Nitrogen Stable Isotope Research Articles

First direct measurements of the nitrogen isotopic composition of vehicle tailpipe-emitted NH3 and implications for the source apportionment of NH3 in urban atmosphere.

The introduction of three-way catalytic converter (TWC) to meet stringent vehicular NOx emission standards worldwide has led to an unintended consequence of vehicle-derived ammonia (NH3) emission, which might degrade air quality and affect human health, especially in urban areas. The nitrogen stable isotope composition of NH3 (δ15N-NH3) may be a useful tool to trace NH3 sources, but the isotopic signature of vehicle-emitted NH3 is lacking. Here we report the δ15N-NH3 measured from tailpipe exhausts collected directly from 19 different vehicles equipped with TWC using "grab" sample technique optimized to avoid isotopic fractionation. We found a large of range of NH3 concentration (from 1 to 37 ppm, x̄ ± 1σ = 10 ± 8 ppm) and δ15N value (from -38.1 ‰ to 49.0 ‰, x̄ ± 1σ = 1.2 ± 20.9 ‰) for our samples (n = 57). Our results indicate a correlation between δ15N-NH3 and NH3 concentrations (i.e. δ15N-NH3 (‰) = 16.9(± 2.2)In(NH3 concentration; ppm) - 31.7(± 4.7) (R2 = 0.53, P < 0.01) that is associated with the catalyst temperature, which is generally agree with the results of theoretical calculation. After consideration of the vehicle emission evolution, dominant driving condition and tunnel δ15N-NH3 variation, a representative δ15N-NH3 value (meanminmax) of vehicle source is identified as 0.8000-2.20005.2000, which is distinct from (larger than) other NH3 volatilization-related emission sources. Using our newly measured δ15N values and Bayesian mixing model, we approximate the overall contribution of vehicles to ambient NH3 before, during, and after an international event in Beijing was 14.1 %, 7.9 %, and 21.5 %, respectively, which agree well with the course of traffic restriction. Collectively, our findings demonstrate the importance of using vehicle-emitted δ15N-NH3 to quantify vehicular NH3 contribution in urban atmospheres.

Source apportionment of organic carbon and black carbon in the surface sediments of the Pearl River Estuary and its adjacent South China Sea: insight from stable carbon and nitrogen isotopes

Coastal estuaries and adjacent continental shelf seas constitute vital global carbon reservoirs, and the sources and transformations of organic carbon in these regions are crucial to global biogeochemical cycles and climate change. This study investigated the total organic carbon (TOC), total nitrogen (TN), black carbon (BC), and their stable carbon and nitrogen isotopes (δ15NTN, δ13CTOC, δ13CBC) in the surface sediments of the Pearl River Estuary (PRE) and its adjacent northern South China Sea (NSCS) aiming to assess the impact of human activities on organic carbon dynamics in these areas. Results showed that the highest TOC concentrations occurred in the inner PRE due to intense human activities, and decreased seaward. The west side of the PRE exhibited higher TOC levels than the east side, which was attributed to differences in hydrodynamic processes and human activities. The westward flow of the Pearl River diluted water, which carried terrestrial organic matter inputs due to the influence of the Coriolis effect and intense local human activities, was a primary contributor to higher TOC levels on the west side (terrestrial source). In contrast, increased productivity and intensive mariculture activities on the east side predominated as sources of organic matter (marine source). Similar to the TOC, BC and TN sources were mainly influenced by human activities. δ15NTN distribution shows that TN in the east side of PRE mainly originated from industrial wastewater input from the Pearl River, while in the east side TN was mainly from domestic sewage discharge. Additionally, BC sources have shifted from primarily biomass combustion in the 1990s to fossil fuel emissions presently. Isotopic analysis revealed that over 70% of BC originated from fossil fuel inputs and C3 plant combustion, highlighting the significant influence of human activities in the PRE and adjacent NSCS, and underscoring the need for effective management and protection of the eco-environment in these regions.

Stable Isotopes Analysis of Black Lion Tamarins Reveals Increasing Arthropod Consumption When Fruit Productivity Decreases in Forest Fragments.

Given the cryptic and elusive nature of prey consumption, quantifying its contribution to the diet of free-ranging primates using behavioral methods is challenging. In this context, the use of carbon and nitrogen-stable isotopes represents a promising alternative approach. Here, we used stable isotope analysis to estimate the proportion of arthropods and fruits in the diet of black lion tamarins (Leontopithecus chrysopygus), an endangered primate endemic to the Brazilian Atlantic Forest. To do so, we ran stable isotope mixing models using isotopic data from hair samples of black lion tamarins living in six forest fragments showing different levels of habitat quality. Furthermore, we ran linear mixed models to assess the influence of habitat quality-fruit productivity (estimated by tree total basal area) and arthropod biomass - and individual characteristics (sex and body mass) on tamarins' δ15N values (a proxy for trophic position). Our results revealed that arthropods contributed more to black lion tamarins' diet than reported in previous behavioral studies, suggesting that behavioral observations may considerably underestimate the importance of arthropodivory in the diet of arboreal primates. The degree of arthropodivory and frugivory was similar within groups, in line with the strong group cohesion and synchronization of feeding behaviors of this species and supporting the role of site-specific habitat characteristics on dietary choice. Arthropod consumption was higher in areas with lower fruit productivity and did not increase when arthropod biomass increased, suggesting that fruits represent a limiting but preferred resource for this species. These results demonstrate the dietary plasticity of black lion tamarins in areas of lower forest quality, where they manage to compensate low fruit productivity by shifting to a diet richer in arthropods. Considering that this species occurs within a highly fragmented landscape, preserving and protecting small forest patches remains crucial for the conservation of this species.

The use of dietary isotopes as a preliminary step in the death investigation of unidentified skeletal human remains in British Columbia, Canada.

In British Columbia, Canada, unidentified skeletal human remains are often recovered by law enforcement or civilians and there is a question if they are modern and of medicolegal significance, or historical or archaeological. We used relatively fast and inexpensive carbon and nitrogen stable isotope analysis of human bone collagen from a selection of these remains (n = 48) combined with a logistic regression model to classify remains as modern, historical, or archaeological. We then confirmed our temporal classification through directly radiocarbon dating each individual and found that we could predict the temporal group with 93% accuracy. In regions where archaeological remains have dietary isotope values distinct from living people, dietary stable isotope analysis can provide a time-, and resource-efficient method to screen cases of unidentified human remains early in death investigation.

Isotopic evidence of diet breadth hunter-gatherers changes during the Holocene in the Central Pampean Dunefields (Argentina, South America).

Based on the analysis of stable carbon and nitrogen isotopes of bone collagen, stable carbon isotopes of bone apatite and an extensive AMS dating series (~10,000-299 years cal BP), the human paleodiets of 34 individuals from the Central Pampean Dunefields (Argentina, South America) are evaluated. These data are interpreted from the isotopic ecology of animals with archaeofaunal evidence of consumption and isotopic models of human diet. Multivariate carbon and nitrogen stable isotope model and Bayesian stable isotope ellipses were used to interpret human diets. Analysis of isotopic values indicates intake of enriched lipids and/or carbohydrates in relation to the proteins consumed throughout the Holocene. The isotopic values of Middle Holocene humans in relation to the values of exploited resources point out that individuals obtained protein mainly from guanaco. Subsequently, there was an increase in the human breadth diet during the Late Holocene, with a greater relevance of small prey of high trophic levels and vegetables. This contrasts with zooarchaeological information indicating generalist human diets during the Middle Holocene and specialized human diets in guanaco during the Late Holocene. It is proposed that during the Middle Holocene arid period, the combination of low human population density and high residential mobility in wide foraging ranges allowed the guanaco to be the main source of protein. During the Late Holocene humid period, there was an increase in human population density and a decrease in residential mobility, which caused greater pressure on foraging territories and increased dietary breadth.

Isotopic analysis of modern sorghum and finger millet from different altitudes in Ethiopia: implications for ancient farming practices

C4 crops such as sorghum (Sorghum bicolor) and finger millet (Eleusine coracana) have played a significant role in the economic livelihood in arid and semi-arid zones of tropical and sub-tropical Africa since prehistoric times. However, to date, our knowledge of their past management practices is limited. Stable isotope analysis of archaeobotanical remains has been recognized as a valuable tool for reconstructing past agricultural practices, e.g. water management, and fertilization. Nonetheless, our limited understanding of the isotopic variability of C4 plants calls for further research on modern plant before application to archaeobotanical remains. In this paper, we aim to enhance our understanding of modern C4 botanical remains' isotopic variability by analyzing sorghum and finger millet plants. These crops were cultivated according to traditional local practices and collected from ten villages located in the Konso Zone (South Ethiopia) and Tigray Regional State (North Ethiopia), where they are among the daily ingredients for food, and traditional alcoholic and non-alcoholic drinks. We analyzed carbon and nitrogen stable isotopes of seeds and biosilica content in chaff, as it has been suggested that a relationship can exist between silicon and C:N. Carbon isotope values show significant variability, positively correlated with altitude. By demonstrating the sensitivity of C4 grain carbon stable isotope to altitude variations, which are likely connected to water availability, this study offers invaluable insights for the accurate assessment of isotopic values derived from ancient C4 crops. The absence of significant correlations with δ15N suggests that nitrogen isotope values may be less effective for understanding environmental variations in this kind of context. This highlights the limitations of nitrogen isotope data for interpreting ancient agricultural practices and underscores the importance of relying more on carbon isotopes for insights related to environmental conditions and altitude. Furthermore, we confirm that the amount of assimilated carbon may depend also on the biosilica content, which is in turn modulated by environmental parameters such as water availability or soil silicon levels.

Prehistoric Italian foodways: Meta-analysis of stable isotope data from the Neolithic to the Iron Age

Italian Later Prehistory was characterised by profound changes that impacted everyday life in many aspects. Whether or not and how such changes were reflected in the subsistence practices of ancient populations is an ongoing question in the archaeological debate. This question has been investigated using stable carbon and nitrogen isotope analysis for several decades. Here, we present a 6000-year-long review of isotopic studies in the Italian Peninsula from the Neolithic to the Iron Age. We reconstruct chronological variations in food practices by observing δ13C and δ15N trends for 776 humans, 382 animals, and 432 C3 plants from 111 archaeological sites. During the Neolithic, when farming is first introduced, a homogenous signal characterised by terrestrial protein consumption is visible. The Copper Age, instead, shows a more varied pattern, possibly representative of a more diversified use of the landscape, characteristic of those millennia. The new cultural paradigm that invested Europe during the Bronze Age is also reflected in food practices in Italy, with the introduction of millets - signalled by high δ13C values in the Northern regions - possibly representing a pivotal shift. Not much data is available for the Iron Age, as only two sites from Northern Italy, showing a diffused consumption of C4 plants, and one site from Southern Italy, with a diet centred around C3 plants, are available for this period. The analysis of this extensive set of data suggests that the “Secondary Products Revolution” probably meant a shift in subsistence practices, with secondary sources substituting meat rather than integrating it.

Variation of carbon and nitrogen stable isotope composition in leaves and roots of Littorella uniflora (L.) Asch. in relation to water pH and nutrient availability

In a phytotron experiment, the effects of pH variation and eutrophication on isoetids plants from soft-water lakes specifically the submerged form of Littorella uniflora (L.) Asch. was investigated by analyzing stable carbon and nitrogen isotopes (δ13C and δ15N). Conducted in late October 2020, 200 specimens from Lake Zawiad, near Gdansk, Poland, were examined over 75 days. The study tested three pH levels (∼4.5, ∼7.0, and ∼8.5) and a detailed 12-step nutrient gradient (nitrogen: 0–10 mg/l; phosphorus: 0–0.3 mg/l). The analysis focused on isotopic composition in leaves and roots, revealing that acidic conditions favored higher δ13C values (leaves: −22.67 ‰; roots: −23.23 ‰), suggesting a preference for lighter carbon forms in photosynthesis and intensive use of limited sources of CO2. The neutral pH variant showed the lowest δ13C values (leaves: −25.53 ‰; roots: −25.47 ‰), indicating less optimal conditions. δ15N values exhibited minimal fluctuation across pH levels, with slight variations in acidic and alkaline environments compared to neutral conditions. An observed decrease in δ13C across all pH levels with increased nutrients, alongside a rise in δ15N values, indicates a complex interaction between isotopic composition and environmental factors. Our findings suggest that L. uniflora shows a distinct isotopic response to varying pH levels, with higher δ13C values under acidic conditions potentially indicating enhanced CO2 uptake through a specialized carbon assimilation strategy. This highlights the species' adaptive mechanisms to environmental stressors, suggesting that the isotopic composition of aquatic vegetation can serve as a sensitive indicator of changes in lake ecosystems.

Habitat dimensionality and feeding strategies but not temperature as determinants of body size-trophic structure relationship in a marine food web.

Disentangling the determinants of trophic structure is central to ecology. The capacity to capture subjugate and consume a prey (i.e. gape limitation) is a relevant limitation to acquire energy for most organisms, especially those in smaller size ranges. This generates a size hierarchy of trophic positions in which large organisms consume small ones. Body size is tightly correlated to gape limitation and explains a large fraction of variance in the body size-trophic position relationship. However, a considerable fraction of variance still remains to be explained. Consumer search space dimensionality (2D or 3D) and feeding strategies, temperature and the size structure of primary producers can alter the trophic structure, but tests based on information from natural food webs are scarce. We generated specific predictions about the body size trophic position relationship and evaluated them using information from a subtropical South Atlantic coastal marine ecosystem: benthic realm (2D, rocky shore and sandy beach) and the pelagic realm (3D). We characterized this marine coastal food web based on stable isotopes of carbon and nitrogen from 256 samples from primary producers (macroalgae and phytoplankton) to large predators (sand shark) in summer and winter. Consumer body size encompassed six orders of magnitude in weight from 10-2 to 6 × 104 g. Isotopic signal corresponded to an integration of carbon sources from basal consumers to top predators. The body size-trophic position relationship showed a linear positive association with different slopes for the benthic and pelagic environments. This implies a smaller predator prey size ratio for pelagic (3D) with respect to benthic consumers (2D) as theoretically expected. No seasonal differences were found in slopes and most of the overall variance in benthic environments was largely explained by feeding strategies of the different taxonomic groups. We provide an integrated evaluation on the role of body size, consumer search space and feeding strategy to understand the determinants of trophic position. Results demonstrate that integrating gape limitation hypothesis, the dimensionality of consumer search space and feeding strategies into a formal robust framework to understand trophic structure is feasible even in complex natural ecosystems.

Monsoonal impacts on the community trophic niches in two temperate headwater tributaries across a land use continuum

Pulsed flows following heavy monsoon rain events alter riverine food webs, but their impact on headwater stream food webs across the continuum from forested canopy to open agricultural land use remains unclear. We investigated carbon and nitrogen stable isotopes in macroinvertebrates and fish in two tributaries of the Suyeung River, Korea, before and after heavy monsoon rains to assess changes in community trophic niches. Basal resources (leaf litter and biofilms) exhibited consistent δ13C and δ15N values across seasons, with biofilms showing higher δ13C values. δ15N values increased from forested to agricultural reaches, indicating varied nutrient inputs. Consumer isotope values remained stable over time but varied longitudinally, reflecting reliance on local resources. Trophic niches differed between watershed locations but overlapped seasonally. Despite a decrease in consumer δ13C ranges after heavy rainfalls, variations in their δ15N ranges and the ellipse centroid (SEAc) of isotopic niches between sites resulted in broadly consistent SEAc across locations and seasons. This indicates limited evidence for directional reshaping of food-web properties across channel reaches following monsoon rains. Downstream isotopic shifts suggest substantial agricultural influences on food webs. Overall, our findings highlight that monsoon rains may have minimal effects on the community trophic niches of stream food webs.

A biogeochemical approach to examining sub-adult diet and the weaning process at Neolithic Tepecik-Çiftlik, Türkiye

Tepecik-Çiftlik, a Neolithic settlement located in the Cappadocia region of Central Anatolia, within the boundaries of Niğde province in modern Türkiye is crucial for helping us to better understand social behaviour and human mobility in the Neolithic, as well as relations between different groups. To investigate dietary habits, subsistence practices, and intra-societal variations stable carbon and nitrogen isotope ratio analysis has been conducted on the Neolithic human and faunal population. Further to this, 21 sub-adults were also sampled for stable carbon and nitrogen isotope ratio analysis to examine sub-adult diet, complementary feeding, and the cessation of breastfeeding as part of the weaning process. This isotopic investigation into the weaning process is complemented by a previously conducted study using Sr/Ca ratios from bone apatite of the same population. The δ13C values of the sampled sub-adults range from −19.8 ‰ to −19.0 ‰ and the δ15N values range from 8.0 ‰ to 15.2 ‰. The isotopic data suggest a very early onset of complementary feeding (ca. 0.2 years of age) and a brief breastfeeding period, relative to other prehistoric populations. The cessation of breastfeeding and this very brief weaning process was likely completed by ca. 1–1.5 years old. This early commencement of complementary feeding was most probably a deliberate social and cultural choice, supported by the presence of bowls and feeding spoons in the graves of very young babies and infants. However, this cultural choice may also have affected the mortality profile of the Neolithic population.

Geographic variability of carbon and nitrogen isotope ratios of nonvolant terrestrial small mammals (Rodentia) across 3 Brazilian biomes

Abstract In this study, we investigated landscape variability of the carbon and nitrogen isotopic composition of nonvolant small mammals in the 3 main Brazilian biomes (Amazon, Atlantic Forest, and Cerrado) while also considering the differential spatial distribution of C4 plants in these biomes. We compiled a subset of data on stable carbon and nitrogen isotope ratios from nonvolant small mammals of the order Rodentia and compared the aggregated isotopic variability at the biome level using classical δ13C–δ15N biplot. The concept of isotopic niche width was used to test whether different foraging attributes drive their isotopic composition, while a Bayesian isotopic mixing model was used to estimate the proportion of 3 main food categories available to these small mammals. We also developed isoscapes in the Brazilian biomes, interpolating animals δ13C and δ15N based on the geographic coordinates of each sample and “sourcescapes” considering geographic variation of the dietary sources. The findings of this study advance our understanding of the foraging ecology of small mammals in biodiversity-rich regions of the Neotropics. Classical methodologies such as stomach content confirmed dietary choices revealed by the stable isotopic composition and also highlighted the importance of C3 and C4 plants in the diet of this group of animals, especially in biomes such as the Atlantic Forest and Cerrado, where there is a predominance of highly altered landscapes. These results confirm that replacing the original vegetation with C4 crops has altered the feeding patterns of small mammals, which could lead to critical ecological changes in the trophic structure of these areas. Vertical stratification of the dietary niche and the interaction between biome and foraging lifestyle were also observed. However, in each biome, there was significant intraspecific and interspecific variation caused by preferences for ingestion of plant and animal material, leading to different degrees of omnivory. Finally, the high local variability between individuals and species requires a larger sampling design that may also contribute to improved spatial resolution of the isoscapes.

Anthropogenic nitrogen accumulation potential of Okinawa mangroves in Japan

The extent of the stable nitrogen (N) isotope ratio (δ15N) of mangrove leaves reflects the anthropogenic N accumulation potential of mangroves. Therefore, the present study was designed to investigate the N accumulation potential of Okinawa mangroves in Japan using three ecological indicators from four mangrove watersheds. The dissolved inorganic nitrogen (DIN) concentration in mangrove creeks, the leaf δ15N and the soil δ15N are considered immediate indicators, short-term indicators, and long-term indicators, respectively. The four mangrove watersheds are classified into two groups, human-affected and forested mangroves, based on the relative land use ratio (%) of the watersheds. The observed values of the ecological indicators were subsequently compared between two groups of watersheds to determine the relative ecosystem conditions. The results showed that both the leaf δ15N (0 to 9 ‰) and the soil δ15N (1.5 to 8.0 ‰) values are significantly greater in human-affected mangroves than in forested mangroves. The DIN of creek water samples does not indicate an immediate risk of excess N input from human perturbation in mangroves. However, the significant relationships among the indicators reflect the anthropogenic N accumulation potential of mangroves in Okinawa, Japan. These findings are highly important, especially for policymakers, environmentalists, and related stakeholders, for initiating conservation and management practices for mangroves. Controlled, limited, and/or restricted human perturbation; proper management of municipal wastes; and planned use of agrochemicals upon necessity may help reduce anthropogenic N inputs in mangrove ecosystems in Okinawa.

Mathematical lipid correction of δ13C and effect of lipid extraction on δ15N of European eel (Anguilla anguilla) muscle: Lipid correction of δ13C in European eels.

Carbon (δ13C) and nitrogen (δ15N) stable isotope analysis is a powerful tool to investigate diverse questions in fish ecology, such as their trophic position or migration strategies. These questions appear particularly important to protect endangered European eel. However, elevated lipid content in eel muscle can bias δ13C values, as lipids are 13C-depleted compared to proteins and carbohydrates. We measured δ13C and δ15N values of bulk and lipid-free samples of eel muscle. Lipid-free samples were obtained after the extraction of lipids with cyclohexane. Lipid-corrected δ13C values, using five different mathematical equations based on bulk δ13C values, were compared to lipid-free δ13C values. We also evaluated the effect of lipid extraction on δ15N values. The analyses were based on linear regression performed on 333 individuals captured in nine lagoons and four rivers. Independently to the capture site or habitat (river or lagoon), the predicted lipid-corrected δ13C values were highly consistent with the measured lipid-free δ13C values (R2 > 0.90). The application of specific equations for each habitat or capture site only slightly increases these R2 (1.5% or less). The lipid extraction treatment significantly decreased by 0.2‰ the δ15N values compared to bulk samples. Given the excellent prediction of mathematical equations and the small decrease of δ15N values after lipids extraction, we propose to use mathematical correction to estimate δ13C values of eel muscle. As the habitats or sites did not strongly influence the results, the coefficients from our study can be applied to other studies on European eel.

To pretreat, or not to pretreat, that is the question. The value of pretreatment protocols in the stable carbon and nitrogen isotope analysis of archaeobotanical cereal grains from Croatia and Serbia

ABSTRACT Isotopic analysis of archaeological charred plant remains is a useful tool to infer past agricultural practices. However, debate continues over whether charred seeds should be untreated or pretreated before analysis, to counteract any residual contamination and retrieve the “true” isotopic signature of the seed. This paper presents a case study examining whether archaeobotanical remains from Croatia and northern Serbia should be pretreated before isotopic analysis with the aim to provide a pragmatic technique for wider application. A small subset was first examined with an ATR-FTIR and then four different protocols were examined: water rinse only, two different acid-only methods and ABA (acid–base-acid). The results were inconsistent, displaying variability in the effect each protocol had on the isotopic values. Overall, it was concluded that the slight differences between untreated and pretreated sub-samples should not impact the archaeological interpretation, removing the need for pretreatment of the remaining archaeobotanical material.

Isotopic variability of short-tailed Albatrosses bone collagen (&lt;i&gt;Phoebastria albatrus&lt;/i&gt;) in the Bering Sea area during the holocene

The short-tailed Albatross (Phoebastria albatrus) is a rare bird species today, whose numbers declined significantly in the Holocene due to human fishing activities. Bone remains of albatrosses from archaeological sites of Chukotka, Kamchatka and Aleutian Islands, and from coastal sediments of the Commander Islands were used to analyze the content of stable carbon and nitrogen isotopes in bone collagen. Analysis showed that the isotopic niches of Aleutian and Commander albatrosses diverged during the Holocene. Short-tailed albatrosses of the Aleutian Islands are closer to Holocene albatrosses of Vancouver Island (Canada) by isotopic characteristics.

Mercury Stable Isotopes Reveal the Vertical Distribution and Trophic Ecology of Deep-Pelagic Organisms over the North-East Atlantic Ocean Continental Slope.

Deep-pelagic species are central to marine ecosystems and increasingly vulnerable to global change and human exploitation. To date, our understanding of these communities remains limited mainly due to the difficulty of observations, calling for complementary innovative tools to better characterize their ecology. We used mercury (Δ199Hg, δ202Hg, Δ201Hg, and Δ200Hg), carbon (δ13C), and nitrogen (δ15N) stable isotope compositions to segregate deep-pelagic species caught on the continental slope of the Bay of Biscay (NE Atlantic) according to their foraging depth and trophic ecology. Decreasing fish Δ199Hg values with corresponding depth estimates from the surface to down to 1,800 m confirmed that mercury isotopes are able to segregate deep species over a large vertical gradient according to their foraging depth. Results from isotopic compositions also identified different mercury sources, likely reflecting different trophic assemblages over the continental slope, in particular, the demersal influence for some species, compared to purely oceanic species. Overall, our results demonstrate how mercury stable isotopes can inform the vertical foraging habitat of little-known species and communities feeding in the deep.

Growth pattern and turnover of carbon and nitrogen measured by stable isotope ratios in the hair of sika deer (Cervus nippon).

Hair is known to preserve diet history and other physiological information during its growth period and is often used in chemical analyses. However, the growth patterns and turnover of hair vary according to the animal species or habitat, so understanding these patterns in the target animal is necessary for interpreting the results of hair analyses. In this study, we aimed to elucidate the growth pattern and dietary information of winter coat hair in captive sika deer (Cervus nippon). Experiments involving hair-staining and shaving were conducted to elucidate the growth pattern of sika deer hair. A diet-switching experiment was conducted to ascertain what dietary information is reflected in the carbon and nitrogen stable isotope values of the deer winter coat. Hair samples collected from each body site (head, shoulder, back, and hip) were analyzed using an elemental analyser interfaced with an isotope-ratio mass spectrometer. The winter coat grows from early September to early November, and then stops after that. During the growth period of the winter coat, the hair of the shoulder and back grew at a constant rate. The carbon and nitrogen stable isotope values of hair reflected the deer's feeding history during hair growth, but there seemed to be a time lag in the hip hair. The results suggest that the guard hair of the shoulder is suitable for hair analysis in sika deer. The obtained information on growth patterns and isotopic change of hair from captive sika deer according to diet be useful for interpreting the results of future analyses using hair samples of wild deer.

The impact of social status and biological sex on diet at 10th century CE Hungarian sites from stable carbon and nitrogen isotope analyses

Stable isotope analysis is a valuable tool to determine the diet of past societies, as well as the relationship that diet has with biological sex and social class. In this research, we performed stable carbon and nitrogen isotope analyses on individuals from four 10th century CE Hungarian sites (Karos-Eperjesszög, Tiszanána, Bodroghalom, and Üllő-Ilona út) to determine if their diet was affected by their sex or social status. We also compared these sites with Kenézlő-Fazekaszug, our previously published, contemporaneous site. The study yielded some unexpected results, indicating that elevated social status was not a reliable indicator of high animal protein consumption among the residents of the upper class Karos site. Additionally, the results suggested that biological sex was only a factor in animal protein consumption at the putative middle-class sites, such as Tiszanána. With its comprehensive sampling, this research provides new stable isotopic data to the Central and Eastern European database, as well as exciting results about a crucial period in Hungarian history. It may also serve as the impetus for future stable isotope analyses of other 10th century Hungarian sites.

Stable isotope analysis of western Lake Superior predatory fishes, part one: Trophic niche overlap

Characterizing food web interactions between introduced and native fish predators is important to quantify niche overlap, assess predator–prey balance, and support fisheries management. Lake Superior provides an ideal setting to investigate potential trophic overlap between native top predators, lake trout (Salvelinus namaycush) and walleye (Sander vitreus), and a diverse assemblage of introduced salmonids. Angler-caught fish were used to measure trophic position and niche overlap between predatory fishes in the western arm of Lake Superior based on carbon and nitrogen stable isotope ratios (δ13C, δ15N). Within a species, we did not find consistent differences in either δ13C or δ15N values by sex, collection year, capture location, or length. Among species, the range in δ15N values was >5 ‰, indicating that these species occupy ∼2 trophic positions, with dietary reliance ranging from primarily invertebrates to primarily fish, whereas the range in δ13C values indicated dietary reliance on a mix of pelagic and benthic prey. Combined, the δ13C and δ15N values revealed siscowet lake trout as the apex predator having a distinct trophic niche, while walleye and lean lake trout were intermediate trophic position predators with overlapping isotopic niches, and introduced salmonids were the lowest trophic position predators with overlapping trophic niches. Overlapping trophic niches indicated similar resource reliance and habitat occupancy among native lake trout and walleye, as well as among introduced salmonids, but less so between native and introduced predators.