Stable Carbon Isotope Research Articles

Determining sugar and molasses origin by non‐exchangeable hydrogen stable isotope of ethanol and carbon isotope ratio mass spectrometry

AbstractThis study explores the differentiation of sugar and molasses produced from sugar beet and cane, which are susceptible to fraudulent labeling due to differing production costs. The research aimed to authenticate these products by botanical origin using novel analytical techniques. Utilizing ethanol isotopic measurement–isotope ratio mass spectrometry (IRMS) for non‐exchangeable hydrogen stable isotopes alongside carbon stable isotopes analysis through elemental analyzer–IRMS, the study accurately identified the origin of various sugar and molasses samples, pinpointed mislabeled goods, and determined the source of products with previously unknown provenance. These methods were also effective in revealing sugar and molasses adulteration and quantifying the extent of such fraud. The combined isotope analyses demonstrated their potential as robust tools for combating misrepresentation and adulteration in the sugar industry.

Characteristics of PM2.5 bounded carbonaceous aerosols, carbon dioxide and its stable carbon isotopes (δ13C) in rural households in northwest China: Effect of different fuel combustion

In order to fully understand the carbon emission from different fuels in rural villages of China, especially in the typical atmospheric pollution areas. The characteristics of carbonaceous aerosols and carbon dioxide (CO2) with its stable carbon isotope (δ13C) were investigated in six households, which two households used coal, two households used wood as well as two households used biogas and liquefied petroleum gas (LPG), from two rural villages in Fenwei Plain from March to April 2021. It showed that the fine particulate matter (PM2.5) emitted from biogas and LPG couldn't be as lower as expected in this area. However, the clean fuels could relatively reduce the emissions of organic carbon (OC) and element carbon (EC) in PM2.5 compare to the solid fuels. The pyrolyzed carbon (OP) accounted more total carbon (TC) in coal than the other fuels use households, indicating that more water-soluble OC existed, and it still had the highest secondary organic carbon (SOC) than the other fuels. Meantime, the coal combustions in the two villages had the highest CO2 concentration of 527.6 ppm and 1120.6 ppm, respectively, while the clean fuels could effectively reduce it. The average δ13C values (−26.9‰) was much lighter than almost all the outdoor monitoring and similar to the δ13C values for coal combustion and vehicle emission, showing that they might be the main contributors of the regional atmospheric aerosol in this area. During the sandstorm, the indoor PM2.5 mass and CO2 were increasing obviously. The indoor cancer risk of PAHs for adults and children were greater than 1 × 10−6, exert a potential carcinogenic risk to human of solid fuels combustion in rural northern China. It is important to continue concern the solid fuel combustion and its health impact in rural areas.

Quantification and isotopic characterization of benzene polycarboxylic acids (BPCA)-derived black carbon in deep oceanic sediments: Towards assessing pyrogenic inputs from marine sources

Methodologies based on benzene polycarboxylic acids (BPCA) selectively target the polymeric aromatic fraction of black carbon (BC) and are considered adequate to quantify pyrogenic inputs in environmental samples such as soils, lakes, and marine dissolved organic carbon. However, the usefulness of these methodologies to quantify BPCA-derived BC in deep-sea sediments has not been fully evaluated. In this manuscript we describe and validate a procedure to quantify BPCAs in deep oceanic sediments with very low organic carbon content. The resulting analytical procedure has produced reproducible quantitative data for BPCAs over a period of 10 months (coefficient of variation, CV = 6.4 − 6.6%). The stable carbon isotopes (δ13C) of BC_BPCA have been characterized using an LC Isolink™-irMS system with an accuracy better than 0.5‰. The quantitative and isotopic composition of several marine sediments has been characterized to investigate the relative contributions of marine/diagenetic and continental/pyrogenic sources to the BC accumulated in oceanic sediments from different contexts, ranging from upwelling systems to remote oceanic locations. Overall, a significant fraction of the sedimentary BC is of marine origin and should be considered in inventories of pyrogenic materials accumulated in the world oceans. However, the continental/pyrogenic sources can be largely dominant in marine settings with large inputs of pyrogenic materials.

CO2 conversion to CO by fluidized bed biomass gasification: Measuring CO2 utilization via stable carbon isotope ratios

Thermochemical conversion of CO2 in biomass gasification is a promising technology for utilizing CO2 as a feedstock to produce a CO-rich gas. Simultaneous decomposition reactions of biomass and various gas-solid and gas-gas reactions form the product gas in this process. The overlap in sub-processes makes it challenging to assess the conversion of feedstock CO2 with common methods like mass balancing. This work introduces stable carbon isotope ratio analysis (δ13C) to identify the sourcing of carbonaceous product gas components and determine the conversion of CO2. This methodology is applied to evaluate experiments conducted for one hour of continuous operation in a lab-scale fluidized bed gasifier. Softwood pellets and wood char are used as fuel, with Olivine as a bed material, a target heating temperature of 1000 °C and atmospheric pressure. Product gas with more than 80 vol% CO was generated when wood char was used as fuel. Stable carbon isotope measurements show that CO2 is converted at 48–93% in this process, underpinning the position of biomass CO2 gasification as carbon capture and utilization technology. These results were up to 25% higher than suggested by mass balancing, with higher discrepancies at lower CO2 conversions when using softwood as fuel. Therefore, stable carbon isotope ratio measurement can be a valuable tool for improving the process understanding of biomass CO2 gasification. The results can be used for carbon accounting and the technical development of gasifiers with high CO2 utilization efficiency.

Contribution of carbonate-derived dissolved inorganic carbon into autochthonous particulate organic carbon in two small temperate Korean rivers (Geum and Seomjin)

In this study, we estimated the contributions of carbonate mineral weathering to dissolved inorganic carbon (DIC) and carbonate-derived DIC to autochthonous particulate organic carbon (POC) in two temperate Korean rivers. We combined stoichiometric and stable carbon isotopic approaches to calculate the contribution of autochthonous POC, considering diverse riverine DIC sources. We collected surface water samples from May 2016 to May 2018 and analyzed the major ion composition of rivers along with the concentrations and stable carbon isotopes of DIC. Our estimates showed that the relative abundances of carbonate mineral weathering (0.41 ± 0.11 in the Geum River and 0.43 ± 0.07 in the Seomjin River) were only slightly lower than those of silicate mineral weathering (0.59 ± 0.1 in the Geum River and 0.57 ± 0.07 in the Seomjin River). The resulting percentage contributions of DIC derived from the carbonate mineral weathering to riverine autochthonous POC, if we consider the additional DIC sources of atmospheric and soil-derived CO2, were 10 ± 3 % in the Geum River and 2 ± 1 % in the Seomjin River. The calculated annual fluxes of carbonate-derived DIC for 2016–2018 were 23.2 ± 0.3 Gg C yr−1 in the Geum River and 1.1 ± 0.4 Gg C yr−1 in the Seomjin River. Moreover, the calculated annual fluxes of carbonate-derived POC were 3.6 ± 0.5 Gg C yr−1 in the Geum River and 0.1 ± 0.7 Gg C yr−1 in the Seomjin River. Accordingly, our study provides the first insight into the contribution of carbonate-derived DIC to riverine autochthonous POC in small temperate Korean river systems, dominated by silicate rocks.

Amino acid carbon isotope profiles provide insight into lability and origins of particulate organic matter

AbstractIdentifying the phytoplankton origin of particulate organic matter (POM) in the deep ocean is challenging due to the changing phytoplankton composition and varied extent of decomposition by heterotrophic bacteria and zooplankton. Here, we report vertical distributions of amino acid stable carbon isotope values (δ13C) measured in particles in the South China Sea. Carbon‐weighted amino acid δ13C values generally parallel bulk POM δ13C profiles with a positive offset from 2.4‰ in the surface water to 6.0‰ in deep. Accordingly, a lability model is introduced to describe the relative distribution and isotopic linkage of labile and refractory particulate organic carbon. Temporal changes of amino acid δ13C were observed during the microbial decomposition of two phytoplankton strains, the prokaryote cyanobacterium Synechococcus and the eukaryote diatom Thalassiosira weissflogii. Principal component analysis of individual amino acid δ13C values from the decomposing cells separate samples into two components, reflecting the influence of microbial decomposition and taxonomic differences, respectively. These two components were further applied to particles. A major contribution from decomposing phytoplankton to particles below the euphotic zone was observed, with more prokaryote organic matter in the basin and a larger contribution from eukaryotes at stations near the productive northern shelf. Our findings show the applicability of amino acid δ13C values in tracing the lability and phytoplankton origins of POM in samples with varied extents of decomposition in marine environments.

Carbonate Stable Isotope Data Suggest Freshwater Environment for the McMurray Formation (Aptian), Alberta, Canada

Stable isotope, trace element, and cathodoluminescence analyses were performed on gastropods and matrix from rock cores of the Middle to Upper McMurray Formation (Lower Cretaceous/Aptian, Northwestern Alberta, Canada) to characterize the extent to which pristine material remained from which depositional environmental conditions could be estimated. Aragonitic gastropod shells retain their original depositional chemistry, and along with other closely associated authigenic carbonate components, indicate that the Middle to Upper McMurray Formation was deposited in a freshwater environment that was part of a continent-scale river system.

Microalgal assemblages response to water quality remediation in coastal waters of Perth, Australia

Nutrient reduction is an essential environmental policy for water quality remediation, but climate change can offset the ecological benefits of nutrient reduction and lead to the difficulty of environmental evaluation. Here, based on the records of three lipid microalgal biomarkers and stable isotopes of carbon and nitrogen in two sediment cores from the embayment of Perth, Australia, we reconstructed the microalgal biomasses (diatoms, dinoflagellates and coccolithophores) over the past century and evaluated the ecological effects of nutrient reduction on them, using Change Point Modeling (CPM) and redundancy analysis (RDA). The CPM result showed that total microalgal biomarkers increased by 25% and 51% in deep and shallow areas, respectively, due to nutrient enrichment caused by industrial wastewater in the 1950s and the causeway construction in the 1970s, and dinoflagellates were beneficiaries of eutrophication. The nutrient reduction policy since the 1980s had not decreased total microalgal biomass, and diatoms were beneficiaries of this period. RDA based on time series of sediment cores and water monitoring data revealed that the increase of sea-surface temperature and the decrease of rainfall since the 1980s may be important factors sustaining the high total microalgal biomass and increasing the degree of diatom dominance. The result also indicated that the variations of microalgal assemblages may better explain the effect of nutrient reduction rather than total microalgal biomass.

Assessment of anthropogenic pollution in Guanabara Bay (SE Brazil) through biogeochemical data and stable isotope mixing models.

This work intends to identify pollution sources along the margins of Guanabara Bay (GB; SE Brazil) through a multiproxy approach and Bayesian stable isotopic mixture model (BSIMM). For this purpose, 33 surface sediment samples were collected and analyzed for granulometry, geochemistry (heavy metals, total organic carbon-TOC, stable isotopes of carbon and nitrogen-δ13C and δ15N, Rock-Eval pyrolysis parameters-REPP), and physicochemical parameters. Metal concentrations (E) dissolved in water (EW), adsorbed by organic matter (EOM) and by Mn hydroxides (EMn), and total extracted concentrations (ET) were analyzed. Sampling was conducted in 2018 after an oil spill from Reduc Oil Refinery. Potential Ecological risk index (PERI), based on metals, classified 85% of the analyzed stations as having moderate to considerable ecological risk. The metals with the potential to cause the highest ecological risk were CdW, CdOM, PbOM, and HgOM. The combination of BSIMM and REPP data was an effective proxy for oil spill detection by indicating the presence of polycyclic aromatic hydrocarbons (PAHs). Relatively high TOC contents suggested that the analyzed stations are eutrophicated environments. BSIMM discriminated three groups of stations with different sources of organic matter (OM), endorsing the result previously shown by the cluster analysis: (A) Niterói region, Botafogo marina, Glória marina, Fiscal and Fundão islands with diffuse sources of OM, including marine phytoplankton and material of continental origin from highly polluted rivers and domestic sewage; (B) region near Fundão and Governador islands and Mangue Channel outlet with OM (≃70%) supplied by highly polluted streams and a small contribution of PAHs; (C) Duque de Caxias and Botafogo-Urca inlet with significant contributions of PAHs, materials from C-3 plants and rivers polluted by urban sewage. Results of linear regressions in conjunction with BSIMM indicate that HgMn and PbOM mainly affect Group A's stations. Although the eastern margin of GB (Niterói; Group A) showed greater oceanic interaction than the other groups, it presented substantial concentrations of metals, potentially harmful (i.e., Hg and Pb) to marine biota and human health.

Dual C–Cl isotope fractionation offers potential to assess biodegradation of 1,2-dichloropropane and 1,2,3-trichloropropane by Dehalogenimonas cultures

1,2-dichloropropane (1,2-DCP) and 1,2,3-trichloropropane (1,2,3-TCP) are hazardous chemicals frequently detected in groundwater near agricultural zones due to their historical use in chlorinated fumigant formulations. In this study, we show that the organohalide-respiring bacterium Dehalogenimonas alkenigignens strain BRE15 M can grow during the dihaloelimination of 1,2-DCP and 1,2,3-TCP to propene and allyl chloride, respectively. Our work also provides the first application of dual isotope approach to investigate the anaerobic reductive dechlorination of 1,2-DCP and 1,2,3-TCP. Stable carbon and chlorine isotope fractionation values for 1,2-DCP (ƐC = −13.6 ± 1.4 ‰ and ƐCl = −27.4 ± 5.2 ‰) and 1,2,3-TCP (ƐC = −3.8 ± 0.6 ‰ and ƐCl = −0.8 ± 0.5 ‰) were obtained resulting in distinct dual isotope slopes (Λ12DCP = 0.5 ± 0.1, Λ123TCP = 4 ± 2). However direct comparison of ΛC-Cl among different substrates is not possible and investigation of the C and Cl apparent kinetic isotope effects lead to the hypothesis that concerted dichloroelimination mechanism is more likely for both compounds. In fact, whole cell activity assays using cells suspensions of the Dehalogenimonas-containing culture grown with 1,2-DCP and methyl viologen as electron donor suggest that the same set of reductive dehalogenases was involved in the transformation of 1,2-DCP and 1,2,3-TCP. This study opens the door to the application of isotope techniques for evaluating biodegradation of 1,2-DCP and 1,2,3-TCP, which often co-occur in groundwaters near agricultural fields.

SISALv3: a global speleothem stable isotope and trace element database

Abstract. Palaeoclimate information on multiple climate variables at different spatiotemporal scales is becoming increasingly important to understand environmental and societal responses to climate change. A lack of high-quality reconstructions of past hydroclimate has recently been identified as a critical research gap. Speleothems, with their precise chronologies, widespread distribution, and ability to record changes in local to regional hydroclimate variability, are an ideal source of such information. Here, we present a new version of the Speleothem Isotopes Synthesis and AnaLysis database (SISALv3), which has been expanded to include trace element ratios and Sr isotopes as additional, hydroclimate-sensitive geochemical proxies. The oxygen and carbon isotope data included in previous versions of the database have been substantially expanded. SISALv3 contains speleothem data from 365 sites from across the globe, including 95 Mg/Ca, 85 Sr/Ca, 52 Ba/Ca, 25 U/Ca, 29 P/Ca, and 14 Sr-isotope records. The database also has increased spatiotemporal coverage for stable oxygen (892) and carbon (620) isotope records compared with SISALv2 (which consists of 673 and 430 stable oxygen and carbon records, respectively). Additional meta information has been added to improve the machine-readability and filtering of data. Standardized chronologies are included for all new entities along with the originally published chronologies. Thus, the SISALv3 database constitutes a unique resource of speleothem palaeoclimate information that allows regional to global palaeoclimate analyses based on multiple geochemical proxies, permitting more robust interpretations of past hydroclimate and comparisons with isotope-enabled climate models and other Earth system and hydrological models. The database can be accessed at https://doi.org/10.5287/ora-2nanwp4rk (Kaushal et al., 2024).

Carotenoid skin ornaments as flexible indicators of male foraging behavior in a marine predator: Variation among Mexican colonies of brown booby (Sula leucogaster)

Carotenoid-dependent ornaments can reflect animals’ diet and foraging behaviors. However, this association should be spatially flexible and variable among populations to account for geographic variation in optimal foraging behaviors. We tested this hypothesis using populations of a marine predator (the brown booby, Sula leucogaster) that forage across a gradient in ocean depth in and near the Gulf of California. Specifically, we quantified green chroma for two skin traits (foot and gular color) and their relationship to foraging location and diet of males, as measured via global positioning system tracking and stable carbon isotope analysis of blood plasma. Our three focal colonies varied in which foraging attributes were linked to carotenoid-rich ornaments. For gular skin, our data showed a shift from a benthic prey-green skin association in the shallow waters in the north to a pelagic prey-green skin association in the deepest waters to the south. Mean foraging trip duration and distance of foraging site from coast also predicted skin coloration in some colonies. Finally, brown booby colonies varied in which trait (foot versus gular skin color) was associated with foraging metrics. Overall, our results indicate that male ornaments reflect quality of diet and foraging–information that may help females select mates who are adapted to local foraging conditions and therefore, are likely to provide better parental care. More broadly, our results stress that diet-dependent ornaments are closely linked to animals’ environments and that we cannot assume ornaments or ornament signal content are ubiquitous within species, even when ornaments appear similar among populations.

The microbiota characterizing huge carbonatic moonmilk structures and its correlation with preserved organic matter

BackgroundMoonmilk represents complex secondary structures and model systems to investigate the interaction between microorganisms and carbonatic rocks. Grotta Nera is characterized by numerous moonmilk speleothems of exceptional size hanging from the ceiling, reaching over two meters in length. In this work we combined microbiological analyses with analytical pyrolysis and carbon stable isotope data to determine the molecular composition of these complex moonmilk structures as well as the composition of the associated microbiota.ResultsThree moonmilk structures were dissected into the apical, lateral, and core parts, which shared similar values of microbial abundance, richness, and carbon isotopes but different water content, microbiota composition, and organic matter. Moonmilk parts/niches showed higher values of microbial biomass and biodiversity compared to the bedrock (not showing moonmilk development signs) and the waters (collected below dripping moonmilk), indicating the presence of more complex microbial communities linked to carbonate rock interactions and biomineralization processes. Although each moonmilk niche was characterized by a specific microbiota as well as a distinct organic carbon profile, statistical analyses clustered the samples in two main groups, one including the moonmilk lateral part and the bedrock and the other including the core and apical parts of the speleothem. The organic matter profile of both these groups showed two well-differentiated organic carbon groups, one from cave microbial activity and the other from the leaching of vascular plant litter above the cave. Correlation between organic matter composition and microbial taxa in the different moonmilk niches were found, linking the presence of condensed organic compounds in the apical part with the orders Nitrospirales and Nitrosopumilales, while different taxa were correlated with aromatic, lignin, and polysaccharides in the moonmilk core. These findings are in line with the metabolic potential of these microbial taxa suggesting how the molecular composition of the preserved organic matter drives the microbiota colonizing the different moonmilk niches. Furthermore, distinct bacterial and archaeal taxa known to be involved in the metabolism of inorganic nitrogen and C1 gases (CO2 and CH4) (Nitrospira, Nitrosopumilaceae, Nitrosomonadaceae, Nitrosococcaceae, and novel taxa of Methylomirabilota and Methanomassiliicoccales) were enriched in the core and apical parts of the moonmilk, probably in association with their contribution to biogeochemical cycles in Grotta Nera ecosystem and moonmilk development.ConclusionsThe moonmilk deposits can be divided into diverse niches following oxygen and water gradients, which are characterized by specific microbial taxa and organic matter composition originating from microbial activities or deriving from soil and vegetation above the cave. The metabolic capacities allowing the biodegradation of complex polymers from the vegetation above the cave and the use of inorganic nitrogen and atmospheric gases might have fueled the development of complex microbial communities that, by interacting with the carbonatic rock, led to the formation of these massive moonmilk speleothems in Grotta Nera.

A guide to precise measurements of isotope abundance by ESI-Orbitrap MS.

Stable isotopes of carbon, hydrogen, nitrogen, oxygen and sulfur are widespread in nature. Nevertheless, their relative abundance is not the same everywhere. This is due to kinetic isotope effects in enzymes and other physical principles such as equilibrium thermodynamics. Variations in isotope ratios offer unique insights into environmental pollution, trophic relationships in ecology, metabolic disorders and Earth history including climate history. Although classical isotope ratio mass spectrometry (IRMS) techniques still struggle to access intramolecular information like site-specific isotope abundance, electrospray ionization-Orbitrap mass spectrometry can be used to achieve precise and accurate intramolecular quantification of isotopically substituted molecules ('isotopocules'). This protocol describes two procedures. In the first one, we provide a step-by-step beginner's guide for performing multi-elemental, intramolecular and site-specific stable isotope analysis in unlabeled polar solutes by direct infusion. Using a widely available calibration solution, isotopocules of trifluoroacetic acid and immonium ions from the model peptide MRFA are quantified. In the second approach, nitrate is used as a simple model for a flow injection routine that enables access to a diverse range of naturally occurring isotopic signatures in inorganic oxyanions. Each procedure takes 2-3 h to complete and requires expertise only in general mass spectrometry. The workflows use optimized Orbitrap IRMS data-extraction and -processing software and are transferable to various analytes amenable to soft ionization, including metabolites, peptides, drugs and environmental pollutants. Optimized mass spectrometry systems will enable intramolecular isotope research in many areas of biology.

Clumped and in situ carbon and oxygen isotopes of calcite as tracers for oxidation of hydrocarbons in deep siliciclastic strata

The oxidation of hydrocarbons, including methane, is part of interrelated hydrogeochemical reactions affecting the carbon budget in Earth’s crust. To investigate these processes in deep siliciclastic strata, we analyzed core samples from Lower Triassic red beds in the Mahu Sag (Junggar Basin, northwest China) by coupling petrological observations with high-resolution in situ secondary ion mass spectroscopy stable carbon and oxygen isotope analyses and clumped isotopes (Δ47) of authigenic calcite. The strata contain variable oil and gas content as well as abundant high-valence Fe and/or Mn oxides. Three sequential generations of cement occur, which are characterized as (1) non-luminescent, early diagenetic calcite (MnO <0.3%, δ13CVPDB [Vienna Peedee belemnite] = −5.6‰ to −4.1‰); (2) bright-orange luminescent late-stage I calcite (0.75%−5.23% MnO, δ13C = −51.4‰ to −25.8‰); and (3) dull-orange late-stage II calcite (4.10%−12.93% MnO, δ13C = −91.4‰ to −30.9‰). Clumped isotopic thermometry reveals that the calcite precipitation temperature increases successively from <40 °C, to 81−107 °C, to finally 107−132 °C, corresponding to three precipitation time periods: before the Late Triassic, from the Early Jurassic to the Early Cretaceous, and from the Early Cretaceous to the present, respectively. δ13C values of −55.7‰ to −25.8‰ indicate that late-stage I calcite is the final product of oxidation of both methane and C2+ hydrocarbons, whereas δ13C values as low as −91‰ indicate that late-stage II calcite is mainly derived from the thermochemical oxidation of methane (δ13C = −46.8‰ to −39.3‰) induced by high-valence Mn and/or Fe oxides. For late-stage I calcite, hydrocarbon oxidation was most likely promoted by high temperatures, although microbial oxidation cannot be completely ruled out. The higher precipitation temperature of late-stage II calcite demonstrates that the oxidation of methane requires higher activation energies than oxidation of C2+ hydrocarbons. We provide reliable geochemical evidence for thermally induced sequential oxidation of hydrocarbons within deep siliciclastic strata.

Endophyte Inoculation and Elevated Potassium Supply on Productivity, Growth and Physiological Parameters of Spring Barley (Hordeum vulgare L.) Genotypes over Contrasting Seasons.

In recent years, recurrent droughts have significantly affected spring barley production, reducing the quantity and quality of grain. This study aims to identify genotype-specific traits and the drought resilience of six different Hordeum vulgare L. (spring barley) genotypes, while also examining the potential of potassium application and fungal endophyte Serendipita indica inoculation to mitigate the negative effects of dry periods during the growing season. Field experiments were conducted over a three-year period from 2020 to 2022, measuring physiological, growth, and yield parameters. To get insight into the physiological state of the plants, we measured the soluble sugars content and the ratio of stable carbon isotopes in the flag leaf tissue, which reflects conditions during its formation. The dominant factors that influenced the measured parameters were the genotypes and seasons, as well as their interaction, rather than other experimental factors. The results showed that the Spitfire and Accordine varieties were the best performing in both the 2020 and 2021 seasons, as indicated by their yield. However, in the drier 2022 season, the yield of these two varieties decreased significantly (to 55% for Spitfire and to 69% for Accordine of their yield in 2021), while for the arid-region genotypes, it remained at the same level as the previous year. This study sheds light on the potential of various genotypes to withstand periods of drought and the effectiveness of using potassium application and S. indica inoculation as mitigation approaches.

Elucidating carbon sources of hydrothermal vent animals using natural 14C abundances and habitat water temperature

AbstractDeep‐sea hydrothermal vents host exceptional ecosystems with lush animal communities primarily relying on organic matter (OM) produced by chemoautotrophic microbes. Though energy sources and food webs at vents have been extensively studied, the exact carbon sources of chemosynthetic primary production, such as methane (CH4) and carbon dioxide (CO2) in the vent fluid or bottom water, have not been elucidated quantitatively across spatial scales. Here, we investigate carbon and nitrogen sources of 12 vent animal species at the Iheya North field, Okinawa Trough inhabiting different distances from the central venting area and with various feeding ecologies using natural‐abundance radiocarbon (Δ14C) in combination with conventional stable carbon and nitrogen isotope ratios (δ13C and δ15N). Our results show that generally, animals living closer to vent orifices were more depleted in 14C, indicating they assimilate more carbon from vent fluid CO2. Those relying on methanotrophs, however, exhibited low Δ14C values regardless of distance due to the lack of methane in the non‐vent‐influenced bottom water. Organisms with low Δ14C values also tend to exhibit low δ15N values, implying NH4+ assimilation into biomass in environments with high NH4+ concentrations. Our results demonstrate that 14C can clearly distinguish between chemoautotrophically fixed carbon originating from the vent fluid and detrital OM derived from surface primary production, and also discriminate between CO2‐ and CH4‐based chemoautotrophy. Although vent animals rely on vent fluid energetically, our results highlight that the dependency on vent fluids as carbon source varies greatly depending on habitat, as well as carbon fixation pathways of microbial primary producers.

The intersection of diet, class, and sex during the Eastern Zhou (770–221 BCE): Bioarchaeological evidence from the Dahan cemetery, China

The Eastern Zhou (770–221 BCE) was an important period of social transformation in ancient China. The development of class- and gender-based stratification of this period had profound effects on human diet. We aim to examine the relationships among diet, class, and sex (as a proxy for gender) during this period through comparative investigations of noble individuals and sacrificial human companions. We analyzed the stable carbon and nitrogen isotope values of bone collagen of 61 human (26 nobles and 35 sacrificial companions) and 32 faunal samples from the Dahan (大韩) cemetery (an Eastern Zhou archaeological site). There are statistically significant class-based dietary differences, with the nobles consuming more socially valued foods (high protein food and millets) compared with sacrificial companions, which is also supported by paleopathological evidence. Sex-based differences were specific to class, with no significant dietary differences found in the nobles, whereas males may have had better diets than females in the lower classes. Our dietary analysis suggests that some sacrificial companions may have benefited from the resources of their noble masters, however, most sacrificial companions had a poorer diet. In addition, one noble individual possibly experienced social mobility in his lifetime, as shown by the discrepancy in his burial treatment and his long-term diet. This cemetery-wide study of dietary differences between nobles and sacrificial companions allows for novel insight into the intersection of class, gender, and diet during the Eastern Zhou period.

Livestock management during times of transition. Exploring the relationship between animal size and diet from Roman to early medieval Augusta Raurica (Switzerland)

Zooarchaeological research all over Europe has suggested a generalised pattern of livestock size decrease during the transition between the Roman times and the Early Middle Ages. Different reasons have been proposed to explain this pattern, including a change in management and feeding practices, in the context of a shift of animal husbandry from large to small scale production. This paper is based on faunal material from Roman and early medieval Augusta Raurica, north-western Switzerland, and provides a first attempt to test this hypothesis, by combining zooarchaeological information (taxonomic frequencies and biometrical analysis) and stable carbon and nitrogen isotope data from bone collagen of cattle and pig. The results suggest important changes in livestock management, such as a shift towards pig husbandry, and evidence for increased use of pannage and forest pastures has been found.

Differences and drivers of leaf stable carbon and nitrogen isotope in herbs under different vegetation types on the eastern Qinghai-Tibet Plateau

The natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) in leaves can provide comprehensive information on the physiological and ecological processes of plants and has been widely used in ecological research. However, recent studies on leaf δ13C and δ15N have focused mainly on woody species, few studies have been conducted on herbs in different vegetation types, and their differences and driving factors are still unclear. In this study, we focused on the herbs in subalpine coniferous forests, alpine shrublands, and alpine mea-dows on the eastern Qinghai-Tibet Plateau, and investigated the differences in leaf δ13C and δ15N of herbs and the driving factors. The results showed that there were significant differences in leaf δ13C and δ15N values of herbs among different vegetation types, with the highest δ13C and δ15N values in alpine meadows, followed by alpine shrublands, and the lowest in subalpine coniferous forests. Using variation partitioning analysis, we revealed that differences in leaf δ13C and δ15N of herbs among various vegetation types were driven by both leaf functional traits and climate factors, with the contribution of leaf functional traits being relatively higher than that of climate factors. Hierarchical partitioning results indicated that mean annual temperature (MAT), chlorophyll content index, leaf nitrogen content per unit area (Narea), and leaf mass per area were the main drivers of leaf δ13C variations of herbs across different vegetation types, while the relative importance of Narea and MAT for variation in leaf δ15N of herbs was much higher than those other variables. There was a strong coupling relationship between leaf δ13C and δ15N as indicated by the result of the ordinary least squares regression. Our findings could provide new insights into understanding the key drivers of leaf δ13C and δ15N variations in herbs across different vegetation types.