rings (intra-annual level) was on average equal to or up to seven-times the range among rings (inter-annual level). Most rings showed a seasonal reduction in N values from early to late growth and a corresponding increase to the early growth of the following season (P < 0.05 to 0.001, Mann–Whitney–Wilcoxon test). By contrast, intra-annual changes in δ15N values were highly variable among years and among trees, ranging from pronounced oscillations (4.0‰) to reasonable consistency. Our results allude to the potential importance of such intra-ring data for interpreting seasonal trends in nitrogen use and increasing understanding of ecological processes in the marine–terrestrial interface.

Nitrogen (N) is a macronutrient essential to all living organisms and its availability in Precambrian oceans may have played an important role in the early evolution and diversification of eukaryotes. It has been hypothesized that the billion-year evolutionary stasis of eukaryotes during the mid-Proterozoic (ca. 1.8–0.8 Ga) was linked with N limitation. As a corollary, the rapid diversification of eukaryotes during the Ediacaran implies the lift of this barrier. Indeed, recent nitrogen isotope (δ15N) studies suggested a stable oceanic nitrate ( N O 3 - ) pool and perhaps oxygenated mid-depth oceans since ca. 750 Ma. This inference, however, contrasts with the iron, sulfur, and trace element geochemical data that suggested much later ocean oxygenation during the Ediacaran or Paleozoic. To better understand the relationship between nitrogen isotope and other redox proxy data, we have conducted a nitrogen isotope study on the organic-rich black shales of the basal Doushantuo Formation (ca. 635–632 Ma) in multiple sections across a shelf-to-basin transect, from which iron, sulfur and trace element geochemical data are available. The results show exclusively positive δ15N values in all sections across the basin, with most values within the range of +3‰ to +12‰ and a modal value of +5 ± 1‰. The positive δ15N values from the basal Doushantuo black shales are comparable with those of the modern ocean (+3‰ to +14‰; modal value of +5‰) and most likely resulted from an aerobic nitrogen cycle with partial water column denitrification in the presence of a stable nitrate pool. In general, it is difficult to maintain a stable oceanic N O 3 - reservoir in strongly stratified oceans. Therefore, the new δ15N data, in combination with other geochemical data, provide evidence for an oxygenated mid-depth ocean during the early Ediacaran. The co-occurrence of aerobic N isotope signal and euxinia in some samples implies that the early Ediacaran ocean in South China could be periodically stratified well below the photic zone, with a chemocline at least down to the mid-depth (e.g., >1000 m) or close to the water column/sediment interface.

Regional sources of nitrogen oxides (NOx) in North China during summer were explored using both a Bayesian isotopic mixing model and a positive matrix factorization (PMF) model. Results showed that the nitrogen isotope (δ15N) composition of particulate nitrate (NO3−) varied between −8.9‰ and +14.1‰, while the oxygen isotope (δ18O) composition ranged from +57.4‰ to +93.8‰. Based on results from the Bayesian isotopic mixing model, the contribution of the hydroxyl radical (•OH) NOx conversion pathway showed clear diurnal fluctuation; values were higher during the day (0.53 ± 0.16) and lower overnight (0.42 ± 0.17). Values peaked at 06:00–12:00 and then decreased gradually until 00:00–06:00 the next day. Coal combustion (31.34 ± 9.04%) was the most significant source of NOx followed by biomass burning (25.74 ± 2.58%), mobile sources (23.83 ± 3.66%), and microbial processes (19.09 ± 5.21%). PMF results indicated that the contribution from mobile sources was 19.83%, slightly lower as compared to the Bayesian model (23.83%). The PMF model also reported a lower contribution from coal combustion (28.65%) as compared to the Bayesian model (31.34%); however, the sum of biomass burning and microbial processes in the Bayesian model (44.83%) was lower than the aggregate of secondary inorganic aerosol, sea salt, and soil dust in PMF model (51.52%). Overall, differences between the two models were minor, suggesting that this study provided a reasonable source quantification for NOx in North China during summer.

The constant increase of anthropogenic emissions of aerosols, usually resulting from a complex mixture from various sources, leads to a deterioration of the ambient air quality. The stable isotope compositions (δ13C and δ15N) of total carbon (TC) and nitrogen (TN) in both PM10 and emissions from potential sources were investigated for first time in a rural and an urban Caribbean costal sites in Cuba to better constrain the origin of the contamination. Emissions from road traffic, power plant and shipping emissions were discriminated by coupling their C and N contents and corresponding isotope signatures. Other sources (soil, road dust and cement plant), in contrast, presented large overlapping ranges for both C and N isotope compositions. δ13CPM10 isotope compositions in the rural (average of −25.4 ± 1.2‰) and urban (average of −24.8 ± 1.2‰) sites were interpreted as a mixture of contributions from two main contributors: i) fossil fuel combustion and ii) cement plant and quarries. Results also showed that this last source is impacting more air quality at the urban site. A strong influence from local wood burning was also identified at the rural site. These conclusions were comforted by a statistical analysis using a conditional bivariate probability function. TN and δ15N values from the urban site demonstrated that nitrogen in PM10 was generated by secondary processes through the formation of (NH4)2SO4. The exchange in the (NH4)2SO4 molecule between gaseous NH3 and particle NH4+ under stoichiometric equilibrium may control the observed 15N enrichment. At low nitrogen concentrations in the aerosols, representing PM10 with both the highest primary N and lowest secondary N proportions, comparison with the δ15N of potential sources indicate that emissions from diesel car and power plant emissions may represent the major vectors of primary nitrogen.

The marine aerosols is mainly produced primary sea salt and secondary form of non-sea salt (nss) sulfate and organic species from marine emission, but get modified significantly by the anthropogenic and terrestrial materials, such as total carbon (TC) and total nitrogen (TN), which transported by the atmospheric circulation from land to the ocean. Rarely studies focus on the TC and TN in marine aerosol in the open ocean due to the sampling difficulty, let alone the annual observation. Concentrations of TC and TN, and their isotope compositions (δ13C-TC and δ15N-TN) were measured in total suspended particulate (TSP) which sampled at Yongxing Island over the South China Sea from March 2014 to February 2015, and coastal mega-city Guangzhou in April/May and October/November 2014. The annual average concentrations of TC and TN at Yongxing Island were 4.20 ± 2.38 μg m−3 and 0.77 ± 0.47 μg m−3, respectively. Much higher concentration of TC and TN were observed at Guangzhou. Contributions of NO3− and NH4+ (inorganic nitrogen, IN) to TN at Yongxing Island averaged 55.7% and 6.8%, respectively, while they averaged 27.4% and 12.2% at Guangzhou, respectively. The average values of δ15N in TN were +0.7 ± 3.3‰, +6.8 ± 6.3‰ and −0.7 ± 2.7‰ during winter, transitional and warm seasons, respectively, with an annual average value of +1.1 ± 4.3‰. The δ13C of TC varied from −16.2 to −26.8‰, with an annual average value of −22.7‰. The average of values of δ13C were −22.9 ± 1.7‰, −22.9 ± 1.4‰, and −22.4 ± 2.6‰ during winter, transitional and warm seasons, respectively. The average values of δ15N in TN and δ13C of TC were +13.2 ± 0.9‰ and −25.8 ± 0.4‰ in winter season, +13.6 ± 0.8‰ and - 26.5 ± 0.3‰ in warm season at Guangzhou, respectively. Based on aerosol δ15N and δ13C values, the marine realm may be an important source of aerosol TN, while aerosol TC may dominantly contributed by the combustion of fossil fuels and biomass burning from continental mass over the South China Sea. The secondary aerosol formation and long-range transport on aerosol chemistry also varied the concentrations and isotopic composition of TN and TC at Yongxing Island.

Matrix-assisted laser desorption/ionization imaging high-resolution mass spectrometry (MALDI-imaging-HRMS) is an important technique for visualizing the spatial distribution of compounds directly on the surface of organisms such as microorganisms, insects, plants, animals, and human tissues. However, MALDI-imaging-HRMS and the stable isotope labeling approach have never been combined for the detection and simultaneous visualization of labeled and unlabeled compounds, their analogues and derivatives, as well as their precursors. Herein, we present a methodology that labels microbial secondary metabolites directly on agar with stable isotopes and allows concurrent spatial distribution analyses by MALDI-imaging-HRMS. Using a thin film of labeled agar supplemented with [1-13C]-l-proline, [methyl-D3]-l-methionine, 15NH4Cl, or [15N]-l-serine overlaid on unlabeled agar, we demonstrate the incorporation of labeled precursors into prodiginines and serratamolides produced by an endophytic bacterium, Serratia marcescens, by MALDI-imaging-HRMS and HPLC-HRMS. Further, we show the incorporation of CD3 into prodigiosin as well as its characteristic fragments directly by MALDI-imaging-HRMS2. Our methodology has several advantages over currently existing techniques. First, both labeled and unlabeled compounds can be visualized simultaneously in high spatial resolution along with their labeled and unlabeled precursors. Second, by using a thin film of labeled agar, we utilize minimum amounts of expensive labeled compounds (1-3 mg) ensuring a cost-effective method for investigating biosynthetic pathways. Finally, our method allows in situ visualization and identification of target and nontarget compounds without the need of isolating the compounds. This is important for compounds that are produced by microorganisms in low, physiologically, or ecologically relevant concentrations.

Stable isotopes are important ecological tools, because the carbon and nitrogen isotopic composition of consumer tissue reflects the diet. Measurements of isotopes of individual amino acids can disentangle the effects of consumer physiology from spatiotemporal variation in dietary isotopic values. However, this approach requires knowledge of assimilation patterns of dietary amino acids. We reared leopard sharks (Triakis semifasciata) on diets of squid (Loligo opalescens; 1250 days; control sharks) or squid then tilapia (Oreochromis sp.; switched at 565 days; experimental sharks) to evaluate consumer-diet discrimination factors for amino acids in muscle tissue. We found that control sharks exhibited lower nitrogen isotope discrimination factors (∆15N) than most previous consumer studies, potentially because of urea recycling. Control sharks also had large carbon isotope discrimination factors (∆13C) for three essential amino acids, suggesting microbial contributions or fractionation upon assimilation. Compared to controls, experimental sharks exhibited higher ∆13C values for four amino acids and ∆15N values for seven amino acids, corresponding with differences between diets in δ13C and δ15N values. This suggests that not all amino acids in experimental sharks had reached steady state, contrary to the conclusion of a bulk isotope study of these sharks. Our results imply that (1) the magnitude of a shift in dietary δ13C and δ15N values temporarily influences the appearance of discrimination factors; (2) slow turnover of amino acid isotopes in elasmobranch muscle precludes inferences about seasonal dietary changes; (3) elasmobranch discrimination factors for amino acids may be affected by urea recycling and microbial contributions of amino acids.

This paper examines the nitrogen isotope fractionation factors (α) associated with the volatilisation of ammonia from water under controlled conditions at two pH values (8.5 and 9.2). This experiment assumed the continuous removal of ammonia at a single purge rate of 10 mL air min

Oxygen deficient zones host up to 50% of marine N2 production and the Eastern Tropical North Pacific (ETNP) is the largest marine oxygen deficient zone. We measured δ15N-NO3-, δ15N-NO2-, and δ15N-N2 at 7 stations along a transect normal to the coast in the heart of the ETNP oxygen deficient zone in 2012. The δ15N-N2 minimum was 0.34‰ at 300 m, which corresponded with the N2:Ar maximum. When the atmospheric N2 background was removed, the biological δ15N-N2 for the ODZ ranged from −7‰ to −22‰. In the ODZ, δ15N-NO3- ranged from 15 to 24‰ while δ15N-NO2- was generally between − 11 and −18‰, generating differences up to 40‰ between δ15N-NO3- and δ15N-NO2-. The isotopic separation between nitrite and nitrogen gas (Δ15N NO2-N2) changed sign from ~5‰ at the top of the oxygen deficient zone to ~−10‰ at 300 m, indicating an important shift in nitrogen cycling with depth. We calculated the closed system Rayleigh isotope effect (e) for N2 production from both the δ15N-DIN (eDIN = 26 ± 11‰) and δ15N-N2 (eN2 = 27 ± 6‰) data. When examined individually by depth, both eDIN and eN2 matched closely and both e depth profiles showed maximal fractionation at 300 m. Additionally, closed system isotope effects were calculated for one offshore station from the Arabian Sea in 2007 using δ15N-N2 ( eN2 = 24 ± 4‰) and δ15N-DIN (eDIN = 26 ± 3‰). The relatively large isotope effects for N2 production appear to be found in both major offshore oxygen deficient zones, which implies a large denitrification term in the marine N budget.

The objective of the present work is to reconstruct the subsistence strategies of an early transitional hunting-gathering/farming population living in dry caves in the southwestern region of Tamaulipas, northeastern Mexico. Specifically, a sample of 12 human individuals from the mortuary cave, Sepultura Cave (TCS) dating to 3100 B.P., is analyzed for stable isotope ratios of carbon, nitrogen, and oxygen. To obtain a nuanced understanding of the lifeways of this population, bone and dentine samples from each individual are analyzed to reconstruct how dietary practices changed over throughout life. Overall, the stable carbon isotope results suggest a high amount of C4 or CAM plant consumption, the stable nitrogen isotope results are consistent with terrestrial omnivory within an arid environment, and the stable oxygen isotope suggest the presence of two non-local individuals. Our results indicate small differences of diet between the individuals, probably reflecting variable stages of mixed economies of hunting-gathering and low intensive agriculture even though consumption of maize is difficult to differentiate from consumption of collected or managed CAM plants.

The isotopic compositions of plants can provide significant insights into paleodiets, ancient agricultural activities, and past environments. Isotopic compositions of charred (aka carbonized) ancient plant remains are typically preferred over those of uncharred/uncarbonized plants, both because charred plants are more commonly preserved and because early research suggested they experience less post-depositional isotopic alteration. In this paper, we re-explore the question of whether uncharred plants experience large-magnitude post-depositional changes in carbon and nitrogen isotope compositions by analyzing Terminal Pleistocene–Early Holocene plant specimens from rockshelters in the Escalante River Basin (Colorado Plateau, southeastern Utah). Several lines of evidence, including C3-CAM differences, plant-part comparisons, and dietary estimates from ancient herbivore collagen, suggest that the original carbon isotope compositions of these plants have not been significantly altered. The preservation status of plant nitrogen isotope compositions is equivocal. The direction of temporal shifts in plant δ15N matches global trends and the magnitude of the shift may have been exacerbated by the extinction of megafauna in an arid environment. However, the Pleistocene plant δ15N values are higher than would be expected based on herbivore bone collagen δ15N. Nevertheless, in contrast to previous research, the ancient uncharred plants in this study did not have exceptionally high δ15N values (> + 25‰). Overall, our research suggests that uncharred plants could be useful substrates for isotopic paleodietary and/or paleoenvironmental studies.

Rationale Stable isotope analysis is widely used to reconstruct diet, delineate trophic interactions, and determine energy pathways. Such ecological inferences are based on the idea that animals are, isotopically, what they eat but with a predictable difference between the isotopic ratio of a consumer and that of its diet, coined as the discrimination factor. Providing correct estimates of diet-consumer isotopic discrimination in controlled conditions is key for a robust application of the stable isotopes technique in the wild. Methods Using a Finnigan Mat Delta Plus isotope-ratio mass spectrometer, we investigated isotopic discrimination of carbon and nitrogen isotope ratios (δ13 C and δ15 N values) in guard hairs of four Arctic predators; the wolf (n = 7), the wolverine (n = 2), the grizzly bear (n = 2), and the polar bear (n = 3). During a 3-month trial, carnivores were fed a mixed diet. The δ13 C and δ15 N values, and the mass (g) of diet items, were monitored weekly for each individual to determine their Total Diet Average ratios. Results Diet-hair isotopic discrimination (Δx) varied according to species, ranging [1.88 ± 0.69‰: 3.2 ± 0.69‰] for δ13 C values, and [1.58 ± 0.17‰: 3.81 ± 0.22‰] for δ15 N values. Adult wolves Δ13 C average (2.03 ± 0.7‰) was lower than that of young wolves (2.60 ± 0.8‰) and any other species (combined average of 2.59 ± 0.28‰), except for the wolverine (2.12 ± 0.23‰). Wolves Δ15 N averages (juveniles: 3.51 ± 0.34‰, adults: 3.68 ± 0.28‰) were higher than those of any other species (combined average: 2.50 ± 0.58‰). Conclusions The discrimination factors for δ13 C and δ15 N values calculated in this study could be used in ecological studies dealing with free-ranging animals, with implications for non-invasive research approaches. As in other controlled discrimination studies, we recommend caution in applying our discrimination factors when the population structure is heterogeneous.

RATIONALE A range of important small seeded C4 crops were domesticated in Africa, but little is known about their carbon and nitrogen isotope ratios (δ13 C and δ15 N values). Understanding natural isotopic variability within and among millets has the potential to help us to understand the conditions under which ancient cereals were grown and has significant implications for the interpretation of ancient diets based on stable isotope signatures. METHODS We conducted carbon and nitrogen isotope analyses of modern and historical pearl millet (Pennisetum glaucum, n = 108) and finger millet (Eleusine coracana, n = 17) seed samples sourced from the United States Department of Agriculture as well as the Harlan Collection curated at the Crop Evolution Laboratory Herbarium at the University of Illinois. RESULTS The millet species have significantly different mean carbon and nitrogen isotope ratios over broad temporal and spatial scales. We also found substantial isotopic variation within species (range of 1.9‰ and 8.5‰ in δ13 C and δ15 N values, respectively). Both water availability and growing season temperature significantly affected the P. glaucum δ13 C and δ15 N values; cumulative annual precipitation was positively correlated with both seed δ13 C and δ15 N values, while temperature was positively correlated with δ15 N values but negatively correlated with seed δ13 C values. CONCLUSIONS The importance of both temperature and precipitation as predictors of δ13 C and δ15 N values in millets suggests that C4 plants may be more sensitive to environmental parameters than previously appreciated. Given the high degree of carbon and nitrogen isotope variability among accessions of these species, it is imperative that site-relevant plant isotope ratios are used for making isotope-based paleo-dietary predictions.

The effect of bicarbonate (HCO3−) on the growth and development of plants varies by species. To better understand inorganic carbon and nitrogen assimilation changes of karst-adaptable plants under different HCO3− treatments, we conducted experiments on seedlings and in vitro plantlets of Orychophragmus violaceus (Ov). We found that the vital photosynthesis potential (as measured by net photosynthetic rate, actual photochemical efficiency of photosystem-II, photochemical quenching coefficient, and the instantaneous carbon isotope ratio of 3-phosphoglycerate) was consistent under different HCO3− treatments of Ov. Bicarbonate’s lack of effect on carbon assimilation of Ov may be related to carbonic anhydrase in Ov converting HCO3− to H2O and CO2. In this way, Ov could prevent HCO3− ion toxicity and high pH from harming its growth and development under HCO3− stress. This study also found that high HCO3− concentrations could promote nitrogen assimilation and utilization of Ov through changes in related indexes (foliar nitrogen isotope fractionation ratio, stable nitrogen isotope assimilation ratio, foliar stable nitrogen isotope fractionation, nitrate nitrogen utilization efficiency, and nitrate utilization share) under different HCO3− treatments. Bicarbonate has different effects on photosynthesis and on inorganic nitrogen assimilation of Ov, which may be connected to photosynthesis providing electrons for nitrate/nitrite reduction through the photosynthetic chain.

The transfer of trace elements from external terrestrial reservoirs (i.e. atmosphere, hydrosphere, crust) to the mantle is mainly controlled by their geochemical behaviors during hydrothermal alteration of the oceanic crust and subsequent subduction metamorphism. Deciphering fluid–rock partitioning and element pathways during hydrothermal and subduction metamorphism is complicated due to a variety of pressure-temperature conditions and variable compositions of fluids interacting with the lithosphere. Fluid–rock interactions can, however, be traced by coupling multiple isotopic systems in a single and uniform type of lithology. Here we present Cu and N isotope relationships in Alpine metagabbros, which were hydrothermally-altered on the seafloor and subsequently buried to different depths in a subduction zone. Our sample set covers non-subducted, as well as blueschist- and eclogite-facies low-strain metagabbros, and veins and mylonites equilibrated in eclogite facies conditions. The low-strain metagabbros have Cu contents ranging from 22.5 to 73.2 ppm, and δ 65 Cu values from −1.66 to − 0.02 ‰ . In contrast, eclogite-facies veins and mylonites have lower Cu contents, below 11.1 ppm (except one sample at 27.7 ppm), but a very large range of δ 65 Cu values from −3.12 to 1.76‰. Nitrogen contents and δ 15 N values on the same samples were reported in a previous study and vary between 2.6 and 55 ppm, and from 0.8 to 8.1‰, respectively. In Cu vs δ 65 Cu and N vs δ 15 N diagrams, the low-strain metagabbros show clear trends, which are not related to subduction-zone metamorphic conditions, and more likely reflect hydrothermal processes. We propose that N and Cu were released concomitantly from metagabbros to hydrothermal fluids. This produced a decrease of N and Cu concentrations in the residual rocks, together with an increase of δ 15 N and a decrease of δ 65 Cu . The Cu isotope data, coupled to mineralogical analyses of the metagabbros by SEM, are compatible with partial dissolution of chalcopyrite under oxidative conditions. Nitrogen is not detected in chalcopyrite or in any major or minor mineral phases, probably reflecting the presence of ammonium (NH 4 + ) in trace amounts substituting for Na+ and/or Ca2+ in major phases. The release of Cu and N during hydrothermal alteration is best modeled by Rayleigh distillation in an open system, although a batch equilibrium model cannot be completely discarded. During subduction of the oceanic crust, N was further released to fluids, while Cu was mostly retained in the rocks, a conclusion supported from isotopic and mineralogical analyses. This step resulted in a decrease of N concentration with moderate increase of δ 15 N ( 0.5 ‰ ), and constant Cu contents and δ 65 Cu values. Accordingly, Cu isotope variability inherited from hydrothermal alteration was preserved in subducted metagabbros, although 90% of the fluids were lost during eclogitization. The present results imply that Cu depletion associated with light isotope enrichments in metagabbros can record the oxidative nature of hydrothermal alteration on the seafloor and be preserved despite late metamorphic overprint.

In the present study, the variation of stable isotopic ratio of carbon and nitrogen in wheat kernel along with milling fractions (bran, germ, break flour, reduction flour) in three genotypes from three different locations in five years (2012–2016) was investigated. Isotope ratio mass spectrometry (IRMS) was used to analyze the samples. Analysis of variance revealed significant differences among regions, genotypes, years, and their interactions for all wheat fractions. Region showed the largest variability in the δ13C and δ15N values of wholemeal and different fractions. A Significant positive correlation was found between whole kernel and different milling fractions for both carbon and nitrogen isotopes suggesting reliability of fractions fingerprints for geographical traceability of wheat. Moreover, a classification model based on the canonical discriminant analysis (CDA) was built which correctly classify 93.8% samples in all regions using light stable carbon and nitrogen isotope of whole wheat and milling fractions. Present findings significantly contribute to understand the variations of isotopic composition in different wheat milling fractions depending on geographical origins and offer valuable insight into the control of mislabeling regarding geographical origin.

The grapevine is one of the most important edible fruit plants cultivated worldwide, and it is highly sensitive to changes in the soil water content. We studied the total carbon and nitrogen contents and stable isotope compositions (C/N WSR , δ 13 C WSR and δ 15 N WSR values) of the solid residues obtained by freeze-drying wines produced from two white grapevine cultivars ( Vitis vinifera L. cv Chasselas and Petite Arvine) field grown under different soil water regimes while maintaining other climatic and ecopedological conditions identical. These experiments simulated the more frequent and extended climate change-induced periods of soil water shortage. The wines were from the 2009–2014 vintages, produced using the same vinification procedure. The plant water status, reflecting soil water availability, was assessed by the predawn leaf water potential ( Ψ pd ), monitored in the field during the growing seasons. For both wine varieties, the δ 13 C WSR values are highly correlated with Ψ pd values and record the soil water availability set by soil water holding capacity, rainfall and irrigation water supply. These relationships were the same as those observed for the carbon isotope composition of fruit sugars (i.e., must sugars) and plant water status. In Chasselas wines, the nitrogen content and δ 15 N WSR values decreased with soil water deficit, indicating control of the flux of soil-water soluble nutrients into plants by soil water availability. Such a correlation was not found for Petite Arvine, probably due to different N-metabolism processes in this genetically atypical cultivar. The results presented in this study confirm and generalize what was previously found for red wine (Pinot noir); the carbon isotope composition of wine solid residues is a reliable indicator of the soil and the plant water status and thus can be used to trace back local climatic conditions in the vineyard's region. In most wines (except Petite Arvine) the C/N WSR and δ 15 N WSR values are indicators of the origin of the nitrogen supplied to the plant's fruit (grape) that can be used to assess the N dynamics in the soil-water-plant system.

Mass coral bleaching events are increasing in frequency and intensity and are predicted to occur annually in the coming decades. However, it remains poorly understood how quickly Caribbean corals can recover from bleaching. To explore the responses to heat stress and subsequent recovery in Caribbean corals, three species ( Porites divaricata , Porites astreoides , and Orbicella faveolata ) were experimentally bleached in outdoor flow-through tanks for 15 days then allowed to recover on the reef for 1.5 and 11 months. At each interval on the reef, endosymbiont concentrations, energy reserves (i.e., total soluble lipid, soluble animal carbohydrate, soluble animal protein), calcification, and stable carbon and nitrogen isotope values of the animal host (δ 13 C h , δ 15 N h ) and endosymbiotic algal fractions (δ 13 C e , δ 15 N e ) were measured in treatment and control fragments of each species. Despite variations in bleaching recovery strategies among the coral species, all corals recovered within one year. Specifically, bleached P. divaricata catabolized lipids and decreased calcification in response to lower endosymbiont concentrations. In contrast, both P. astreoides and O. faveolata maintained energy reserves despite lower endosymbiont concentrations, yet both decreased calcification rates after bleaching. Overall, these findings indicate that these corals are capable of surviving and recovering from a mild bleaching event within one year. Though these finding indicate that P. astreoides and O. faveolata may be resilient through single isolated bleaching events under annual bleaching, many Caribbean coral reefs may still experience a decline over the coming decades.

The expansion of the upper boundary of the oxygen minimum zone (OMZ) has been associated with the low solubility of oxygen in the surface ocean due to global warming in tropical regions. However, sedimentary records of δ15N of sinking particulate organic matter and sediments suggest that oxygen solubility is controlled by oceanographic forcing in the tropical equatorial region. To determine the intensification of the OMZ within its upper border, δ15N analysis of the organic matter in superficial sediments of La Paz Bay was carried out. In the present work, 115 samples of superficial sediment were collected in the interval of 2–407 m depth in La Paz Bay. The surface sediments were analysed for the nitrogen isotopic composition of their organic matter. Hypoxia conditions (

The ratio of stable isotopes of nitrogen (15N and 14N) has been assessed in leaves of the forest plants from different functional groups (with ectomycorrhiza, ericoid, and arbuscular mycorrhiza; in a nitrogen-fixing symbiosis) under the conditions of strong transformation of ecosystems by the Karabashsky Copper-Smelting Plant effluents in the Southern Urals. The abundance of 15N in the plants generally increases in polluted habitats. The abundance of the heavy isotope 15N increases significantly with pollution in ericaceous dwarf shrubs (by 3.3‰) and herbs with arbuscular mycorrhizae (by 2.8‰). This indicates a strong alteration in conditions or modes of plant mineral nutrition under the influence of heavy metal pollution of forest ecosystems.