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Stable isotope data have made pivotal contributions to nearly every discipline of the physical and natural sciences. As the generation and application of stable isotope data continues to grow exponentially, so does the need for a unifying data repository to improve accessibility and promote collaborative engagement. This paper provides an overview of the design, development, and implementation of IsoBank (www.isobank.org), a community-driven initiative to create an open-access repository for stable isotope data implemented online in 2021. A central goal of IsoBank is to provide a web-accessible database supporting interdisciplinary stable isotope research and educational opportunities. To achieve this goal, we convened a multi-disciplinary group of over 40 analytical experts, stable isotope researchers, database managers, and web developers to collaboratively design the database. This paper outlines the main features of IsoBank and provides a focused description of the core metadata structure. We present plans for future database and tool development and engagement across the scientific community. These efforts will help facilitate interdisciplinary collaboration among the many users of stable isotopic data while also offering useful data resources and standardization of metadata reporting across eco-geoinformatics landscapes., Competing Interests: The authors declare no competing interests., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. We assessed diet and distribution of ECA killer whales using bulk and compound-specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada. Bulk ECA killer whale skin δ 15 N and δ 13 C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)-specific δ 15 N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ 15 N-phenylalanine δ 15 N (δ 15 N Glx-Phe ) and threonine δ 15 N (δ 15 N Thr ) as mammal-eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish-eating ENP ecotype based δ 15 N Thr . Distinctive essential AA δ 13 C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long-distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic-endemic species., (© 2024 The Author(s). Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

In countries like South Korea and the USA, origin labeling of shiitake grown using imported Chinese-inoculated medium is an issue. Therefore, we evaluated the use of compound-specific isotope analysis (CSIA) for the accurate identification of the geographical origin of shiitake (Korean, Chinese-inoculated medium, and Chinese); Chinese-inoculated medium shiitake were cultivated in Korea using inoculated sawdust medium from China. The CSIA-discriminant model showed an overall accuracy of 100% in the geographical classification of the original set and 96.4% for the cross-validated set. Glutamate and aspartate δ 15 N values were the most important variables for differentiating shiitake based on their origins. Compared to that observed upon using the bulk stable isotope analysis, the CSIA model was associated with significantly improved predictability of origin identification. Our findings elucidate the importance of isotope signatures in developing a reliable origin labeling method for shiitake cultured on the sawdust medium for the global market., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Herein, we improve the procedure for organic rice authentication using compound-specific δ 13 C and δ 15 N analyses of fatty acids and amino acids, addressing the increasing demand for accurate methods to confirm organic authenticity. Organic rice (OR) and pesticide-free rice (PFR) featured higher values of δ 15 N bulk than conventional rice (CR), whereas the corresponding differences between OR and PFR were insignificant. Additionally, OR, PFR, and CR could be discriminated based on some δ 13 C amino-acid and δ 15 N amino-acid values. δ 13 C bulk was correlated with most δ 13 C fatty-acid (r ≥ 0.596) values, and δ 15 N bulk was strongly correlated with most δ 15 N amino-acid (r ≥ 0.834) values. The first component in the orthogonal projection to latent structure-discriminant analysis model allowed for a clear separation between OR and PFR, and good predictability (Q 2 Y = 0.506). Thus, the present study improves the reliability of organic authentication when bulk stable isotope ratio analysis alone is insufficient for the accurate discrimination of OR, PFR, and CR., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The present study describes compound-specific δ 13 C and δ 15 N analyses of fatty acids and amino acids for improving the accurate authentication of organic milk (OM) against conventional milk (CM) collected in Korea. Most δ 13 C fatty-acid and δ 13 C amino-acid values were lower in OM than in CM ( P < 0.05); however, most δ 15 N amino-acid values displayed weak discriminative power for OM authentication. Higher isotopic fractionation was observed in δ 13 C fatty-acid than in δ 13 C amino-acid and δ 15 N amino-acid , with fractionation trends differing with individual amino acids. In particular, δ 13 C linoleic-acid of -33.5‰ and δ 13 C myristic-acid of -28‰ were determined to be promising year-round threshold values for Korean OM authentication. The δ 13 C bulk was highly correlated with δ 13 C Ala ( r = 0.92) and δ 13 C oleic-acid, trans ( r = 0.77), and strong positive correlations were observed between δ 13 C Val and δ 13 C Ile ( r = 0.98) and between δ 15 N Thr and δ 15 N Ser ( r = 0.90). Chemometric modeling for OM authentication produced a high quality model ( R 2 X = 0.547, R 2 Y = 0.865, and Q 2 = 0.689) with reliable chemical markers, notably δ 13 C myristic-acid , δ 13 C linoleic-acid , and δ 13 C stearic-acid . Furthermore, the models developed for seasonal separation in OM ( Q 2 = 0.954) and CM ( Q 2 = 0.791) were of good quality. Our findings, based on compound-specific isotope data, improve the reliability of OM authentication in cases where bulk stable isotope ratio analysis alone is insufficient. They also provide valuable insight into the control of fraudulent OM labeling in Korea, with potential application in other countries.

Rationale: Within the last decade, applications of compound-specific stable isotope analysis of nitrogen (δ 15 N values) in amino acids (CSIA-AA) have developed rapidly, particularly within organismal ecology. Unlike with bulk stable isotope analysis (BSIA), the reproducibility of δ 15 N-AA measurements has not been critically assessed. Two primary concerns include the diversity of techniques available for the derivatization of amino acids prior to analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) and the myriad of standardization practices and quality assurance procedures used across studies., Methods: We examined the relative effect of three normalization procedures, (1) internal reference calibration, (2) compound-specific calibration, and (3) scale-normalization, on the accuracy and precision of δ 15 N-AA measurements by GC/C/IRMS and the comparability of δ 15 N-AA measurements by two derivatization techniques, methoxycarbonylation-esterification and acetylation-esterification, across a range of organisms., Results: The overall accuracy and precision of δ 15 N-AA measurements were improved following both compound-specific calibration and scale-normalization, as was the comparability of δ 15 N-AA measurements of individual amino acids between derivatization techniques across organisms. The mean difference of scale-normalized δ 15 N-AA values across all organisms between the two derivatization techniques was 0.19‰, much less than the typical analytical error associated with δ 15 N-AA measurements (±1‰) . CONCLUSIONS: Adoption of standardized calibration procedures will be important to establishing reproducibility in δ 15 N-AA measurements, particularly across derivatization techniques. It is both technically practical and desirable for users of CSIA-AA to adopt practices in quality control and assessment similar to those outlined for BSIA, including the compound-specific calibration of δ 15 N-AA values, followed by scale-normalization. Copyright © 2017 John Wiley & Sons, Ltd., (Copyright © 2017 John Wiley & Sons, Ltd.)

Rationale: In recent years, research and applications of the N2O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N2O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N2O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N2O reference materials and an uncertain compatibility of different laboratories and analytical techniques., Methods: In a first comparison approach, eleven laboratories were each provided with N2O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N2O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N2O reference materials for improving compatibility between laboratories., Results: Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ(15)N values, while the performance of laser spectroscopy was superior with respect to N2O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N2O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ(15)N values was only minor., Conclusions: The study reveals that for future research on N2O isotopocules, standardisation against N2O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N2O in whole air as a unifying scale anchor., (Copyright © 2014 John Wiley & Sons, Ltd.)

Rationale: Compound-specific stable isotope analysis of amino acids has proven informative to many ecological systems, but only a handful of analytical methods are routinely employed. We evaluated a simple, rapid procedure in which biological samples undergo short-duration acid hydrolysis and the resulting amino acids are derivatized with methyl chloroformate for gas chromatography/combustion/isotope-ratio mass spectrometry (GC/C/IRMS)., Methods: Amino acid derivatives were separated on a polar gas chromatography column, combusted, and δ(13)C and δ(15)N values were measured. Tests of reproducibility and accuracy were conducted for amino acid reference mixtures and biological samples. A brief case study of turtles was used to assess whether isotopic data were consistent with a priori ecological expectations., Results: The methyl chloroformate based reaction successfully converted 15 amino acids from acid hydrolysates of biological materials into separable derivatives. The δ(13)C and δ(15)N values had high average measurement precision (σ <1‰). Reference materials were measured accurately, with good agreement between EA/IRMS and GC/C/IRMS determinations. Analysis of turtle blood samples yielded data consistent with their trophic ecology., Conclusions: This derivatization method is a rapid means of determining carbon and nitrogen isotopic ratios of amino acids present in the biological materials often sampled for ecological studies. While amino acids with charged or polar side chains do not have uniformly high recoveries, the average precision of measurements is comparable with that of other, more established methods. Batches of samples may be prepared from many raw materials in less than a day, representing a significant reduction in preparation time over prevailing methods., (Copyright © 2013 John Wiley & Sons, Ltd.)