Stable Carbon Isotope Analysis Research Articles

SEQUENTIAL THERMAL ANALYSIS OF COMPLEX ORGANIC MIXTURES: PROCEDURAL STANDARDS AND IMPROVED CO2 PURIFICATION CAPACITY

ABSTRACTSequential thermal analysis allows for deconvoluting the refractory nature and complexity of carbon mixtures embedded in mineral matrices for subsequent offline stable carbon and radiocarbon (14C) isotope analyses. Originally developed to separate Holocene from more ancient sedimentary organic matter to improve dating of marine sediments, the Ramped Pyrolysis and Oxidation (RPO) apparatus, or informally, the “dirt burner” is now used to address pressing questions in the broad field of biogeochemistry. The growing interest in the community now necessitates improved handling and procedures for routine analyses of difficult sample types. Here we report on advances in CO2 purification during sample processing, modifications to the instrumentation at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility, and introduce sodium bicarbonate procedural standards with differing natural abundance 14C signatures for blank assessment. Measurements from different environmental samples are used to compare the procedure to the different generations of sequential thermal analyses. With this study, we aim to improve the standardization of the procedures and prepare this instrumentation for innovations in online stable carbon isotopes and direct AMS-interface measurements in the future.

The subsistence economy in the Pingcheng area during the Northern Wei Dynasty: Stable isotope analysis of human bones obtained from the Datong Erzhong cemetery in Shanxi, China

Evidence indicates that diverse subsistence economies existed in the Pingcheng area (now Datong) during the Northern Wei Dynasty. This article details carbon and nitrogen stable isotope analyses conducted on human bones (n = 48) from the Datong Erzhong cemetery in Shanxi, China, to reveal the extent of agricultural factor development in diverse subsistence economies. The results show that, at the time, most humans (−10.4 ± 0.8 ‰, 9.7 ± 0.7 ‰, n = 40) primarily relied on millet-based foods. A few individuals (−14.7 ± 2.4 ‰, 10.9 ± 1.1 ‰, n = 8) lived on C3/C4 mixed food with abundant animal proteins. The isotope results of human and animal remains and charred millet obtained from nine contemporaneous cemeteries and/or sites indicate that millet-based agriculture was the dominant form of subsistence economy during the Pingcheng period (398–494 CE). Analysis of the proportion of millet-based food consumed by the individuals whose remains have been examined show that a dietary shift toward gradient millet consumption occurred in the Pingcheng area over time, indicating that millet agriculture became a dominant economic strategy.

An Overview of Lipid Biomarkers in Terrestrial Extreme Environments with Relevance for Mars Exploration.

Lipid molecules are organic compounds, insoluble in water, and based on carbon-carbon chains that form an integral part of biological cell membranes. As such, lipids are ubiquitous in life on Earth, which is why they are considered useful biomarkers for life detection in terrestrial environments. These molecules display effective membrane-forming properties even under geochemically hostile conditions that challenge most of microbial life, which grants lipids a universal biomarker character suitable for life detection beyond Earth, where a putative biological membrane would also be required. What discriminates lipids from nucleic acids or proteins is their capacity to retain diagnostic information about their biological source in their recalcitrant hydrocarbon skeletons for thousands of millions of years, which is indispensable in the field of astrobiology given the time span that the geological ages of planetary bodies encompass. This work gathers studies that have employed lipid biomarker approaches for paleoenvironmental surveys and life detection purposes in terrestrial environments with extreme conditions: hydrothermal, hyperarid, hypersaline, and highly acidic, among others; all of which are analogous to current or past conditions on Mars. Although some of the compounds discussed in this review may be abiotically synthesized, we focus on those with a biological origin, namely lipid biomarkers. Therefore, along with appropriate complementary techniques such as bulk and compound-specific stable carbon isotope analysis, this work recapitulates and reevaluates the potential of lipid biomarkers as an additional, powerful tool to interrogate whether there is life on Mars, or if there ever was.

Strong temporal variation of consumer δ13C value in an oligotrophic reservoir is related to water level fluctuation

Using stable carbon and nitrogen isotope analysis (δ13C and δ15N) to assess trophic interactions in freshwater ecosystems is a well established method, providing insight into ecosystem functioning. However, the spatial and temporal variability of isotope values, driven by environmental fluctuation is poorly understood and can complicate interpretations. We investigated how the temporal variation of stable isotopes in consumers (fish, crayfish and macrozoobenthos) of a canyon-shaped oligotrophic reservoir is associated with environmental factors such as water temperature, transparency, flooded area, and water quality measures. Consumers and their putative food sources were sampled and analyzed for carbon and nitrogen stable isotopes annually, and environmental parameters were measured monthly from 2014 to 2016. Results revealed significant differences in δ13C and δ15N values in each consumer among studied years. Over the years, fish and crayfish expressed differences in δ13C between 3 and 5‰, whereas in zoobenthos differences were 12‰. Variability in δ15N was similar across all consumers (2–4‰). Moreover, results suggest that the flooded area of the reservoir was a major driver of δ13C stable isotope values variation in consumers, while variation in δ15N was not linked to any of the studied environmental factors. Bayesian mixing models further showed significant changes in the origin of detritivorous zoobenthos carbon sources (reversal shift from terrestrial detritus to algae origin) between years with low water level to years with the standard water level. Other species showed only slight differences in food source utilization among years. Our study highlights the importance of environmental factors as sources of variation in consumer’s stable isotope values which should be considered especially when studied ecosystem strongly fluctuate in some environmental factor.

Effects of dissolved organic matter derived from two herbs on the growth, physiology, and physico-chemical characteristics of four bloom-forming algae species

While algal blooms occur frequently in lakes and reservoirs worldwide, the effects of dissolved organic matter (DOM) from lakeside and riparian zones on bloom formation are not well understood. In this study, we characterized the molecular composition of DOM from Cynodon dactylon (L.) Pers. (CD-DOM) and Xanthium sibiricum Patrin ex Widder (XS-DOM) and assessed their effects on the growth, physiology, volatile organic compounds (VOCs), and stable carbon isotope in four bloom-forming algae species (Microcystis aeruginosa, Anabaena sp., Chlamydomonas sp., and Peridiniopsis sp.). Stable carbon isotope analysis showed that the four species were affected by DOM. Both DOM types increased the cell biomass, polysaccharide and protein contents, chlorophyll fluorescence parameter values, and VOCs release of Anabaena sp., Chlamydomonas sp. and Microcystis aeruginosa, suggesting that DOM stimulated algal growth by increasing nutrient sources, photosynthetic efficiency, and stress tolerance. And in general, these three strains exhibited better growth at higher DOM concentrations. However, DOM treatment inhibited the growth of Peridiniopsis sp., as indicated by the increases in reactive oxygen species, damage in photosystem II reaction centers, and blockage in electron transport. Fluorescence analysis showed that tryptophan-like compounds were the main DOM components that affected algal growth. Molecular-level analysis suggested that unsaturated aliphatic compounds may be the most important DOM components. The findings indicate that CD-DOM and XS-DOM promote the blue-green algal blooms formation and thus should be considered in the management of natural water quality.

Early Holocene dietary patterns on the Neolithic Jeju Island, South Korea: Evidence from stone tools and stable carbon isotope analysis

This study investigates Neolithic subsistence on Jeju Island in Korea during the Early Holocene. Gosanri, our main site, provides evidence of the Early Holocene peopling to the Island by 10,000 cal. BP with pottery making tradition, while the Neolithic sites appeared in the Korean peninsula only 2000 years later. Gosanri and most of the Early Holocene sites, collectively called the Incipient Neolithic (10,000–8000 cal. BP), are located along the coastal lines of Jeju, and thus Incipient Neolithic people were assumed to conduct marine-based subsistence activities. This assumption has not been tested partly as most sites did not preserve any organic remains that can reflect diet. We examine this unanswered question by providing direct evidence on diet through the compound specific isotope analysis on pottery and by examining the stone tool compositions for procuring food. Our analyses suggest that Early Holocene islanders relied on terrestrial resource substantially. The proximity to the coast is not a self-sufficient evidence for the assumption of marine-oriented diet. Instead, the seasonality of food resources, the seasonal climate fluctuation, and the locational merit to a quarry, all equally affected Jeju islanders’ diet preference and subsistence practice. Overall Gosanri provides another convincing case of the broad-spectrum resource use to the transition to the Early Holocene.

Multiproxy approach to reconstruct fossil primate feeding behavior: Case study for macaque from the Plio-Pleistocene site Guefaït-4.2 (eastern Morocco)

The genus Macaca belongs to Cercopithecidae (Old World monkeys), Cercopithecinae, Papionini. The presence of Macaca in North Africa is well known from the Late Miocene to the Late Pleistocene. However, the diet of fossil Macaca has been poorly described in the literature. In this study, we investigated the feeding habits of Macaca cf. sylvanus (n = 4) from the Plio-Pleistocene site Guefaït-4.2 in eastern Morocco through multiproxy analysis combining analyses of stable carbon and oxygen isotopes from tooth enamel, buccal microtexture, and low-magnification occlusal dental microwear. For both microwear analyses, we compared the macaques with a new reference collection of extant members of Cercopithecoidea. Our occlusal microwear results show for the fossil macaque a pattern similar to the extant Cercocebus atys and Lophocebus albigena, African forest-dwelling species that are characterized by a durophagous diet based mainly on hard fruit and seed intake. Buccal microtexture results also suggest the consumption of some grasses and the exploitation of more open habitats, similar to that observed in Theropithecus gelada. The δ13C of M. cf. sylvanus indicates a C3 based-diet without the presence of C4 plants typical of the savanna grassland in eastern Africa during this period. The high δ18O values of M. cf. sylvanus, compared with the contemporary ungulates recovered from Guefaït-4.2, could be associated with the consumption of a different resource by the primate such as leaves or fresh fruits from the upper part of trees. The complementarity of these methods allows for a dietary reconstruction covering a large part of the individual’s life.

Living in the dry zone: Stable isotope insights into palaeodiet in ancient Myanmar

Southeast Asia is becoming a region of increasing interest in discussions of past migration, the origins of agriculture, and past impacts of human land-use change on environments. Myanmar, situated at a geographic and cultural crossroads between East, South and Mainland Southeast Asia, is potentially a critical region for exploring these themes. However, direct data relating to subsistence in the region has been lacking. Here, we apply stable carbon and oxygen isotope analysis to tooth enamel from humans and associated fauna to examine the subsistence economy of two communities from Myanmar, Oakaie and Nyaung’gan, spanning the transitional period from the late Neolithic to the early Bronze Age (ca. 1300-700BC). Situated within the broader regional and local environmental context, our data demonstrate the δ13C values of the individuals from the communities of Oakaie and Nyaung’gan are significantly higher, and the δ18O values are significantly lower, than individuals from the other sites in Southeast Asia, however, neither are significantly different to the Chinese sites and they overlap broadly with individuals from Mayutian in Southern Yunnan Province. These findings provide a unique insight into the subsistence economy of the ancient inhabitants of the Central Dry Zone of Myanmar.

Enrichment of geogenic phosphorus in a coastal groundwater system: New insights from dissolved organic matter characterization

High concentrations of geogenic phosphorus (P) in coastal aquifer systems pose a serious and continuous threat to the health of marine ecosystems. A major source for geogenic P enrichment in aquifer systems is the mineralization of P-containing organic matter. However, the mechanisms that drive the enrichment remain unclear. Therefore, our study sought to characterize the occurrence, sources, and enrichment mechanisms of geogenic P in a coastal confined aquifer system of the Pearl River Delta, southern China. To achieve this, we conducted Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and fluorescence excitation-emission-matrix spectra (EEMs) as well as hydrochemistry and stable carbon isotope analyses. Our findings indicated that intense degradation of P-containing organic matter produced up to 8.07 mg/L of geogenic P in a reducing environment with abundant organic matter. The dissolved organic matter (DOM) of high-P groundwater (P > 1 mg/L) contained more humic-like fluorophores and exhibited higher humification. Groundwater with high P concentrations contained more aliphatic compounds and highly unsaturated-low O compounds, and the enrichment of P was mostly associated with CHOP compounds in the region of aliphatic compounds and CHON2P compounds in the region of highly unsaturated-low O compounds. Different types of dissolved organic phosphorus (DOP) can be mineralized into P, and even the mineralization of phosphonates takes precedence over the more unstable phosphate esters. P produced by the metabolism of different types of DOP was assimilated by marine microorganisms (e.g., heterotrophic bacteria and archaea), and the newly synthesized organic P compounds by chemosynthesis were subsequently released into the groundwater. Over time, P continues to be enriched in the aquifer system. This study provides new insights into subsurface P cycling in coastal aquatic systems.

Dietary plasticity linked to divergent growth trajectories in a critically endangered sea turtle

Foraging habitat selection and diet quality are key factors that influence individual fitness and meta-population dynamics through effects on demographic rates. There is growing evidence that sea turtles exhibit regional differences in somatic growth linked to alternative dispersal patterns during the oceanic life stage. Yet, the role of habitat quality and diet in shaping somatic growth rates is poorly understood. Here, we evaluate whether diet variation is linked to regional growth variation in hawksbill sea turtles (Eretmochelys imbricata), which grow significantly slower in Texas, United States versus Florida, United States, through novel integrations of skeletal growth, gastrointestinal content (GI), and bulk tissue and amino acid (AA)-specific stable nitrogen (δ15N) and carbon (δ13C) isotope analyses. We also used AA δ15N ΣV values (heterotrophic bacterial re-synthesis index) and δ13C essential AA (δ13CEAA) fingerprinting to test assumptions about the energy sources fueling hawksbill food webs regionally. GI content analyses, framed within a global synthesis of hawksbill dietary plasticity, revealed that relatively fast-growing hawksbills stranded in Florida conformed with assumptions of extensive spongivory for this species. In contrast, relatively slow-growing hawksbills stranded in Texas consumed considerable amounts of non-sponge invertebrate prey and appear to forage higher in the food web as indicated by isotopic niche metrics and higher AA δ15N-based trophic position estimates internally indexed to baseline nitrogen isotope variation. However, regional differences in estimated trophic position may also be driven by unique isotope dynamics of sponge food webs. AA δ15N ΣV values and δ13CEAA fingerprinting indicated minimal bacterial re-synthesis of organic matter (ΣV < 2) and that eukaryotic microalgae were the primary energy source supporting hawksbill food webs. These findings run contrary to assumptions that hawksbill diets predominantly comprise high microbial abundance sponges expected to primarily derive energy from bacterial symbionts. Our findings suggest alternative foraging patterns could underlie regional variation in hawksbill growth rates, as divergence from typical sponge prey might correspond with increased energy expenditure and reduced foraging success or diet quality. As a result, differential dispersal patterns may infer substantial individual and population fitness costs and represent a previously unrecognized challenge to the persistence and recovery of this critically endangered species.

The formation conditions of gigantic dolomite concretions including whale bones exposed in Unosaki coast, Oga peninsula, Japan

Carbonate concretions occur in sedimentary rocks of widely varying geological ages throughout the world. Recently, more than 100 gigantic carbonate concretions with diameters ranging from 1 to 9 m have been identified along the Unosaki coast of Oga Peninsula, Akita Prefecture, Japan. The formation process of such gigantic concretions, some of which along the Unosaki coast contain whale bones, remains uncertain. A mineral composition analysis reveals that the major mineral of the concretions is dolomite. Considering the location of dolomite precipitation, their composition implies that the concretions were formed in a reducing environment in which sulfate ions were removed. Stable carbon and oxygen isotopic analysis reveals that the CaCO3 of whale bone and concretions contains light δ13C and heavy δ18O, suggesting that whale organic matter contributed to the formation of the concretions. The gigantic carbonate concretions were presumably formed by the accumulation and burial of whale carcasses with high sedimentation rates, and subsequent reaction of carbon decomposed by benthic and microbial activity with seawater.

Paired stable carbon and oxygen isotope analyses of human enamel for forensic human geolocation: An exploratory study

Stable carbon isotope analysis has proven utility for reconstructing dietary information in humans in past populations. The usefulness of stable carbon for forensic geolocation has been little investigated, largely because of the globalization of the human diet seemingly rendering it inconsequential. This study queried this assumption at a country-wide level on a known sample group. Stable carbon isotope values were obtained from human enamel with known biographical and geographical information to determine whether stable carbon, when paired with stable oxygen isotope values, could differentiate Canadians from non-Canadians. Samples originating outside of Canada were separated into three regions, and a linear discriminant analysis was used to generate discriminant functions that best separate the regions according to the stable carbon and oxygen isotope values. The results revealed two functions, where the first function explained 92.1% and the second 7.9% of the variance. Although some overlap in stable carbon and oxygen values was observed for individuals from both the United States and Canada, differences were observed between those from Canada and other geographical regions. This study demonstrated that pairing the dietary isotope carbon with the geolocator stable oxygen isotope, produced an interesting separation geographically, one that might well be helpful when attempting a geolocation query on unknown human remains.

Highland pastoralism in the Early Bronze Age Kura-Araxes cultural tradition: Stable oxygen (δ18O) and carbon (δ13C) isotope analyses of herd mobility at Köhne Shahar in northwestern Iran

Nomadic pastoralism and long-distance transhumance are often invoked as primary explanatory mechanisms for human migrations and regional interactions in the Early Bronze Age Kura-Araxes cultural tradition of the West Asian highlands. Based on established archaeological proxies of pastoralism, these arguments have rendered homogenous reconstructions of a complex pastoral landscape because of the effect of site formation processes that smooth out diagnostic archaeological signatures of diverse herd mobility strategies. Overcoming this equifinality requires an interdisciplinary approach that can empirically measure animal movements in the past. In this paper we use stable oxygen (δ18O) and carbon (δ13C) isotope analyses of incrementally-sampled teeth to investigate sheep, goat, and cattle herding strategies at the Kura-Araxes settlement of Köhne Shahar. Our δ18O analysis reveals that cattle and caprines accessed different water sources, with cattle staying closer to the settlement and the more permanent bodies of water that it provided. Restricted intra-annual ranges in δ13C values also show that nearly all herd animals were managed locally, involving limited transhumance that was supplemented with dry foddering. We contextualise our observations with published zooarchaeological data to call for more nuanced interpretations of Kura-Araxes pastoral landscapes that deemphasise the role of long-distance pastoral mobilities.

Paleoenvironmental changes in the Brazilian Pampa based on carbon and oxygen stable isotope analysis of Pleistocene camelid tooth enamel

ABSTRACTHere we present paleoenvironmental and paleoclimatic reconstructions of the Brazilian Pampa based on stable isotopes (δ13C, δ18O) in tooth enamel of the Pleistocene camelidsLama guanicoeandHemiauchenia paradoxafrom the Chuy Creek fossil assemblage, including oneH. paradoxafrom a stratigraphic level within a loess unit deposited during the Last Glacial Maximum (26.5–19 ka b2k). The δ13C results show that both species fed mostly on C3 plants, although the mixed diets ofL. guanicoeincluded ~30% C4 or CAM plants.H.paradoxahad C3 diets with <10% C4 or CAM plants. Both species exhibit higher δ18O and aridity indexes compared to other mammals from the assemblage, consistent with ingestion of18O‐enriched water from plants growing in arid/semi‐arid conditions. A comparison with δ13C of camelids from Argentina indicates the camelids from Chuy Creek fed on vegetation similar to that of Dry Pampa, Monte and Patagonic xerophytic steppes. Aridification and expansion of dry steppes in southern Brazil suggest a climate‐driven northeastwards shift of the Arid Diagonal of South America that may have contributed to local extinction of the Pleistocene megafauna. These Lateglacial environmental changes are reflected in the characteristics of the plant and mammalian assemblages of the modern Brazilian Pampa.

Mechanistic investigation of phosphonate photolysis in aqueous solution by simultaneous LC-IRMS and HRMS analysis

The mechanism of photolytic degradation of aminotrimethylphosphonic acid (ATMP) in an aqueous solution is not completely elucidated with respect to the transformation products formed during technical photodegradation. For the first time, the degradation of ATMP was investigated with simultaneous analysis by isotope ratio and high-resolution mass spectrometry (LC-IRMS+HRMS). This instrumental coupling combines quantitative data on degradation with compound-specific stable carbon isotope analysis (CSIA) in terms of kinetic isotope effects while identifying transformation products. Additionally, in combination with wet chemical analysis of ortho-phosphate (o-PO4), phosphorus balances were established to elucidate and interpret the degradation mechanism of ATMP under photolysis. Various experimental conditions during photolysis (temperature, dissolved oxygen concentration, and wavelength range) were investigated.ATMP was transformed to iminodimethylphosphonic acid (IDMP), aminomethylphosphonic acid (AMPA), and o-PO4 as main products during photolysis with a medium pressure mercury lamp. UV radiation < 310 nm was found to be required for ATMP degradation. The degradation of ATMP and its transformation products is slightly affected by temperature and dissolved oxygen concentration. Considering possible reactive oxygen species, such as hydroxyl radicals, it is assumed that the degradation of ATMP occurs to a small extent via a parallel degradation pathway in addition to photolysis. Complementary CSIA revealed an inverse carbon isotopic effect of ATMP due to direct photolysis, unaffected by the experimental conditions considered, while no isotopic effect was associated with the hydroxyl radical (H2O2) oxidation of ATMP. In UV/H2O2 oxidation of ATMP, four of five additional unknown transformation products, which have not yet been described in literature, could be assigned to postulated structures based on HRMS data. The findings achieved in this study demonstrate the advantages of simultaneous analysis by LC-IRMS+HRMS as a tool to elucidate reaction mechanisms for the first time.

Geoarchaeology at the marine waterfront of a coastal urban center: Human activities and sea-land interface processes on the Late Bronze and early Iron Age coast of Tel Dor, Israel

Geoarchaeological research at coastal urban sites in the Levant focused until recently on two research directions: the identification of ancient harbors and the study of occupation deposits in settlement portions that are located well above sea level (i.e., 'dry' excavations). Here we present a geoarchaeological study of the southern maritime waterfront of Tel Dor following a coastal excavation at an elevation that is close to current sea level. The research addresses stratigraphic relationships between underwater, coastal and fully terrestrial architectural features (wall remains) and these provide the context for deposits found within the site's perimeter. These coastal deposits were then studied using sediment micromorphology as well as stable carbon and oxygen isotope analysis. Three depositional units have been identified. The lower was found to be coastal deposits earlier than the Iron Age IB (Ir1b, 11-10th c. BCE). The middle unit is an ash deposit containing pottery and bone refuse dating to the Ir1b, probably a town dump, that became indurated due to sea level rise and resembles beachrock. The upper unit is composed of tell occupation deposits, including phytolith-rich layers and evidence for wood ash and compacted livestock dung as in stabling deposits. The latter, dated to the Ir1b – Ir2a (i.e. up-to and including the 9th c. BCE), reflects dumped refuse and livestock keeping in a terrestrial (i.e. non-marine) environment. Overall, this study provides initial insights into site formation processes and human activities at Dor's maritime interface during the Iron Age.

Deciphering the complex trophic relationship of the black-spotted croaker (Teleostei: Sciaenidae) and its parasites using stable isotope analysis

The stable isotope values of nitrogen (δ15N) and carbon (δ13C) have been widely used in ecological studies to decipher the trophic relationships and interactions that occur between living organisms. The aim of this study was to determine the trophic relationship between a commercially important tropical Australian marine fish ( Protonibea diacanthus (Lacepède, 1802)) (Sciaenidae) and its associated parasites, through stable isotope analysis of nitrogen and carbon (δ15N and δ13C). We examined the stable isotope ecology of four parasitic organisms: adult ectoparasitic copepods, and endoparasitic adult digeneans and nematodes and plerocercoids. Nitrogen in endoparasites was consistently depleted when compared with the host; however, digeneans expressed nitrogen signatures almost equivalent to those of the host. Ectoparasitic copepods were the only parasite that was substantially enriched in nitrogen compared with the host. All adult parasitic organisms were carbon depleted when compared with the host tissue associated with the site of infection; however, plerocercoids were enriched. Our findings emphasize the complexity of parasite–host interactions and the varying values of isotopic discrimination between parasite type, life-cycle stage, and location in host.

Variability in feeding habitats of red deer sensu lato in Eurasia in the Late Pleistocene and Holocene

Red deer (Cervus elaphus) is one of the species that is rather wide spread and survived across Europe over the Holocene. The analyses of carbon and nitrogen stable isotopes in bone collagen of ungulate remains have been applied in paleoecological studies as environmental and dietary indicators. In this study we present the carbon and nitrogen stable isotope compositions of previously radiocarbon-dated red deer bone samples (N = 68) found in Central, Southern and Eastern Europe and Asia and aligned to one of two species: European red deer (Cervus elaphus) and wapiti (Cervus canadensis). We showed that the values of carbon and nitrogen stable isotope ratios of European red deer and wapiti overlapped. Among all analysed independent factors (determined for the locality and time period relevant for each of the analysed samples), the variability of δ13C values in European red deer dated to the Holocene is best explained by forest cover and mean July temperature, and variability of δ15N values by the mean July temperature, annual precipitation and altitude. Additionally, combining the results of the present study with isotopic data on European red deer collected from published sources, we revealed that the values of δ13C and of δ15N in C. elaphus bones changed according to environmental oscillations that took place in Europe over the last 50 000 years. We concluded that red deer shifted their feeding habitats in relation to changing environmental conditions, for example, forest expansion during the climate warming, and in the mid to later Holocene in response to deforestation caused by human activity and the spread of agriculture. We also found out that red deer reacted in varied ways to changing local conditions in different regions of Europe. Modern individuals of C. elaphus had the lowest δ13C values among all analysed specimens, so they probably inhabited the most densely forested areas in comparison to other European red deer populations during the last 50 000 years.

Exploring the effects of weaning age on adult infectious disease mortality among 18th-19th century Italians.

The developmental origins of health and disease (DOHaD) hypothesis describes how early childhood stress affects morbidity and mortality later in life. The role of early childhood stress in mortality from infectious disease is understudied. Stressors in early childhood that weaken the immune system may result in increased susceptibility to infectious disease in adulthood. Weaning is one of the earliest potential periods of significant stress in early childhood. This research investigates the effect of weaning after ~6months of age on cholera mortality among 18th-19th-century Italian populations by determining if earlier breastfeeding cessation is associated with earlier mortality, analyzing childhood dietary variation and physiological stress markers, and determining if age-at-weaning completion differs between catastrophic and attritional populations. Serial dentin stable carbon and nitrogen isotope analyses from canines are compared between catastrophic (n=45) and attritional groups (n=23). Canines are sectioned serially from crown to apex, and the increment's δ15 N and δ13 C are used to estimate age-at-weaning completion. Catastrophic and attritional groups exhibit similar age-at-weaning completion (~2.8 years). Seventy-four percent of individuals lack elevated δ15 N values in dentin that formed during infancy. Age-at-weaning completion was not a predisposing factor in cholera mortality in adulthood in this sample. Age-at-weaning completion may not be significantly associated with infectious disease mortality because weaning completion likely occurred after infants had adapted to consuming contaminated weanling foods. Individuals without detectable weaning curves may represent infants who received supplementary foods since birth or were weaned before the age of 6-9months.

A new technique to study nutrient flow in host-parasite systems by carbon stable isotope analysis of amino acids and glucose

Stable isotope analysis of individual compounds is emerging as a powerful tool to study nutrient origin and conversion in host-parasite systems. We measured the carbon isotope composition of amino acids and glucose in the cestode Schistocephalus solidus and in liver and muscle tissues of its second intermediate host, the three-spined stickleback (Gasterosteus aculeatus), over the course of 90 days in a controlled infection experiment. Similar linear regressions of δ13C values over time and low trophic fractionation of essential amino acids indicate that the parasite assimilates nutrients from sources closely connected to the liver metabolism of its host. Biosynthesis of glucose in the parasite might occur from the glucogenic precursors alanine, asparagine and glutamine and with an isotope fractionation of − 2 to – 3 ‰ from enzymatic reactions, while trophic fractionation of glycine, serine and threonine could be interpreted as extensive nutrient conversion to fuel parasitic growth through one-carbon metabolism. Trophic fractionation of amino acids between sticklebacks and their diets was slightly increased in infected compared to uninfected individuals, which could be caused by increased (immune-) metabolic activities due to parasitic infection. Our results show that compound-specific stable isotope analysis has unique opportunities to study host and parasite physiology.