Search Results (72)

Anadromous and freshwater-resident Coilia nasus frequently share spawning grounds, yet exhibit distinct feeding habits during migration; therefore, we hypothesized that the isotopic profiles of mature eggs from these two ecotypes would differ. In the present study, a total of 102 C. nasus individuals were collected from a spawning ground in Poyang Lake, China; among them, 20 mature females with intact ovaries were selected for further analysis. Their migratory history was confirmed by otolith microchemistry, and carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios of mature eggs were analyzed. Otolith microchemical results showed that some of the 20 females exhibited three Sr/Ca stages (1.51 ± 0.46, 4.79 ± 1.00, and 2.09 ± 0.79), identifying them as anadromous, whereas the remaining females showed stable low Sr/Ca ratios (1.49 ± 0.45), indicating freshwater residency. Both δ¹³C and δ¹⁵N values of mature eggs from the anadromous individuals were significantly higher than those from the freshwater-resident individuals (p < 0.01, Mann–Whitney U test). And the results of linear discriminant analysis (LDA) showed no misclassification. These results demonstrated that δ¹³C and δ¹⁵N showed strong discriminatory performance for mature eggs from anadromous and freshwater-resident C. nasus within the present dataset. However, because all analyses were performed on mature eggs collected directly from ovaries, this method has not yet been tested on naturally spawned or fertilized eggs in the field. Therefore, future studies should first validate this method on field-collected fertilized eggs to determine its practical efficacy for locating spawning grounds. Full article

Stepwise functionalization of graphene oxide (GO) into polymerizable derivatives requires analytical evidence able to distinguish chemical modification from the spectral overlap typical of oxidized carbon frameworks. Here, pristine GO, amine-functionalized GO (GO–ED), and the methacrylamide-modified derivative GRAPHYMERE^® were compared by elemental analysis and stable isotope ratio mass spectrometry. Carbon content increased progressively from GO to GRAPHYMERE^®, while nitrogen was reproducibly incorporated after amination and retained after methacrylamide modification. The materials also showed a monotonic δ¹³C shift and distinct δ¹⁵N signatures for the nitrogen-containing derivatives, consistent with progressive bulk chemical modification. These elemental–isotopic trends provide complementary support for the proposed functionalization pathway and for the analytical distinction among the starting material, intermediate, and final derivative. EA–IRMS is therefore proposed as an additional batch-screening tool for chemically complex GO-based precursors intended for future polymeric and dental-material applications, without replacing bond-specific structural techniques. Full article

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis of bone collagen has become a cornerstone method for reconstructing the diets of past populations. This critical review moves beyond the mere presentation of data to examine the theoretical foundations, methodologies, and applications of this approach. The principles of the method are based on isotopic fractionation during photosynthetic pathways (C₃, C₄, and CAM) and the trophic-level enrichment of ¹⁵N, which together enable the differentiation of plant food sources and the identification of consumer trophic position, respectively. The methodology encompasses sampling strategies, challenges posed by diagenesis, collagen extraction protocols, including the Longin method, and quality-control criteria (collagen yield, C:N ratio). Key applications include the reconstruction of baseline diets, the determination of weaning practices, and the identification of social inequalities. However, confounding factors—such as climate-driven variation in baseline nitrogen values, physiological effects (disease, lactation), and the consequences of human activities (manuring)—can complicate interpretation. Future directions include compound-specific amino acid analysis, multi-isotope approaches, and Bayesian modelling. In conclusion, isotopic data require a contextual and interdisciplinary approach to achieve a realistic understanding of diet and socio-cultural dynamics during the Quaternary. Full article

The development of sustainable and climate-resilient food systems increasingly relies on robust analytical methodologies capable of integrating environmental, biochemical, and management-related signals. In this study, a multi-isotope framework based on δ²H, δ¹⁸O, δ¹³C, and δ¹⁵N was applied to assess its capacity to discriminate between contrasting raspberry production systems and to provide chemically grounded indicators of agroecosystem functioning. Raspberry fruits (Rubus idaeus L.; cultivars Opal and Delniwa) were collected during the 2024–2025 growing seasons from two distinct systems in Romania: an organic open-field system and a rainfed agroforestry system. Stable isotope ratio analysis revealed system-dependent isotopic patterns, with the strongest differentiation observed for δ¹⁵N. Nitrogen isotope composition (δ¹⁵N) provided the strongest discrimination, with enriched values in organic fruits (2.73–9.77‰) and depleted values in agroforestry fruits (−3.01 to 0.62‰), reflecting differences in nitrogen sources and cycling pathways. Hydrogen and oxygen isotopes (δ²H: −60.46 to −4.62‰; δ¹⁸O: −6.19 to 10.41‰) were consistent with hydroclimatic variability and evaporative fractionation processes associated with soil–plant–atmosphere interactions. Carbon isotopes (δ¹³C: −28.14 to −22.62‰) provided complementary insights into plant water-use conditions. Multivariate statistical analysis supported the separation between production systems, while short-term fertilisation effects were secondary to system-level controls. The results suggest that raspberry fruits preserve an integrated isotopic fingerprint of production environment and management practices. From an analytical chemistry perspective, this work highlights the relevance of multi-isotope approaches as transferable tools for food authentication, traceability, and sustainability assessment, contributing to the broader application of stable isotope techniques across complex biological systems. Full article

Honey is a high-value food product that is vulnerable to adulteration with exogenous sugars, posing challenges for food authenticity and consumer protection. This study applied Stable Isotope Ratio Analysis (SIRA) to assess the authenticity of honey collected from three major honey-producing regions of Ghana (Volta, Bono and Bono East). A total of 28 honey samples were analysed by elemental analysis–isotope ratio mass spectrometry (EA-IRMS) to obtain carbon (δ¹³C), nitrogen (δ¹⁵N) and sulphur (δ³⁴S) isotope composition. Honey authenticity was evaluated according to AOAC Official Method 998.12 by comparing δ¹³C values of bulk honey and the corresponding protein fraction. The δ¹⁵N and δ³⁴S values in honey protein were used to investigate environmental and regional variability. Samples without detectable C4 adulteration exhibited δ¹³C_protein values consistent with C3 floral sources, whereas several samples showed Δδ¹³C values more negative than −1.0‰, indicating the presence of C4-derived sugars above the AOAC adulteration threshold. Calculated C4 sugar contents ranged from 8 to 12% in moderately adulterated samples to as high as 78–79% in severely adulterated samples, confirming substantial dilution with C4 sugars. Nitrogen and sulphur isotope ratios provide additional information on environmental and regional variability among the sampled regions. Principal Component Analysis revealed that the first two principal components (PC1 and PC2) accounted for 83.8% of the total variance 83.8% of the total variance and showed separation between samples with detectable C4 adulteration and those without, while highlighting regional isotopic differences. These results demonstrate that stable isotope analysis is an effective tool for detecting C4 sugar adulteration in honey and that the combined use of carbon, nitrogen and sulphur isotopes can provide additional information on environmental and regional variability. These findings provide preliminary isotopic data on honey collected from three major honey-producing regions of Ghana and support the application of the stable isotope approach for honey authenticity assessment and quality control. Full article

Understanding how plants regulate nitrogen (N) and carbon (C) allocation among their organs under adverse environmental and climatic conditions remains a significant challenge, despite its direct impact on the value of plant residues and agricultural products. Therefore, this study aimed to examine the dynamics of N and C through their stable isotope ratios in two soybean varieties of differing maturity groups (Merlin and Laulema) inoculated with various nitrogen-fixing Bradyrhizobium japonicum bacterial strains. The contents of N and C as well as their isotopic ratios in soybean plant parts were analyzed at full-flowering (R2) and full-maturity (R8) stages. The results demonstrated overall compatibility between soybean varieties and selected B. japonicum strains, resulting in up to 32 nodules per plant; however, significant variation in root nodule numbers was observed. From a physiological perspective, both the soybean variety and the strain of nitrogen-fixing bacteria significantly influenced nitrogen stable isotope ratios across different plant organs, including roots, shoots, stems, pods, and seeds, with similar trends in δ(¹⁵N) variation among plant parts observed in both varieties. In contrast, the main differences in carbon stable isotope composition were observed among varieties less affected by the amendment strategy. N content was higher in roots and shoots during flowering and declined by twofold in roots and fivefold in aboveground biomass at maturity, reflecting extensive nitrogen remobilization to support seed formation. From an agronomic perspective, the highest yields were achieved by the inoculated soybean Merlin, with more than 3 t ha⁻¹. However, the positive effects of symbiosis can improve yields in less productive varieties like Laulema, making them comparable to those of more productive varieties. Soybean inoculation not only influenced the isotopic redistribution within the plant but also proved to be an effective practice for increasing seed N content, with strain AGF78 producing the highest number of nodules and a significantly high amount of nitrogen in seeds, followed by SEMIA5079, the least effective being RF10. Full article

Background/Objectives: Oral squamous cell carcinoma (OSCC) exhibits substantial biological heterogeneity, and current clinicopathological risk stratification incompletely reflects tumor metabolic behavior. Stable isotope ratio mass spectrometry enables the quantitative assessment of carbon and nitrogen isotopic composition, potentially capturing cumulative metabolic reprogramming associated with tumor aggressiveness. This study evaluated whether isotopic signatures of tumor tissue and surgical margins are associated with lymph node metastasis and survival outcomes in OSCC. Methods: In this prospective study, 54 consecutive patients undergoing primary surgical treatment for OSCC were enrolled. Paired samples derived from tumor tissue and surgical margins were analyzed using isotope ratio mass spectrometry to determine the relative abundance of nitrogen-15 and carbon-13 isotopes. The primary endpoint was pathological lymph node metastasis. Secondary endpoints included disease-free survival and overall survival. Paired comparisons were performed using Wilcoxon signed-rank tests with false discovery rate correction. Logistic regression models for nodal metastasis were constructed using Firth penalization with bootstrap internal validation, while survival outcomes were evaluated using Cox proportional hazards models with model complexity restricted according to the number of events. Results: Tumor tissues demonstrated significantly lower δ¹³C and δ¹⁵N values and higher nitrogen-to-carbon ratios compared with surgical margins (all adjusted p < 0.05). In multivariable analysis, tumor δ¹⁵N was independently associated with lymph node metastasis and modestly improved model discrimination. However, it was not independently associated with disease-free or overall survival. Exploratory analyses indicated that higher δ¹³C values in surgical margins were independently associated with shorter disease-free survival. Conclusions: These findings suggest that isotope ratio mass spectrometry-based isotopic profiling identifies reproducible metabolic differences between tumor and margin tissues in OSCC. Tumor δ¹⁵N is associated with lymph node metastasis, whereas margin δ¹³C may reflect recurrence risk and potentially capture metabolic field effects. These findings are hypothesis-generating and warrant validation in larger, independent cohorts. Full article

To elucidate the sources and spatial variations in organic matter in surface sediments from Lingdingyang of the Pearl River Estuary, 18 surface sediment samples were collected and analyzed for obtaining total organic carbon (TOC), total nitrogen (TN), atomic TOC/TN ratio (C/N_atom), stable carbon and nitrogen isotopes (δ¹³C, δ¹⁵N), and glycerol dialkyl glycerol tetraethers (GDGTs). A three-endmember framework was constructed using the BIT and δ¹³C to constrain the sources of the organic matter. The results showed a significant positive correlation between TOC and TN, with relatively higher values in Jiaoyi Bay and western Lingdingyang, lower values in eastern Lingdingyang, and intermediate values in Shenzhen Bay. The C/N_atom, δ¹³C, and δ¹⁵N results revealed that the sedimentary organic matter in the study area exhibits mixed-source characteristics, influenced by soil, C₃ plants, and marine autochthonous organic matter. Among the subregions, Jiaoyi Bay is more strongly influenced by terrestrial inputs, while Shenzhen Bay receives relatively higher contributions from marine autochthonous organic matter. The GDGTs results showed that Jiaoyi Bay is characterized by elevated abundances of both brGDGTs and isoGDGTs, whereas isoGDGTs were also relatively enriched in Shenzhen Bay. brGDGTs exhibited a significant negative correlation with δ¹³C, whereas BIT showed no significant correlation with either brGDGTs or δ¹³C, indicating that BIT cannot be simply regarded as a unique proxy for soil input, but rather reflects the combined effects of in situ production, changes in archaeal lipids, and sedimentary preservation. The three-endmember model further revealed significant spatial variations in the sources of organic matter in surface sediments from Lingdingyang. Overall, the combined use of multiple proxies is more effective than any single proxy in revealing the sources and spatial differentiation of sedimentary organic matter in this subtropical, complex estuarine environment. Full article

Monitoring the soil–plant system in forest ecosystems is crucial for preserving their ecological functions and services. This study assessed carbon and nitrogen stable isotopes and ecoenzymatic stoichiometry as suitable indicators for characterizing the soil–plant system as a functional unit of ecological processes. To this end, in June 2021 six plots (1 m² each) were selected in two typical Mediterranean forest ecotypes: a coastal stone pine forest (Pinus pinea L., PF) and a meso-hygrophilous broadleaf forest (RV). Soil samples (0–15 and 15–30 cm depth) and litter samples (40 × 40 cm) were collected and characterized in terms of physical, chemical and biochemical properties. t-tests revealed significant differences between RV and PF, indicating distinct microbial nutrient acquisition strategies. The higher C:N ratio in PF suggested lower litter quality and greater recalcitrance to microbial decomposition. Consistently, RV showed a more pronounced ¹³C and ¹⁵N enrichment from litter to SOM down to a 30 cm depth, confirming faster organic matter decomposition and mineralization. Enzyme activity patterns supported these findings. The higher β-glucosidase and butyrate esterase activities in RV reflected its greater microbial potential to activate biogeochemical cycles. Both forests exhibited a higher microbial demand for C and P than for N to maintain ecological stoichiometric balance, with stronger C limitation at the surface and P limitation in the subsoil, particularly in RV soil. This integrated monitoring approach provides insights into nutrient cycling and ecosystem resilience and offers tools to evaluate ecosystem functionality under changing environmental conditions, supporting sustainable forest management. Full article

Geographical origin determination for seafood products is a fundamental aspect due to its implications for fraud prevention, ensuring food safety, and promoting resource sustainable management. In this research, different machine learning (ML) models based on random forests, support vector machines, and artificial neural networks were fed with trace element fingerprinting (TEF) and stable isotope ratio analysis (SIRA) to determine the origin of mussels that have been farmed in eight regions and ten locations around the world (areas of the European Atlantic coast, the Mediterranean Sea, and the Pacific coast of Chile). Fourteen trace elements in shells and carbon and nitrogen isotope ratios of mussel tissue were used singly, in combination, or reduced to develop the different approach models. All the selected models present high prediction accuracies for the independent variables (except for SIRA models), for their combination, or for their optimisation, highlighting the artificial neural network and random forest models that presented a 100% accuracy for all cases using a combination of variables selected based on a random forest model TEF to predict region and location, respectively. This fact confirms that ML models are suitable approximation techniques to determine the region and location of Mediterranean mussel origin, with key applications in food safety and global sustainability. Full article

The majority of research on food webs has focused on temperate lakes, and little is known about the food web of lakes in polar regions. Subarctic lakes are particularly sensitive to climate change, which affects their stability. Therefore, the trophic structure of the food web in such lakes was considered as the object of this study. We studied a clear-water oligotrophic lake located in the subarctic region of Eurasia, specifically in northern Karelia and the White Sea coast of Russia. The study examined both open water periods (summer–autumn) and ice-covered periods (winter–spring) in this lake. Stable isotope analysis of carbon (¹³C/¹²C ratio or δ¹³C value) and nitrogen (¹⁵N/¹⁴N, δ¹⁵N) in producers and consumers was applied and revealed significant seasonal variations in the structure of the food web. The results indicate the presence of both pelagic and littoral/benthic food web compartments, with a notable contribution of autochthonous carbon derived from benthic sources. Omnivorous fish (perch, Perca fluviatilis; vendace, Coregonus albula; nine-spined sticklebacks, Pungitius pungitius) and some benthic invertebrates (mayfly, Ephemera vulgata; bivalves, Sphaerium corneum) had intermediate δ¹³C values, integrating these compartments by obtaining resources from both. Planktonic invertebrates had significantly depleted ¹³C, with the lowest δ¹³C value reaching −41.7‰, indicating an important contribution of methane-derived carbon. The study also revealed close trophic relationships between lake invertebrates and cyanobacteria, namely with planktonic Dolichospermum lemmermannii and benthic Phormidium sp. Seasonal changes in δ¹⁵N values and in trophic position have been observed among predacious omnivorous fish and crustaceans (amphipods, Gammaracanthus loricatus, and copepods, Cyclops scutifer), which are capable of a generalist feeding strategy depending on food availability. Using the example of this lake, it can be concluded that polar lake ecosystems are characterized by different seasonal intakes of allochthonous organic carbon from wetland catchment (humic compounds) and nitrogen because of nitrogen fixation in the air by cyanoprocaryotes. Alternative energy sources, such as carbon derived from methane, can also contribute to the energy balance of lake ecosystems. This study contributes to our understanding of energy flow and connectivity between producers and consumers in high-latitude lakes. Full article

This study investigates, for the first time, the relationship between carbon (δ¹³C) and nitrogen stable isotopic composition of Aspergillus niger mycelium, used as chitin and chitosan sources, and the fungus diet under controlled cultivation conditions. Four diets were tested, combining different carbon (C3- and C4-glucose) and nitrogen sources (KNO₃ and NH₄Cl). Results showed that carbon sources significantly influenced δ¹³C values of the mycelium: C4-glucose diets led to more negative Δ¹³C values (δ¹³C_MYCELIUM-δ¹³C_DIET) compared to C3-glucose diets. Nitrogen sources also affected isotopic fractionation, with KNO₃ leading to negative Δ¹⁵N (δ¹⁵N_MYCELIUM-δ¹⁵N_DIET) and NH₄Cl yielding positive Δ¹⁵N. Conversely, pH and temperature showed negligible effects on δ¹⁵N, while continuous aeration during growth significantly decreased δ¹⁵N, possibly due to partial assimilation of atmospheric nitrogen. These findings demonstrate that both nutrient and cultivation parameters can modulate the isotopic fractionation in A. niger, particularly for nitrogen. Although a direct correlation between diet composition and δ¹⁵N could not be established, this work provides the first experimental link between fungal metabolism and its isotopic fingerprint. The results offer a scientific foundation for applying stable isotope ratio analysis to authenticate and trace fungal-derived chitin and chitosan, with potential applications in food and winemaking industries. Full article

Background: Cervical lymph node metastases are a major prognostic factor in patients with oral squamous cell carcinoma (OSCC). Despite advances in imaging, accurate preoperative prediction of nodal involvement remains a challenge. This study evaluated the utility of Isotope Ratio Mass Spectrometry (IRMS) in assessing the risk of lymph node metastases in patients with OSCC. We hypothesize that alterations in the abundance of ¹³C and ¹⁵N stable isotopes in OSCC tumor tissues reflect metabolic reprogramming associated with tumor progression and may correlate with cervical lymph node metastases. Methods: A prospective cohort of 61 patients with primary OSCC undergoing surgical treatment was analyzed. Tumor tissue samples were evaluated for the relative abundance of nitrogen-15 (¹⁵N) and carbon-13 (¹³C) isotopes using IRMS. Correlations between isotopic values and nodal metastases, as well as established clinicopathological risk factors, were assessed. Results: IRMS measurements of ¹³C and ¹⁵N abundance did not directly correlate with the presence of lymph node metastases but were associated with advanced tumor stages and negative prognostic features, such as angioinvasion/neuroinvasion. The median of the average nitrogen ¹⁵N content was higher in patients with more advanced clinical stages (11.89% in stage IV vs. 11.12% in stages I–III; p = 0.04‰), and the median δ¹³C was lower in stage IV compared to stages I–III (−22.40‰ vs. −22.88‰; p < 0.05). Patients with angioinvasion/neuroinvasion also had a lower median δ¹³C (−22.26‰ vs. −22.75‰; p < 0.05). These findings suggest that IRMS reflects metabolic changes in tumor biology rather than specifically predicting nodal metastases. Multivariate logistic regression identified age, gender, and clinical tumor stage as independent predictors of nodal involvement. Conclusion: IRMS-based isotopic profiling may reflect key metabolic alterations associated with OSCC progression. Although IRMS parameters of carbon ¹³C and nitrogen ¹⁵N were not independently predictive of lymph node status, they were associated with key adverse prognostic features, indicating their potential as adjunctive biomarkers that may complement traditional histopathological evaluation. Full article

In this study, we applied a new technique for vegetatively transplanting kelp Eisenia bicyclis to restore macroalgal habitats. We aimed to assess the restoration success of the E. bicyclis bed by comparing the carbon and nitrogen stable isotope ratios of macrobenthic consumers and their isotopic niches in artificial and control (barren ground) habitats. Except for the deposit feeding group, no significant differences were observed in isotopic values of the other feeding groups (suspension feeders, herbivores, omnivores, and carnivores) between the two sites. In contrast, our results showed wider isotopic niche indices for all feeding groups at the transplantation site compared to those at the control site, suggesting increased trophic diversity in the artificial habitat. Overall, these results indicate that the macroalgal bed created using the new method can play an ecological role in restoring functional properties of food web structures via trophic support of degraded coastal ecosystems. Full article

Soil organic carbon (SOC) pool plays an extremely important role in regulating the global carbon (C) cycle and climate change. Atmospheric nitrogen (N) and phosphorus (P) deposition caused by human activities has significant impacts on soil C sequestration potential of terrestrial ecosystem. To investigate the effects of N and P deposition on soil C sequestration and C-N coupling relationship in broad-leaved evergreen forests, a 6-year field nutrient regulation experiment was implemented in subtropical Castanopsis sclerophylla forests with four different N and P additions: N addition (100 kg N·hm⁻²·year⁻¹), N + P (100 kg N·hm⁻²·year⁻¹ + 50 kg P·hm⁻²·year⁻¹), P addition (50 kg P·hm⁻²·year⁻¹), and CK (0 kg N·hm⁻²·year⁻¹). The changes in the C and N contents and stable isotope distributions (δ¹³C and δ¹⁵N) of different soil organic fractions were examined. The results showed that the SOC and total nitrogen (STN) (p > 0.05) increased with N addition, while SOC significantly decreased with P addition (p < 0.05), and N + P treatment has low effect on SOC, STN (p > 0.05). By density grouping, it was found that N addition significantly increased light fraction C and N (LFOC, LFN), significantly decreased the light fraction C to N ratio (LFOC/N) (p < 0.05), and increased heavy fraction C and N (HFOC, HFN) accumulation and light fraction to total organic C ratio (LFOC/SOC, p > 0.05). Contrary to N addition, P addition was detrimental to the accumulation of LFOC, LFN and reduced LFOC/SOC. It was found that different reactive oxidized carbon (ROC) increased under N addition but ROC/SOC did not change, while N + P and P treatments increased ROC/SOC, resulting in a decrease in SOC chemical stability. Stable isotope analysis showed that N addition promoted the accumulation of new soil organic matter, whereas P addition enhanced the transformation and utilization of C and N from pre-existing organic matter. Additionally, N addition indirectly increased LFOC by significantly decreasing pH; significantly contributed to LFOC and ROC by increasing STN accumulation promoted by NO₃⁻-N and NH₄⁺-N; and decreased light fraction δ¹³C by significantly increasing dissolved organic C (p < 0.05). P addition had directly significant negative effect on LFOC and SOC (p < 0.05). In conclusion, six-year N deposition enhances soil C and N sequestration while the P enrichment reduces the content of soil C, N fractions and stability in Castanopsis sclerophylla forests. The results provide a scientific basis for predicting the soil C sink function of evergreen broad-leaved forest ecosystem under the background of future climate change. Full article