Essential and nonessential fatty acid composition and use in overwintering monarch butterflies.

Monarch butterflies (Danaus plexippus) undertake one of the most remarkable long-distance insect migrations, travelling thousands of kilometres to overwinter in the central trans-volcanic belt of Mexico. This study explored how monarch butterflies use essential fatty acids (EFA) and nonessential fatty acids (NFA) during overwintering. We collected 150 (male/female) butterflies from the Sierra Chincua wintering colony from the time of arrival (December 2022) to before departure (February 2023) and analysed their lipid content.

Exploring hydrogen isotope fractionation in lipid biomolecules of freshwater algae: implications for ecological and paleoenvironmental studies.

Understanding the stable hydrogen isotope (H) composition and fractionation in lipid biomolecules of primary producers, such as terrestrial and aquatic plants, is crucial for deciphering past environmental conditions, as well as applying compound-specific stable isotope analysis for the study of metabolic and ecological processes. We conducted a new tracer experiment to explore the H composition of algal fatty acid biomarkers, focusing on freshwater algae, which form the base of aquatic food webs. We selected a range of algal species widely found in freshwater ecosystems and cultivated them under controlled conditions.

Enhancing low-level tritium detection in environmental waters: assessing the Hidex ULLA liquid scintillation counter.

Tritium (³H) is a vital tracer in isotope hydrology and environmental studies, necessitating accurate and precise low-level detection methods. This study evaluated the performance of the new Hidex ULLA Liquid Scintillation Counter for ultra-low-level tritium assays in environmental water samples. The optimization of instrumental parameters enabled accurate and reproducible H measurements.

Isotope hydrology of the intermontane Elk Valley, British Columbia: an assessment of water resources around coal mining operations.

This study aimed to synthesise and interpret stable isotopic data (H and O) from various sources to understand the isotope hydrology around coal mine operations in Elk Valley, B.C., Canada.

Non-invasive determination of critical dissolved oxygen thresholds for stress physiology in fish using triple-oxygen stable isotopes and aquatic respirometry.

Understanding the critical thresholds of dissolved oxygen (O) that trigger adaptive physiological responses in aquatic organisms is long hampered by a lack of robust, non-lethal or non-invasive methodologies. The isotope fractionation of triple O isotopes (O/O/O) during respiration is linked to the amount of oxygen utilised, offering a potential avenue for new insights. Our experimental research involved measuring the oxygen isotope fractionation of dissolved O in closed-system aquatic respirometry experiments with wild sticklebacks ().

Compound-specific stable isotope analyses of fatty acids indicate feeding zones of zooplankton across the water column of a subalpine lake.

Spatial and temporal zooplankton feeding dynamics across the water column of lakes are key for understanding site-specific acquisition of diet sources. During this 6-week lake study, we examined stable carbon (δC) and nitrogen (δN) isotopes and conducted compound-specific fatty acid (FA) stable isotope analysis (CSIA) of edible seston in the epi-, meta-, and hypolimnion, and zooplankton of Lake Lunz, Austria. We predicted that CSIA of essential FA can discern the foraging grounds of zooplankton more accurately than the commonly used bulk stable isotopes.

Evaluation of lipid extraction methods for fatty acid quantification and compound-specific δC and δH analyses.

Lipids, with fatty acids (FA) as a crucial subset, have become a focal point for diverse medical, physiological, and ecological studies. However, a comprehensive assessment of the various pre-analytical FA extraction methods published in the scientific literature remains lacking. In this study, we examined the efficacy of seven well-established sample preparation methods, specifically focusing on their effectiveness in total lipid and fatty acid extraction and their impact on compound-specific stable hydrogen (δH) and carbon (δC) isotope values.

Protocols for sample preparation and compound-specific stable-isotope analyses (δH, δC) of fatty acids in biological and environmental samples.

Compound-specific stable-isotope analysis (CSIA) of fatty acids is a powerful tool to better understand the trophic transfer of fatty acids and their biochemical fate in and across ecosystems, including tracing animal migration and understanding physiological processes. The non-exchangeable nature of C-H bonds in acyl chains, hydrogen (H) and carbon (C) stable-isotope values of fatty acids (FA) provide independent information about the origins of fatty acids. Several technical obstacles must be overcome to ensure accurate and reproducible measurements of FA-CSIA can be made.

Radiocarbon integrity of dissolved inorganic carbon (DIC) samples stored in plastic and glass bottles: implications for reliable groundwater age dating.

Various approaches based on the natural variations of carbon isotopes (C and C) in dissolved inorganic carbon (DIC) are routinely used to study groundwater dynamics and to estimate recharge rates by deriving groundwater ages. However, differences in C activities in groundwater samples collected repeatedly from the same wells and discordantly young C groundwater ages compared to noble gases led some authors to question the validity of radiocarbon dating. Poor sampling protocols and storage effects (C contamination) for radiocarbon analysis are a critical factor in explaining age determination discrepancies.

Assessing the performance of international laboratories analysing the stable isotope composition (δ N, δ O, δ O) of nitrate in environmental waters.

Rationale: Stable-isotope analyses of nitrate (NO ) in various water sources are crucial for understanding nitrogen pollution and its impact on aquatic ecosystems. We evaluated the accuracy and precision of stable-isotope analyses of nitrate conducted by international laboratories.

Methods: Six samples with nitrate (2 mg L NO -N) were sent to 47 laboratories.

Global and local meteoric water lines for δO/δO and the spatiotemporal distribution of Δ'O in Earth's precipitation.

Recently, δO and its excess (Δ'O) have become increasingly significant "triple-oxygen-isotope" indicators of distinctive hydrological processes in hydrology and climatology. This situation mirrors the research regarding δO and δH in the 1960s towards a solid theoretical base and a surge in application examples and field studies worldwide. Currently, systematic global measurements for δO in precipitation are still lacking.

Automated rapid triple-isotope (N, O, O) analyses of nitrate by Ti(III) reduction and NO laser spectrometry.

The nitrogen and oxygen (N, O, O) stable isotopic compositions of nitrate () are crucial tracers of nutrient N sources and dynamics in aquatic and atmospheric systems. Methods to reduce aqueous to NO gas (microbial or Cd method) before N and O isotope analyses require multi-step conversion or toxic chemicals, and O in NO cannot be disentangled by IRMS due to isobaric interferences. This technical note describes the automation of the stable-isotope analyses of nitrate by coupling the new Ti method with a headspace autosampler and an NO triple-isotope laser analyzer based on off-axis integrated cavity output spectroscopy.

Response of stable isotopes (δH, δC, δN, δO) of lake water, dissolved organic matter, seston, and zooplankton to an extreme precipitation event.

Lake ecosystems process and cycle organic substrates, thus serving as important bioreactors in the global carbon cycle. Climate change is predicted to increase extreme weather and precipitation events that can flush nutrients and organic matter from soils to streams and lakes. Here we report changes in stable isotopes (δH, δC, δN, or δO) of water, dissolved organic matter (DOM), seston, and zooplankton in a subalpine lake at short time resolution following an extreme precipitation event between early July to mid-August 2021.

Balancing precision and throughput of O and Δ'O analysis of natural waters by Cavity Ringdown Spectroscopy.

O and Δ'O are emerging tracers increasingly used in isotope hydrology, climatology, and biochemistry. Differentiating small relative abundance changes in the rare O isotope from the strong covariance with O imposes ultra-high precision requirements for this isotope analysis. Measurements of O by Cavity Ringdown Spectroscopy (CRDS) are attractive due to the ease of sample preparation, automated throughput, and avoidance of chemical conversions needed for isotope-ratio mass spectrometry.

Nitrate isotopes (N, O) in precipitation: best practices from an international coordinated research project.

Stable isotope ratios of nitrogen and oxygen (N/N and O/O) of nitrate (NO) are excellent tracers for developing systematic understanding of sources, conversions, and deposition of reactive atmospheric nitrogen (N) in the environment. Despite recent analytical advances, standardized sampling of NO) isotopes in precipitation is still lacking. To advance atmospheric studies on N species, we propose best-practice guidelines for accurate and precise sampling and analysis of NO isotopes in precipitation based on the experience obtained from an international research project coordinated by the International Atomic Energy Agency (IAEA).

Reproducible measurements of the δH composition of non-exchangeable hydrogen in complex organic materials using the UniPrep2 online static vapour equilibration and sample drying system.

Non-exchangeable hydrogen-isotope ( H) measurements of complex organic samples are used in forensics to determine sample authenticity, traceability, and provenance. However, H assays of organics are usually complicated by uncontrolled "exchangeable hydrogen" and residual moisture contamination; hence, H assays are persistently incomparable amongst laboratories. We introduce a revised technical solution (UniPrep2) to control hydrogen-isotope exchange and for robust online sample drying and vapour equilibration.

Nitrate isotopes reveal N-cycled waters in a spring-fed agricultural catchment.

Nitrate stable isotopes provide information about nitrate contamination and cycling by microbial processes. The Fischa-Dagnitz (Austria) spring and river system in the agricultural catchment of the Vienna basin shows minor annual variance in nitrate concentrations. We measured nitrate isotopes (N, O) in the source spring and river up to the confluence with the Danube River (2019-2020) with chemical and water isotopes to assess mixing and nitrate transformation processes.

Quantifying denitrification in a field-scale bioremediation experiment.

Nitrate (NO-) in mine waste rock derived from undetonated NHNO can contaminate receiving waters. An in-situ bioremediation experiment was conducted at a coal mining operation in Elk Valley, British Columbia, Canada to remediate NO- from large volumes of mine water. Over the test period (201 d), 5000 to 7500 m d of NO--rich (mean concentration 22 mg N L) mine water was injected into saturated waste rock along with methanol, nutrients, and a conservative tracer (Br-).

Assessment of Compound-Specific Fatty Acid δC and δH Values to Track Fish Mobility in a Small Sub-alpine Catchment.

Methods for identifying origin, movement, and foraging areas of animals are essential for understanding ecosystem connectivity, nutrient flows, and other ecological processes. Telemetric methods can provide detailed spatial coverage but are limited to a minimum body size of specimen for tagging. In recent years, stable isotopes have been increasingly used to track animal migration by linking landscape isotope patterns into movement (isoscapes).

High spatial resolution prediction of tritium (H) in contemporary global precipitation.

Tritium (H) in Earth's precipitation is vigilantly monitored since historical nuclear bomb tests because of radiological protection considerations and its invaluable role as a tracer of the global water cycle in quantifying surface, groundwater, and oceanic fluxes. For hydrological applications, accurate knowledge of H in contemporary local precipitation is prerequisite for dating of critical zone water and calibrating hydrogeologic transport and groundwater protection models. However, local tritium input in precipitation is hard to constrain due to few H observation sites.

Nitrate sources and mixing in the Danube watershed: implications for transboundary river basin monitoring and management.

Dispersed and unknown pollution sources complicate water management in large transboundary watersheds. We applied stable isotopes of water and nitrate together with contaminants of emerging concern (CECs: carbamazepine, caffeine, sulfamethoxazole, perfluorooctanoic acid and 2,4-dinitrophenol) to evaluate mixing and inputs of water and contaminants from tributaries into the mainstem of the transboundary Danube River. Stable isotope (δO, δH) variations from low values (- 13.

Assessment of rapid low-cost isotope (δ N, δ O) analyses of nitrate in fruit extracts by Ti(III) reduction to differentiate organic from conventional production.

Rationale: The isotopic composition (δ N, δ O) of nitrate in fruits and vegetables differentiates organic from conventional food production practices. Organic systems do not use synthetic nitrate fertilizers high in O and low in N and thereby help reveal producers' fertilization claims. Isotope analyses of nitrate extracted from fruits and vegetables are done by bacterial reduction which is costly and by specialized laboratories.

Stable isotopes in global lakes integrate catchment and climatic controls on evaporation.

Global warming is considered a major threat to Earth's lakes water budgets and quality. However, flow regulation, over-exploitation, lack of hydrological data, and disparate evaluation methods hamper comparative global estimates of lake vulnerability to evaporation. We have analyzed the stable isotope composition of 1257 global lakes and we find that most lakes depend on precipitation and groundwater recharge subsequently altered by catchment and lake evaporation processes.

Temperature and precipitation effects on the isotopic composition of global precipitation reveal long-term climate dynamics.

Earth's climate history is traced through the long-term covariance between the isotopic (δ O) composition of archived meteoric waters (groundwater, ice cores) with air temperature (T) and amount of precipitation (P). To assess recent multi-decadal climatic changes, we analysed δO, T and P, and the relationships between these parameters at 20 stations having 60 years of continuous monthly isotopic records. Using nonparametric regressions and time series modelling we found significant linear and non-linear relationships for δO with T and P and showed that the δO dependency on these two parameters varied over decadal scales, thereby revealing complex relationships related to recycled moisture, large-scale convective processes and atmospheric-oceanic oscillations.

Progress and challenges in dual- and triple-isotope (δ O, δ H, Δ O) analyses of environmental waters: An international assessment of laboratory performance.

Rationale: Stable isotope analyses of environmental waters (δ H, δ O) are an important assay in hydrology and environmental research with rising interest in δ O, which requires ultra-precise assays. We evaluated isotope analyses of six test water samples for 281 laboratory submissions measuring δ H and δ O along with a subset analyzing δ O and Δ O by laser spectrometry and isotope ratio mass spectrometry (IRMS).

Methods: Six test waters were distributed to laboratories spanning a wide δ range of natural waters for δ H, δ O and δ O and Δ O.