Soil δ13C and δ15N baselines clarify biogeographic heterogeneity in isotopic discrimination of European badgers (Meles meles)

Isotopic techniques have been used to study phenomena in the geological, environmental, and ecological sciences. For example, isotopic values of multiple elements elucidate the pathways energy and nutrients take in the environment. Isoscapes interpolate isotopic values across a geographical surface and are used to study environmental processes in space and time. Thus, isoscapes can reveal ecological shifts at local scales, and show distribution thresholds in the wider environment at the macro-scale. This study demonstrates a further application of isoscapes, using soil isoscapes of ¹³C/¹²C and ¹⁵N/¹⁴N as an environmental baseline, to understand variation in trophic ecology across a population of Eurasian badgers (Meles meles) at a regional scale. The use of soil isoscapes reduced error, and elevated the statistical signal, where aggregated badger hairs were used, and where individuals were identified using genetic microarray analysis. Stable isotope values were affected by land-use type, elevation, and meteorology. Badgers in lowland habitats had diets richer in protein and were adversely affected by poor weather conditions in all land classes. It is concluded that soil isoscapes are an effective way of reducing confounding biases in macroscale, isotopic studies. The method elucidated variation in the trophic and spatial ecology of economically important taxa at a landscape level. These results have implications for the management of badgers and other carnivores with omnivorous tendencies in heterogeneous landscapes.

Functional macrophyte trait variation as a response to the source of inorganic carbon acquisition

BACKGROUND

This study aims to compare variation in a range of aquatic macrophyte species leaf traits into three carbon acquisition groups: HCO3 -, free CO2 and atmospheric CO2.

METHODS

The leaf functional traits were measured for 30 species from 30 softwater lakes. Macrophyte species were classified into (1) free CO2, (2) atmospheric CO2 and (3) bicarbonate HCO3 - groups. In each lake we collected water samples and measured eight environmental variables: depth, Secchi depth, photosynthetically active radiation (PAR), pH of water, conductivity, calcium concentration, total nitrogen and total phosphorus. In this study we applied the RLQ analysis to investigate the relationships between species functional traits (Q) and their relationship with environmental variables (R) constrained by species abundance (L).

RESULTS

The results showed that: (1) Aquatic macrophytes exhibited high leaf trait variations as a response to different inorganic carbon acquisition; (2) Traits of leaves refer to the acquisition of carbon for photosynthesis and serve to maximise this process; (3) In the wide softwater habitat, macrophyte species exhibited an extreme range of leaf economic spectrum (leaf area, leaf dry weight and specific leaf area) and wide range of shape trait expressed as circularity; (4) Macrophyte leaf traits are the result of adaptation to carbon acquisition in ambient environment.

Multiproxy Holocene Fire Records From the Tropical Savannas of Northern Cape York Peninsula, Queensland, Australia

Paleoecology has demonstrated potential to inform current and future land management by providing long-term baselines for fire regimes, over thousands of years covering past periods of lower/higher rainfall and temperatures. To extend this potential, more work is required for methodological innovation able to generate nuanced, relevant and clearly interpretable results. This paper presents records from Cape York Peninsula, Queensland, Australia, as a case study where fire management is an important but socially complex modern management issue, and where palaeofire records are limited. Two new multiproxy palaeofire records are presented from Sanamere Lagoon (8,150–6,600 cal BP) and Big Willum Swamp (3,900 cal BP to present). These records combine existing methods to investigate fire occurrence, vegetation types, and relative fire intensity. Results presented here demonstrate a diversity of fire histories at different sites across Cape York Peninsula, highlighting the need for finer scale palaeofire research. Future fire management planning on Cape York Peninsula must take into account the thousands of years of active Indigenous management and this understanding can be further informed by paleoecological research.

Determination of enantiomeric and stable isotope ratio fingerprints of active secondary metabolites in neroli (Citrus aurantium L.) essential oils for authentication by multidimensional gas chromatography and GC-C/P-IRMS

Neroli essential oil (EO), extracted from bitter orange blossoms, is one of the most expensive natural products on the market due to its poor yield and its use in fragrance compositions, such as cologne. Multiple adulterations of neroli EO are found on the market, and several authentication strategies, such as enantioselective gas chromatography (GC) and isotope ratio mass spectrometry (IRMS), have been developed in the last few years. However, neroli EO adulteration is becoming increasingly sophisticated, and analytical improvements are needed to increase precision. Enantiomeric and compound-specific isotopic profiling of numerous metabolites using multidimensional GC and GC-C/P-IRMS was carried out. These analyses proved to be efficient for geographical tracing, especially to distinguish neroli EO of Egyptian origin. In addition, δ²H values and enantioselective ratios can identify an addition of 10% of petitgrain EO. These results demonstrate that enantioselective and stable isotopic metabolite fingerprint determination is currently a necessity to control EOs.

Analysis of 14C, 13C and Aspartic Acid Racemization in Teeth and Bones to Facilitate Identification of Unknown Human Remains: Outcomes of Practical Casework

The identification of unknown human remains represents an important task in forensic casework. If there are no clues as to the identity of the remains, then the age, sex, and origin are the most important factors to limit the search for a matching person. Here, we present the outcome of application of so-called bomb pulse radiocarbon (14C derived from above-ground nuclear bomb tests during 1955-1963) analysis to birthdate human remains. In nine identified cases, 14C analysis of tooth crowns provided an estimate of the true date of birth with an average absolute error of 1.2 ± 0.8 years. Analysis of 14C in tooth roots also showed a good precision with an average absolute error of 2.3 ± 2.5 years. Levels of 14C in bones can determine whether a subject has lived after 1955 or not, but more precise carbon turnover data for bones would be needed to calculate date of birth and date of death. Aspartic acid racemization analysis was performed on samples from four cases; in one of these, the year of birth could be predicted with good precision, whereas the other three cases are still unidentified. The stable isotope 13C was analyzed in tooth crowns to estimate provenance. Levels of 13C indicative of Scandinavian provenance were found in known Scandinavian subjects. Teeth from four Polish subjects all showed higher 13C levels than the average for Scandinavian subjects.

Trophic ecology of a Late Pleistocene early modern human from tropical Southeast Asia inferred from zinc isotopes

Tam Pà Ling, a cave site in northeastern Laos, has yielded the earliest skeletal evidence of Homo sapiens in mainland Southeast Asia. The reliance of Pleistocene humans in rainforest settings on plant or animal resources is still largely unstudied, mainly due to poor collagen preservation in fossils from tropical environments precluding stable nitrogen isotope analysis, the classical trophic level proxy. However, isotopic ratios of zinc (Zn) in bioapatite constitute a promising proxy to infer trophic and dietary information from fossil vertebrates, even under adverse tropical taphonomic conditions. Here, we analyzed the zinc isotope composition (⁶⁶Zn/⁶⁴Zn expressed as δ⁶⁶Zn value) in the enamel of two teeth of the Late Pleistocene (63-46 ka) H. sapiens individual (TPL1) from Tam Pà Ling, as well as 76 mammal teeth from the same site and the nearby Nam Lot cave. The human individual exhibits relatively low enamel δ⁶⁶Zn values (+0.24‰) consistent with an omnivorous diet, suggesting a dietary reliance on both plant and animal matter. These findings offer direct evidence of the broad utilization of resources from tropical rainforests by one of the earliest known anatomically modern humans in Southeast Asia.

Stable isotopes reveal intensive pig husbandry practices in the middle Yellow River region by the Yangshao period (7000-5000 BP)

It is well-known that pigs (Sus scrofa) were domesticated very early in Neolithic China, but far less is known about the processes by which pig husbandry intensified so that pork became the most important animal protein for humans are less clear. Here, we explore pig feeding practices using the carbon and nitrogen isotope composition of bone collagen, focusing on developments in pig husbandry during the Yangshao period (7000-5000 BP) in the middle Yellow River region of China, and at the site of Xipo (5800-5000 BP) in particular. The results show that the diets of domestic pigs at Xipo were dominated by millet foods. Comparisons with other Yangshao sites in the region show a trend of increasing millet foddering for pigs throughout the Yangshao period. These results, and comparisons of the isotopic data for pigs against those for humans from the Xipo cemetery (5300-5000 BP), suggest that pigs were closely managed by humans. The evidence points to an intensification of Neolithic pig husbandry in the middle Yellow River region from this period.

Cattle management in an Iron Age/Roman settlement in the Netherlands: Archaeozoological and stable isotope analysis

Cattle were the predominant domestic animal in the Iron Age and Roman Netherlands, yet their management is still incompletely understood. Some aspects of cattle management, such as birth season and the provision of fodder, have received little or no attention so far. This paper is the first to investigate these aspects for the Iron Age and Roman Netherlands, through a case study of the site of Houten-Castellum. The rural settlement of Houten-Castellum was inhabited from the Middle Iron Age to the Middle Roman period, allowing a comparison between the Iron Age and Roman period. Excavations at this site have yielded a large, well-preserved animal bone assemblage. This paper investigates cattle husbandry by using an integrated approach, combining a multi-isotope analysis (oxygen, carbon and strontium) with archaeozoological and archaeobotanical results from Houten-Castellum and comparing the results with archaeobotanical evidence for fodder and evidence for dairy use for the Iron Age and Roman Netherlands in general. While our data set is small and results must therefore be interpreted cautiously, there is convincing evidence for an extended birth season in the Middle Iron Age, as well as the use of fodder.

Can stable isotopes quantify soil carbon build-up from organic fertilizers?

The application of organic fertilizers (OF) can supply carbon (C) to the soil in crop fields. OF-derived C (OF-C) is often estimated using the differential method that can be biased due to indirect effects of OF on soil C. This study tested three methods to quantify OF-C: (i) the widespread differential method, (ii) the synchronic isotope method comparing plots with and without OF and (iii) the asynchronic isotope method mimicking a trial without a control plot. These methods were implemented on an Arenosol and an Andosol supplied during 13 years with slurry or compost. The results highlighted the relevance of using the synchronic isotope method, which focuses on the direct effect of OFs on the soil organic matter (without bias of vegetation change) and considers control soil's evolution. The higher the isotopic difference between soil and OF, the shorter the method implementation time needed: for an initial difference of 7.5 ‰ and 3.5 ‰, quantification is suitable after 4 and 9 years of fertilization respectively. Attention should be paid to OF-δ¹³C variability to guarantee the method validity. The method proved to be suitable to study the factors controlling the OF-C fate in tropical soils.

A chimpanzee enamel-diet δ13C enrichment factor and a refined enamel sampling strategy: Implications for dietary reconstructions

Reconstructing diets from stable carbon isotopic signals in enamel bioapatite requires the application of a δ¹³C enamel-diet enrichment factor, or the isotopic offset between diet and enamel, which has not been empirically determined for any primate. In this study, an enamel-diet enrichment factor (ε∗_enamel-diet) of 11.8 ± 0.3‰ is calculated for chimpanzees (Pan troglodytes) at Ngogo in Kibale National Park, Uganda, based on a comprehensive isotopic assessment of previously analyzed dietary plant data and new isotopic analyses of enamel apatite. Different enamel sampling methods are evaluated to determine the potential influence of weaning on isotopic enamel values and dietary interpretations. The new chimpanzee enrichment factor and a sampling strategy that excludes teeth that formed before weaning completion are applied to all known chimpanzee δ¹³C_enamel data, either previously published or newly derived in this study, resulting in a dietary range of almost 6‰ across all chimpanzees sampled. This new chimpanzee enamel-diet enrichment factor is then used to reassess dietary reconstructions of 12 fossil hominin species whose isotopic enamel signatures have been determined. Results reveal hominin diets that are isotopically more positive than previously reconstructed, highlighting the widespread contribution of ¹³C-enriched C₄/crassulacean acid metabolism (CAM) resources in fossil hominin diets and emphasizing the broad use of these resources during human evolution. These findings stress the importance of ascertaining and employing an appropriate enrichment factor for dietary reconstructions of specific taxa as well as standardizing the sampling protocol for tooth enamel in isotopic paleodietary reconstructions.

Changes of lake organic carbon sinks from closed basins since the Last Glacial Maximum and quantitative evaluation of human impacts

BACKGROUND

Closed basins occupy 21% of the world's land area and can substantially affect global carbon budgets. Conventional understanding suggests that the terminal areas of closed basins collect water and carbon from throughout the entire basin, and changes in lake organic carbon sinks are indicative of basin-wide organic carbon storages. However, this hypothesis lacks regional and global validation. Here, we first validate the depositional process of organic carbon in a typical closed-basin region of northwest China using organic geochemical proxies of both soil and lake sediments. Then we estimate the organic carbon sinks and human impacts in extant closed-basin lakes since the Last Glacial Maximum (LGM).

RESULTS

Results show that 80.56 Pg organic carbon is stored in extant closed-basin lakes mainly found in the northern mid-latitudes. Carbon accumulation rates vary from 17.54 g C m^-2 yr^-1 during modern times, 6.36 g C m^-2 yr^-1 during the mid-Holocene and 2.25 g C m^-2 yr^-1 during the LGM. Then, we evaluated the influence by human activities during the late Holocene (in the past three thousand years). The ratio of human impacts on lake organic carbon storage in above closed basins is estimated to be 22.79%, and human-induced soil organic carbon emissions in the past three thousand years amounted to 207 Pg.

CONCLUSIONS

While the magnitude of carbon storage is not comparable to those in peatland, vegetation and soil, lake organic carbon sinks from closed basins are significant to long-term terrestrial carbon budget and contain information of climate change and human impact from the whole basins. These observations improve our understanding of carbon sinks in closed basins at various time scales, and provide a basis for the future mitigation policies to global climate change.

The qNMR Summit 5.0: Proceedings and Status of qNMR Technology

The goal of the qNMR Summit is to take stock of the status quo and the recent developments in qNMR research and applications in a timely and accurate manner. It provides a platform for both advanced and novice qNMR practitioners to receive a well-rounded update and discuss potential qNMR-related applications and collaborations. For over a decade, scientists from academia, industry, nonprofit institutions, and governmental bodies have focused on the standardization of qNMR methodology, as well as its metrological and pharmacopeial utility. This paper reviews key content of qNMR Summits 1.0 to 4.0 and puts into perspective the outcomes and available transcripts of the October 2019 Summit 5.0, with attendees from the United States, Canada, Japan, Korea, and several European countries. Summit presentations focused on qNMR methodology in the pharmaceutical industry, advanced quantitation algorithms, and promising developments.

The genetic architecture of leaf stable carbon isotope composition in Zea mays and the effect of transpiration efficiency on leaf elemental accumulation

With increased demand on freshwater resources for agriculture, it is imperative that more water-use efficient crops are developed. Leaf stable carbon isotope composition, δ13C, is a proxy for transpiration efficiency and a possible tool for breeders, but the underlying mechanisms effecting δ13C in C4 plants are not known. It has been suggested that differences in specific leaf area (SLA), which potentially reflects variation in internal CO2 diffusion, can impact leaf δ13C. Furthermore, although it is known that water movement is important for elemental uptake, it is not clear how manipulation of transpiration for increased water-use efficiency may impact nutrient accumulation. Here, we characterize the genetic architecture of leaf δ13C and test its relationship to SLA and the ionome in five populations of maize. Five significant QTL for leaf δ13C were identified, including novel QTL as well as some that were identified previously in maize kernels. One of the QTL regions contains an Erecta-like gene, the ortholog of which has been shown to regulate transpiration efficiency and leaf δ13C in Arabidopsis. QTL for δ13C were located in the same general chromosome region, but slightly shifted, when comparing data from two different years. Our data does not support a relationship between δ13C and SLA, and of the 19 elements analyzed, only a weak correlation between molybdenum and δ13C was detected. Together these data add to the genetic understanding of leaf δ13C in maize and suggest that improvements to plant water use may be possible without significantly influencing elemental homeostasis.

Methane emissions and δ13C composition from beef steers consuming increasing proportions of sericea lespedeza hay on bermudagrass hay diets

An experiment was conducted to evaluate the effects of different proportions of 'Au Grazer' sericea lespedeza [SL, Lespedeza cuneata (Dum. Cours.) G. Don], a legume rich in condensed tannins (CT), on nutrient intake and digestibility, and to estimate methane (CH4) emissions and 13C isotopic composition (δ13CCH4) from beef steers consuming a forage-based diet. Twenty-five Angus-crossbred steers were distributed in a randomized complete block design (344 ± 48 kg initial BW), and randomly assigned to one of five treatments: 0SL, 25SL, 50SL, 75SL, and 100SL, diets containing 0%, 25%, 50%, 75%, and 100% of SL hay, respectively, mixed with 'Tifton-85' bermudagrass hay (Cynodon spp.). The study was carried out for two experimental periods of 21-d each. The statistical model included the fixed effect of treatment and random effects of block, experimental period, and their interaction. Apparent total tract digestibility of crude protein, neutral detergent fiber, and acid detergent fiber was linearly decreased (P < 0.001) by the inclusion of SL. No effects were observed for total CH4 emissions per day, nor for CH4 relative to organic matter intake or digestible organic matter with the inclusion of SL. However, emission of CH4 in relation to intake of CT was affected by treatment (P < 0.001). A linear (P < 0.001) decrease and a quadratic effect (P < 0.001) were observed for δ13C of diets and gas, respectively, in which diets and enteric CH4 with greater inclusion of SL were more depleted in 13C. Moreover, the difference in δ13C between diets and gas (Δδ13C) had a linear decrease (P = 0.001) with the inclusion of SL. The model developed to predict the C3 proportions in the enteric CH4 fitted to predicted values (P < 0.0001). Therefore, greater proportions of SL resulted in lesser CH4 emission when CT intake was considered and the isotopic composition from enteric CH4 was able to predict the contribution of SL in the emissions.

Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana, the world's highest elevation tree species

Tree growth is generally considered to be temperature limited at upper elevation treelines, yet climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polylepis tarapacana Philipi, the world's highest elevation tree species, which is found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4400 m in elevation, along a 500 km latitude aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon sink processes along the gradient. Current growing-season temperature regulated RWI at northern-wetter sites, while prior growing-season precipitation determined RWI at arid southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site water availability. By contrast, warm and dry growing seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes along the gradient. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. This manuscript also highlights a coupling (decoupling) between physiological processes at leaf level and wood formation as a function of similarities (differences) in their climatic sensitivity. This study contributes to a better understanding and prediction of the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

Biomagnification and trophic transfer of total mercury and methylmercury in a sub-tropical montane forest food web, southwest China

Little is known about the bioaccumulation and trophic transfer of total mercury (THg) and methylmercury (MeHg) via food webs in terrestrial ecosystems, especially in subtropical forest ecosystems. In the present study, THg and MeHg were determined as well as the carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope composition in samples of soils, plants, invertebrates, and songbird feathers to construct food webs in a remote subtropical montane forest in Mt. Ailao, southwest China and assess the bioaccumulation, biomagnification, and trophic transfer of Hg. Results showed that the trophic levels (TLs) of all consumers ranged from 0.8 to 3.3 and followed the order of songbirds > spiders > omnivorous insects > herbivorous insects > plants, and THg and MeHg exhibited a clear biomagnification up the food chain from plants-herbivorous/omnivorous insects-spiders-songbirds. The lowest MeHg concentration was observed in pine needles ranged from 0.104 to 0.949 ng g^-1 with only a 1.6% ratio of MeHg to THg (MeHg%), while the highest MeHg concentrations ranged from 425 to 5272 ng g^-1 in songbirds with MeHg% values of up to 96%. High values of trophic magnification slope (TMS) for THg (0.22) and MeHg (0.38) were observed in plant-invertebrate-songbird food chain, verifying the significant bioaccumulation of Hg, particularly MeHg, in the remote subtropical forest ecosystem. This study confirmed the production and efficient biomagnification of MeHg in remote subtropical montane forest and the significant bioaccumulation of MeHg in terrestrial top predators.

Evolution of crassulacean acid metabolism (CAM) as an escape from ecological niche conservatism in Malagasy Bulbophyllum (Orchidaceae)

Despite growing evidence that niche shifts are more common in flowering plants than previously thought, little is known of whether such shifts are promoted by changes in photosynthetic pathways. Here we combine the most complete phylogeny for epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope ratios to infer the group's spatial-temporal history, and the role of strongly expressed crassulacean acid metabolism (CAM) in facilitating niche shifts and diversification. We find that most extant species still retain niche (Central Highland) and photosynthesis (C₃ ) states as present in the single mid-Miocene (c. 12.70 million yr ago (Ma)) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub-humid highland first into the island's humid eastern coastal, and then into the seasonally dry 'Northwest Sambirano' rainforests, yet without significant effect on diversification rates. These findings indicate that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary 'gateway' trait that considerably widened the spatial-ecological amplitude of Madagascar's most species-rich orchid genus.

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

Assessment of Pollution Sources and Contribution in Urban Dust Using Metal Concentrations and Multi-Isotope Ratios (13C, 207/206Pb) in a Complex Industrial Port Area, Korea

The metal concentrations and isotopic compositions (13C, 207/206Pb) of urban dust, topsoil, and PM10 samples were analyzed in a residential area near Donghae port, Korea, which is surrounded by various types of industrial factories and raw material stockpiled on empty land, to determine the contributions of the main pollution sources (i.e., Mn ore, Zn ore, cement, coal, coke, and topsoil). The metal concentrations of urban dust in the port and residential area were approximately 85~112 times higher (EF > 100) in comparison with the control area (EF < 2), especially the Mn and Zn ions, indicating they were mainly derived from anthropogenic source. These ions have been accumulating in urban dust for decades; furthermore, the concentration of PM10 is seven times higher than that of the control area, which means that contamination is even present. The isotopic (13C, 207/206Pb) values of the pollution sources were highly different, depending on the characteristics of each source: cement (−19.6‰, 0.8594‰), Zn ore (−24.3‰, 0.9175‰), coal (−23.6‰, 0.8369‰), coke (−27.0‰, 0.8739‰), Mn ore (−24.9‰, 0.9117‰), soil (−25.2‰, 0.7743‰). As a result of the evaluated contributions of pollution source on urban dust through the Iso-source and SIAR models using stable isotope ratios (13C, 207/206Pb), we found that the largest contribution of Mn (20.4%) and Zn (20.3%) ions are derived from industrial factories and ore stockpiles on empty land (Mn and Zn). It is suggested that there is a significant influence of dust scattered by wind from raw material stockpiles, which are stacked near ports or factories. Therefore, there is evidence to support the idea that port activities affect the air quality of residence areas in a city. Our results may indicate that metal concentrations and their stable isotope compositions can predict environmental changes and act as a powerful tool to trace the past and present pollution history in complex contexts associated with peri-urban regions.

Authenticity and the Potability of Coconut Water - a Critical Review

BACKGROUND

The content of the endosperm of the coconut (Cocos nucifera L.) contains "coconut water". This practically sterile liquid which is prized for its delicate, albeit labile, flavor when fresh, has had a recent dramatic increase in global demand. The organoleptic superiority of water from young coconuts means that degree of maturity at harvesting is the most influential factor in yield and composition.

OBJECTIVE

To provide a guide to establishing the authenticity and the potability of samples of coconut water.

METHOD

Review and evaluate the literature on the factors that determine the composition and stability of coconut water.

RESULTS

Data is presented on the variances in natural composition, maturity, processing-induced compositional changes, adulterations, product recalls, classical and instrumental methods of analysis and on the available composition standards of coconut water.

CONCLUSIONS

Advice is provided for official food analysts, and others, on prudent approaches as how to ascertain the authenticity and potability, or otherwise, of coconut water samples.

How spatial and dietary overlap with domestic livestock affect African wild ass nutrition on the Messir Plateau (Eritrea)

Competition with livestock over forage resources has been identified as a potential threat to the survival of the African wild ass (Equus africanus) in the Danakil ecosystem (Eritrea). The Messir Plateau is an important breeding area for the African wild ass but also hosts cattle, sheep, goats, donkeys, and camels. Locations and fecal samples of African wild ass and livestock were collected in dry and rainfall months. Stable carbon isotopes [δ 13C ‰] in fecal samples were used to assess diet composition and overlaps with domestic herbivores. Fecal samples also were used to assess the nutritional quality of African wild ass and domestic donkey diets. During the dry months, African wild ass were concentrated in the northern section of the Messir Plateau, approximately 9 km from the permanent water source, and overlapped spatially with local livestock. During the rainfall months, African wild ass dispersed throughout the Messir Plateau (124 km2) when a high number of livestock, particularly cattle from the highlands with herders, were concentrated in the northern section. During the rainfall months, the northern section had relatively better vegetation cover and access to seasonal water. The grass contribution to the diet of the African wild ass in both dry and rainfall months overlapped significantly with that of domestic donkeys and cattle. In rainfall months, the percent fecal nitrogen and phosphorus contents of African wild ass were significantly lower than those of domestic donkey samples. The lower nutrient levels in fecal samples of African wild ass during rainfall months may be due to their displacement from the northern sector by the high number of immigrant highland cattle with people. Our work provides evidence as to how the presence of domestic herbivores, particularly cattle, may negatively impact the nutrient level of wild equids and threaten the survival of the critically endangered African wild ass.

Assessment of bias in carbon isotope composition of organic leaf matter due to pre-analysis milling methods

RATIONALE

Stable isotope analysis of leaf material has many applications including assessment of plant water-use efficiency and palaeoclimatology. To facilitate interpretations of small shifts in the carbon isotope composition (δ13 C) of leaves, accurate and repeatable results are required. Pre-sample homogenisation is essential to ensure a representative sample is analysed, but can also introduce error.

METHODS

We investigate how different grinding methods (freezer-milling and ball-milling) affect the carbon content and δ13 C of tree leaves from a wetland in Queensland, Australia, commenting on how increased temperature, sample contamination, sample loss or poor homogenisation may impact results.

RESULTS

No alteration of leaf δ13 C is observed due to different milling methods, although there may be a significant increase in %C of samples processed using ball-milling.

CONCLUSIONS

We suggest %C variability is possibly due to contamination from abraded plastic vials or insufficient homogenisation during ball-milling, with no significant impact on δ13 C. Overall, we suggest that intermittent ball-milling may be the best solution to reduce costs, preparation time and use of liquid nitrogen, aiming to achieve complete homogenisation using the shortest possible duration of milling.

CO2 fertilization of Sphagnum peat mosses is modulated by water table level and other environmental factors

Sphagnum mosses account for most accumulated dead organic matter in peatlands. Therefore, understanding their responses to increasing atmospheric CO₂ is needed for estimating peatland C balances under climate change. A key process is photorespiration: a major determinant of net photosynthetic C assimilation that depends on the CO₂ to O₂ ratio. We used climate chambers to investigate photorespiratory responses of Sphagnum fuscum hummocks to recent increases in atmospheric CO₂ (from 280 to 400 ppm) under different water table, temperature, and light intensity levels. We tested the photorespiratory variability using a novel method based on deuterium isotopomers (D6^S /D6^R ratio) of photosynthetic glucose. The effect of elevated CO₂ on photorespiration was highly dependent on water table. At low water table (-20 cm), elevated CO₂ suppressed photorespiration relative to C assimilation, thus substantially increasing the net primary production potential. In contrast, a high water table (~0 cm) favored photorespiration and abolished this CO₂ effect. The response was further tested for Sphagnum majus lawns at typical water table levels (~0 and -7 cm), revealing no effect of CO₂ under those conditions. Our results indicate that hummocks, which typically experience low water table levels, benefit from the 20th century's increase in atmospheric CO₂ .

Niche-trait relationships at individual and population level in three co-occurring passerine species

The niche variation hypothesis (NVH) predicts that populations with wider niches exhibit greater morphological variation through increased interindividual differences in both niche and morphology. In this study, we examined niche-trait relationships in three passerine species (Cyanoderma ruficeps, Sinosuthora webbiana, and Zosterops simplex). A total of 289 C. ruficeps from 7 sites, 259 S. webbiana from 8 sites, and 144 Z. simplex from 6 sites were sampled along an elevation gradient (0-2,700 m) in Taiwan from 2009 to 2017. We measured bill traits (length, width, and depth of bill) and body size traits (length of head, tarsus, and wing) of the birds, which were reduced to four principal components (bill PC1, bill PC2, body size PC1, and body size PC2). We collected feather tissues for stable carbon and nitrogen isotope analyses to quantify their isotope niche. We quantified interindividual differences in isotope space and trait space with four diversity metrics (divergence, dispersion, evenness, and uniqueness) and tested whether interindividual differences in isotope space and trait space are positively associated. We quantified population isotope niche width by Bayesian ellipse area and population morphological variation by variances of the PCs. The results showed that individual uniqueness in isotope niche and bill morphology (average closeness of individuals within the population isotope/trait space) were positively associated across three species. Furthermore, isotope niche width and bill PC1 (reflecting the size of bill) variation at population level were also positively associated across the three species, supporting the NVH. Of the three species, C. ruficeps and S. webbiana showed stronger support for the NVH than Z. simplex, possibly due to the latter having narrower elevational distribution and a more specialized, plant-based diet. The diversity metrics represented different aspects of interindividual differences in niche/trait space, and for the passerines, individual uniqueness appeared to play an important role in their niche-trait dynamics.

The carbon isotopic signature of C4 crops and its applicability in breeding for climate resilience

KEY MESSAGE

Carbon isotope discrimination is a promising trait for indirect screening for improved water use efficiency of C4 crops. In the context of a changing climate, drought is one of the major factors limiting plant growth and yield. Hence, breeding efforts are directed toward improving water use efficiency (WUE) as a key factor in climate resilience and sustainability of crop production. As WUE is a complex trait and its evaluation is rather resource consuming, proxy traits, which are easier to screen and reliably reflect variation in WUE, are needed. In C3 crops, a trait established to be indicative for WUE is the carbon isotopic composition (δ13C) of plant material, which reflects the preferential assimilation of the lighter carbon isotope 12C over 13C during photosynthesis. In C4 crops, carbon fixation is more complex and δ13C thus depends on many more factors than in C3 crops. Recent physiological and genetic studies indicate a correlation between δ13C and WUE also in C4 crops, as well as a colocalization of quantitative trait loci for the two traits. Moreover, significant intraspecific variation as well as a medium to high heritability of δ13C has been shown in some of the main C4 crops, such as maize, sorghum and sugarcane, indicating its potential for indirect selection and breeding. Further research on physiological, genetic and environmental components influencing δ13C is needed to support its application in improving WUE and making C4 crops resilient to climate change.

Mass-Transfer-Limited Biodegradation at Low Concentrations-Evidence from Reactive Transport Modeling of Isotope Profiles in a Bench-Scale Aquifer

Organic contaminant degradation by suspended bacteria in chemostats has shown that isotope fractionation decreases dramatically when pollutant concentrations fall below the (half-saturation) Monod constant. This masked isotope fractionation implies that membrane transfer is slow relative to the enzyme turnover at μg L^-1 substrate levels. Analogous evidence of mass transfer as a bottleneck for biodegradation in aquifer settings, where microbes are attached to the sediment, is lacking. A quasi-two-dimensional flow-through sediment microcosm/tank system enabled us to study the aerobic degradation of 2,6-dichlorobenzamide (BAM), while collecting sufficient samples at the outlet for compound-specific isotope analysis. By feeding an anoxic BAM solution through the center inlet port and dissolved oxygen (DO) above and below, strong transverse concentration cross-gradients of BAM and DO yielded zones of low (μg L^-1) steady-state concentrations. We were able to simulate the profiles of concentrations and isotope ratios of the contaminant plume using a reactive transport model that accounted for a mass-transfer limitation into bacterial cells, where apparent isotope enrichment factors *ε decreased strongly below concentrations around 600 μg/L BAM. For the biodegradation of organic micropollutants, mass transfer into the cell emerges as a bottleneck, specifically at low (μg L^-1) concentrations. Neglecting this effect when interpreting isotope ratios at field sites may lead to a significant underestimation of biodegradation.

An eco-parametric method to derive sedimentation rates for coastal saltmarshes

The saltmarsh plant Spartina alterniflora was introduced to the Jiangsu coasts, China and serves as an ecological engineer to reduce near-bed shear stress, trap fine-grained sediments and protect the coast from wave-induced erosion. The saltmarshes thus could record the Spartina colonization-driven changes within the sedimentary layers. Based on these ecological and sedimentological changes in sediments, we present a new eco-parametric method to estimate the sedimentation rate for the newly-formed wetlands in the Yancheng Wetland Nature Reserve for Rare Birds, Jiangsu. Sediment cores and satellite imagery were used to identify the thickness of accumulated sediment layers and the time since the Spartina colonization. We defined the original ground on which Spartina alterniflora initially colonized using pigment concentrations, grain size and stable carbon isotopic compositions of organic matter (δ¹³C) in sediments. We also determined the time mark of the Spartina colonization by examining the Landsat images over 1982-2018 to discriminate the Spartina alterniflora from other native plants and geomorphological features. These two datasets yielded a sedimentation rate of 3.3 cm/yr for Core A and of 9.6 cm/yr for Core B, the latter evidenced by an increase of ~ 0.51 m in the bed level from 2008 to 2014. Combining the ²¹⁰Pb dating method, we further estimated the sedimentation rate for the layers beneath the original ground, which was comparable to that of the bare flats in the Jiangsu coast. Even though this new method is only applicable to newly-formed saltmarshes, it helps identify the recent sedimentation events as well as reveal the environmental changes and the evolution of saltmarsh-bare flat systems due to the interplay between vegetation, hydrodynamics and sediment dynamics. It thus could be an efficient and cost-effective tool for an improved understanding of the response of coastal wetlands to a changing climate/environment.

Authenticating bioplastics using carbon and hydrogen stable isotopes - An alternative analytical approach

RATIONALE

A combination of stable carbon (δ¹³ C) and hydrogen (δ² H) isotope ratios and carbon content (% C) was evaluated as a rapid, low-cost analytical approach to authenticate bioplastics, complementing existing radiocarbon (¹⁴ C) and Fourier transform infrared (FTIR) analytical methods.

METHODS

Petroleum- and bio-based precursor materials and in-market plastics were analysed and their δ¹³ C, δ² H and % C values were used to establish isotope criteria to evaluate plastic claims, and the source and biocontent of the samples. ¹⁴ C was used to confirm the findings of the isotope approach and FTIR analysis was used to vertify the plastic type of the in-market plastics.

RESULTS

Distinctive carbon and hydrogen stable isotope ratios were found for authentic bio-based and petroleum-based precursor plastics, and it was possible to classify in-market plastics according to their source materials (petroleum, C3, C4, and mixed sources). An estimation of C4 biocontent was possible from a C4-petroleum isotope mixing model using δ¹³ C which was well correlated (R²  = 0.98) to ¹⁴ C. It was not possible to establish a C3-petroleum isotope mixing model due to δ¹³ C isotopic overlap with petroleum plastics; however, the addition of δ² H and % C was useful to evaluate if petroleum-bioplastic mixes contained C3 bioplastics, and PLS-DA modelling reliably clustered each plastic type.

CONCLUSIONS

A combined dual stable isotope and carbon content approach was found to rapidly and accurately identify C3 and C4 bio-based products from their petroleum counterparts, and identify instances of petroleum and bio-based mixes frequently found in mislabelled bioplastics. Out of 37 in-market products labelled as bioplastic, 19 were found to contain varying amounts of petroleum-based plastic and did not meet their bio-based claims.

Initiation of efficient C4 pathway in response to low ambient CO2 during the bloom period of a marine dinoflagellate

Dinoflagellates are important primary producers and major causative agents of harmful algal blooms in the global ocean. Despite the great ecological significance, the photosynthetic carbon acquisition by dinoflagellates is still poorly understood. The pathways of photosynthetic carbon assimilation in a marine dinoflagellate Prorocentrum donghaiense under both in situ and laboratory-simulated bloom conditions were investigated using a combination of metaproteomics, qPCR, stable carbon isotope and targeted metabolomics approaches. A rapid consumption of dissolved CO₂ to generate high biomass was observed as the bloom proceeded. The carbon assimilation genes and proteins including intracellular carbonic anhydrase 2, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase and RubisCO as well as their enzyme activities were all highly expressed at the low CO₂ level, indicating that C₄ photosynthetic pathway functioned in the blooming P. donghaiense cells. Furthermore, δ¹³ C values and content of C₄ compound (malate) significantly increased with the decreasing CO₂ concentration. The transition from C₃ to C₄ pathway minimizes the internal CO₂ leakage and guarantees efficient carbon fixation at the low CO₂ level. This study demonstrates the existence of C₄ photosynthetic pathway in a marine dinoflagellate and reveals its important complementary role to assist carbon assimilation for cell proliferation during the bloom period.

Intrataxonomic trends in herbivore enamel δ13C are decoupled from ecosystem woody cover

Analysis of enamel stable carbon isotopes (δ¹³C_enamel) of fossil herbivores is an important tool for making inferences about Plio-Pleistocene vegetation structure in Africa and the environmental context of hominin evolution. Many palaeoecological studies implicitly or explicitly assume that individual variation in C₃-C₄ plant consumption among fossil herbivores directly reflects the abundance of C₃ (trees, shrubs) or C₄ (low-altitude tropical grasses) vegetation. However, a strong link between δ¹³C_enamel of herbivores and ecosystem vegetation structure has not been rigorously established. Here we combine δ¹³C_enamel data from a large dataset (n = 1,643) with multidecadal Landsat estimates of C₃ woody cover across 30 African ecosystems to show that there is little relationship between intrataxonomic variation in δ¹³C_enamel and vegetation structure. This is especially true when removing forested ecosystems (>80% woody cover)-which numerous lines of evidence suggest are rare in the Plio-Pleistocene fossil record of eastern Africa-from our analyses. Our findings stand in contrast with the common assumption that variation in herbivore δ¹³C_enamel values reflects changes in the relative abundance of C₃-C₄ vegetation. We conclude that analyses using herbivore δ¹³C_enamel data to shed light on the environmental context of hominin evolution should look to explicitly community-level approaches for making vegetation inferences.

Isotopic Indications of Late Pleistocene and Holocene Paleoenvironmental Changes at Boodie Cave Archaeological Site, Barrow Island, Western Australia

This paper presents the first application of mammal tooth enamel carbonate stable isotope analysis for the purpose of investigating late Pleistocene-early Holocene environmental change in an Australian archaeological context. Stable carbon (δ13C) and oxygen (δ18O) isotope ratios were analyzed from archaeological and modern spectacled hare wallaby (Lagorchestes conspicillatus) and hill kangaroo (Osphranter robustus) tooth enamel carbonates from Boodie Cave on Barrow Island in Western Australia. δ18O results track the dynamic paleoecological history at Boodie Cave including a clear shift towards increasing aridity preceding the onset of the Last Glacial Maximum and a period of increased humidity in the early to mid-Holocene. Enamel δ13C reflects divergent species feeding ecology and may imply a long-term shift toward increasing diversity in vegetation structure. This study contributes new data to the carbonate-isotope record for Australian fauna and demonstrates the significant potential of stable isotope based ecological investigations for tracking paleoenvironment change to inter-strata resolution.

Drought, axe and goats. More variable and synchronized growth forecasts worsening dieback in Moroccan Atlas cedar forests

Understanding how climate warming and land-use changes determine the vulnerability of forests to drought is critical. However, we still lack: (i) robust quantifications of long-term growth changes during aridification processes, (ii) links between growth decline, changes in forest cover, stand structure and soil conditions, and (iii) forecasts of growth variability to projected climate warming. We investigated tree-ring records over the past 400-700 years, quantified changes in grazing area and forest cover during the 20th century, sampled current stand structure, and analyzed soil organic carbon δ¹³C and total nitrogen δ¹⁵N of Atlas cedar (Cedrus atlantica (Endl.) Manetti ex Carrière) Moroccan forests to characterize their dieback. Atlas cedar forests experienced massive dieback after the 1970s, particularly in the xeric High Atlas region. Forest cover increased in the less xeric regions (Middle Atlas and Rif) by almost 20%, while it decreased about 18% in the High Atlas, where soil δ¹³C and δ¹⁵N showed evidences of grazing. Growth declined and became more variable in response to recent droughts. The relative growth reduction (54%) was higher in the Middle Atlas than elsewhere (Rif, 32%; High Atlas, 36%). Growth synchrony between forests located within the Middle and High Atlas regions increased after the 1970s. Simulations based on a worst-case emission scenario and rapid warming forecast a stronger limitation of growth by low soil moisture in all regions, but particularly in the Middle Atlas and after the mid-21st century. Climate warming is expected to strengthen growth synchronization preceding dieback of conifer forests in xeric regions. The likelihood of similar dieback episodes is further exacerbated by historical degradation of these forests.

Using Bioelements Isotope Ratios and Fatty Acid Composition to Deduce Beef Origin and Zebu Feeding Regime in Cameroon

The purpose of this study was to address the lack of knowledge regarding the stable isotopic composition of beef from zebu cattle reared in tropical Africa. Sixty beef carcasses belonging to the most common zebu breeds (Goudali, white Fulani, and red Mbororo) were selected and classified according to their subcutaneous fat color (white, cream or yellow). The stable isotope ratios of five bioelements—H, O, C, N, and S—in muscle fractions and the fatty acids composition were analyzed. Zebu meat from Cameroon shows peculiar δ¹³C values, related to the almost exclusive intake of grazed tropical grasses with photosynthetic cycle C4. It also shows δ²H and δ¹⁸O values higher than those reported in other areas of the world and correlated with the isotopic composition of animal drinking water. The white subcutaneous fat (“white type”) zebu showed higher δ²H and lower δ¹³C than the “yellow type”, that is correlated with a higher content of polyunsaturated fatty acid (PUFA) and a lower amount of saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA). Multielement analysis seems to provide promising results for tracing the regional origin of Cameroon beef and some aspects of the livestock system, such as the nutritional status of the animals.

The photosynthetic pathways of plant species surveyed in Australia's national terrestrial monitoring network

The photosynthetic pathway of plants is a fundamental trait that influences terrestrial environments from the local to global level. The distribution of different photosynthetic pathways in Australia is expected to undergo a substantial shift due to climate change and rising atmospheric CO2; however, tracking change is hindered by a lack of data on the pathways of species, as well as their distribution and relative cover within plant communities. Here we present the photosynthetic pathways for 2428 species recorded across 541 plots surveyed by Australia's Terrestrial Ecosystem Research Network (TERN) between 2011 and 2017. This dataset was created to facilitate research exploring trends in vegetation change across Australia. Species were assigned a photosynthetic pathway using published literature and stable carbon isotope analysis of bulk tissue. The photosynthetic pathway of species can be extracted from the dataset individually, or used in conjunction with vegetation surveys to study the occurrence and abundance of pathways across the continent. This dataset will be updated as TERN's plot network expands and new information becomes available.

Measuring the impact of corn on mammalian omnivores

In human-dominated landscapes throughout the world, wildlife seek out anthropogenic foods because they are high in nutritional value and are consistently available. To investigate this mode of foraging, some researchers use stable isotope analysis to detect these animals in populations and estimate their individual diets. In this study, we develop an integrative approach to measure the proportion of corn, a C4 plant, in the diets of free-ranging mammalian omnivores in C3-dominated ecosystems. We fed captive mice corn, C3 plants, and meat until carbon stable isotopes (δ 13C) from each diet equilibrated in their hair. We then used carbon discrimination factors (Δ 13C; offsets between stable isotope values of consumer tissues and their foods) for mice from these feeding trials and a simple carbon stable isotope mixing model to estimate the corn-based diets of free-ranging American black bears in Wisconsin and brown bears in Slovenia. We used Δ 13C factors for mice to estimate the diets of bears because mouse models are used commonly to study mammalian diet and health, including humans and bears, and body mass has no effect on carbon discrimination factors in monogastric mammalian omnivores. In this study, we found that mice grew fastest, largest, and δ 13C values equilibrated quickest in the hair of mice fed meat versus plant-based diets, suggesting protein quantity (quality was the same) has an effect on Δ 13C. Evidence also suggests that Δ 13C did not increase with animal growth rate as all mice grew throughout the 109-day feeding trials, but isotopic equilibration occurred early while mice still were subadults and was maintained throughout their adult lives. We also found that Δ 13C was highest and most variable in the hair, serum, and liver, of mice fed a mixed diet of C3 plants, supporting our mixed diet hypothesis that states that Δ 13C varies more among tissues of animals fed mixed diets than animals fed nonmixed diets because the former are composed of multiple foods, each with different macromolecular and isotopic compositions. Lastly, we found that corn may have been a more important component of bear diets in Wisconsin than previously thought (adults: x¯ = 29%; x¯ = 33%; subadults: x¯ = 22%; x¯ = 28%), and male brown bears may have fed on 50% more corn (x¯ = 47% versus 31%) in autumn during a year when beechnut availability was low. In a world that is rapidly changing, it is more important than ever to develop the appropriate quantitative tools to measure the impact people have on wildlife. Here, we provide such a tool for monogastric mammalian omnivores and encourage other researchers to do the same for other taxa of interest.

Online Biogenic Carbon Analysis Enables Refineries to Reduce Carbon Footprint during Coprocessing Biomass- and Petroleum-Derived Liquids

To mitigate green-house gas (GHG) emissions, governments around the world are enacting legislation to reduce carbon intensity in transportation fuels. Coprocessing biomass and petroleum-derived liquids in existing refineries is a near-term, cost-effective approach for introducing renewable carbon in fuels and enabling refineries to meet regulatory mandates. However, coprocessing biomass-derived liquids in refineries results in variable degrees of biogenic carbon incorporation, necessitating accurate quantification to verify compliance with mandates. Existing refinery control and instrumentation systems lack the means to measure renewable carbon accurately, reliably, and quickly. Thus, accurate measurement of biogenic carbon is key to ensuring refineries meet regulatory mandates. In this Perspective, we present existing methods for measuring biogenic carbon, point out their challenges, and discuss the need for new online analytical capabilities to measure biogenic carbon in fuel intermediates.

The carbon isotope ratios of nonessential amino acids identify sugar-sweetened beverage (SSB) consumers in a 12-wk inpatient feeding study of 32 men with varying SSB and meat exposures

BACKGROUND

The carbon isotope ratios (CIRs) of individual amino acids (AAs) may provide more sensitive and specific biomarkers of sugar-sweetened beverages (SSBs) than total tissue CIR. Because CIRs turn over slowly, long-term controlled-feeding studies are needed in their evaluation.

OBJECTIVE

We assessed the responses of plasma and RBC CIRAA's to SSB and meat intake in a 12-wk inpatient feeding study.

METHODS

Thirty-two men (aged 46.2 ± 10.5 y) completed the feeding study at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona. The effects of SSB, meat, and fish intake on plasma and RBC CIRAA's were evaluated in a balanced factorial design with each dietary variable either present or absent in a common weight-maintaining, macronutrient-balanced diet. Fasting blood samples were collected biweekly from baseline. Dietary effects on the postfeeding CIR of 5 nonessential AAs (CIRNEAA's) and 4 essential AAs (CIREAA's) were analyzed using multivariable regression.

RESULTS

In plasma, 4 of 5 CIRNEAA's increased with SSB intake. Of these, the CIRAla was the most sensitive (β = 2.81, SE = 0.38) to SSB intake and was not affected by meat or fish intake. In RBCs, all 5 CIRNEAA's increased with SSBs but had smaller effect sizes than in plasma. All plasma CIREAA's increased with meat intake (but not SSB or fish intake), and the CIRLeu was the most sensitive (β = 1.26, SE = 0.23). CIRs of leucine and valine also increased with meat intake in RBCs. Estimates of turnover suggest that CIRAA's in plasma, but not RBCs, were in equilibrium with the diets by the end of the study.

CONCLUSIONS

The results of this study in men support CIRNEAA's as potential biomarkers of SSB intake and suggest CIREAA's as potential biomarkers of meat intake in US diets. This trial was registered at clinicaltrials.gov/ct2/show/NCT01237093 as NCT01237093.

Rainfall as a trigger of ecological cascade effects in an Australian groundwater ecosystem

Groundwaters host vital resources playing a key role in the near future. Subterranean fauna and microbes are crucial in regulating organic cycles in environments characterized by low energy and scarce carbon availability. However, our knowledge about the functioning of groundwater ecosystems is limited, despite being increasingly exposed to anthropic impacts and climate change-related processes. In this work we apply novel biochemical and genetic techniques to investigate the ecological dynamics of an Australian calcrete under two contrasting rainfall periods (LR—low rainfall and HR—high rainfall). Our results indicate that the microbial gut community of copepods and amphipods experienced a shift in taxonomic diversity and predicted organic functional metabolic pathways during HR. The HR regime triggered a cascade effect driven by microbes (OM processors) and exploited by copepods and amphipods (primary and secondary consumers), which was finally transferred to the aquatic beetles (top predators). Our findings highlight that rainfall triggers ecological shifts towards more deterministic dynamics, revealing a complex web of interactions in seemingly simple environmental settings. Here we show how a combined isotopic-molecular approach can untangle the mechanisms shaping a calcrete community. This design will help manage and preserve one of the most vital but underrated ecosystems worldwide.

Compound-specific isotope analysis with nested sampling approach detects spatial and temporal variability in the sources of suspended sediments in a Scottish mesoscale catchment

Intensification of land use is a primary cause of increased suspended sediment load in freshwater systems, hence land-use-specific sediment source tracing is necessary to inform sustainable land and water management. Here we tested the application of compound-specific isotope analysis (CSIA) of vegetation biomarkers to fingerprint suspended sediment sources from the mesoscale agricultural Tarland catchment (74 km²) in NE Scotland. Our aim was to test a parsimonious nested sampling approach from a headwater sub-catchment to apportion suspended sediment sources across headwater to catchment-wide scales. Compound-specific carbon isotopic signatures (δ¹³C) of long-chain fatty acids (LCFAs) from source soils were able to successfully distinguish between forest, heather moorland, permanent grassland, and arable land cover. Permanent grassland was a prominent source of sediment at both headwater and catchment scales, with an annual average contribution of 79% and 56%, respectively, indicating grazing pressure and runoff via preferential pathways. Increased sediment input from arable land at the catchment scale (40%) compared to the headwater sub-catchment (18%) indicated land use intensification in lowland areas. Forest and heather moorland contributed marginally to suspended sediments (~2%), despite covering 43% area of the catchment area. Temporal variability of sediment sources observed over fourteen months (May 2017 - June 2018) showed a higher relative contribution from arable land during summer and autumn and a higher contribution from permanent grassland during winter and spring, likely linked to seasonality of rainfall and agronomic activities. These results demonstrate a successful use of δ¹³C values of LCFAs to quantify land-use-specific suspended sediment sources. Comparison of two suspended sediment techniques showed usefulness of time-integrated mass samplers for representative and cost-effective sampling. We recommend that future nested sampling designs should include spatially distributed source soil tracer characterization covering the whole catchment area to reduce the uncertainty in sediment source attribution from headwaters to the catchment outlet.

Science to Commerce: A Commercial-Scale Protocol for Carbon Trading Applied to a 28-Year Record of Forest Carbon Monitoring at the Harvard Forest

Forest carbon sequestration offset protocols have been employed for more than 20 years with limited success in slowing deforestation and increasing forest carbon trading volume. Direct measurement of forest carbon flux improves quantification for trading but has not been applied to forest carbon research projects with more than 600 site installations worldwide. In this study, we apply carbon accounting methods, scaling hours to decades to 28-years of scientific CO2 eddy covariance data for the Harvard Forest (US-Ha1), located in central Massachusetts, USA and establishing commercial carbon trading protocols and applications for similar sites. We illustrate and explain transactions of high-frequency direct measurement for CO2 net ecosystem exchange (NEE, gC m−2 year−1) that track and monetize ecosystem carbon dynamics in contrast to approaches that rely on forest mensuration and growth models. NEE, based on eddy covariance methodology, quantifies loss of CO2 by ecosystem respiration accounted for as an unavoidable debit to net carbon sequestration. Retrospective analysis of the US-Ha1 NEE times series including carbon pricing, interval analysis, and ton-year exit accounting and revenue scenarios inform entrepreneur, investor, and landowner forest carbon commercialization strategies. CO2 efflux accounts for ~45% of the US-Ha1 NEE, an error of ~466% if excluded; however, the decades-old coupled human and natural system remains a financially viable net carbon sink. We introduce isoflux NEE for t13C16O2 and t12C18O16O to directly partition and quantify daytime ecosystem respiration and photosynthesis, creating new soil carbon commerce applications and derivative products in contrast to undifferentiated bulk soil carbon pool approaches. Eddy covariance NEE methods harmonize and standardize carbon commerce across diverse forest applications including, a New England, USA regional eddy covariance network, the Paris Agreement, and related climate mitigation platforms.

A calibration of cellulose isotopes in modern prostrate Nothofagus and its application to fossil material from Antarctica

Carbon and oxygen isotopes (δ¹³C and δ¹⁸O) in tree rings are widely used to reconstruct palaeoclimate variables such as temperature during the Holocene (12 thousand years ago - present), and are used increasingly in deeper time. However, their use is largely restricted to arboreal trees, which excludes potentially important data from prostrate trees and shrubs, which grow in high latitude and altitude end-member environments. Here, we calibrate the use of δ¹³C and δ¹⁸O as climatic archives in two modern species of southern beech (Nothofagus) from Tierra del Fuego, Chile, at the southern limit of their current range. We show that prostrate trees are potentially suitable archives for recording climatological means over longer periods (on the order of decades), which opens up these important environments for tree ring isotope analysis. We then apply our new understanding to a remarkable late Neogene (17-2.5 Ma) fossil Nothofagus assemblage from the Transantarctic Mountains, Antarctica, representative of a prostrate tundra shrub growing during a period of significant ice sheet retreat. The δ¹³C of the fossil cellulose was found to be ~4‰ enriched relative to that of the modern tress. This is likely to be due to a combination of a more positive δ¹³C of contemporaneous atmospheric CO₂ and enhanced water use efficiency at the fossil site. Using the cellulose-δ¹⁸O in the fossil wood, we are able to reconstruct precipitation oxygen isotopes over the Antarctic interior for the first time for this time period. The results show that δ¹⁸O_precip over Antarctica was -16.0 ± 4.2‰, around 12‰ enriched relative to today, suggesting changes in the hydrological cycle linked to warmer temperatures and a smaller ice sheet.

Nutritional consequences of breeding away from riparian habitats in Bank Swallows: new evidence from multiple endogenous markers

The Bank Swallow (Riparia riparia), a threatened species in Canada, breeds primarily in banks at lakeshores and rivers and in artificial (typically inland) aggregate mining pits. Inland pits may be ecological traps for this species, but relative dietary trade-offs between these two nesting habitats have not been investigated. The availability of aquatic emergent insects at lakeshores may have associated nutritional benefits for growing nestlings due to increased omega-3 fatty acids (FAs) in prey. We compared the diets of juvenile swallows from lakeshore and inland pit sites using assays of stable isotope values (δ¹³C, δ¹⁵N, δ²H) of feathers, faecal DNA metabarcoding and blood plasma FAs. Colony proximity to Lake Erie influenced the use of aquatic versus terrestrial insects by Bank Swallow adults and juveniles. Feather δ²H was particularly useful as a tracer of aquatic emergent versus terrestrial prey, and inland juveniles had feathers enriched in ²H, reflective of diets composed of fewer aquatic emergent insects. DNA metabarcoding of juvenile and adult faecal material indicated that lakeshore birds consumed more aquatic-emergent chironomids than inland birds. Lakeshore juveniles had elevated plasma omega-3 eicosapentaenoic acid levels compared with inland pit-breeding birds. We discuss the need to consider 'nutritional landscapes' and the importance of this concept in conservation of declining species and populations.

Characterization of Microbial Diversity and Community Structure in Fermentation Pit Mud of Different Ages for Production of Strong-Aroma Baijiu

In the traditional fermentation process of strong-aroma Baijiu, a fermentation pit mud (FPM) provides many genera of microorganisms for fermentation. However, the functional microorganisms that have an important effect on the quality of Baijiu and their changes with the age of fermentation pit (FP) are poorly understood. Herein, the Roche 454 pyrosequencing technique and a phospholipid fatty-acid analysis were employed to reveal the structure and diversity of prokaryotic communities in FPM samples that have been aged for 5, 30, and 100 years. The results revealed an increase in total prokaryotic biomass with an FP age; however, Shannon’s diversity index decreased significantly (p < 0.01). These results suggested that a unique microbial community structure evolved with uninterrupted use of the FP. The number of functional microorganisms, which could produce the flavor compounds of strong-aroma Baijiu, increased with the FP age. Among them, Clostridium and Ruminococcaceae are microorganisms that directly produce caproic acid. The increase of their relative abundance in the FPM might have improved the quality of strong-aroma Baijiu. Syntrophomonas, Methanobacterium, and Methanocorpusculum might also be beneficial to caproic acid production. They are not directly involved but provide possible environmental factors for caproic acid production. Overall, our study results indicated that an uninterrupted use of the FP shapes the particular microbial community structure in the FPM. This research provides scientific support for the concept that the aged FP yields a high-quality Baijiu.