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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 (δ 13 C) 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 δ 13 C, indicating breastmilk consumption. Subtle changes in glutamate δ 13 C likely result from its 'non-essential' status. Additionally, δ 13 C 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 δ 13 C of amino acids may change over an individual's lifespan or be altered due to various forms of stress., Competing Interests: Declarations. Competing interest: The authors declare that there are no known financial interests or personal relationships that could have influenced the work reported in this article. All study participants gave their informed consent for inclusion before partaking in the study. This study is in accordance with the Tri-Council Policy Statement Ethical Conduct for Research Involving Humans (TCPS2) and the Ontario Personal Health Information Protection Act (PHIPA, 2004). The protocol used in this study was approved by the Non-Medical Research Ethics Board of Western University (Project ID 119889)., (© 2024. The Author(s).)

Annual antler growth begins in the spring and is completed by late summer for male caribou ( Rangifer tarandus groenlandicus ) from the Qamanirjuaq herd (Nunavut, Canada), aligned with both the spring migration and a seasonal dietary shift. Antlers may provide a non-lethal means of studying short- and long-term changes in caribou ecology through incorporated isotopes of carbon (δ 13 C) and nitrogen (δ 15 N). We sampled the antlers of 12 male caribou from the Qamanirjuaq herd culled in September 1967. We predicted that serial sampling of antlers would reflect the known seasonal dietary change from lichen to grass-like and shrub diet based on rumen contents from individuals culled during the same period. The δ 13 C and δ 15 N were analyzed in food sources and every 3 cm along each antler's length. The carbon isotope compositions of collagen (δ 13 C col ) varied by ~0.5‰ among individuals and within antlers, while the carbon isotope compositions of antler bioapatite (δ 13 C CO3 ) increased by 1-1.5‰ from pedicle to tip. Values of δ 15 N col increased within antlers by 1-3‰ from pedicle to tip and varied by 3‰ among the individuals sampled. Antler collagen was lower in δ 15 N col by ~1‰ relative to bone collagen. Bayesian mixing models were conducted to test for changes in dietary proportions from antler isotope compositions. Mixing models did not indicate significant dietary shifts for any individual during antler formation, showing consistently mixed diets of fungi, horsetail, lichen, and woody plants. Increases in δ 15 N col in antler tissue could, therefore, correspond to subtle seasonal dietary changes and/or the physiological stress of antler tissue development., (© 2024 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

This dataset contains measurements of modern water and ancient core materials from Lake Simcoe, the fourth largest lake wholly in Ontario, Canada. These data consist of: (i) oxygen, hydrogen and carbon isotope ( δ 18 O, δ 2 H and δ 13 C) compositions for modern water samples; (ii) physical measurements of one piston core, PC-5; (iii) δ 13 C and δ 18 O values of ostracods collected from PC-5, and (iv) δ 13 C and δ 18 O values of ancient DIC and water, respectively, inferred from item (iii) . Physical measurements performed on core PC-5 include magnetic susceptibility, mineralogy and grain size. Mass accumulation rates are also reported. These data will be of interest to those aiming to better characterize the timing and pathway of meltwater flow during and following deglaciation of the Laurentide Ice Sheet in the Laurentian Great Lakes region. These data will also be useful to researchers investigating the influence of deglaciation on the oxygen and carbon isotope systematics of ancient lake environments. A discussion of these data is available in "A ∼14 000-year record of environmental change from Lake Simcoe, Canada" [1]., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2022 Published by Elsevier Inc.)

Migration is energetically expensive and is predicted to drive similar morphological adaptations and physiological trade-offs in migratory bats and birds. Previous studies suggest that fixed traits like wing morphology vary among species and individuals according to selective pressures on flight, while immune defences can vary flexibly within individuals as energy is variably reallocated throughout the year. We assessed intraspecific variation in wing morphology and immune function in silver-haired bats Lasionycteris noctivagans, a species that follows both partial and differential migration patterns. We hypothesized that if bats experience energy constraints associated with migration, then wing morphology and immune function should vary based on migratory tendency (sedentary or migratory) and migration distance. We predicted that long-distance migrants would have reduced immune function and more migration-adapted wing shapes compared to resident or short-distance migrating bats. We estimated breeding latitude of spring migrants using stable hydrogen isotope techniques. Our sample consisted primarily of male bats, which we categorized as residents, long-distance northern migrants, short-distance northern migrants and southern migrants (apparent breeding location south of capture site). Controlling for individual condition and capture date, we related wing characteristics and immune indices among groups. Some, but not all, aspects of wing form and immune function varied between migrants and residents. Long-distance northern migrants had larger wings than short-distance northern migrants and lower wing loading than southern migrants. Compared with resident bats, short-distance northern migrants had reduced IgG while southern migrants had heightened neutrophils and neutrophil-to-lymphocyte ratios. Body fat, aspect ratio, wing tip shape and bacteria killing ability did not vary with migration status or distance. In general, male silver-haired bats do not appear to mediate migration costs by substantially downregulating immune defences or to be under stronger selection for wing forms adapted for fast, energy-efficient flight. Such phenotypic changes may be more adaptive for female silver-haired bats, which migrate farther and are more constrained by time in spring than males. Adaptations for aerial hawking and the use of heterothermy by migrating bats may also reduce the energetic cost of migration and the need for more substantial morphological and physiological trade-offs., (© 2022 British Ecological Society.)

The data reported here consist of oxygen and hydrogen isotope compositions for 145 modern water samples, and geochemical measurements for gravity cores of sediment, all collected from Barry Lake, a small kettle lake located in Ontario, Canada. The geochemical measurements for the sediment organic matter include organic carbon and total nitrogen isotope compositions, organic carbon and total nitrogen contents and chlorophyll a content. The carbon and oxygen isotope compositions of marl contained in these sediments are also reported, along with the calcite and quartz contents of the sediment sample. Mass accumulation rates of total organic carbon, total nitrogen, chlorophyll a and calcite are reported. Dating of these sediments shows that they span ∼900 years. The stable isotope compositions of the modern waters and marl are useful to researchers studying how effective moisture (the net of water inputs vs outputs) changed in southern Ontario across the last ∼900 years. Proxies derived from the organic fraction of the lake sediments will be of interest to researchers of small Ontario lakes seeking to contextualize recent increases in primary production related to eutrophication. A discussion of these data, and a comparison of these data to other cores in the Great Lakes Region, is available in "A 900-year record of effective moisture in the Great Lakes Region" (Doyle et al., 2021)., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that have or could be perceived to have influenced the work reported in this article., (© 2022 The Authors.)

Background: Phytoglycogen (PHY; PhytoSpherix; Mirexus Biotechnologies), a highly branched polysaccharide extracted from sweet corn, has considerable potential for exercise oxidation due to its low viscosity in water, high water retention, and exceptional stability., Objectives: Using gas chromatography-isotope ratio mass spectrometry, we investigated dose-response oxidation of ingested PHY during prolonged, moderate-intensity exercise., Methods: Thirteen men (≥1 y endurance-training experience, ≥6 d·wk-1, ∼1-1.5 h·d-1; age, 25.7 ± 5.5 y; mass, 79.3 ± 10.0 kg;  V̇O2max, 59.9 ± 5.5 mL·kg-1·min-1; means ± SDs) cycled for 150 min (50% maximal watt output) while ingesting PHY concentrations of 0.0% (0.0 g·min-1), 3.6% (0.5 g·min-1), 7.2% (1.0 g·min-1), 10.8% (1.5 g·min-1), or 14.4% (2 g·min-1) in water (2100 mL) (n = 7-10/dose). Substrate oxidation was determined using stable-isotope methods and indirect calorimetry., Results: PHY oxidation plateaued between 60 and 150 min of exercise and increased (P < 0.001) from 0.49 to 0.72 g·min-1 with 0.5- and 1.0-g·min-1 doses without further increases (0.76 and 0.73 g·min-1; P > 0.05) with 1.5 or 2 g·min-1. Peak PHY oxidation (0.84 ± 0.04 g·min-1) occurred in the final 30 min of exercise with 2 g·min-1. Exercise blood glucose was greater (5.1 mmol·L-1) with 1.0-, 1.5-, and 2-g·min-1 doses compared with that of 0.5 (4.7 mmol·L-1) or 0.0 g·min-1 (4.2 mmol·L-1) (P < 0.0001). Gastrointestinal distress was minimal except with 2 g·min-1 (P < 0.001)., Conclusions: In male endurance athletes, PHY oxidation plateaued at 0.72-0.76 g·min-1 during 150 min of cycling at 50% Wmax (peak oxidation of 0.84 g·min-1 occurred during the final 30 min). This trial was registered at clinicaltrials.gov as NCT02909881., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.)

Oxygen and hydrogen isotope data of meteoric water samples are compiled from several States across Mexico. This dataset includes 287 oxygen and hydrogen (and deuterium excess) isotope data corresponding to meteoric water collected from the surface, groundwater wells, irrigation and observation wells, and water supply boreholes. These data facilitate the development of maps to determine the spatial distribution of water stable isotopes, also known as "isoscapes", of the Mexican territory. As such, this dataset (and the isoscapes built from it) is useful in geographic mobility studies that aim to evaluate geographic origins and residency of particular human and/or non-human individuals in antiquity and in contemporary times. Further discussion about the data and an example of an isoscape of Mexico using the meteoric water oxygen isotope data are provided in "Residential Patterns of Mexica Human Sacrifices at Mexico-Tenochtitlan and Mexico-Tlatelolco: Evidence from Phosphate Oxygen Isotopes" (Moreiras Reynaga et al., 2021). Overall, the dataset is useful in developing interpolated maps of water stable isotopes for relevant archeological, bioarchaeological, forensic, hydrogeological, and ecological research., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships which have or could be perceived to have influenced the work reported in this article., (© 2021 The Author(s). Published by Elsevier Inc.)

Killer whales (Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species' distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ 18 O P ) and structural carbonate (δ 18 O SC , δ 13 C SC ) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ 18 O of marine water (δ 18 O marine ) at location of origin was estimated from dentine δ 18 O P values, and then compared with predicted isoscape values to assign individual distributions. Dentine δ 18 O P values were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ 18 O P and estimated δ 18 O marine values consistent with 18 O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ 18 O values occurs. Several individuals, however, had relatively high values that reflected origins in 18 O-enriched, low-latitude waters below this boundary. Within-tooth δ 18 O SC ranges on the order of 1-2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.

Modern beavers (Castor) are prolific ecosystem engineers and dramatically alter the landscape through tree harvesting and dam building. Little is known, however, about the evolutionary drivers of their woodcutting behaviour. Here we investigate if early woodcutting behaviour in Castoridae was driven by nutritional needs. We measured stable carbon and nitrogen isotopes (δ 13 C and δ 15 N) of coeval subfossil plants and beaver collagen (Dipoides sp.) from the Early Pliocene, High Arctic Beaver Pond fossil locality (Ellesmere Island), in order to reconstruct Dipoides sp. diet. Isotopic evidence indicates a diet of woody plants and freshwater macrophytes, supporting the hypothesis that this extinct semiaquatic beaver engaged in woodcutting behaviour for feeding purposes. In a phylogenetic context, the isotopic evidence implies that woodcutting and consumption of woody plants can be traced back to a small-bodied, semiaquatic Miocene castorid, suggesting that beavers have been consuming woody plants for over 20 million years. We propose that the behavioural complex (swimming, woodcutting, and consuming woody plants) preceded and facilitated the evolution of dam building. Dam building and food caching behaviours appear to be specializations for cold winter survival and may have evolved in response to late Neogene northern cooling.

The ~180-km-diameter Chicxulub peak-ring crater and ~240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth's crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified ~1.4 × 10 5 km 3 of Earth's crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 10 6 years., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Low atmospheric CO2 conditions prevailed for most of the recent evolutionary history of plants. Such concentrations reduce plant growth compared with modern levels, but low-CO2 effects on plant performance may also be affected by nitrogen availability, since low leaf nitrogen decreases photosynthesis, and CO2 concentrations influence nitrogen assimilation. To investigate the influence of N availability on plant performance at low CO2, we grew Elymus canadensis at ambient (~400 μmol mol-1) and subambient (~180 μmol mol-1) CO2 levels, under four N-treatments: nitrate only; ammonium only; a full and a half mix of nitrate and ammonium. Growth at low CO2 decreased biomass in the full and nitrate treatments, but not in ammonium and half plants. Low CO2 effects on photosynthetic and maximum electron transport rates were influenced by fertilisation, with photosynthesis being most strongly impacted by low CO2 in full plants. Low CO2 reduced stomatal index in half plants, suggesting that the use of this indicator in paleo-inferences can be influenced by N availability. Under low CO2 concentrations, nitrate plants discriminated more against 15N whereas half plants discriminated less against 15N compared with the full treatment, suggesting that N availability should be considered when using N isotopes as paleo-indicators.

We provide the dataset of climate variables related to the research article "Paleoclimate reconstruction of the Prince Creek Formation, Arctic Alaska, during Maastrichtian global warming" [1]. The dataset includes mean annual precipitation (MAP) values determined using two independent proxies, estimates of the oxygen isotope composition of meteoric water (δ 18 O w ) obtained from smectites and a comparison with previously published siderite data. We also provide the data used to calculate the total flux of CO 2 required for the weathering of silicates. This dataset is an example of a multi proxy approach that could add further insight for researchers in the selection of suitable proxies for paleoclimatic interpretations., (© 2020 The Author(s).)

We present a procedure for the determination of the isotopic ratios of silicon and oxygen from the same aliquot of anhydrous silicate material. The sample is placed in a bromine pentafluoride atmosphere as it is heated with a CO 2 laser system releasing silicon tetrafluoride and oxygen gasses. The oxygen gas is then purified to remove other reaction by-products through several liquid nitrogen traps before being captured onto a molecular sieve and transferred to an isotope ratio mass spectrometer. The silicon tetrafluoride gas is then purified using a supplementary line by repeatedly freezing to -196°C with liquid nitrogen and then thawing with an ethanol slurry at -110°C through a series of metal and Pyrex traps. The purified gas is then condensed into a Pyrex sample tube before it is transferred to an isotope ratio mass spectrometer for silicon isotope ratio measurements. This system has silicon yields of greater than 90% for pure quartz, olivine, and garnet standards and has a reproducibility of ±0.1‰ (2σ) for pure quartz for both oxygen and silicon isotope measurements. Meteoritic samples were also successfully analyzed to demonstrate this system's ability to measure the isotopic ratio composition of bulk powders with precision. This unique technique allows for the fluorination of planetary material without the need for wet chemistry. Though designed to analyze small aliquots of meteoritic material (1.5 to 3 mg), this approach can also be used to investigate refractory terrestrial samples where traditional fluorination is not suitable., (© 2019 John Wiley & Sons, Ltd.)

This is a multi-individual (n = 11), stable carbon and nitrogen isotope study of bone collagen (δ 13 C col and δ 15 N col ) from the giant beaver (genus Castoroides). The now-extinct giant beaver was once one of the most widespread Pleistocene megafauna in North America. We confirm that Castoroides consumed a diet of predominantly submerged aquatic macrophytes. These dietary preferences rendered the giant beaver highly dependent on wetland habitat for survival. Castoroides' δ 13 C col and δ 15 N col do not support the hypothesis that the giant beaver consumed trees or woody plants, which suggests that it did not share the same behaviours as Castor (i.e., tree-cutting and harvesting). The onset of warmer, more arid conditions likely contributed to the extinction of Castoroides. Six new radiocarbon dates help establish the chronology of the northward dispersal of the giant beaver in Beringia, indicating a correlation with ice sheet retreat.

Tree-ring carbon isotope discrimination (Δ 13 C) and oxygen isotopes (δ 18 O) collected from white pine (Pinus strobus) trees adjacent to Lake Superior show potential to produce the first winter-specific paleoclimate reconstruction with inter-annual resolution for this region. Isotopic signatures from 1976 to 2015 were strongly linked to antecedent winter minimum temperatures (T min ), Lake Superior peak ice cover, and regional to continental-scale atmospheric winter pressure variability including the North American Dipole. The immense thermal inertia of Lake Superior underlies the unique connection between winter conditions and tree-ring Δ 13 C and δ 18 O signals from the following growing season in trees located near the lake. By combining these signals, we demonstrate feasibility to reconstruct variability in T min , ice cover, and continental-scale atmospheric circulation patterns (r ≥ 0.65, P < 0.001).

Stable isotopes are powerful tools for elucidating ecological trends in extant vertebrate communities, though their application to Mesozoic ecosystems is complicated by a lack of extant isotope data from comparable environments/ecosystems (e.g. coastal floodplain forest environments, lacking significant C 4 plant components). We sampled 20 taxa across a broad phylogenetic, body size, and physiological scope from the Atchafalaya River Basin of Louisiana as an environmental analogue to the Late Cretaceous coastal floodplains of North America. Samples were analysed for stable carbon, oxygen and nitrogen isotope compositions from bioapatite and keratin tissues to test the degree of ecological resolution that can be determined in a system with similar environmental conditions, and using similar constraints, as those in many Mesozoic assemblages. Isotopic results suggest a broad overlap in resource use among taxa and considerable terrestrial-aquatic interchange, highlighting the challenges of ecological interpretation in C 3 systems, particularly when lacking observational data for comparison. We also propose a modified oxygen isotope-temperature equation that uses mean endotherm and mean ectotherm isotope data to more precisely predict temperature when compared with measured Atchafalaya River water data. These results provide a critical isotopic baseline for coastal floodplain forests, and act as a framework for future studies of Mesozoic palaeoecology., Competing Interests: We have no competing interests.

A magnificent repository of Late Pleistocene terrestrial megafauna fossils is contained in ice-rich loess deposits of Alaska and Yukon, collectively eastern Beringia. The stable carbon (δ13C) and nitrogen (δ15N) isotope compositions of bone collagen from these fossils are routinely used to determine paleodiet and reconstruct the paleoecosystem. This approach requires consideration of changes in C- and N-isotope dynamics over time and their effects on the terrestrial vegetation isotopic baseline. To test for such changes between the Late Pleistocene and modern time, we compared δ13C and δ15N for vegetation and bone collagen and structural carbonate of some modern, Yukon, arctic ground squirrels with vegetation and bones from Late Pleistocene fossil arctic ground squirrel nests preserved in Yukon loess deposits. The isotopic discrimination between arctic ground squirrel bone collagen and their diet was measured using modern samples, as were isotopic changes during plant decomposition; Over-wintering decomposition of typical vegetation following senescence resulted in a minor change (~0-1 ‰) in δ13C of modern Yukon grasses. A major change (~2-10 ‰) in δ15N was measured for decomposing Yukon grasses thinly covered by loess. As expected, the collagen-diet C-isotope discrimination measured for modern samples confirms that modern vegetation δ13C is a suitable proxy for the Late Pleistocene vegetation in Yukon Territory, after correction for the Suess effect. The N-isotope composition of vegetation from the fossil arctic ground squirrel nests, however, is determined to be ~2.8 ‰ higher than modern grasslands in the region, after correction for decomposition effects. This result suggests a change in N dynamics in this region between the Late Pleistocene and modern time.

We examine here the carbon and nitrogen isotopic compositions of bulk soils (8 topsoil and 7 subsoils, including two soil profiles) and five different plant parts of 79 C3 plants from two main functional groups: herbs and shrubs/subshrubs, from 18 different locations in grasslands of southern Yukon Territory, Canada (eastern shoreline of Kluane Lake and Whitehorse area). The Kluane Lake region in particular has been identified previously as an analogue for Late Pleistocene eastern Beringia. All topsoils have higher average total nitrogen δ15N and organic carbon δ13C than plants from the same sites with a positive shift occurring with depth in two soil profiles analyzed. All plants analyzed have an average whole plant δ13C of -27.5 ± 1.2 ‰ and foliar δ13C of -28.0 ± 1.3 ‰, and average whole plant δ15N of -0.3 ± 2.2 ‰ and foliar δ15N of -0.6 ± 2.7 ‰. Plants analyzed here showed relatively smaller variability in δ13C than δ15N. Their average δ13C after suitable corrections for the Suess effect should be suitable as baseline for interpreting diets of Late Pleistocene herbivores that lived in eastern Beringia. Water availability, nitrogen availability, spacial differences and intra-plant variability are important controls on δ15N of herbaceous plants in the study area. The wider range of δ15N, the more numerous factors that affect nitrogen isotopic composition and their likely differences in the past, however, limit use of the modern N isotopic baseline for vegetation in paleodietary models for such ecosystems. That said, the positive correlation between foliar δ15N and N content shown for the modern plants could support use of plant δ15N as an index for plant N content and therefore forage quality. The modern N isotopic baseline cannot be applied directly to the past, but it is prerequisite to future efforts to detect shifts in N cycling and forage quality since the Late Pleistocene through comparison with fossil plants from the same region.

Microplastics contamination of Lake Ontario sediments is investigated with the aim of identifying distribution patterns and hotspots in nearshore, tributary and beach depositional environments. Microplastics are concentrated in nearshore sediments in the vicinity of urban and industrial regions. In Humber Bay and Toronto Harbour microplastic concentrations were consistently >500 particles per kg dry sediment. Maximum concentrations of ~28,000 particles per kg dry sediment were determined in Etobicoke Creek. The microplastic particles were primarily fibres and fragments <2mm in size. Both low- and high-density plastics were identified using Raman spectroscopy. We provide a baseline for future monitoring and discuss potential sources of microplastics in terms of how and where to implement preventative measures to reduce the contaminant influx. Although the impacts of microplastics contamination on ecosystem health and functioning is uncertain, understanding, monitoring and preventing further microplastics contamination in Lake Ontario and the other Great Lakes is crucial., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Spatial variation in marine oxygen isotope ratios (δ (18)O) resulting from differential evaporation rates and precipitation inputs is potentially useful for characterizing marine mammal distributions and tracking movements across δ (18)O gradients. Dentine hydroxyapatite contains carbonate and phosphate that precipitate in oxygen isotopic equilibrium with body water, which in odontocetes closely tracks the isotopic composition of ambient water. To test whether dentine oxygen isotope composition reliably records that of ambient water and can therefore serve as a proxy for odontocete distribution and movement patterns, we measured δ (18)O values of dentine structural carbonate (δ (18) OSC) and phosphate (δ (18) OP) of seven odontocete species (n = 55 individuals) from regional marine water bodies spanning a surface water δ (18)O range of several per mil. Mean dentine δ (18) OSC (range +21.2 to +25.5‰ VSMOW) and δ (18) OP (+16.7 to +20.3‰) values were strongly correlated with marine surface water δ (18)O values, with lower dentine δ (18) OSC and δ (18) OP values in high-latitude regions (Arctic and Eastern North Pacific) and higher values in the Gulf of California, Gulf of Mexico, and Mediterranean Sea. Correlations between dentine δ (18) OSC and δ (18) OP values with marine surface water δ (18)O values indicate that sequential δ (18)O measurements along dentine, which grows incrementally and archives intra- and interannual isotopic composition over the lifetime of the animal, would be useful for characterizing residency within and movements among water bodies with strong δ (18)O gradients, particularly between polar and lower latitudes, or between oceans and marginal basins.

Disruptive selection is a process that can result in multiple subgroups within a population, which is referred to as diversification. Foraging-related diversification has been described in many taxa, but many questions remain about the contribution of such diversification to reproductive isolation and potentially sympatric speciation. Here, we use stable isotope analysis of diet and morphological analysis of body shape to examine phenotypic divergence between littoral and pelagic foraging ecomorphs in a population of pumpkinseed sunfish (Lepomis gibbosus). We then examine reproductive isolation between ecomorphs by comparing the isotopic compositions of nesting males to eggs from their nests (a proxy for maternal diet) and use nine microsatellite loci to examine genetic divergence between ecomorphs. Our data support the presence of distinct foraging ecomorphs in this population and indicate that there is significant positive assortative mating based on diet. We did not find evidence of genetic divergence between ecomorphs, however, indicating that isolation is either relatively recent or is not strong enough to result in genetic divergence at the microsatellite loci. Based on our findings, pumpkinseed sunfish represent a system in which to further explore the mechanisms by which natural and sexual selection contribute to diversification, prior to the occurrence of sympatric speciation., (© 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.)

Humans have altered Earth's nitrogen cycle so dramatically that reactive nitrogen (Nr) has doubled. This has increased Nr in aquatic ecosystems, which can lead to reduced water quality and ecosystem health. Apportioning sources of Nr to specific ecosystems, however, continues to be challenging, despite this knowledge being critical for mitigation and protection of water resources. Here we use Δ(17)O, δ(18)O and δ(15)N from Uinta Mountain (Utah, USA) snow, inflow and lake nitrate in combination with a Bayesian-based stable isotope mixing model, to show that at least 70% of nitrates in aquatic systems are anthropogenic and arrive via the atmosphere. Moreover, agricultural activities, specifically nitrate- and ammonium-based fertilizer use, are contributing most (∼60%) Nr, and data from other North American alpine lakes suggest this is a widespread phenomenon. Our findings offer a pathway towards more effective mitigation, but point to challenges in balancing food production with protection of important water resources.

Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths' diet and physiology have been hampered by the 'mammoth conundrum': woolly mammoths have anomalously high collagen δ(15)N values, which are more similar to coeval carnivores than herbivores, and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species, and discovered greater  (15)N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization, and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores.

Understanding childhood experiences of health and well-being is essential to reconstructing ancient life-ways. Here, archaeological hair samples from five juveniles from Cahuachi and near Huaca del Loro in the Nasca Region, Peru, are analyzed for their carbon- and nitrogen-isotope compositions and cortisol levels. Stable isotopic data are used to investigate dietary change and nitrogen metabolism, and cortisol levels are used to infer exposure to stress. Using a case study approach, we determined that juveniles have distinct, individualized experiences of diet and morbidity, which are, in some cases, similar to adult experiences in the same region. Overall, Nasca Region juveniles have high systemic cortisol levels (1444±402ng/g) compared to Peruvian adults (281±35ng/g; Webb et al., 2010). Younger juveniles have comparatively high δ 15 N values that decrease over several months, suggesting transition from breast milk to a weaning diet. Older juveniles exhibit patterns of dietary shifting similar to those determined for adults in the region, or suggestive of particular socioeconomic roles. This study demonstrates the value of applying biomolecular methods to juvenile mummified remains to better understand the life histories of children in archaeological contexts., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Archeological hair from 14 adults from the Nasca Region, Peru (c. AD1-1000) was analyzed for carbon and nitrogen isotopic compositions and cortisol levels. We investigated the relationship between isotopic compositions, which reflect diet, and cortisol, which reflects biogenic cortisol production and chronic stress. Using a case study approach, we determined that there are consistent changes in cortisol production associated with the rapid dietary change characteristic of local mobility. Moreover, changes in nitrogen- and carbon-isotope compositions, when integrated with cortisol levels, enabled inferences to be made about nitrogen metabolism and carbon routing, and elucidated the nature of potential stressors in the months before death. The isotopic and cortisol data suggested a relatively high rate of exposure to stress that is consistent with what is known about the Nasca Region social and physical environments. Of the 14 adults included in this study, six likely suffered from illness/trauma before death, and a further three experienced stress without an observable associated change in isotopic composition. Five individuals also experienced increased stress related to local mobility, inferred from co-occurring changes in cortisol production and dietary shifting. The integration of cortisol and isotopic data revealed individual characteristics of hidden frailty and risk that would not be apparent using more traditional methods of evaluating health status. This approach will provide a powerful enhancement to the understanding of stress, morbidity, and well-being developed through skeletal analysis., (© 2014 Wiley Periodicals, Inc.)

Existing radiocarbon ((14)C) dates on American mastodon (Mammut americanum) fossils from eastern Beringia (Alaska and Yukon) have been interpreted as evidence they inhabited the Arctic and Subarctic during Pleistocene full-glacial times (∼ 18,000 (14)C years B.P.). However, this chronology is inconsistent with inferred habitat preferences of mastodons and correlative paleoecological evidence. To establish a last appearance date (LAD) for M. americanum regionally, we obtained 53 new (14)C dates on 36 fossils, including specimens with previously published dates. Using collagen ultrafiltration and single amino acid (hydroxyproline) methods, these specimens consistently date to beyond or near the ∼ 50,000 y B.P. limit of (14)C dating. Some erroneously "young" (14)C dates are due to contamination by exogenous carbon from natural sources and conservation treatments used in museums. We suggest mastodons inhabited the high latitudes only during warm intervals, particularly the Last Interglacial [Marine Isotope Stage (MIS) 5] when boreal forests existed regionally. Our (14)C dataset suggests that mastodons were extirpated from eastern Beringia during the MIS 4 glacial interval (∼ 75,000 y ago), following the ecological shift from boreal forest to steppe tundra. Mastodons thereafter became restricted to areas south of the continental ice sheets, where they suffered complete extinction ∼ 10,000 (14)C years B.P. Mastodons were already absent from eastern Beringia several tens of millennia before the first humans crossed the Bering Isthmus or the onset of climate changes during the terminal Pleistocene. Local extirpations of mastodons and other megafaunal populations in eastern Beringia were asynchrononous and independent of their final extinction south of the continental ice sheets.

Paleodiet research traditionally interprets differences in collagen isotopic compositions (δ(13) C, δ(15) N) as indicators of dietary distinction even though physiological processes likely play some role in creating variation. This research investigates the degree to which bone collagen δ(13) C and δ(15) N values normally vary within the skeleton and examines the influence of several diseases common to ancient populations on these isotopic compositions. The samples derive from two medieval German cemeteries and one Swiss reference collection and include examples of metabolic disease (rickets/osteomalacia), degenerative joint disease (osteoarthritis), trauma (fracture), infection (osteomyelitis), and inflammation (periostitis). A separate subset of visibly nonpathological skeletal elements from the German collections established normal intraindividual variation. For each disease type, tests compared bone lesion samples to those near and distant to the lesions sites. Results show that normal (nonpathological) skeletons exhibit limited intraskeletal variation in carbon- and nitrogen-isotope ratios, suggesting that sampling of distinct elements is appropriate for paleodiet studies. In contrast, individuals with osteomyelitis, healed fractures, and osteoarthritis exhibit significant intraskeletal differences in isotope values, depending on whether one is comparing lesions to near or to distant sites. Skeletons with periostitis result in significant intraskeletal differences in nitrogen isotope values only, while those with rickets/osteomalacia do not exhibit significant intraskeletal differences. Based on these results, we suggest that paleodiet researchers avoid sampling collagen at or close to lesion sites because the isotope values may be reflecting both altered metabolic processes and differences in diet relative to others in the population., (Copyright © 2013 Wiley Periodicals, Inc.)

The development of isotopic baselines for comparison with paleodietary data is crucial, but often overlooked. We review the factors affecting the carbon (δ(13)C) and nitrogen (δ(15)N) isotopic compositions of plants, with a special focus on the carbon and nitrogen isotopic compositions of twelve different species of cultivated plants (n = 91) and 139 wild plant species collected in northern Peru. The cultivated plants were collected from nineteen local markets. The mean δ(13)C value for maize (grain) was -11.8±0.4 ‰ (n = 27). Leguminous cultigens (beans, Andean lupin) were characterized by significantly lower δ(15)N values and significantly higher %N than non-leguminous cultigens. Wild plants from thirteen sites were collected in the Moche River Valley area between sea level and ∼4,000 meters above sea level (masl). These sites were associated with mean annual precipitation ranging from 0 to 710 mm. Plants growing at low altitude sites receiving low amounts of precipitation were characterized by higher δ(15)N values than plants growing at higher altitudes and receiving higher amounts of precipitation, although this trend dissipated when altitude was >2,000 masl and MAP was >400 mm. For C(3) plants, foliar δ(13)C was positively correlated with altitude and precipitation. This suggests that the influence of altitude may overshadow the influence of water availability on foliar δ(13)C values at this scale.

The contributions of phenotypic plasticity to photosynthetic performance in winter (cv Musketeer, cv Norstar) and spring (cv SR4A, cv Katepwa) rye (Secale cereale) and wheat (Triticum aestivum) cultivars grown at either 20°C [non-acclimated (NA)] or 5°C [cold acclimated (CA)] were assessed. The 22-40% increase in light-saturated rates of CO₂ assimilation in CA vs NA winter cereals were accounted for by phenotypic plasticity as indicated by the dwarf phenotype and increased specific leaf weight. However, phenotypic plasticity could not account for (1) the differential temperature sensitivity of CO₂ assimilation and photosynthetic electron transport, (2) the increased efficiency and light-saturated rates of photosynthetic electron transport or (3) the decreased light sensitivity of excitation pressure and non-photochemical quenching between NA and NA winter cultivars. Cold acclimation decreased photosynthetic performance of spring relative to winter cultivars. However, the differences in photosynthetic performances between CA winter and spring cultivars were dependent upon the basis on which photosynthetic performance was expressed. Overexpression of BNCBF17 in Brassica napus generally decreased the low temperature sensitivity (Q₁₀) of CO₂ assimilation and photosynthetic electron transport even though the latter had not been exposed to low temperature. Photosynthetic performance in wild type compared to the BNCBF17-overexpressing transgenic B. napus indicated that CBFs/DREBs regulate not only freezing tolerance but also govern plant architecture, leaf anatomy and photosynthetic performance. The apparent positive and negative effects of cold acclimation on photosynthetic performance are discussed in terms of the apparent costs and benefits of phenotypic plasticity, winter survival and reproductive fitness., (Copyright © Physiologia Plantarum 2011.)

Background: Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ(15)N). Animal excrement is known to impact plant δ(15)N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint., Methodology/principal Findings: This paper presents isotopic (δ(13)C and δ(15)N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano under controlled conditions. The level of (15)N enrichment in fertilized plants is very large, with δ(15)N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ(15)N values ranged between -0.3 and 5.7‰. Intraplant and temporal variability in δ(15)N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ(13)C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk., Conclusions/significance: The results presented in this study demonstrate the very large impact of seabird guano on maize δ(15)N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs). Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must be considered when interpreting isotopic data from archaeological material.

Background: Annual movements of tri-colored bats (Perimyotis subflavus) are poorly understood. While this species has been considered a regional migrant, some evidence suggests that it may undertake annual latitudinal migrations, similar to other long distance North American migratory bat species., Methodology/principal Findings: We investigated migration in P. subflavus by conducting stable hydrogen isotope analyses of 184 museum specimen fur samples and comparing these results (δD(fur)) to published interpolated δD values of collection site growing season precipitation (δD(precip)). Results suggest that the male molt period occurred between June 23 and October 16 and 33% of males collected during the presumed non-molt period were south of their location of fur growth. For the same time period, 16% of females were south of their location of fur growth and in general, had not travelled as far as migratory males. There were strong correlations between δD(fur) from the presumed molt period and both growing season δD(precip) (males--r(2) = 0.86; p<0.01; females--r(2) = 0.75; p < 0.01), and latitude of collection (males--r(2) = 0.85; p<0.01; females--r(2) = 0.73; p<0.01). Most migrants were collected at the northern (>40 °N; males and females) and southern (<35 °N; males only) extents of the species' range., Conclusions/significance: These results indicate a different pattern of migration for this species than previously documented, suggesting that some P. subflavus engage in annual latitudinal migrations and that migratory tendency varies with latitude and between sexes. We suggest that this species' hibernation ecology makes it particularly susceptible to long winters, making migration from the northern extent of the species' range to more southern hibernacula preferable for some individuals. Fur δD values for some of the northern individuals may indicate an increase in the currently accepted northern range of this species. Sex-biased differences in migration may be the result of differences in reproductive pressures.

The causes of megafaunal extinctions in North America have been widely debated but remain poorly understood. Mammoths (Mammuthus spp.) in the American Southwest were hunted by Clovis people during a period of rapid climate change, just before the regional onset of Younger Dryas cooling and mammoth extirpation. Thus, these mammoths may provide key insights into late Pleistocene extinction processes. Here we reconstruct the seasonal diet and climatic conditions experienced by mammoths in the San Pedro Valley of Arizona, using the carbon ((13)C/(12)C) and oxygen ((18)O/(16)O) isotope compositions of tooth enamel. These records suggest that Clovis mammoths experienced a warm, dry climate with sufficient summer rainfall to support seasonal C(4) plant growth. Monsoon intensity may have been reduced relative to the preceding time period, but there is no isotopic evidence for severe drought. However, it is possible that the "Clovis drought", inferred from stratigraphic evidence, occurred suddenly at the end of the animals' lives and thus was not recorded in the enamel isotopic compositions. Unlike mammoths that lived before the Last Glacial Maximum, Clovis mammoths regularly increased C(4) grass consumption during summer, probably seeking seasonally green grasslands farther from the river valley. This predictable seasonal behavior may have made mammoths easier to locate by Clovis hunters. Furthermore, Clovis mammoths probably had no previous experience of such sudden climatic change as is believed to have occurred at the time of their extinction.

A recent trend in stable isotopic analysis involves the reconstruction of short-term variations in diet using hair segments. However, bulk hair samples typically contain a growth cycle error, which may conceal or confound the most recently incorporated isotopic information. It is assumed that, at any given time, ∼85-90% of scalp hairs are actively growing, while the remaining 10-15% have transitioned into a resting or inactive phase, which lasts up to 4 months before hairs are shed. This study uses growth phase to determine the effects of age, sex, and health status on carbon and nitrogen isotopic ratios of hair analyzed in sequential segments. For this study, we selected archaeological hair samples from 10 individuals from Dakhleh Oasis, Egypt. Isotopic analyses of actively growing hair segments were compared to those for mixed growth phase segments from each individual. These data demonstrate the presence of growth cycle error and show that an understanding of structural-functional relationships is essential for interpreting normal versus pathological changes in hair follicle and fiber production. In situations where diet change and mobility produce variations in an individual's isotopic composition, elimination of positional-temporal error in sequential segment hair analyses can facilitate greater understanding of intraindividual metabolic reactions and changes in hair growth cycles. Phase identification may aid in determining the presence of pathological conditions in individuals, especially in those lacking skeletal indications, and provide a more precise estimation of seasonal dietary patterns, access to changing food resources, and metabolic equilibration to a new locality., (Copyright © 2011 Wiley-Liss, Inc.)

Stable isotope analysis is an increasingly valuable tool in ecological studies and shows promise as a measure of nutritional stress in wild animals. Thus far, however, the only studies on endotherms that have conclusively shown changes in delta(15)N and delta(13)C values in response to nutritional stress were conducted on fasting animals and animals growing under extreme levels of food restriction. We conducted a laboratory experiment to test whether delta(15)N and delta(13)C values provide a general index of nutritional stress. We compared the isotopic composition of whole blood, liver, muscle and feathers between two groups of juvenile song sparrows (Melospiza melodia) hand-reared in captivity under identical conditions except for feeding regime. To verify that our experimental treatment induced a biologically meaningful level of nutritional stress, we simultaneously measured the effects on physiology, growth and development at multiple scales. While food-restricted birds were physiologically stressed, physically smaller, and showed poorer growth and brain development compared to ad libitum-fed birds, there was no effect of feeding regime on either delta(15)N or delta(13)C values in any tissue. Instead of a continuum where the level of change in (15)N or (13)C contents corresponds to the level of nutritional stress, we suggest there may be a threshold level of nutritional stress below which such isotopic changes are likely to be negligible.

The weaning process was investigated at two Maya sites dominated by Postclassic remains: Marco Gonzalez (100 BC-AD 1350) and San Pedro (1400-AD 1650), Belize. Bone collagen and bioapatite were analyzed from 67 individuals (n < or = 6 years = 15, n > 6 years = 52). Five isotopic measures were used to reconstruct diet and weaning: stable nitrogen- and carbon-isotope ratios in collagen, stable carbon- and oxygen-isotope ratios in bioapatite, and the difference in stable carbon-isotope values of coexisting collagen and bioapatite. Nitrogen-isotope ratios in infant collagen from both sites are distinct from adult females, indicating a trophic level effect. Collagen-to-bioapatite differences in infant bone from both sites are distinct from adult females, indicating a shift in macronutrients. Oxygen-isotope ratios in infant bioapatite from both sites are also distinct from adult females, indicating the consumption of breast milk. Among infants, carbon- and nitrogen-isotope ratios vary, indicating death during different stages in the weaning process. The ethnohistoric and paleopathological literature on the Maya indicate cessation of breast-feeding between ages 3-4 years. Isotopic data from Marco Gonzalez and San Pedro also indicate an average weaning age of 3-4 years. Based on various isotopic indicators, weaning likely began around age 12 months. This data set is not only important for understanding the weaning process during the Postclassic, but also demonstrates the use of collagen-to-bioapatite spacing as an indicator of macronutrient shifts associated with weaning., (2005 Wiley-Liss, Inc.)

Much uncertainty still exists regarding spatial and temporal variability of stable isotope ratios (13C/12C and D/H) in different CH4-emission sources. Such variability is especially prevalent in freshwater wetlands where a range of processes can influence stable isotope compositions, resulting in variations of up to approximately 50% for delta13C-CH4 and approximately 50% for deltaD-CH4 values. Within a temperate-zone bog and marsh situated in southwestern Ontario, Canada, gas bubbles in pond sediments exhibit only minor seasonal and spatial variation in delta13C-CH4, deltaD-CH4 and delta13C-CO2 values. In pond sediments, CO2 appears to be the main source of carbon during methanogenesis either directly via CO2 reduction or indirectly through dissimilation of autotrophic acetate. In contrast, CH4 production occurs primarily via acetate fermentation at shallow depths in peat soils adjacent to ponds at each wetland. At greater depths within soils, sigmaCO2 and H2O increasingly exert an influence on delta13C- and deltaD-CH4 values. Secondary alteration processes (e.g., methanotrophy or diffusive transport) are unlikely to be responsible for depth-related changes in stable isotope values of CH4. Recent models that attempt to predict deltaD-CH4 values in freshwater environments from D/H ratios in local precipitation do not adequately account for such changes with depth. Subenvironments (i.e., soil-forming and open water areas) in wetlands should be considered separately with respect to stable isotope signatures in CH4 emission models.

Epilithic microbial communities, ubiquitously found in biofilms on submerged granite, limestone, and sandstone, as well as on the concrete support pillars of bridges, were examined in the Speed River, Ontario, Canada. Transmission electron microscopy showed that attached bacteria (on all substrata) were highly mineralized, ranging from Fe-rich capsular material to fine-grained (<1 mum) authigenic (primary) mineral precipitates. The authigenic grains exhibited a wide range of morphologies, from amorphous gel-like phases to crystalline structures. Energy-dispersive X-ray spectroscopy indicated that the most abundant mineral associated with epilithic bacteria was a complex (Fe, Al) silicate of variable composition. The gel-like phases were similar in composition to a chamositic clay, whereas the crystalline structures were more siliceous and had compositions between those of glauconite and kaolinite. The consistent formation of (Fe, Al) silicates by all bacterial populations, regardless of substratum lithology, implies that biomineralization was a surface process associated with the anionic nature of the cell wall. The adsorption of dissolved constituents from the aqueous environment contributed significantly to the mineral formation process. In this regard, it appears that epilithic microbial biofilms dominate the reactivity of the rock-water interface and may determine the type of minerals formed, which will ultimately become part of the riverbed sediment. Because rivers typically contain high concentrations of dissolved iron, silicon, and aluminum, these findings provide a unique insight into biogeochemical activities that are potentially widespread in natural waters.