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Southern hemisphere blue (Balaenoptera musculus intermedia) and fin (Balaenoptera physalus) whales are the largest predators in the Southern Ocean, with similarities in morphology and distribution. Yet, understanding of their life history and foraging is limited due to current low abundances and limited ecological data. To address these gaps, historic Antarctic blue (n = 5) and fin (n = 5) whale baleen plates, collected in 1947-1948 and recently rediscovered in the Smithsonian National Museum of Natural History, were analyzed for bulk (δ13C and δ15N) stable isotopes. Regular oscillations in isotopic ratios, interpreted as annual cycles, revealed that baleen plates contain approximately 6 years (14.35 ± 1.20 cm year-1) of life history data in blue whales and 4 years (16.52 ± 1.86 cm year-1) in fin whales. Isotopic results suggest that: (1) while in the Southern Ocean, blue and fin whales likely fed at the same trophic level but demonstrated niche differentiation; (2) fin whales appear to have had more regular annual migrations; and (3) fin whales may have migrated to ecologically distinct sub-Antarctic waters annually while some blue whales may have resided year-round in the Southern Ocean. These results reveal differences in ecological niche and life history strategies between Antarctic blue and fin whales during a time period when their populations were more abundant than today, and before major human-driven climatic changes occurred in the Southern Ocean.

Arbuscular mycorrhizal fungi (AMF) transport substantial plant carbon (C) that serves as a substrate for soil organisms, a precursor of soil organic matter (SOM), and a driver of soil microbial dynamics. Using two-chamber microcosms where an air gap isolated AMF from roots, we 13CO2-labeled Avena barbata for 6 wk and measured the C Rhizophagus intraradices transferred to SOM and hyphosphere microorganisms. NanoSIMS imaging revealed hyphae and roots had similar 13C enrichment. SOM density fractionation, 13C NMR, and IRMS showed AMF transferred 0.77 mg C g-1 of soil (increasing total C by 2% relative to non-mycorrhizal controls); 33% was found in occluded or mineral-associated pools. In the AMF hyphosphere, there was no overall change in community diversity but 36 bacterial ASVs significantly changed in relative abundance. With stable isotope probing (SIP)-enabled shotgun sequencing, we found taxa from the Solibacterales, Sphingobacteriales, Myxococcales, and Nitrososphaerales (ammonium oxidizing archaea) were highly enriched in AMF-imported 13C (> 20 atom%). Mapping sequences from 13C-SIP metagenomes to total ASVs showed at least 92 bacteria and archaea were significantly 13C-enriched. Our results illustrate the quantitative and ecological impact of hyphal C transport on the formation of potentially protective SOM pools and microbial roles in the AMF hyphosphere soil food web.

Since 2016 there have been intense discussions within several established communities and networks regarding the consequences of the withdrawal of the LSVEC lithium carbonate reference material for carbon isotope‐delta measurement calibration. These include the Isotope Ratio Working Group (IRWG) of the Consultative Committee for the Amount of Substance (CCQM, French: Comité Consultatif pour la Quantité de Matière) of the International Committee of Weights and Measures (CIPM, French: Comité International des Poids et Mesures); participants within the 2016, 2021 and 2024 Technical Meetings on International Atomic Energy Agency (IAEA) stable isotope ratio reference products; and the International Union of Pure and Applied Chemistry's Commission on Isotopic Abundances and Atomic Weights (IUPAC CIAAW) amongst others. The reasons for these intensive discussions relate to the privileged position that LSVEC has occupied for traceability of carbon isotope‐delta measurements relative to Vienna Peedee belemnite (VPDB) and the potential implications of its withdrawal for all current and future measurements of carbon isotope‐delta values. This perspective summarises the background information regarding the LSVEC material in the context of the VPDB carbon isotope‐delta scale. The various proposals to address the LSVEC problem that have been discussed within those committees and networks are also presented. The information herein was used as a foundation for discussions at the 2024 IAEA Consultancy Meetings on the Development of IAEA Stable Isotope Reference Materials and Related Products and on the Definition and Realisation of the Isotopic Delta Scales for Light Elements (22–26 January 2024, Vienna, Austria). A summary of those 2024 meetings and associated outcomes can be found elsewhere. [ABSTRACT FROM AUTHOR]

Summary: To evaluate the nutritional modes of orchids associated with 'rhizoctonia' fungi, analyses of hydrogen (δ2H), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios are usually adopted. However, previous studies have not fully accounted for exchangeable hydrogens, which could affect these evaluations.Here, we performed standard δ13C, δ15N, and δ2H analyses on bulk samples. Additionally, we conducted δ2H analysis on α‐cellulose and cellulose nitrate samples to investigate whether the heterogeneity of exchangeable hydrogens among plant species influences the assessment of nutritional modes.The δ2H of orchids were consistently higher than those of surrounding autotrophic plants, irrespective of the three pretreatments. Although the rhizoctonia‐associated orchid exhibited lower δ13C, its δ2H was higher than those of the autotrophs. Notably, among all response variables, δ15N and δ2H exhibited high abilities for discriminating the nutritional modes of rhizoctonia‐associated orchids.These results indicate that a time‐efficient bulk sample analysis is an effective method for evaluating plant nutritional modes, as the heterogeneity of exchangeable hydrogens does not significantly impact the estimation. Using δ15N and δ2H benefits the assessment of partial mycoheterotrophy among rhizoctonia‐associated orchids. [ABSTRACT FROM AUTHOR]

Fishing has significant trophodynamic impacts on marine communities, including reductions in the mean trophic position (TP) of the ecosystem resulting from a decrease in the abundance and size of species and individuals with high TPs. This study demonstrates the erosion of fish TP, an additional process that results in lower TP of individuals of a given size, which may exacerbate the effects of fishing on the food web. A stable isotope approach based on the tRophicPosition Bayesian method was used to quantify the TP of 12 target marine species at a given length, and compare their TP between fishery-restricted areas and trawled areas. The results show a difference in the TP of six benthic and apical nekto-benthic predators, which feed in the median at about 0.5 TP lower in trawled areas. It appears that current 'fishing down marine food webs' analyses may underestimate the trophic effects of fishing. Accounting for changes in trophodynamics of individuals at a given size is important to detect indirect effects through food web interactions. The application of a trawling ban may lead to the restoration of lost trophic structure; however, trophic changes may occur more slowly than changes in biomass. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'. [ABSTRACT FROM AUTHOR]

The landscape theory of food web architecture (LTFWA) describes relationships among body size, trophic position, mobility, and energy channels that serve to couple heterogenous habitats, which in turn promotes long‐term system stability. However, empirical tests of the LTFWA are rare and support differs among terrestrial, freshwater, and marine systems. Further, it is unclear whether the theory applies in highly altered ecosystems dominated by introduced species such as the Laurentian Great Lakes. Here, we provide an empirical test of the LTFWA by relating body size, trophic position, and the coupling of different energy channels using stable isotope data from species throughout the Lake Michigan food web. We found that body size was positively related to trophic position, but for a given trophic position, organisms predominately supported by pelagic energy had smaller body sizes than organisms predominately supported by nearshore benthic energy. We also found a hump‐shaped trophic relationship in the food web where there is a gradual increase in the coupling of pelagic and nearshore energy channels with larger body sizes as well as higher trophic positions. This highlights the important role of body size and connectivity among habitats in structuring food webs. However, important deviations from expectations are suggestive of how species introductions and other anthropogenic impacts can affect food web structure in large lakes. First, native top predators appear to be flexible couplers that may provide food web resilience, whereas introduced top predators may confer less stability when they specialize on a single energy pathway. Second, some smaller bodied prey fish and invertebrates, in addition to mobile predators, coupled energy from pelagic and nearshore energy channels, which suggests that some prey species may also be important integrators of energy pathways in the system. We conclude that patterns predicted by the LTFWA are present in the face of species introductions and other anthropogenic stressors to a degree, but time‐series evaluations are needed to fully understand the mechanisms that promote stability. [ABSTRACT FROM AUTHOR]

Stalagmites are useful archives in reconstructing paleoclimates: most paleoclimate studies used stalagmites that are distributed in specific locations and ages. We examined a stalagmite (GYM-1) collected from Nara Prefecture, central Japan, where limestone areas are limited. Applying 238U–234U method, the ages of GYM-1 were determined as 744 ± 70 to 677 ± 74 ka (based only on analytical uncertainties, 1σ). Even assuming a 10% uncertainty in the initial activity of 234U/238U, (234U/238U)0, this age could be still older than 460 ka. Temperatures calculated based on δD in the fluid inclusions and δ18O in the calcium carbonate ranged from 9.0 to 11.9 °C (10.8 ± 0.9 °C on average) or from 6.0 to 9.1 °C (7.9 ± 0.9 °C on average) depending on the equation. The estimated temperature suggests that GYM-1 formed during an interglacial period of the Middle Pleistocene. Synchronous behavior of isotopic values with lamination likely reflects seasonal temperature in a highly ventilated cave system. [ABSTRACT FROM AUTHOR]

In the lower atmosphere, CO2 emissions impact human health and ecosystems, making data at this level essential for addressing carbon-cycle and public-health questions. The atmospheric concentration of CO2 is crucial in urban areas due to its connection with air quality, pollution, and climate change, becoming a pivotal parameter for environmental management and public safety. In volcanic zones, geogenic CO2 profoundly affects the environment, although hydrocarbon combustion is the primary driver of increased atmospheric CO2 and global warming. Distinguishing geogenic from anthropogenic emissions is challenging, especially through air CO2 concentration measurements alone. This study presents survey results on the stable isotope composition of carbon and oxygen in CO2 and airborne CO2 concentration in Naples' urban area, including the Campi Flegrei caldera, a widespread hydrothermal/volcanic zone in the metropolitan area. Over the past 50 years, two major volcanic unrests (1969–72 and 1982–84) were monitored using seismic, deformation, and geochemical data. Since 2005, this area has experienced ongoing unrest, involving the pressurization of the underlying hydrothermal system as a causal factor of the current uplift in the Pozzuoli area and the increased CO2 emissions in the atmosphere. To better understand CO2 emission dynamics and to quantify its volcanic origin a mobile laboratory was used. Results show that CO2 levels in Naples' urban area exceed background atmospheric levels, indicating an anthropogenic origin from fossil fuel combustion. Conversely, in Pozzuoli's urban area, the stable isotope composition reveals a volcanic origin of the airborne CO2. This study emphasizes the importance of monitoring stable isotopes of atmospheric CO2, especially in volcanic areas, contributing valuable insights for environmental and public health management. [ABSTRACT FROM AUTHOR]

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ13C and δ15N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within‐individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations. [ABSTRACT FROM AUTHOR]

Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (2H) and oxygen-18 (18O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ18O in rainwater exhibit higher variability, resulting in −4.49 ± 3.18 ‰ VSMOW, while δ18O values from the well show minor variations, similar to those of the spring, recording −7.25 ± 0.32 ‰ and −6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model’s outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region. [ABSTRACT FROM AUTHOR]

Numerous geothermal systems are hosted by extensional rifts that transect the Himalayas and Lhasa block in the Himalayan–Tibetan orogen. However, the relationships between hydrogeological processes and geothermal fluid circulation in different tectonic units remain unclear. Here, we report an integrated dataset of chemical and isotopic compositions (including major and trace elements, δD, δ18O, and 87Sr/86Sr) of thermal spring water from the Tingri-Tangra Yumco rift to assess their origins and circulation processes. δ18O (− 21.3 to − 17.0‰) and δD (− 166 to − 135‰) values of thermal springs indicate dominant recharge of meteoric waters from areas with elevation of > 6000 m and minor addition of magmatic fluids. Meteoric water could infiltrate to depths of about 1700–2900 m along the faults, whereby it is influenced by geothermal gradient and/or conductive heat transfer of magmatic fluids. The thermal spring waters are mainly Na-HCO3 type and are controlled by dissolution of silicate and carbonate minerals and mixing with deep fluids. The results of chemical and multicomponent geothermometers indicate reservoir temperatures of 115 − 195 ℃, corresponding to a convection heat flux of 3.96 × 105 J/s to 1.78 × 107 J/s from geothermal systems, which are comparable to that of the low-enthalpy geothermal systems in southern Italy. Geochemical modeling is conducted to assess the water–mineral equilibria in the reservoir. Trace elements and 87Sr/86Sr data suggest spatially variable controlling factors for the rift-related geothermal systems: (1) interaction with granitoid and carbonate in the Himalayas; (2) cold groundwater mixing with that leaching from granite and volcanic rocks in the Lhasa block; (3) the input of vapors from magmatic degassing. The geochemistry of thermal springs associated with extensional rift is largely induced by the interaction between fluid and different reservoir rocks in the Himalayas and Lhasa block. Based on these findings, a genetic model is proposed for exploration and development of geothermal resources in the Tingri-Tangra Yumco rift. [ABSTRACT FROM AUTHOR]

Trace elements released into the atmosphere by human activities, such as fossil fuel combustion, flow into forest ecosystems via wet and dry deposition and can flow out via mountainous stream water. The Kajikawa catchment site in Niigata Prefecture, located on the Sea of Japan side in central Japan, suffers from large amounts of acidic substance deposition due to its geographical conditions and meteorological seasonality and is affected by transboundary air pollution originating from the Asian continent due to northwesterly seasonal winds in winter. This study determined the concentrations of trace elements dissolved in precipitation and stream water to comprehensively evaluate the effects of transboundary air pollution on forest ecosystems. The results showed that the concentrations of trace elements and major inorganic ions in precipitation tended to be high in winter and low in summer. The fluxes of many trace elements also increased in winter, reflecting high precipitation amount. Except for Sr, the enrichment factors of the highly enriched trace elements did not show clear seasonality. Therefore, they were continuously influenced by anthropogenic activities. Furthermore, the stable Pb isotope ratio changed significantly during the observation period; however, this was not explained by seasonal changes. This study revealed that trace elements are transported to the Sea of Japan side in central Japan, especially in winter; however, their quantity and content change in response to changes in local and transboundary air pollution. [ABSTRACT FROM AUTHOR]

Pacific Islands present unique challenges for water resource management due to their environmental vulnerability, dynamic climates, and heavy reliance on groundwater. Quantifying connections between meteoric, ground, and surface waters is critical for effective water resource management. Analyses of the stable isotopes of oxygen and hydrogen in the hydrosphere can help illuminate such connections. This study investigates the stable isotope composition of rainfall on O'ahu in the Hawaiian Islands, with a particular focus on how altitude impacts stable isotope composition. Rainfall was sampled at 20 locations from March 2018 to August 2021. The new precipitation stable isotope data were integrated with previously published data to create the most spatially and topographically diverse precipitation collector network on O'ahu to date. Results show that δ18O and δ2H values in precipitation displayed distinct isotopic signatures influenced by geographical location, season, and precipitation source. Altitude and isotopic compositions were strongly correlated along certain elevation transects, but these relationships could not be extrapolated to larger regions due to microclimate influences. Altitude and deuterium excess were strongly correlated across the study region, suggesting that deuterium excess may be a reliable proxy for precipitation elevation in local water tracer studies. Analysis of spring, rainfall, and fog stable isotope composition from Mount Ka'ala suggests that fog may contribute up to 45% of total groundwater recharge at the summit. These findings highlight the strong influence of microclimates on the stable isotope composition of rainfall, underscore the need for further investigation into fog's role in the water budget, and demonstrate the importance of stable isotope analysis for comprehending hydrologic dynamics in environmentally sensitive regions. [ABSTRACT FROM AUTHOR]

In this study, we explore the utility of stable isotopes of water (δ2H and δ18O) as integrative proxies for evaporative condition in high-mountain tropical lakes using a set of small Ecuadorian lakes in the Cajas National Park. Specifically, we (1) characterize the variability of stable water isotopic composition across several lakes of varying size and depth and (2) determine the evaporation as a fraction of inflow using stable isotopes of water for these lakes. We have used the Hydrocalculator tool for estimation of the evaporation to inflow (E/I) ratio. Results indicated that larger lakes have lower seasonal variability in isotopic composition across their depth compared with the smaller lakes. Further, there was clear seasonal variation across the monthly E/I ratios estimated in several lakes, indicating that evaporation likely plays some (albeit limited) role in the water level variability experienced within a year. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizal (ECM) fungi distribute tree‐derived carbon (C) via belowground hyphal networks in forest ecosystems. Here, we asked the following: (1) Is C transferred belowground to a neighboring tree retained in fungal structures or transported within the recipient tree? (2) Is the overlap of ectomycorrhizal fungi in mycorrhizal networks related to the amount of belowground C transfer?We used potted sapling pairs of European beech (Fagus sylvatica) and North‐American Douglas‐fir (Pseudotsuga menziesii) for 13CO2 pulse‐labeling. We compared 13C transfer from beech (donor) to either beech or Douglas‐fir (recipient) and identified the ECM species. We measured the 13C enrichment in soil, plant tissues, and ECM fractions of fungal‐containing parts and plant transport tissues.In recipients, only fungal‐containing tissue of ectomycorrhizas was significantly enriched in 13C and not the plant tissue. Douglas‐fir recipients shared on average one ECM species with donors and had a lower 13C enrichment than beech recipients, which shared on average three species with donors.Our results support that recently assimilated C transferred belowground is shared among fungi colonizing tree roots but not among trees. In mixed forests with beech and Douglas‐fir, the links for C movement might be hampered due to low mycorrhizal overlap with consequences for soil C cycling. [ABSTRACT FROM AUTHOR]

Flatfish are ecologically diverse species that commonly occur in marine environments, but also in estuarine and riverine habitats. This complicates the examination of the potential role of flatfish in the 'marine fish event horizon', an economic shift in human exploitation from freshwater to marine fish species during the 10–11th centuries CE around the southern North Sea. This study represents the first multi‐disciplinary investigation of flatfish remains to make species‐specific interpretations of flatfish exploitation. Peptide mass fingerprinting and multi‐isotope analysis of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) was performed on collagen from 356 archaeological flatfish and 120 comparative archaeological marine or freshwater species to explore the catch habitat of individual flatfish species between 600 and 1600 CE from the North Sea area. European flounder show signals reflecting both freshwater and marine environments, while other flatfish show only those of marine habitats. A subtle shift towards more marine exploitation towards the end of the period is identified, corresponding to the observed transition in targeted species from flounder to plaice throughout the medieval period. Sites show slight differences in δ13C and δ34S within the same species, related to the local environments. Remarkable is the high abundance of marine plaice and flounder during the early medieval period, which shows clear marine or coastal exploitation of flatfish early on, well before the previously accepted onset of the marine fish event horizon. This indicates a gradual shift from coastal to open marine fish exploitation over the medieval period. [ABSTRACT FROM AUTHOR]

Provenance is becoming increasingly important in meat supply chains as it lends products higher perceived quality. However, its precise definition and interpretation along with its associated characteristics factors have remained somewhat elusive. This review meticulously defines meat provenance while dissecting the essential factors and associated quality attributes that constitute its essence and are subsequently employed to establish pertinent markers for provenance. Meat provenance emerges as a multi‐dimensional construct stemming from the adept management of a constellation of factors relating to geographical origin, farm production system, traceability, and authenticity. Through intricate interactions, these factors unveil innate originality that not only forges a distinct reputation but also imparts a unique typicity to the meat product. Gaining insights into a meat product's provenance becomes attainable by scrutinizing its pertinent composition and organoleptic quality traits. Trace elements and stable isotopes stand out as provenance markers, forging a direct connection to both geographical origin and dietary sources. While somewhat less direct in linkage, other markers such as plant biomarkers, fatty acid composition, pH levels, flavour and aromatic compounds along with organoleptic characteristics contribute to the overall understanding of provenance. Additionally, the identification of animal species and breeds serves as key markers, particularly in the context of protected geographical indications. The study findings are useful for the various stakeholders of how the information for meat provenance can be linked with intrinsic and extrinsic factors for meat quality and protecting the integrity of the supply chain with special reference to traceability and authenticity. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In the 19th century, a lower intertidal macrophyte, Fucus serratus (Linnaeus), from western Europe was introduced to Nova Scotia, Canada, where it successfully established, co-existing with native macrophytes Fucus vesiculosus (Linnaeus) and Ascophyllum nodosum (Linnaeus). We first examined whether a common gastropod in Nova Scotia, Littorina obtusata (Linnaeus, 1758), which grazes on the native macrophytes, has exploited the invasive and on finding this, we secondly examined whether there has been any phenotypic differentiation on the invasive. Among 98 sites surveyed around Nova Scotia and Newfoundland in May and June 1994, 11 had the invasive macrophyte, all of which showed colonization by L. obtusata including egg masses, juveniles, and adults. Among 2135 shells photographed for digital image analyses, those on the invasive differed from those on the native macrophytes with respect to (1) RGB (red/green/blue) channels, (2) HSV (hue, saturation, brightness) phenotypes, (3) protoconch pattern, and (4) adult shell size. Nitrogen and carbon stable isotope signatures on muscle tissues from a subset of L. obtusata indicate foraging fidelity on the invasive rather than temporary occupation. We suggest that these cumulative phenotypic responses to the invasive macrophyte that vary in extent and direction within and among localities reflect localized adaptation and offer a unique opportunity for quantifying early stages of phenotypic and genomic differentiation in a novel ecological niche. [ABSTRACT FROM AUTHOR]

In recent decades, the Eurasian native and invasive gastropod Radix auricularia has been found widely dispersed in the endemic communities of Lake Baikal. A comparative analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes in the foot tissues of individuals of this species and endemics with similar shell sizes, filter-feeding Parabaikalia florii (Baicaliidae) and grazer-scraper Benedictia baicalensis (Benedictiidae), was carried out to identify possible competition for food resources between the three coexisting species. Despite the similarity of the δ15N values (P = 0.37), R. auricularia and P. florii have non-overlapping isotopic niches (P = 0.001), assimilating different components of phytonutrients. Radix auricularia and B. baicalensis differed in the δ15N values (P = 0.001) with a significant overlap of the isotopic niches (P = 0.66) due to the ability of the latter to consume food of animal origin. We additionally discuss the disparities and similarities of the basic components in the food boluses of the alien and endemic species. [ABSTRACT FROM AUTHOR]

Organic geochemical and stable isotope records of Oligocene and late Miocene–Pliocene sediments from IODP hole U1501C and Pliocene–Pleistocene sediments from U1499A of South China Sea (SCS) were studied to investigate clock sources of organic matter and carbonates and their spatiotemporal variations with East Asian climatic variability. Geochemical data was constrained using shipboard information. CaCO3 and total organic carbon contents (wt%) varied between 1.32 to 56.52 and 0.12 to 1.13, respectively. δ13Ccarb, δ18Ocarb and δ13Corg ranged from −4.89 to 1.98‰, −5.54 to 1.96‰, and −24.66 to −28.13‰, respectively. Contributions from mixed sources of carbon were observed in the Oligocene, while the late Miocene–Pleistocene exhibited terrestrial dominance. Early Oligocene carbonate, low and higher TOC are attributed to the opening of SCS, increased terrigenous input, and prevalence of cooler climate. Stable isotopes suggest the expansion of the marine environment and the probable dawning of the East Asian Winter Monsoon (EAWM) during the Oligocene. The late Oligocene marked a transition to a warmer climate. The strengthening of EAWM since the late Miocene is indicated by moderate organic carbon and high carbonates with enriched isotopes. Glacial low sea levels and higher terrestrial inputs increased TOC, while dissolution affected late Plio–early Pleistocene carbonates. Higher carbonates and productivity since the mid-Pleistocene were influenced by alternate weakening and strengthening of EAWM. Research highlights: Organic matter, carbonates, C and O isotopes from Oligocene and late Miocene–Pleistocene sediments, northern SCS. Productivity in the South China Sea fluctuated, being low during the Oligocene, with a subsequent increase since the late Miocene. δ13Corg and δ13Ccarb indicate cold climatic conditions and probable winter monsoon signatures since the early Oligocene, transitioning to warmer conditions during the late Oligocene. During the late Miocene (~8–5.6 Ma), deep-water circulation and intensified winter monsoons led to higher productivity. Pliocene sediments (since ~5.6 Ma) showed signs of climatic cooling, sea level fluctuations, and enhanced winter monsoons with carbonate dilution. The Plio-Pleistocene period witnessed glacial and interglacial cycles reflecting changing monsoon intensities. [ABSTRACT FROM AUTHOR]

Despite years of debate, the factors that control the long-term carrying capacity of human populations are not well understood. In this paper, we assess the effect of changes in resource extraction and climate-driven changes in ecosystem productivity on the carrying capacity of hunter-gatherer populations in a terrestrial and coastal ecosystem. To make this assessment, we build time-series estimates of changes in resource extraction using stable isotopes and ecosystem productivity using paleoclimate models and geomorphic records of flood events. These estimates of resource extraction and ecosystem productivity allow us to assess a complex model of population expansion that proposes linked changes between population density, resource extraction, and intensification. We find that changes in resource extraction had a larger effect on carrying capacity in both the terrestrial and coastal ecosystems than climate drivers of ecosystem productivity. Our results are consistent with the idea that both Malthusian limits on resources and Boserupian pressures to reorganize economic systems operate in hunter-gatherer populations over the long term. Our data and analysis contribute to evaluating complex models of population growth and subsistence change across archaeological cases. [ABSTRACT FROM AUTHOR]

Water is the most important basic need for sustaining life, and groundwater remains the primary source of this need in the coastal area of Semarang City. This indicates that the recharge of the source must be monitored as an important part of water resource management. Therefore, this study aimed to determine the origin of groundwater through the analysis of stable isotopes 18O and ²H, as well as the calculation of the sodium adsorption ratio (SAR) in Semarang City. The purpose is to determine the origin of deep wells and the quality of water for irrigation. The methods used in this study included hydrogeological mapping, testing groundwater samples, and the analysis of stable isotopes 18O and ²H. Semarang City was located in an area with geological components, including the Alluvium and Damar Formation, as well as geological structures such as rectification. Chemical parameter testing was carried out by comparing the SAR aspect of 30 samples with their electrical conductivity (EC). From the analysis of stable isotopes 18O and ²H, most of the samples were obtained from deep groundwater, while 1 was found in shallow aquifers. Furthermore, the stable isotope composition of 29 samples still followed the Global Meteoric Water Line (GMWL), indicating that they were obtained from global rainwater and had experienced mixing. [ABSTRACT FROM AUTHOR]

Salamanders serve as bioindicators of mercury (Hg) in both terrestrial and aquatic habitats and are an important link in the food web between low‐trophic prey and higher‐trophic predators. We investigated the drivers of methylmercury (MeHg) exposure in three common plethodontid salamander species in New York State, USA, including comparisons among regions, habitat types (terrestrial and semiaquatic), and color morphs of Plethodon cinereus (striped and unstriped). Nonlethal tail samples were collected from one terrestrial species (P. cinereus) and two semiaquatic species (Eurycea bislineata and Desmognathus spp.) in the Adirondack Mountains (ADK) and the Finger Lakes National Forest (FLNF) regions. Samples were analyzed for MeHg and stable isotopes, including δ15N and δ13C which are proxies of trophic position and diet, respectively. Despite elevated biota Hg concentrations typically found in the ADK, salamander MeHg concentrations did not differ by region in the terrestrial species and one of the semiaquatic species. In addition, diet and trophic level did not explain MeHg exposure in salamanders. Semiaquatic salamanders exhibited higher MeHg concentrations than terrestrial salamanders in the FLNF only. Within species, only snout–vent length predicted MeHg concentrations in E. bislineata with few other variables significant as predictors of MeHg concentrations in path models. Among P. cinereus individuals in the FLNF, the striped morph had greater MeHg concentrations than the unstriped morph, and food web tracers were not different between morphs. Overall, New York State salamander Hg concentrations were elevated compared to other locations where these species are present. The present study establishes baseline Hg data in salamanders for future assessments of changes in Hg bioavailability to forests of New York State. Environ Toxicol Chem 2024;43:2045–2057. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Mountainous zones are often characterized by complex orography and contacts between different aquifers that usually complicate the use of isotope hydrology techniques. The Apennine chain (Italy) and 10 mountain and mid‐mountain areas belonging to it are the objective of this study. An original isotopic data treatment, able to identify the most probable recharge area for several springs/springs' groups/wells, has been developed. The method consists of a two‐step approach: (1) the determination of the spring/wells computed isotope recharge elevation; (2) an advanced δ18O precipitation distribution model over the study area supported by statistical and GIS‐based procedures implemented by two processes: first, the clipping of precipitation δ18O values (depicted from the δ18O–elevation relationships obtained for each study area) over a most probable recharge area for each analyzed spring or well and, second, the calculation of the overlapping distribution between the spring/well mean δ18O values ± σ and the precipitation δ18O content for each outcropping aquifer. A new regional δ18O gradient covering 150 km latitudinal length of central Italy has been defined. Seven LMWL and δ18O–elevation relationships able to represent the local precipitation isotopic composition have been obtained. The mean elevation of the springs and wells recharge areas have been assessed by a comparison between the obtained gradient with nine δ18O gradients available in the literature and those obtained at a local scale. The new isotopic modeling approach can stress whether the mere isotope modeling based on the stable isotope of oxygen agrees with the hydrogeological setting of the study areas. [ABSTRACT FROM AUTHOR]

Background and Aims The earliest-diverging orchid lineage, Apostasioideae, consists only of two genera: Apostasia and Neuwiedia. Previous reports of Apostasia nipponica indicated a symbiotic association with an ectomycorrhiza-forming Ceratobasidiaceae clade and partial utilization of fungal carbon during the adult stage. However, the trophic strategy of Neuwiedia throughout its development remains unidentified. To further improve our understanding of mycoheterotrophy in the Apostasioideae, this study focused on Neuwiedia malipoensis examining both the mycorrhizal association and the physiological ecology of this orchid species across various development stages. Methods We identified the major mycorrhizal fungi of N. malipoensis protocorm, leafy seedling and adult stages using molecular barcoding. To reveal nutritional resources utilized by N. malipoensis , we compared stable isotope natural abundances (δ 13C, δ 15N, δ 2H, δ 18O) of different developmental stages with those of autotrophic reference plants. Key Results Protocorms exhibited an association with saprotrophic Ceratobasidiaceae rather than ectomycorrhiza-forming Ceratobasidiaceae and the 13C signature was characteristic of their fully mycoheterotrophic nutrition. Seedlings and adults were predominantly associated with saprotrophic fungi belonging to the Tulasnellaceae. While 13C and 2H stable isotope data revealed partial mycoheterotrophy of seedlings, it is unclear to what extent the fungal carbon supply is reduced in adult N. malipoensis. However, the 15N enrichment of mature N. malipoensis suggests partially mycoheterotrophic nutrition. Our data indicated a transition in mycorrhizal partners during ontogenetic development with decreasing dependency of N. malipoensis on fungal nitrogen and carbon. Conclusions The divergence in mycorrhizal partners between N. malipoensis and A. nipponica indicates different resource acquisition strategies and allows various habitat options in the earliest-diverging orchid lineage, Apostasioideae. While A. nipponica relies on the heterotrophic carbon gain from its ectomycorrhizal fungal partner and thus on forest habitats, N. malipoensis rather relies on own photosynthetic carbon gain as an adult, allowing it to establish in habitats as widely distributed as those where Rhizoctonia fungi occur. [ABSTRACT FROM AUTHOR]

Short-term (4 weeks) supplementation with n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has recently been shown to improve protein metabolism in a dose dependent way in normal weight patients with Chronic Obstructive Pulmonary Disease (COPD). Furthermore, EPA/DHA supplementation was able to increase extremity lean soft tissue but not muscle function. No studies are available combining n-3 PUFAs and the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) supplementation in chronic clinical conditions. Whether adding HMB to daily EPA/DHA supplementation for 10 weeks enhances muscle and brain health, daily functional performance, and quality of life of patients with COPD by further improving their protein and amino acid homeostasis remains unknown. Patients with COPD (GOLD: II-IV, n = 46) received daily for 10 weeks, according to a randomized double-blind placebo-controlled three-group design, EPA/DHA (n = 16), EPA/DHA to which HMB was added (n = 14), or placebo (n = 16). The daily dose of 2.0 g of EPA/DHA or soy + corn oil as the placebo was provided via gel capsules, and 3.0 g of Ca-HMB or maltodextrin as placebo as powders. At pre- and post-intervention, a pulse mixture of multiple amino acids was administered to measure postabsorptive net protein breakdown (netPB as primary endpoint) and whole body production (WBP) and conversion rates of the amino acids. As secondary endpoints, lean soft tissue and fat mass were assessed by dual-energy X-ray absorptiometry, upper and lower muscle function by handgrip and single leg isokinetic dynamometry, brain (cognitive, wellbeing) health by assessments, daily functional performance by measuring 6-min walk distance, 4-m gait speed, and postural balance, and quality of life by questionnaire. Plasma enrichments and concentrations were analyzed by LC-MS/MS, and systemic inflammatory profile and metabolic hormones by Luminex. HMB + EPA/DHA but not EPA/DHA supplementation increased postabsorptive netPB (p = 0.028), and WBPs of glutamine (p = 0.024), taurine (p = 0.039), and tyrosine (p = 0.036). Both EPA/DHA and HMB + EPA/DHA supplementation resulted in increased WBP of phenylalanine (p < 0.05). EPA/DHA but not HMB + EPA/DHA was able to increase WBP of arginine (p = 0.030), citrulline (p = 0.008), valine (p = 0.038), and conversion of citrulline to arginine (p = 0.009). Whole body and extremity fat mass were reduced after HMB + EPA/DHA supplementation only, whereas lean soft tissue was increased after EPA/DHA (p = 0.049) and HMB + EPA/DHA (p = 0.073). No other significant findings were observed. Reductions in several proinflammatory cytokines were observed in the HMB + EPA/DHA group including IL-2, IL-17, IL-6, IL-12P40, and TNF-β (p < 0.05). Ten weeks of supplementation with 2 g of EPA/DHA daily is sufficient to induce muscle gain in COPD but HMB is needed to induce fat loss. Whether HMB is solely responsible for the fat mass loss or has a synergistic effect with EPA/DHA remains unclear. The increase in net protein breakdown observed with HMB + EPA/DHA supplementation may indicate a beneficial enhanced protein turnover cycling associated with increased lean soft tissue. ClinicalTrials.gov; NCT03796455. [ABSTRACT FROM AUTHOR]

The Sechelt inlet system (SIS), situated on the inner Sunshine Coast of British Columbia, lies within the territory of the shíshálh Nation. This study focuses on ∼1000 years of shíshálh shellfish harvesting from 930-0 cal. BP. Specifically, we investigated the seasonal timing of shellfish collection, relative shellfish harvesting pressure and paleo-temperature reconstruction at four archaeological sites. Thirty archaeological butter clam shells (Saxidomus gigantea) from the SIS underwent high-resolution shell oxygen isotope (δ18O) analysis and 662 individual archaeological shell fragments were analysed for growth stage determination. The δ18O results showed a pattern of year-round collection with an emphasis on spring collection at village sites. Results from shell growth stage analysis suggest an intensive pattern of shellfish harvesting in the region, regardless of the site type. Archaeological shells show a larger δ18Oshell range, possibly reflecting a greater sea surface temperature amplitude than modern shells (i.e. a difference of ∼6.5°C; modern range: ∼3.7–20.4°C; archaeological range: ∼ −0.8–22.4°C). We contextualise our results with previous studies of seasonal timing and intensity of shellfish harvesting from the Pacific Northwest Coast, while interpreting these new data in the context of shíshálh occupation and landscape use. [ABSTRACT FROM AUTHOR]

In this study we analyse the mobility of complex hunter-gatherers in the Lower Paraná wetland (South America) through δ18O values. To do this, we characterise the isotopic composition of water and bioapatite of stenoic and sedentary species from the region and the surrounding Pampa plain, and then we compare them with those obtained in human bones recovered at local archaeological sites. The results show that humans appear to have developed spatial stability strategies within certain areas, which is consistent with archaeological models of social circumscription among these pre-Columbian populations. Other finding of this study shows that any organism that moves along the middle and lower Paraná valley will not present differences in its δ18O values, but small transverse movements will produce significant variations, which relativises to some degree, the concept of 'local' and 'non-local' in the region. This study also addresses the methodological problems related to the characterisation of δ18O values in irregular environments, highlighting the importance of developing baselines based on local biocenoses. [ABSTRACT FROM AUTHOR]

Renewed excavations at Shimao, the largest stone walled urban site in northern China dating to around 4200–3700 BP, have focused on Shimao's unusual architecture and material culture, but there remains much to be known about the subsistence system and agricultural strategies the inhabitants employed around this site. In this paper we provide new archaeobotanical and isotopic evidence for the agricultural systems and strategies that supported Shimao and nearby sites, from 5000 to 3000 BP. Our data show that the system gradually shifted from one based on common millet as the main staple—requiring a high level of labour-input—to a system dependent on extensive cultivation of foxtail millet, which is better suited to dryland cultivation in colder environments. We argue that this shift in cultivation coincided with regional climate change, and helped sustain early Bronze Age state societies, which fuelled the rapid emergence of social complexity in the semi-arid and arid area of the northern Loess Plateau from 4200 to 3000 BP. [ABSTRACT FROM AUTHOR]

As the urgency to reduce carbon emission increases, seagrass ecosystems have recently received attention due to their capacity to take up and store high amounts of carbon. Protection of this ecosystem is key to increase resilience to climate change. However, in some of the Marine Protected Areas (MPAs), seagrass ecosystems are still under threat. This study aims to investigate the current condition of seagrass ecosystems and compare it to the previous study before MPA was established in the Berau coastal water. SeagrassWatch method was used to measure seagrass community structure. Other proxies were also used to explain factors affecting seagrass condition such as total suspended solid (TSS) and sedimentary stable isotopes to identify the source of organic carbon. The percentage cover of seagrass in this study were categorized as not healthy (<29-59.9%), which was statistically related to TSS. The higher TSS resulted in the lower seagrass cover, as observed in the Rabu Rabu island located adjacent to mainland. Changes in seagrass composition were observed, including the emergence of larger species of E. acoroides and T. hemprichii in the islands located adjacent to mainland. The spatial and temporal changes of seagrass ecosystems observed in Berau MPA should be taken into consideration that conservation on seagrass ecosystems needs to be prioritized by improving the MPA function to avoid further loss of carbon from seagrass ecosystems. [ABSTRACT FROM AUTHOR]

Sea urchin species are ecologically important in the Gulf of California and are becoming popular as a local fishery due to their commercial value. The most abundant species are Echinometra vanbrunti, Eucidaris thouarsii, and Tripneustes depressus. The objective of this study was to evaluate cadmium, lead, copper, zinc, and iron concentrations, as well as stable isotope values in these sea urchin species in the Santa Rosalia mining area (STR), in three sites: Punta Gorda, Punta el Aterrizaje, and Punta Salina. The highest Fe concentration (100.2 mg kg−1) was found in E. vanbrunti, while the highest concentrations of Pb (15.1 mg kg−1), Cu (14.5 mg kg−1), and Zn (347.7 mg kg−1) were recorded in E. thouarsii, and the highest Cd concentration (10.8 mg kg−1) was found in T. depressus. The main health risk of trace metal pollution in STR may be caused by Cd and Pb. δ15N and δ13C values were higher in E. thouarsii and T. depressus, respectively; E. thouarsii has the highest trophic position. Specimen size was not related to metal concentrations, but a positive relationship was observed between specimen size and isotopic values in T. depressus. The three species showed different bioaccumulation patterns for the metals analyzed. Additionally, collection sites and seasons play an important role in the variability of metal concentration. [ABSTRACT FROM AUTHOR]

Reservoir construction promotes many environmental impacts, including the enhancement of mercury concentrations in fish. The processes that can influence mercury concentrations in fish in Amazonian reservoirs are still little explored in depth, especially when we consider the possible particularities of the ecosystems in question. This study aims to investigate how mercury concentrations in fish could be influenced by the Tucuruí dam, considering possible changes in their feeding and trophic position according to the dam position (up or downstream). Fish were sampled upstream and downstream of the Tucuruí reservoir, and total mercury (THg) and stable isotopes of carbon and nitrogen (δ15N and δ13C) were measured in muscles. We observed three different Hg bioaccumulation patterns influenced by the dam. These differences occurred due to species trophic niche changes corroborated by the isotope analysis. Higher THg concentrations downstream compared to those upstream ones were only observed for Geophagus proximus. On the contrary, Plagioscion squamosissimus, from downstream, presented lower concentrations than upstream ones. The isotopic niche of these two species presented different changes according to the sampled site. THg biomagnification was higher upstream compared to downstream, considering that the regression slope was approximately two times higher upstream versus downstream. THg concentrations in fish were explained by the differences in their feeding habits according to their location in relation to the dam. The difference in THg biomagnification was able to reflect differences in structure of the food web chain in ecosystems under the dam's influence. [ABSTRACT FROM AUTHOR]

Isotopes are atoms of an element having the same atomic number but different mass numbers. Isotopes in hydrology and water resources are used for identifying its occurrence, movement, residence times, recharge, and discharge process. Stable isotopes of hydrogen(δ2H) and oxygen(δ2O) are used for identifying the surface and groundwater interactions as they constitute hydrogen and oxygen. In this study oxygen and hydrogen stable isotopes are used to identify surface and groundwater interaction in Old Mahabalipuram Road (OMR) regions of Chengalpattu district. The precipitation, lake, surface, and groundwater were collected during pre-monsoon, monsoon, and post-monsoon seasons. The collected sample is analyzed for stable isotopic compositions of oxygen and hydrogen seasonal-wise. The measured stable isotopic compositions during pre-monsoon season of stable oxygen are -4.29 to -2.00 and stable hydrogen are -29.39 to -24.67. The isotopic compositions during monsoon season range from -4.72 to -4.00 and for hydrogen ranges from -29.39 to -23.50. During monsoon season the depletion of isotopic composition is seen and the enrichment of isotopic composition is observed during pre-monsoon season. The variation in stable isotopic composition of oxygen and hydrogen are observed. A Groundwater Water Meteoric Water Line (GMWL) is developed for the study area, and it is compared with a Local Meteoric Water Line (LMWL) for better interpretation of the results. A slight deviation is observed from that of GMWL to LMWL mostly due to isotopic depletion and evaporation effects. From the analysis, a good correlation exists between precipitation and surface water in the study area indicating about recharge mechanism existing in the study area. The groundwater recharge is observed during monsoon seasons and discharge is more towards the pre-monsoon seasons. [ABSTRACT FROM AUTHOR]

Foundation species support highly productive and valuable ecosystems, but anthropogenic disturbances and environmental changes are increasingly causing foundation species shifts, where one foundation species replaces another. The consequences of foundation shifts are not well understood, as there is limited research on the equivalency of different foundation species and the functions they support. Here, we provide insight into community-level consequences of foundation shifts in the Gulf of Mexico, where the typical marsh foundation species (Spartina alterniflora) is being replaced with a mangrove foundation species (Avicennia germinans), forcing marsh fauna to rely on Avicennia for foundational support. We evaluated the interactions of two common and ecologically valuable basal consumers, fiddler crabs (Uca spp.) and marsh periwinkle snails (Littoraria irrorata), with both foundation species across sites with different levels of mangrove encroachment. By investigating both physical support, measured as habitat association and co-occurrence, and trophic support, as basal resource diet contributions, we found that Avicennia can physically replace Spartina for some consumers, but is not providing equivalent trophic support. Uca and Littoraria commonly occupy encroached sites and associate with mangroves but incorporate almost no mangrove plant matter into their diets. The ultimate consequences of a foundation shift in the case of mangrove encroachment may include shifting energy flows and resource use and decreased populations of basal consumers. Looking at interactions with foundation species from multiple perspectives is necessary to obtain a complete picture of the effects that foundational shifts are having, especially as such shifts are becoming increasingly common. [ABSTRACT FROM AUTHOR]

Macroalgae and phytoplankton support the base of highly productive nearshore ecosystems in cold-temperate regions. To better understand their relative importance to nearshore food webs, this study considered four regions in the northern Gulf of Alaska where three indicator consumers were collected, filter-feeding mussels (Mytilus trossulus), pelagic-feeding Black Rockfish (Sebastes melanops), and benthic-feeding Kelp Greenling (Hexagrammos decagrammus). The study objectives were to (1) estimate the proportional contributions of macroalgal and phytoplankton organic matter using carbon and nitrogen stable isotopes, (2) determine if macroalgal use affected consumer growth using annual growth rings in shells or otoliths, and (3) describe changes in organic matter use and growth during the Pacific Marine Heatwave (PMH; 2014–2016) in one consumer, mussels. Macroalgae were the major organic matter source (> 60%) to the diet for all three consumers. The relationships between macroalgal contribution and growth were neutral for both fish species and significantly positive for mussels. During the PMH, mussels had a drop (> 10%) in macroalgal contributions and grew 45% less than in other time periods. Simultaneously, the relationship between macroalgal contribution and mussel growth was strongest during the PMH, explaining 48% variation compared to 3–12% before or after the PMH. Collectively, the results suggest that macroalgae is likely more important to cold-temperate nearshore food webs than phytoplankton. Management actions aimed at conserving and expanding macroalgae are likely to benefit nearshore food webs under all climate scenarios and especially during marine heatwaves. [ABSTRACT FROM AUTHOR]

Stable isotope techniques are precise methods for studying various aspects of hydrology, such as precipitation characteristics. However, understanding the variations in the stable isotope content in precipitation is challenging in Iran due to numerous climatic and geographic factors. To address this, forty-two precipitation sampling stations were selected across Iran to assess the fractional importance of these climatic and geographic parameters influencing stable isotopes. Additionally, deep learning models were employed to simulate the stable isotope content, with missing data initially addressed using the predictive mean matching (PMM) method. Subsequently, the recursive feature elimination (RFE) technique was applied to identify influential parameters impacting Iran’s precipitation stable isotope content. Following this, long short-term memory (LSTM) and deep neural network (DNN) models were utilized to predict stable isotope values in precipitation. Interpolated maps of these values across Iran were developed using inverse distance weighting (IDW), while an interpolated reconstruction error (RE) map was generated to quantify deviations between observed and predicted values at study stations, offering insights into model precision. Validation using evaluation metrics demonstrated that the model based on DNN exhibited higher accuracy. Furthermore, RE maps confirmed acceptable accuracy in simulating the stable isotope content, albeit with minor weaknesses observed in simulation maps. The methodology outlined in this study holds promise for application in regions worldwide characterized by diverse climatic conditions. [ABSTRACT FROM AUTHOR]

Abstract\nKEY POINTSThe Watershed scheelite deposit is located in an extinct fore-arc basin in the Mossman Orogen of North Queensland. This fore-arc region comprises multiply deformed, Ordovician–Silurian metasedimentary rocks of the Hodgkinson Formation, and it was intruded by Carboniferous–Permian granites of the Kennedy Igneous Association. At Watershed, the Hodgkinson Formation includes strongly deformed skarn-altered conglomerate, psammite and slate units, which record four deformation events that evolved from ductile (D1–3) to brittle–ductile (D4). Early, D1–2 scheelite mineralisation in Carboniferous monzonite and skarn-altered conglomerate formed during regional prograde metamorphism, which reached upper greenschist to lower amphibolite facies conditions. Permian, D4 scheelite mineralisation was deposited in transtensional, shear-related veins, vein haloes and skarn-altered conglomerate during retrograde, lower greenschist facies metamorphism. During D4, four stages of retrograde alteration (retrograde stages 1–4) affected the rocks. Fluid inclusion assemblages in retrograde stage 2, vein scheelite and quartz are characterised by a low-salinity H2O–NaCl ± CH4 fluid (XCH4 <0.01, 1.4–8.0 wt% NaCleq). The fluid inclusions show evidence for fluid mixing between a low (∼0 wt% NaCleq) and a medium (<8 wt% NaCleq) saline fluid. Scheelite mineralisation P–T conditions were determined at ∼300 °C and 1–1.8 kbar (i.e. a depth of 3.7–6.7 km), indicative of a high geothermal gradient (35–75 °C/km), which was likely caused by the heat from the Permian granites. The presence of pyrrhotite and arsenopyrite in D4 veins (retrograde stage 4), plus graphite and methane in the fluid inclusions in scheelite, indicates reduced mineralisation conditions. Oxygen isotope compositions (δ18OVSMOW) of retrograde stage 2 scheelite (+3.8 to +7.3‰), plagioclase (+7.0 to +11.8‰) and quartz (+12.6 to +15.5‰) indicate a fluid temperature of 306 ± 56 °C with δ18OVSMOW values between +4.7 and +8.3‰. Retrograde stage 3 muscovite δDVSMOW (−73.4 to −62.7‰) and δ18OVSMOW (+11.5 to +13.2‰) values were used to calculate the O–H isotopic compositions of the fluids in equilibrium with the minerals at various possible temperatures (250–300 °C). The results are consistent with a metamorphic origin for the mineralising fluid. Sulfur isotope compositions (δ34SCDT between −2.5 and +2.8‰) for vein-hosted, retrograde stage 4 sulfides indicate that sulfur could have come from seawater or seawater sulfate, which is consistent with the local geology, even though this range overlaps with magmatic sulfur isotope compositions. Metamorphic fluids probably originated from devolatilisation reactions in the Hodgkinson Formation during prograde metamorphism. Permian intrusions acted as heat source enhancing metamorphic fluid flow and metal transport.The main economic D4 scheelite mineralisation in veins occur at temperatures of 306 ± 56 °C and depths between 3.7 and 6.7 km.D4 scheelite mineralisation precipitated predominantly from a low- to medium-salinity metamorphic fluid, and with both H2O–NaCl and H2O–NaCl–CH4 compositions.The presence of methane (CH4) plus graphite in some fluid inclusions and the sulfide mineral phases indicates reduced mineralisation conditions.D4 scheelite mineralisation precipitated predominantly from a low- to medium-salinity metamorphic fluid, and with both H2O–NaCl and H2O–NaCl–CH4 compositions.The presence of methane (CH4) plus graphite in some fluid inclusions and the sulfide mineral phases indicates reduced mineralisation conditions. [ABSTRACT FROM AUTHOR]

Nitrogen (N)-fixing symbiosis is critical to terrestrial ecosystems, yet possession of this trait is known for few plant species. Broader presence of the symbiosis is often indirectly determined by phylogenetic relatedness to taxa investigated via manipulative experiments. This data gap may ultimately underestimate phylogenetic, spatial, and temporal variation in N-fixing symbiosis. Still needed are simpler field or collections-based approaches for inferring symbiotic status. N-fixing plants differ from non-N-fixing plants in elemental and isotopic composition, but previous investigations have not tested predictive accuracy using such proxies. Here we develop a regional field study and demonstrate a simple classification model for fixer status using nitrogen and carbon content measurements, and stable isotope ratios (δ15N and δ13C), from field-collected leaves. We used mixed models and classification approaches to demonstrate that N-fixing phenotypes can be used to predict symbiotic status; the best model required all predictors and was 80–94% accurate. Predictions were robust to environmental context variation, but we identified significant variation due to native vs. non-native (exotic) status and phylogenetic affinity. Surprisingly, N content—not δ15N—was the strongest predictor, suggesting that future efforts combine elemental and isotopic information. These results are valuable for understudied taxa and ecosystems, potentially allowing higher-throughput field-based N-fixer assessments. [ABSTRACT FROM AUTHOR]

Nickel stable isotopes (δ60Ni) provide insight to Ni biogeochemistry in the modern and past oceans. Here, we present the first Pacific Ocean high‐resolution dissolved Ni concentration and δ60Ni data, from the US GEOTRACES GP15 cruise. As in other ocean basins, increases in δ60Ni toward the surface ocean are observed across the entire transect, reflecting preferential biological uptake of light Ni isotopes, however the observed magnitude of fractionation is larger in the tropical Pacific than the North Pacific Subtropical Gyre. Such surface ocean fractionation by phytoplankton should accumulate isotopically lighter Ni in the deep Pacific, yet we find that North Pacific deep ocean δ60Ni is similar to previously reported values from the deep Atlantic. Finally, we find that seawater dissolved δ60Ni in regions with hydrothermal input can be either higher or lower than background deep ocean δ60Ni, depending on vent geochemistry and proximity. Plain Language Summary: A habitable Earth relies on the growth of microscopic plants, called phytoplankton, in the ocean. Phytoplankton help regulate Earth's climate and their growth requires various nutrients in seawater, including a suite of metal elements such as iron, zinc, and nickel (Ni). These metals are called trace metals in the ocean because their concentrations are extremely low in seawater, yet they are essential micronutrients. Therefore, it is important to understand how much and how these elements are supplied to and removed out of the ocean, and how they are used by phytoplankton. To study this question, we analyzed Ni isotope ratios of hundreds of seawater samples collected from the Pacific Ocean—which is the ratio of naturally occurring Ni atoms with different numbers of neutrons and therefore slightly different masses. We find that surface seawater is more enriched in heavier Ni isotopes than the deep seawater, in particular around the tropical Pacific. The deep ocean has similar Ni isotope ratios across different ocean basins, from the Atlantic to the Pacific. Seawater Ni isotope ratios are impacted by rivers near Alaska, submarine volcanos near Hawaiʻi, and a submarine volcanic chain called the East Pacific Rise. Key Points: Enrichment of heavier Ni isotopes is observed in the surface ocean across the GP15 transect, particularly in the equatorial PacificNorth Pacific deep ocean Ni isotope composition is nearly homogeneous and similar to previously reported values from other ocean basinsHydrothermal activity can both decrease and increase seawater Ni isotope composition, depending on vent geochemistry and proximity [ABSTRACT FROM AUTHOR]

Chironomids are keystone primary benthic consumers with semi‐aquatic life cycles. They support aquatic and terrestrial consumers at higher trophic levels by conveying dietary nutrients, such as fatty acids. In this study, we combined field sampling and laboratory experiments to examine the effects of environmental parameters, including diet, on fatty acid composition and metabolism in chironomid larvae and imagines. Results from 53 lakes showed that lake size, depth, dissolved organic carbon (DOC) concentrations, and trophic state had only marginal effects on the content of long‐chain polyunsaturated fatty acids (LC‐PUFA) in chironomids. Compound‐specific stable hydrogen isotope analyses confirmed that chironomids actively bioconvert dietary fatty acid precursors to LC‐PUFA in all lake types, independent of nutrient or DOC concentrations. Moreover, fatty acid‐specific stable carbon isotope data indicated that the diet of chironomids was subsidized, particularly in oligotrophic lakes in spring, by terrestrial C18 fatty acid precursors that were converted to LC‐PUFA. Data from feeding experiments further confirmed that decreased dietary availability of LC‐PUFA enhanced the conversion of dietary short‐chain precursors to LC‐PUFA. These results suggest that chironomids are PUFA regulators that can sustain LC‐PUFA levels under varying environmental conditions. Furthermore, our results indicate that they bioconvert terrestrial low‐quality material to high‐quality resources, which, via chironomid emergence, support terrestrial food webs. Chironomids are abundant and widespread, and thus, the trophic transfer of LC‐PUFA can have significant implications for the fitness and production of upper trophic level consumers in both aquatic and terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Beluga whales play a critical role in the subsistence economies and cultural heritage of Indigenous communities across the Arctic, yet the effects of Indigenous hunting on beluga whales remain unknown. Here, we integrate paleogenomics, genetic simulations, and stable δ13C and δ15N isotope analysis to investigate 700 y of beluga subsistence hunting in the Mackenzie Delta area of northwestern Canada. Genetic identification of the zooarchaeological remains, which is based on radiocarbon dating, span three time periods (1290 to 1440 CE; 1450 to 1650 CE; 1800 to 1870 CE), indicates shifts across time in the sex ratio of the harvested belugas. The equal number of females and males harvested in 1450 to 1650 CE versus more males harvested in the two other time periods may reflect changes in hunting practices or temporal shifts in beluga availability. We find temporal shifts and sex-based differences in δ13C of the harvested belugas across time, suggesting historical adaptability in the foraging ecology of the whales. We uncovered distinct mitochondrial diversity unique to the Mackenzie Delta belugas, but found no changes in nuclear genomic diversity nor any substructuring across time. Our findings indicate the genomic stability and continuity of the Mackenzie Delta beluga population across the 700 y surveyed, indicating the impact of Inuvialuit subsistence harvests on the genetic diversity of contemporary beluga individuals has been negligible. [ABSTRACT FROM AUTHOR]

Understanding the key drivers controlling rainfall stable isotope variations in inland tropical regions remains a global challenge. We present novel high‐frequency isotope data (5–30 min intervals) to disentangle the evolution of six stratiform rainfall events (N = 112) during the passage of convective systems in inland Brazil (September 2019–June 2020). These systems produced stratiform rainfall of variable cloud features. Depleted stratiform events (δ18Oinitial ≤ −4.2‰ and δ18Omean ≤ −6.1‰) were characterized by cooler cloud‐top temperatures (≤−38°C), larger areas (≥48 km2), higher liquid‐ice ratios (≥3.1), and higher melting layer heights (≥3.8 km), compared to enriched stratiform events (δ18Oinitial ≥ −3.8‰ and δ18Omean ≥ −5.1‰). Cloud vertical structure variability was reflected in a wide range of δ18O temporal patterns and abrupt shifts in d‐excess. Our findings provide a new perspective to the ongoing debate about isotopic variability and the partitioning of rainfall types across the tropics. Plain Language Summary: Stable water isotopes were used to analyze the formation of stratiform rainfall in the inland tropics of Brazil. The growth of this type of precipitation is associated with continuous condensation‐deposition processes. High‐resolution isotopic variations were analyzed using meteorological information, including satellite products and vertical micro rain radar observations. Our results showed that for stratiform rainfall, clouds with higher temperatures are related to more heavy isotopes, while less heavy isotopes are more frequent for stratiform rainfall coming from colder clouds. Our findings provide a detailed framework to improve isotope enabled models skills to represent the isotopic composition for different cloud types based on observations. Key Points: Weather systems and cloud development modulate rainfall isotope depletionsCloud top temperature, rain area, and water content (liquid‐ice ratio) are key parameters to decipher tropical rainfall isotope variationsIsotopic variations during intra‐evens are controlled by cloud phases, rainfall vertical structure, and the height of the melting layer [ABSTRACT FROM AUTHOR]

Summary: Recent droughts have strongly impacted forest ecosystems and are projected to increase in frequency, intensity, and duration in the future together with continued warming. While evidence suggests that tree diversity can regulate drought impacts in natural forests, few studies examine whether mixed tree plantations are more resistant to the impacts of severe droughts.Using natural variations in leaf carbon (C) and nitrogen (N) isotopic ratios, that is δ13C and δ15N, as proxies for drought response, we analyzed the effects of tree species richness on the functional responses of tree plantations to the pan‐European 2018 summer drought in seven European tree diversity experiments.We found that leaf δ13C decreased with increasing tree species richness, indicating less drought stress. This effect was not related to drought intensity, nor desiccation tolerance of the tree species. Leaf δ15N increased with drought intensity, indicating a shift toward more open N cycling as water availability diminishes. Additionally, drought intensity was observed to alter the influence of tree species richness on leaf δ15N from weakly negative under low drought intensity to weakly positive under high drought intensity.Overall, our findings suggest that dual leaf isotope analysis helps understand the interaction between drought, nutrients, and species richness. [ABSTRACT FROM AUTHOR]

High Ba-Sr granites are geochemically distinct from the more familiar I-, S- and A-types (of igneous, sedimentary or anorogenic/anhydrous/alkaline parentage), in particular by their lack of depletion in Ba and Sr relative to other large-ion lithophile elements (LILE). These differences are sufficient enough to indicate different petrogenetic processes which are still the subject of considerable debate. High Ba-Sr plutons from the classic Caledonian type location in NW Scotland show a range of elemental and isotopic enrichment, ideal for novel petrogenetic investigations such as the application of "non-traditional" stable isotope systems. Two directly comparable plutons have been analysed for Ba and Mg isotopes, from either end of the range of enrichment. Barium isotopes (δ 138/134Ba values of −0.05 to +0.23 ‰ in the relatively "depleted" Strontian pluton and −0.19 to +0.03 ‰ in the enriched Rogart comparator) overlap normal mantle values but extend to lighter compositions, consistent with addition of up to 5 % pelagic sediment that has incorporated variable amounts of biogenic barite. Magnesium isotopes (δ26Mg values of −0.30 to −0.25 ‰ versus −0.42 to −0.23 ‰ in Strontian and Rogart, respectively) lie largely within the normal mantle range, with two light outliers possibly indicative of carbonate involvement but for which fractional crystallization cannot be excluded. Associated relationships between fluid-mobile and melt-mobile elements suggest that sediment melting transfers the crustal isotope signature to a dominantly mantle source, itself variable between isotopically depleted mantle wedge and previously enriched lithospheric mantle. The combined Ba, Mg, O, Sr, and Nd isotope and elemental data are all consistent with a small percentage of pelagic sediment in a mantle source for high Ba-Sr granites, and this is sufficient to disguise these essentially mantle-derived rocks as reworked continental crust. First-order estimates suggest that some 10 % of granites worldwide may have high Ba-Sr character, although the proportion of these that represent largely juvenile origin is currently unknown. Nevertheless, as compositional equivalents of Archean sanukitoids, they may represent unrecognized mantle contributions to crustal growth over some 3 billion years of Earth history. [ABSTRACT FROM AUTHOR]

Low-Mg calcite, precipitating from meteoric fluids, is a common mineral that forms in a variety of near-surface diagenetic environments. However, recent studies, based on a combination of analyses of δ18O and Δ 47 values, have suggested that this mineral might form in disequilibrium and consequently yield kinetic bias in Δ 47 -derived temperatures and fluid δ18O values. Here, we use dual clumped isotope proxies (Δ 47 and Δ 48) to investigate the influence of kinetic isotope effects within different meteoric diagenetic zones of Holocene and Pleistocene carbonates from the southern Florida and the Dominican Republic. In the Miami Oolite, the primary aragonite ooids and secondary low-Mg calcite cements in the bulk sample were separated from each other and their isotopic compositions (δ13C, δ18O, Δ 47 and Δ 48 values) were measured. The Δ 47 and Δ 48 values of the separated aragonite are consistent with the modern ooid sediments and in approximate equilibrium with the surface seawater. In contrast, the low-Mg calcite cement shows the higher Δ 48 and lower Δ 47 values, than expected, with the disequilibrium arising as a result of CO 2 degassing in the vadose zone. Such deviations of Δ 47 and Δ 48 values are also observed in low-Mg calcite vadose cements in the Dominican Republic. While low-Mg calcites formed in the lower freshwater phreatic zone in the Dominican Republic have the Δ 47 - and Δ 48 -derived temperatures close to expected, the same mineral forming near the water-table and upper phreatic zone shows much higher Δ 48 -derived temperatures (up to ∼ 90 °C). The possible origin of such elevated temperatures can be attributed to non-equilibrium processes caused by changes in pH and pCO 2 , mediated by microbial sulfate reduction. Such differential kinetic behavior of Δ 48 values between vadose and phreatic zones could be used as a proxy marker for the presence and the location of a water-table. This study demonstrates the great potential of dual clumped isotopes in the investigation of meteoric diagenesis and will help understand the alteration of ancient sequences and the interpretation of stable C isotope trends that they contain. [ABSTRACT FROM AUTHOR]

A stratigraphic sequence from Ghar-e Boof, a cave site in Iran, covering a period of c. 80,000–30,000 BP and containing more than 20,000 seed and chaff remains, allows a detailed study of the use of annual seed species of Palaeolithic hunter-gatherer groups and its evolution under the influence of changing environmental conditions. Taxonomic changes in the archaeobotanical assemblage and the stable carbon isotope data of pistachio support a considerable change in environmental conditions over the sequence from MIS 5a to MIS 3. The exceptional dominance of wild ancestors of modern crop species, including glume wheat and large-seeded legumes from Middle Palaeolithic layers AH VI (OSL ranges 72–81 ka BP), coincides broadly with the transition from MIS 5a to MIS 4. With the beginning of MIS 4 these taxa are strongly reduced, corresponding with a strong decrease in global CO2 concentrations and in the Δ13C values of Pistacia khinjuk/atlantica from the site. Wild glume wheat completely disappears after Middle Palaeolithic AH Vb and never reappears at the site. We hypothesize that the Middle Palaeolithic niche that allowed the harvesting and consumption of wild cereals and legumes ended with a destabilization of the vegetation in early MIS 4. [ABSTRACT FROM AUTHOR]

The aging of Pb added to soils has not been studied by the isotopic technology because of difficulties in determination of isotopically exchangeable Pb in soil, so that a set of 10 typical agricultural soils in China and a one-year aging experiment with the addition of water-soluble Pb to the soils were carried out. A modified stable isotope dilution technique to determine isotopically exchangeable Pb in soil was developed where 0.2 mM EDTA (ethylenediaminetetraacetic acid) as the extractant. When water-soluble Pb was added to soil, the isotopically exchangeable Pb (Eadd%, the percentage of isotopically exchangeable Pb to total Pb added to soil) initially decreased rapidly and gradually slowly. A semi-mechanistic aging model of Pb added to soils, including precipitation/nucleation (Y1), micropore diffusion (Y2), and organic matter encapsulation processes (Y3) was developed with the root mean square error 8.3% where Y1, Y2, and Y3 accounted for 0.02~26.9%, 1.4~21.8% and 3.8~11.3%, respectively, when the pH 4.0~8.0 and organic matter 2.0~6.0%. Soil pH was a vital factor affecting the aging rate. When the pH increased by 1 unit, the Eadd value decreased by approximately 9%. The model could be used to scale ecotoxicological data of Pb in soil generated in different aging times. [ABSTRACT FROM AUTHOR]

Kinship plays a role at the grassroots of social organization, especially in the Shang and Zhou dynasties, which is an important research topic in China. However, the relationship between diet and the social status of kinship and kinship members has been little explored in previous studies. In this article, 52 skeletal bone collagen samples from humans and buried dogs from three different kinships in the Xisima cemetery in China were analysed by stable C and N isotope analysis to reveal dietary strategies, and thus explore subsistence patterns and social structure. Overall, the mean human δ13C was −8.4‰ ± 1.3‰ (n = 44), with a range of −10.0‰ to −7.4‰, and the mean δ15N was 9.0‰ ± 0.7‰ (n = 44), with a wide range of 7.9–11.1‰, which shows that C4 food dominates people’s diet, and that their diet was varied. There are differences in diet and rank among different kinships. Similar situations exist among kinship members based on platforms. Along with previous research, this study provides unprecedented dietary details of different social stratification from martyrs, common people and small nobles to high‐ranking nobles in order to better understand the hierarchical Shang and Zhou dynasties society based on kinship. [ABSTRACT FROM AUTHOR]

Hydrogen and oxygen-stable isotopes are widely used as tracers of the water cycle, and surface water is an integral part of the water cycle. Compared with other water bodies, surface water is more susceptible to different natural and anthropogenic factors, and an accurate understanding of surface water changes is of great significance in ensuring regional water security, maintaining ecological balance, and promoting sustainable economic and social development. Due to the influence of observation conditions and instrumental analysis, global surface water isotopes' spatial and temporal distribution could be more balanced worldwide. For this reason, we have compiled and analyzed the stable hydrogen and oxygen isotope data in surface water from 22432 sampling stations worldwide from 1956 to 2023, with 102862 data records. The results found that (1) surface water stable isotopes are gradually depleted from the equator to the poles and from the coast to the interior. However, there are significant differences in the spatial and temporal distributions of surface water isotopes in different regions. (2) The variation of stable isotopes in surface water is controlled by geographic location, topographic conditions, and meteorological factors (especially temperature), and its heterogeneity is considerable. The global stable isotope dataset of surface water provides vital information for an in-depth understanding of the water cycle and climate change. It can provide essential data references for global water resource management and research. The Global Surface Water Stable Isotope Dataset is available at https://doi.org/10.17632/fs7rwp7fpr.1 (Zhu, 2024). [ABSTRACT FROM AUTHOR]

Precipitation plays a crucial role in the hydrological cycle and is vital for water resources management, climate change research, and ecosystem conservation. Precipitation stable isotopes serve as the 'fingerprints' of precipitation, which can clearly trace the formation, transport, and subsequent processes of precipitation. However, due to the scarcity of precipitation stable isotope data, we face challenges of temporal discontinuity and spatial heterogeneity when studying it at large to medium scales. Therefore, we compiled precipitation hydrogen and oxygen stable isotope data (δ18O and δ2H) from 2059 global sites spanning from 1961 to 2023, totaling 141,624 records. Our study indicates significant variations of global precipitation stable isotopes both spatially and temporally. Spatially, the isotopic composition of precipitation in different regions varies significantly due to factors such as geographical location, underlying surface conditions, and atmospheric circulation. Temporally, δ18O and δ2H show decreasing trends, while d-excess shows an increasing trend, with the impact of global temperature rise being very apparent. This precipitation stable isotope dataset provides robust support for our understanding of global precipitation changes and climate change. Through further investigation of precipitation stable isotope data, we hope to uncover more mechanisms and influencing factors of precipitation processes, providing a more accurate basis for the assessment and prediction of climate and water resource changes. [ABSTRACT FROM AUTHOR]