Stable Isotope Analysis Research Articles

Trophic habitat shifts during ontogeny of the scalloped hammerhead shark Sphyrna lewini using stable isotopes analysis in vertebrae

Trophic habitat shifts during ontogeny of the scalloped hammerhead shark Sphyrna lewini using stable isotopes analysis in vertebrae

Evidence of eastern rockhopper penguin feeding on a key commercial arrow squid species

Cephalopods are crucial to the Southern Ocean ecosystem, connecting top predators with mid-trophic organisms, yet their ecology in the Pacific sector is not well understood. This research used stable isotope analysis to explore the habitat and trophic ecology of cephalopods found in the diet of eastern rockhopper penguins (Eudyptes chrysocome filholi) around Campbell Island, a New Zealand sub-Antarctic island. Eastern rockhopper penguins were used as biologic samplers, revealing some differences in cephalopod diversity and ecology between two breeding seasons—1986–87 and 2012–13—, and the squid Nototodarus sloanii, a commercially valuable species, was described for the first time in the 2012–13 season. Stable isotope values (δ13C and δ15N) for the squid species Moroteuthopsis ingens were consistent between seasons, indicating ecological stability, whereas the octopod species Octopus campbelli showed changes, suggesting shifts in habitat and feeding. Warmer oceanic temperatures in 2012–13 may have facilitated the emergence of N. sloanii on the diet of the eastern rockhopper penguins. These findings highlight potential changes in cephalopod biodiversity in the Pacific sector of the Southern Ocean, emphasizing the need for further research on ecological dynamics of this region.

Trophic niche differentiation and foraging plasticity of long-finned pilot whales (Globicephala melas edwardii) in Tasmanian waters: insights from isotopic analysis

Understanding the foraging preference of cetaceans is crucial for assessing their role as apex predators and indicators of marine ecosystem health. Using stable isotope analysis, we investigated trophic niche differentiation and foraging plasticity in 141 long-finned pilot whales (Globicephala melas edwardii) that stranded along the Tasmanian coast at three locations (Marion Bay, King Island, and Maria Island). Stranding location accounted for most of the variability in skin isotopic values (δ13C: - 17.9 ± 0.2 ‰ to –16.9 ± 0.2 ‰, Principal Coordinate 1 = 89%), likely reflecting differences in foraging habitats. In addition, isotopic niche overlap ranged from minimal (0-10% between Marion Bay and Maria Island) to moderate (between Marion Bay and King Island, and King Island and Maria Island). While sex related differences in isotopic niche space were minimal overall, there was some variability in the core niche space between males and females at Maria Island. Dietary proportions from our mixing model support a predominantly cephalopod diet for pilot whales in Tasmanian waters (91%, CI: 63-90%), with greater contributions from offshore dietary sources (68%, CI: 25-95%). The dietary variability across the three strandings highlights the foraging plasticity of pilot whales, which despite their preferences for a wide range of oceanic cephalopods, can adopt a more generalist feeding strategy when necessary. These findings provide valuable insights into the ecological role and adaptability of pilot whales in Tasmanian waters, highlighting the importance of monitoring apex predators to inform conservation and ecosystem management strategies in dynamic marine ecosystems.

Stable isotope analysis reveals individual variations in feeding habits among wild Japanese macaques

AbstractWe employed stable isotope ratio analysis to quantitatively assess the feeding behaviors of individual macaques within a wild group of Japanese macaques (Macaca fuscata). The primary objective was to evaluate macaque's feeding habits at the individual scale and to clarify the relationship between feeding habits and social factors, including age, sex, and social rank. The study population consisted of the Main group of Japanese macaques on Koshima Island. We collected 78 body hair samples and 29 food resource samples for isotopic analysis. The variability in carbon, nitrogen, and sulfur isotope ratios among individuals in the Main group has ranges of 5.5‰, 6.5‰, and 6.8‰, respectively. Furthermore, the Bayesian mixture model revealed that there were individual differences in the utilization of forest‐derived (62.3%–90.5%), marine‐derived (6.1%–27.6%), and human‐derived (1.7%–23.4%) food resources, driven by the effect of sex, rank, and year. These findings particularly emphasize the utility of sulfur stable isotope ratios and demonstrate how the combined use of three stable isotope ratios enables effective analysis of the relationships between Japanese macaques and their food resources. Furthermore, our results provide a valuable opportunity for the advancement of future research that integrates stable isotope approaches with field investigations. This study not only highlights the applicability of sulfur isotope ratios as a tool for uncovering the use of marine resources by primates in other regions but also shows the potential of using isotopic techniques to distinguish human‐derived resources, such as wheat, and to develop strategies for managing crop‐raiding by macaques.

Use of a groundwater model to evaluate groundwater–surface water interaction at a riverbank filtration site: a case study in Binh Dinh, Vietnam

A comprehensive understanding of groundwater–surface water (GW–SW) interaction is important for sustainable water resource management. Riverbank filtration (RBF) serves as a natural method to enhance groundwater recharge, especially in systems where surface water and groundwater are closely connected. Thus, RBF is a feasible option for water management particularly in regions dealing with water scarcity and overexploitation of groundwater. This study investigated GW–SW interaction at a well-field next to the Dai An River in Phu Cat district, Binh Dinh province, Vietnam, with the primary goal of evaluating the feasibility of RBF for water supply at this site. Using FEFLOW 7 software, numerical modelling was conducted to simulate groundwater flow and estimate groundwater recharge rates from riverbank filtration during wet and dry seasons. The model incorporated key aquifer parameters, including hydraulic conductivity and porosity. Additionally, stable (water) isotope analysis of hydrogen (δ2H) and oxygen (δ18O) was performed to trace GW–SW interaction. The modelling results demonstrated that approximately 72% of total groundwater recharge came from riverbank filtration, confirming a strong hydraulic connection between the river and the aquifer. Stable isotope analysis revealed seasonality in mixing rates, with the surface water contribution to the aquifer ranging from 2% during the dry season up to 54% during the wet season. The travel time from the riverbank to the nearest abstraction well was estimated to be less than 3 days. These findings contribute to understanding of GW–SW interaction in the region and also offer general guidance for optimizing well placement and sustainable groundwater extraction practices.

Cultural diversity shaped neolithic subsistence in the Carpathian Basin

Stable carbon and nitrogen isotope analysis from archaeological human and animal bone collagen is a powerful tool to enlighten past socio-agricultural systems and their close links to environmental conditions. To assess whether isotopic patterns are a function of cultural behavior or rather determined by environmental diversity, we test the spatio-temporal effects of conditional and multivariate exploratory and environmental models on stable isotope variability in the Neolithic and Chalcolithic Carpathian Basin (6000–2800 BCE). Our results stress that variation in environmental settings influence both the isotope baselines and the subsistence strategies of early agricultural societies. Major shifts in isotopic patterns are, however, culturally-driven, which is particularly visible with the development and intensification of adapted agropastoral practices from 5500 − 5350 BCE and among the diet between different cultural groups. We conclude that socio-cultural diversity was the main driver of dietary habits and isotopic variability in early agropastoral societies of Neolithic Hungary.

Amino acid δ15N in eye lens laminae reveals life-time ontogenetic trophic shifts of a highly migratory species.

Investigating the feeding ecology through the ontogenesis of highly migratory species such as the Pacific Bluefin tuna (PBFT; Thunnus orientalis) is difficult due to its extensive home range and cross-oceanic migration. Here, we show the potential of conducting nitrogen stable isotope (δ15N) analyses in bulk tissue and amino acids (AAs) in consecutive eye lens laminae of PBFT to reconstruct the trophic life history for an individual tuna. The δ15Nbulk profiles between individuals caught in the wild and pen-raised were compared. For all individuals, δ15Nbulk values increased with increasing eye lens diameter or fork length, and exhibited low variation among individual profiles despite tuna being captured in different months. Large δ15Nbulk shifts (6.8‰-8.5‰) were quantified between the first and last deposited laminae for each individual, suggesting major ontogenetic changes in either foraging areas or trophic position. AA δ15N values indicate that this highly migratory schooling predator switches feeding areas from lower to higher δ15N baseline values, reflecting feeding on both sides of the north Pacific, and tends to feed on prey of higher trophic position as it grows. Together, stable isotope analysis in bulk tissue and individual AAs in eye lens laminae could be a powerful approach to investigate changes in the foraging habitat and trophic status of highly migratory species.

Testing Assumptions for Stable Isotope Analysis of Marine Mammal Dentin Growth Layer Groups.

Stable isotope analysis of growth layer groups (GLGs) in mammal dentin is an increasingly prevalent and noninvasive approach to study animal foraging ecology. However, empirical evidence to support assumed proper methodologies for sampling GLGs is lacking. Here, we examine the effects of intratooth and intertooth variations with respect to targeted GLGs, as well as the effects of common pretreatments (e.g., formic acid and graphite) to enhance GLG visibility, on stable isotope values (δ13C and δ15N) from dentin. We measured the δ13C and δ15N values of killer whale (Orcinus orca) dentin. We used dentin from 37 teeth to compare stable carbon (δ13C) and nitrogen (δ15N) isotope values from multiple locations within a GLG (intratooth variation), from corresponding GLGs among teeth of an individual (intertooth variation), and from treated and untreated teeth. We observed no significant differences in the δ13C or δ15N values when sampling a single GLG from multiple locations (intratooth variation) or when comparing the same GLG across duplicate teeth of individuals (intertooth variation). One tooth in a triplicate set showed a significantly different but likely biologically inconsequential δ13C value. Lastly, formic acid and graphite highlighting to accentuate GLGs did not significantly influence measured stable isotope values. We validate several previous assumptions in this field of study. First, dentin samples for stable isotope analysis can be sampled from different locations across a GLG. Second, researchers can compare stable isotope values from the same GLGs of different teeth collected from the same individual in most cases, as the δ13C and δ15N values did not vary with the sampled tooth. Third, a common protocol of formic acid and graphite treatment to enhance GLG visibility does not bias the δ13C and δ15N values from dentin. We also describe factors to consider and cautions associated with these conclusions.

Insights into anaerobic biotransformation of Polychlorinated Biphenyls in Dehalococcoides mccartyi CG1 through Kinetic and Stable Isotopic Analysis

Insights into anaerobic biotransformation of Polychlorinated Biphenyls in Dehalococcoides mccartyi CG1 through Kinetic and Stable Isotopic Analysis

Trophic position and periphyton carbon sources for macroinvertebrates in the litter patches of forested streams, with special reference to predatory species

Abstract Most research on lotic food webs has focused on reach-scale webs, whereas research on the structure and system openness of lotic food webs has not focused on the microhabitat scale. In forested streams, plant litter from riparian vegetation accumulates as discrete patches, forming a microhabitat for macroinvertebrates. We primarily aimed to determine the relative trophic position and contribution of periphyton to the assimilated diet of macroinvertebrate species in pool litter patches via stable isotope analysis. We specifically focused on predatory species in the context of their indirect effects on litter breakdown and estimated the range of their absolute trophic positions. The mean δ15N values of the 19 macroinvertebrate predator species considered ranged from 0.0 ‰ to 5.3 ‰. This range was greater than the overall mean enrichment factor of δ15N (Δ15N = 1.8 ‰) estimated from aquatic invertebrate predators based on five existing data sources, indicating that the absolute trophic position of predator species can extend across more than one level. The estimated periphyton contributions to the diets of predator species were almost half or more, indicating that the food webs of pool litter patches are closely connected with external periphyton-based webs. Our findings suggest that the top-down effect of predatory macroinvertebrates in litter patches is likely to be dissipated by the shift to the grazing food chains instead of cascading down to the litter.

Comprehensive Assessment of the Jebel Zaghouan Karst Aquifer (Northeastern Tunisia): Availability, Quality, and Vulnerability, in the Context of Overexploitation and Global Change

Karst aquifers in the Mediterranean region are crucial for water supply and agriculture but are increasingly threatened by climate change and overexploitation. The Jebel Zaghouan aquifer, historically significant for supplying Carthage and Tunis, serves as the focus of this study, which aims to evaluate its availability, quality, and vulnerability to ensure its long-term sustainability. To achieve this, various methods were employed, including APLIS and COP for recharge assessment and vulnerability mapping, SPEI and SGI drought indices, and stable and radioactive isotope analysis. The findings revealed severe groundwater depletion, primarily caused by overexploitation linked to urban expansion. Minimal recharge was observed, even during wet periods. APLIS analysis indicated moderate infiltration rates, consistent with prior reservoir models and the MEDKAM map. Isotopic analysis highlighted recharge from the Atlantic and mixed rainfall, while Tritium and Carbon-14 dating showed a mix of ancient and recent water, emphasizing the aquifer’s complex hydrodynamics. COP mapping classified 80% of the area as moderately vulnerable. Monitoring of nitrate levels indicated fluctuations, with peaks during wet years at Sidi Medien Spring, necessitating control measures to safeguard water quality amid agricultural activities. This study provides valuable insights into the aquifer’s dynamics, guiding sustainable management and preservation efforts.

Strengthening the evidence for seasonal intertidal exploitation in Mesolithic Europe and new insights into Early Holocene environmental conditions in the Bay of Biscay from the oxygen isotope composition of Phorcus lineatus (da Costa, 1778) shells

Marine molluscs have been exploited by human societies since prehistoric times. Such practices have often resulted in large accumulations of shell remains in archaeological sites that offer unique information on biological, ecological and cultural aspects of human interaction with coastal systems in the past. In this study, stable oxygen isotope (δ18O) analysis was carried out on archaeological shells of Phorcus lineatus (da Costa, 1778) from the Mesolithic shell midden site of J3 (northern Iberian coast) to determine the seasonality of intertidal collection. The results indicate a consistent pattern of winter exploitation, supporting the emerging view that collections were governed by cost-benefit and management principles that are now widespread documented in other coastal Mesolithic sites in Europe. The consistent seasonal collections of P. lineatus during colder months can be taken as evidence of specie-specific management strategy to optimize yield while preserving local populations for future exploitation. Our results reinforce the view that European hunter-gatherers developed ecological knowledge on specific animal resources that persisted over large geographic areas. Additionally, from a palaeoenvironmental perspective, the sea surface temperatures (SST) inferred from δ18O values derived from mollusc shells (SSTδ18O) indicate that coastal marine waters during the Early Holocene in the southern Bay of Biscay were warmer than those of today. These environmental conditions are evaluated in relation to changes in insolation and ocean currents over time.

Insight into natural attenuation of tributyl phosphate by indigenous anaerobic microbes in soils: Implication by stable carbon isotope fractionation and microbial community structures.

Organophosphate esters (OPEs) are widespread in the environment, with high persistence and toxicity. However, the underlying mechanisms of anaerobic microbial degradation of OPEs remain elusive in the field environment. In this study, the natural attenuation mechanisms of tributyl phosphate (TnBP) by indigenous anaerobic microorganisms in soils were investigated by using compound-specific stable isotope analysis (CSIA) and characterization of microbial communities. The results indicated that dibutyl phosphate (DnBP) was the major degradation product of TnBP. Significant carbon isotope fractionation was observed for TnBP during the anaerobic microbial degradation, and the carbon isotope enrichment factor (εC) was determined to be -2.71±0.13‰. Unlike aerobic degradation with P-O bond cleavage, C-O bond cleavage was verified as the mode to removal a butyl side chain for TnBP to generate DnBP during the anaerobic microbial degradation. Microbial community analysis indicated that Sphingomonans, Nocardioides and Streptomyces were the important contributors to microbial degradation of TnBP in anoxic soils. TnBP altered microbial metabolic functions in anoxic soils, mainly enhancing the biosynthesis of ansamycins, ketone bodies and amino acids, and flagellar assembly, which promoted microbial degradation of TnBP. This study provided a better method to characterize the chemical bond cleavage mode and effect of OPEs on microbial communities, which was a prerequisite for the bioremediation of OPE pollution in soils.

Diet and trophic niches of sympatric Seriola species revealed by stomach content and multi-tissue stable isotope analyses

Diet and trophic niches of sympatric Seriola species revealed by stomach content and multi-tissue stable isotope analyses

Role of membrane porosity in passive sampling of aquatic contaminants for stable isotope analysis: enhancement of analyte accumulation rates and selectivity.

Compound-specific isotope analysis (CSIA) is a potent method for illustrating the in situ degradation of aquatic contaminants. However, its application to surface and groundwater is hindered by low contaminant concentrations, typically in the nanogram-per-litre range, requiring the processing of large water volumes. Polar organic chemical integrative samplers (POCIS) have shown promising results when combined with CSIA, yet their extended deployment time to accumulate sufficient analyte mass remains a major limitation. In our study, we addressed this issue by increasing the pore size of the polyethersulfone membrane (PES) from 0.1 to 8 m. This resulted in significant increases in the mass accumulation rates of atrazine (3.5-fold), S-metolachlor (3.4-fold), and boscalid (3.0-fold). Importantly, the larger pore sizes did not compromise isotopic integrity, with C ‰ and N ‰, both within accepted uncertainties. Additionally, we observed an enhanced selectivity of the larger pores towards the target analytes over humic acids, whereas no significant increase in (bio)fouling potential was detected for the 8 m membrane, as demonstrated by gravimetric analysis, SEM measurements, mass accumulation rates, and isotope ratios of fouled and unfouled POCIS. Our findings show that increasing the membrane pore size from 0.1 to 8 m reduces deployment time and expedites the accumulation of analyte mass required for gas chromatography isotope ratio mass spectrometry, offering a promising method to expand CSIA for low-concentration pesticide analysis in the field.

Amino acid stable carbon isotopes in nail keratin illuminate breastfeeding and weaning practices of mother - infant dyads.

Compound-specific stable carbon isotope analysis of amino acids (CSIA-AA) is widely used in ecological studies to analyze food-webs and is gaining use in archaeology for investigating past diets. However, its use in reconstructing breastfeeding and weaning practices is not fully understood. This study evaluates the efficacy of stable carbon isotope analysis of amino acids in early life diet reconstruction by analyzing keratin from fingernail samples of three mother-infant pairs during late gestation and early postpartum periods. Our results show that stable carbon isotope ratios (δ13C) of glycine, and to a lesser extent glutamate, effectively trace the onset of exclusive breastfeeding and the end of weaning in infants. We propose that glycine's 'conditionally essential' metabolic pathway during infancy allows it to reflect maternal glycine δ13C, indicating breastmilk consumption. Subtle changes in glutamate δ13C likely result from its 'non-essential' status. Additionally, δ13C values of glycine and glutamate indicate maternal physiological and pathological stress due to catabolic effects such as gluconeogenesis. These findings have significant implications for ecological and archaeological research using CSIA-AA for dietary reconstructions. They highlight the need to understand how metabolic pathways affecting δ13C of amino acids may change over an individual's lifespan or be altered due to various forms of stress.

Feather forensics: tracing the origins of parrots in wildlife trade with stable isotopes and citizen science

AbstractTo supply the high demand for wildlife as exotic pets, animals may be illegally and unsustainably harvested from the wild and laundered as captive bred. Consequently, there is considerable interest in wildlife forensic tools that are capable of verifying captive origins. Stable isotope analysis is an emerging tool for verifying captive and wild origins by identifying key differences in dietary intake. While previous studies have effectively classified origins by differences in their stable isotope ratios, these studies are often limited to species with small population sizes and geographic ranges, masking potential variation caused by different environments and diets. We tested the accuracy of stable carbon (δ13C) and nitrogen (δ15N) isotope analyses to verify captive and wild origins using bird species that are common in pet trade, and have widespread distributions and generalist diets. Through a citizen science project in South Australia, we collected naturally dropped feathers from four native Australian cockatoo (Cacatuidae) species: Galahs (Eolophus roseicapilla); and three Cacatua species; sulphur‐crested cockatoos (Cacatua galerita), little corellas (C. sanguinea) and long‐billed Corellas (C. tenuirostris). We compared isotope ratios of captive and wild birds and calculated the classification accuracy of using stable isotopes to determine origin. Stable isotope values were significantly different between captive and wild adult birds, where captive birds had significantly higher δ13C and δ15N than wild birds. Captive and wild origins of individual Eolophus could be classified with relatively high accuracy (88%). However, Cacatua showed low repeatability and large overlaps between the origin groups, which reduced their classification accuracy (74%). Stable isotope analysis can be a potential classification tool in wildlife trade; however, before on‐ground implementation, we recommend that variation from different diets across a species' geographical range be more thoroughly investigated to better understand and explain the full range of possible δ13C and δ15N values.

Trophic ecology of squids in the Benguela Upwelling System elucidated by combining stomach content, stable isotope and fatty acid analyses

Squids occur worldwide in marine ecosystems and play a major role in pelagic food webs by connecting lower and higher trophic levels. Their high feeding intensities and pronounced diel vertical migrations make squids important components of nutrient cycles in marine ecosystems. This study assessed the trophic position and nutritional ecology of a squid species assemblage in the Benguela Upwelling System (BUS) by combining stomach content, stable isotope and fatty acid trophic marker analyses. Samples were collected in the northern (nBUS) and southern (sBUS) BUS in austral spring 2021. A total of 20 squid species from eleven families were identified. Stomach content analyses showed that squid species preyed on a variety of organisms ranging from crustaceans to lanternfishes (Myctophidae) and flying squids (Ommastrephidae). Stable isotope analyses revealed significant differences in δ15N values of small squids (dorsal mantle length < 10 cm) between the two subsystems, but none in those of large squids (dorsal mantle length > 10 cm). Trophic levels ranged from 2.2 to 5.0. Isotopic niche width was widest in the families Ommastrephidae and Cranchiidae. Principal component analyses of fatty acid compositions displayed distinct clusters separating squid families and different prey taxa. This study shows that nBUS and sBUS squids exploit a large variety of pelagic prey organisms and that trophic differences are primarily dependent on squid species and size. The results emphasize the squids’ importance as interlinking element in pelagic food webs and their key function in energy transfer between epi- and mesopelagic layers.

The use of 13C,14C and 18O of dental enamel to estimate the year of birth and geographic origin from Mexican individuals

Abstract In recent times, forensic science has increasingly relied on methods that use stable and radioactive isotope analysis to identify human remains. The use of 14C-AMS dating of dental enamel and dentine of an individual allows the estimation of the year of birth, while that of stable isotopes of carbon and oxygen can provide information on their geographical origin. Isotopic analysis of a tissue complements existing identification techniques, enhancing the capacity to refine, exclude, and affirm investigative approaches directed towards individual identification. The primary aim of this exploratory study is to amalgamate diverse isotopic methodologies conducive to the prompt and accurate identification of a deceased individual. In this manuscript, we elucidate the application of a rapid processing technique for whole molars from individuals with documented ages, employed to ascertain age through 14C-AMS dating. Furthermore, an investigation was undertaken to assess the capacity of carbon and oxygen-stable isotopes in distinguishing regional disparities. To achieve this, we conducted a comparative analysis of tooth samples sourced from individuals residing in three cities within the Mexican Republic: Mexico City in the central region, Oaxaca City in the southern region, and Tepic Nayarit on the western Pacific coast. The age of dental piece formation, as estimated through 14C-AMS, exhibited a precise correlation with the actual age. By means of the stable isotope outcomes, the data disclosed substantial disparities in 13C and 18O abundances among teeth from individuals residing in the three cities.

Two-Dimensional Liquid Chromatography-Isotope Ratio Mass Spectrometry Opens New Possibilities in the Field of Compound-Specific Stable Isotope Analysis.

Compound-specific stable isotope analysis (CSIA) using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) is a powerful tool for determining the isotopic composition of carbon in analytes from complex mixtures. However, LC-IRMS methods are constrained to fully aqueous eluents. Previous efforts to overcome this limitation were unsuccessful, as the use of organic eluents in LC-IRMS was deemed impossible. In our study, we developed a two-dimensional (2D) LC-IRMS method that, for the first time, enables the use of organic-containing eluents in an LC-IRMS setting. Initial experiments with caffeine were performed using a sample loop modulator with 20% methanol in the mobile phase of the first dimension, while separating the organic fraction from the analyte in the second dimension. Comparing results with one-dimensional (1D) LC-IRMS methods showed high precision with δ13C values in 2D measurements (-34.98 ± 0.04 ‰) closely matching 1D results (-34.95 ± 0.12 ‰). In the next step, incorporation of an at-column dilution (ACD) modulator allowed for the successful use of methanol concentrations up to 40% in the first dimension, with the ACD modulator effectively mitigating both peak fronting and carbon background interference, without losing any precision or accuracy of the measurements (δ13CCaffeine = -34.92 ± 0.03 ‰). All developed methods showed a method detection limit lower than 5 mg of carbon L-1 (mgC L-1), which is a major improvement compared with previous studies on caffeine analysis with LC-IRMS. This proof-of-concept study on 2D-LC-IRMS opens vast new possibilities for future CSIA research across diverse fields, including environmental science, pharmaceuticals, and food chemistry.