Search

Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical observation that source amino acids (SAAs) (i.e., phenylalanine), fractionate 15 N very little (< 0.5‰) during trophic transfer, whereas trophic AAs (TAAs) (i.e., glutamic acid), are greatly (∼6–8‰) enriched in 15 N during each trophic step. The differential fractionation of these two AA groups can provide a valuable estimate of consumer trophic position that is internally indexed to the baseline δ 15 N value of the integrated food web. In this paper, we critically review the analytical methods for determining the nitrogen isotopic composition of AAs by gas chromatography–isotope-ratio mass spectrometry. We also discuss methodological considerations for accurate trophic position assessment of organisms using CSIA-AA. We then discuss the advantages and challenges of the CSIA-AA approach using published case studies across a range of topics, including trophic position assessment in various ecosystems, reconstruction of ancient human diets, reconstruction of animal migration and environmental variability, and assessment of marine organic matter dynamics with new classification of microbial fractionation patterns. It is clear that the CSIA-AA approach can provide unique insight into the sources, cycling, and trophic modification of organic nitrogen as it flows through systems. However, this approach will be greatly improved through continued exploration into how biochemical, physiological, and ecological mechanisms affect isotopic fractionation of individual AAs. We end this review with a perspective on future work that will promote the evolution of the rapidly growing field of CSIA-AA. [ABSTRACT FROM AUTHOR]

Precipitation in Japan is strongly affected by the East Asian monsoon system, resulting in wet summer conditions and relatively dry winter conditions. Few paleo-monsoon records exist from northeastern Asia, especially records showing decadal- to centennial-scale variability. Here we present a molecular hydrogen isotope (δD) record from Lake Kaiike, a small coastal lake in southwest Japan, to provide insight into monsoonal precipitation over the past two millennia. The δD record of friedelin, a terrestrial higher plant lipid, reveals three major shifts in precipitation: a decline from >−185‰ to <−190‰ at 1700 cal yr BP suggests a change to wetter conditions; values between −187.5‰ and −180‰ from 1480 to 800 cal yr BP indicate reduced precipitation; and a decline to below −195‰ after 800 cal yr BP reflects moist conditions during the Little Ice Age. These results highlight variability in the intensity of the East Asian Summer Monsoon occurring on decadal to centennial time scales. El Niño-like conditions are likely responsible for periods of high monsoon intensity, but comparison with other records in the region (northeast China and Japan) shows that contradicting patterns also exist, and so explaining these rainfall patterns is not straightforward. [ABSTRACT FROM AUTHOR]

The ram's horn squid, Spirula spirula (Spirulida, Coleoidea), inhabits subsurface waters of the tropical and subtropical oceans. Because of the presence of an internal chambered shell in this species, it has frequently been used as a model species to investigate the paleobiology of fossil coleoids. However, the feeding and dietary habits of S. spirula in the nature are poorly known. In this study, we applied a new method (amino acid nitrogen isotopic analysis) to estimate the trophic position of S. spirula specimens captured off Suriname, as well as three cuttlefish Sepia species ( Sepia officinalis, S. latimanus, and S. esculenta), with a calcified chambered shell from the shallower water. The trophic position of S. spirula was estimated to be 2.5-2.8, which was significantly lower than that for the three Sepia species (3.4-3.6). The results and available data on the gastric contents of S. spirula suggest that it feeds mainly on detritus and zooplankton, including crustaceans, from the overlying water column. The method used in this study can potentially be applied to the estimation of the trophic position of the fossil cephalopods having calcified chambered shells. [ABSTRACT FROM AUTHOR]

Abstract: We conducted an in situ feeding experiment using 13C-labeled unicellular algae in Sagami Bay, Japan (water depth, 1450m), in order to understand the fate of lipid compounds in phytodetritus at the deep-sea floor. We examined the incorporation of excess 13C into lipid compounds extracted from bulk sediments and benthic foraminiferal cells. 13C-enriched fatty acids derived from 13C-labeled algae were exponentially degraded during 6 days of incubation in the sediment. Subsequent enrichments in 13C in sedimentary n-C15, anteiso-C17, and C17 fatty acids indicated the microbial degradation of algal material and production of bacterial biomass in the sediment. We observed the incorporation of 13C-labeled algal phytol and fatty acids into foraminiferal cells. The compositions of 13C-labeled algal lipids in foraminiferal cells were different from those in the bulk sediments, indicating that foraminiferal feeding and digestion influenced the lipid distribution in the sediments. Furthermore, some sterols in Globobulimina affinis (e.g., 24-ethylcholesta-5,22-dien-3β-ol, 24-ethylcholest-5-en-3β-ol, and 23,24-dimethylcholesta-5,22E-dien-3β-ol) were newly produced via the modification of dietary algal sterols within 4–6 days. In addition to the effects of bacteria, feeding by benthic foraminifera can result in a significant reorganization of the composition of organic matter and influence benthic food webs and carbon cycling at the deep-sea floor. [Copyright &y& Elsevier]

Abstract: We report carbon isotopic compositions of tetrapyrrole nuclei (chlorophyllides) and side chains (phytol or farnesol) of chlorophyll a, bacteriochlorophyll a, and bacteriochlorophylls e isolated from several depths in the saline meromictic Lake Kaiike, Japan. The chlorophyllides are substantially enriched in 13C relative to the side chains in all the depths of the lake, namely oxic mixolimnion, chemocline, anoxic monimolimnion, and benthic microbial mat. The isotopic compositions of chlorophyllide moieties are strongly related to those of the whole molecule (chloropigments; r 2 =0.94) with the former being 1.8±0.8‰ (1σ, n =18) enriched in 13C relative to the latter. No significant difference was observed between chlorophyll species. The heterogeneity of 13C in the chloropigments can be ascribed to differences between the biosynthetic pathways of chlorophyllides and side chains. The alkyl porphyrins in the geological samples are derived from the chlorophyllides, whose carbon skeleton is ultimately inherited from glutamate, one of the major amino acids in the cell. Together with the isotopic relationship between chlorophylls and cell previously reported, we estimate that the carbon isotopic composition of DPEP, a major C32 alkyl porphyrin in the geological samples, is ∼1.8‰ enriched in 13C relative to the cell. [Copyright &y& Elsevier]

Abstract: Copper-chelated bacteriochlorophyll e homologues have been identified in laminated sediment from the meromictic Lake Abashiri using atmospheric pressure chemical ionization liquid chromatography/mass spectrometry. Since they are the second most abundant chloropigment derivatives in the sediments, these novel compounds may be important intermediate products of BChl e diagenesis in this anaerobic environment. [Copyright &y& Elsevier]

Stable carbon and nitrogen isotopic compositions were determined for individual photosynthetic pigments isolated and purified from the saline meromictic Lake Kaiike, Japan, to investigate species-independent biogeochemical processes of photoautotrophs in the natural environment. In the anoxic monimolimnion and benthic microbial mats, the carbon isotopic compositions of BChlseand isorenieratene related to brown-coloured strains of green sulfur bacteria are substantially (∼10‰) depleted in13C relative to those found in the chemocline. In conjunction with 16S rDNA evidence reported previously, it strongly suggests thatPelodyctyon luteoluminhabited and photosynthesized in the anoxic monimolimnion and benthic microbial mats by using13C-depleted regenerated CO2. By contrast, both Chlaand BChlain the monimolimnion and microbial mats have similar isotopic compositions as they do in the chemocline, implying that the source organisms live only in the chemocline. In the chemocline, the nitrogen isotopic compositions of BChlehomologues ranges from−7.7 to− 6.5‰, whereas that of BChlais−2.1‰. These isotopic compositions suggest that green sulfur bacteriaChlorobium phaeovibrioideswould conduct nitrogen fixation in the chemocline, whereas purple sulfur bacteriaHalochromatiumsp. and cyanobacteriaSynechococcussp. may assimilate nitrite. [ABSTRACT FROM AUTHOR]

Abstract: Relative abundances and distribution patterns of mineral components in finely laminated “Livello Bonarelli (LB)” black shale from the Cenomanian/Turonian boundary, Cretaceous, were investigated by 10 μm-resolution compositional mapping using an electron probe microanalyzer. Sedimentary components such as biogenic silica (Sibio), calcium phosphate, calcium carbonate, and pyrite were reconstructed by image processing of the compositional maps. Total organic carbon (Corg) content was also determined at a sampling interval of 1.5 mm. The depth profiles of these sedimentary components, covering ∼60% of the total 104-cm LB sequence, indicate the highly variable nature of their deposition. Especially, the Corg contents vary widely, ranging from <0.1% to 26%. Intervals enriched in Corg are clearly discernible in the LB, and correspond to “dark” colored intervals. Repeated occurrences of Corg-rich and Sibio-rich intervals are one of the most prominent features in the LB. These features could be explained partly by dilution of Corg by Sibio, but largely by the presence of two distinct paleoenvironmental settings: one involves predominant deposition of organic matter and the other is dominated by Sibio deposition. The thickness of individual intervals varies widely, mostly ranging from 1.5 to 35 mm, representing oceanic changes on the order of 103–104 years. Furthermore, we found 100-μm-scale laminations of fine-grained pyrite, aluminosilicate, and calcium carbonate, which when superimposed on the alternation of Corg-rich and Sibio-rich intervals, suggests 102-year scale fluctuations in oceanic environments. [Copyright &y& Elsevier]

Deep‐sea hydrothermal vents host exceptional ecosystems with lush animal communities primarily relying on organic matter (OM) produced by chemoautotrophic microbes. Though energy sources and food webs at vents have been extensively studied, the exact carbon sources of chemosynthetic primary production, such as methane (CH4) and carbon dioxide (CO2) in the vent fluid or bottom water, have not been elucidated quantitatively across spatial scales. Here, we investigate carbon and nitrogen sources of 12 vent animal species at the Iheya North field, Okinawa Trough inhabiting different distances from the central venting area and with various feeding ecologies using natural‐abundance radiocarbon (Δ14C) in combination with conventional stable carbon and nitrogen isotope ratios (δ13C and δ15N). Our results show that generally, animals living closer to vent orifices were more depleted in 14C, indicating they assimilate more carbon from vent fluid CO2. Those relying on methanotrophs, however, exhibited low Δ14C values regardless of distance due to the lack of methane in the non‐vent‐influenced bottom water. Organisms with low Δ14C values also tend to exhibit low δ15N values, implying NH4+ assimilation into biomass in environments with high NH4+ concentrations. Our results demonstrate that 14C can clearly distinguish between chemoautotrophically fixed carbon originating from the vent fluid and detrital OM derived from surface primary production, and also discriminate between CO2‐ and CH4‐based chemoautotrophy. Although vent animals rely on vent fluid energetically, our results highlight that the dependency on vent fluids as carbon source varies greatly depending on habitat, as well as carbon fixation pathways of microbial primary producers. [ABSTRACT FROM AUTHOR]

Studies the latitudinal distribution of polynuclear aromatic hydrocarbon (PAH) deposition on the deep sea floor in the Central Pacific. Increase in the accumulation rates of PAH during the twentieth century; Suggestion that the PAH were transported as mixtures attached to some aerosol particles but not free forms.

The sulfur (S) mass fraction of carbonate minerals can be used to reconstruct the environmental conditions and S sources at the time of precipitation. As S is present in a wide range of host materials, there is an urgent need to develop a method to extract S from a single mineral phase. We have developed a method to extract structurally substituted sulfate, termed carbonate‐associated sulfate (CAS), from geological and biogenic carbonate minerals using weakly acidic cation exchange resins. Two types of weakly acidic cation exchange resin (methacrylic acid and acrylic acid types) were tested to minimise the blank S contents and decompose carbonate. After repeated cleaning of the resins with high‐purity water or HCl, the blank S contents were reduced to < 0.1 μg, which is < 0.1% of the CAS in the samples. The cleaned resin was used to dissolve 10 and 25 mg of the JCp‐1 carbonate certified reference material (CRM; Japanese National Institute of Advanced Industrial Science and Technology, AIST). Samples and resin were added to 8 ml of high‐purity water at resin/sample ratios of 2, 5, 10 and 20, set on a shaking table, and reacted. The supernatant solutions were sampled sequentially from 0.5 h to 87 h after the start of experiments. The results show that the optimal conditions for decomposing 10 mg of carbonate is a resin/sample ratio of ≥ 10 with a reaction time of ≥ 40 h. Carbonate‐associated S mass fractions were measured for six geological and biogenic carbonate CRMs. The coefficient of variation in carbonate‐associated S mass fractions was ≤ 7%, regardless of the type of resins used. The mass fractions determined with this method recover 74–94% of the total S mass fractions reported in previous studies, suggesting that this method dissolved carbonate, and did not leach other S‐bearing fractions that are not resistant to weak acids. Another benefit of this method is that the decomposed solution can be introduced directly into the ion chromatograph, allowing for more sensitive analyses. We emphasise that this method can also be used for S isotopic measurements, as S contamination from other S‐bearing mineral phases is low. [ABSTRACT FROM AUTHOR]

Extraterrestrial nucleobases are of key interest owing to their implications for the chemical evolution of primordial molecules in the solar system and their potential contributions to prebiotic chemistry on the early Earth. Recent advances in analytical techniques capable of detecting femto-mole-order nucleobases have allowed us to identify all five exogenous nucleobases—uracil, cytosine, thymine, adenine, and guanine—in carbonaceous chondrites and to quantify uracil obtained from the carbonaceous asteroid (162173) Ryugu. In this study, we optimized the analytical method using hot-water extraction followed by 6 M hydrochloric acid (HCl) extraction from a sample of the CM2 Murchison meteorite to reassess the abundances and distributions of extraterrestrial nucleobases. The target analyses performed using high-performance liquid chromatography paired with electrospray-ionization, high-resolution mass spectrometry revealed that purine nucleobases were substantially more enriched in the subsequent 6 M HCl extract (951 ± 104 parts per billion, ppb) than in the hot-water extract (199 ± 3 ppb). The most abundant nucleobase was guanine (649 ± 103 ppb in total). The 6 M HCl extract not only contained canonical nucleobases but also included rare nucleobase analogs from the purine family, such as 8-substituted purines. Unlike purines, we preferentially detected pyrimidine nucleobases in the hot-water extract and the acid hydrolysate (185 ± 17 ppb and 297 ± 5 ppb, respectively) rather than in the 6 M HCl extract (51 ± 4 ppb). The disparate distributions of purine and pyrimidine bases in the Murchison meteorite suggests that purines are more robustly incorporated than pyrimidines into meteoritic matrices and/or insoluble macromolecular organic matter. We propose a unified formation mechanism for purine nucleobases—which involves the synthesis of 5-aminoimidazole derivatives from hydrogen cyanide and its related molecules—that can account for the molecular distributions of the extraterrestrial purine nucleobases found in the Murchison meteorite. [ABSTRACT FROM AUTHOR]

Rationale: Isolation of underivatized amino acids (AAs) using high‐performance liquid chromatography (HPLC) is becoming a popular method for carbon (δ13C) and nitrogen isotope (δ15N) analyses of AAs because of the high analytical precision and for performing dual‐isotope analysis. However, some AAs in natural samples, especially small, hydrophilic AAs, are not suitably separated using reversed‐phase columns (e.g., C18) and ion‐exchange columns (e.g., Primesep A). Methods: We developed a new method for HPLC using a porous graphitic carbon column for the separation of nine hydrophilic AAs. After purification, δ13C and δ15N values of AAs were determined using elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). We demonstrated the application of this method by determining δ13C and δ15N values of individual hydrophilic AAs in a biological sample, the muscle of blue mackerel (Scomber australasicus). Results: Chromatographically, the baseline separation of hydrophilic AAs was achieved in both the standard mixture and the biological sample. We confirmed that δ13C and δ15N values of AA standards remained unchanged during the whole experimental procedure. The δ13C values of AAs in mackerel muscle are also in good agreement with the values obtained using another verified method for δ13C analysis. Conclusions: The good separation performance of hydrophilic AAs and the reliability of δ13C and δ15N analyses of individual AAs using the porous graphite column offer a significant advantage over conventional settings. We suggest that, in the future, the HPLC × EA/IRMS method can be used for reliable δ13C and δ15N analyses of AAs in natural samples. [ABSTRACT FROM AUTHOR]

Biomass pyramids in natural food webs provide insights into multitrophic ecosystem functioning. We measured the integrated trophic position (iTP), which reflects the average efficiency of biomass transfer through trophic pathways, of 14 mesozooplankton communities in the western North Pacific. Compound-specific nitrogen isotope analysis of amino acids for composite mesozooplankton biomass indicated that the iTP values of marine mesozooplankton communities and their biomass pyramids are essentially controlled by biodiversity, body weight, and species turnover. Offshore communities with lower diversity and higher iTP were dominated by large copepods with slow turnover, such as Neocalanus, whereas nearshore communities with higher diversity and lower iTP were characterized by several smaller, fast turnover species belonging to Calanus, Paracalanidae, Eucalanidae, and Metridinidae. The observed iTP values (2.36 ± 0.32) indicate different topologies in biomass pyramids in different sites, where inverted pyramids are found in less diverse communities. The results also suggest that iTP can be linked to food chain length (FCL), a conventional proxy for the biomass pyramid. Combining iTP and FCL in the future studies will be a powerful approach to better understand factors controlling food web structure and dynamics. [ABSTRACT FROM AUTHOR]

The unidentified infrared (UIR) bands, whose carriers are thought to be organics, have been widely observed in various astrophysical environments. However, our knowledge of the detailed chemical composition and formation process of the carriers is still limited. We have synthesized laboratory organics named Quenched Nitrogen-included Carbonaceous Composite (QNCC) by quenching plasma produced from nitrogen gas and hydrocarbon solids. Infrared and X-ray analyses of QNCC showed that infrared properties of QNCC well reproduce the UIR bands observed in novae and amine structures contained in QNCC play an important role in the origin of the broad 8 m feature, which characterizes the UIR bands in novae. QNCC is at present the best laboratory analog of organic dust formed around dusty classical novae, which carries the UIR bands in novae via thermal emission process [Endo et al.(2021)]. [ABSTRACT FROM AUTHOR]

Objectives: We applied stable carbon and nitrogen isotope analyses to wild Bornean orangutans (Pongo pygmaeus morio) to investigate the feeding ecology of wild orangutans. Compared with African great ape species, orangutans are adapted to environments with chronic lower nutrition. But the usefulness of stable isotope analysis in the study of wild orangutan feeding ecology has not been fully explored. Methods: The study site was a primary lowland dipterocarp forest in the Danum Valley, Sabah, Malaysia. A total of 164 plant and 94 fecal samples collected across 18 months were analyzed. Results: Carbon and nitrogen stable isotope ratios of plant food samples do not systematically vary by plant parts (i.e., bark, fruits, and leaves). Elemental composition and stable isotope ratios of orangutan feces do not systematically vary by orangutans' sex and age classes, although fecal stable isotope ratios showed seasonal fluctuations. No isotopic contribution of breast milk was found in fecal samples collected from individuals at 2.7–6.5 years of age. Conclusions: This study revealed key characteristics of the stable isotope ecology of wild orangutans living in a primary lowland forest. Although there was little isotopic variation among plant foods and orangutan individuals, seasonal fluctuations in baseline isotope ratios or orangutans' diet were found in Danum valley. [ABSTRACT FROM AUTHOR]

In the high‐productivity subarctic ocean, phytoplankton growth is assumed to rely mainly on nitrate, based on snapshot observations conducted in spring or summer. However, the year‐round utilization of nitrate and ammonium by phytoplankton remains unexplored. Here, we show the seasonal transition of the dominant nitrogen source for phytoplankton by using the nitrogen isotopic composition (δ15N) of nitrate, ammonium, and sinking particles in the northwestern North Pacific. To decouple the combined effects of nitrogen sources for phytoplankton and subsequent trophic transfers in δ15N of sinking particles, we used compound‐specific δ15N analysis of amino acids (δ15NAA) in sinking particles. The seasonal change in δ15NAA revealed that most of the seasonal variation in δ15N of sinking particles arose from changes in the availability of nitrogenous nutrients in the euphotic layer. The δ15N of sinking particles suggested that the dominant nitrogen source for phytoplankton switches from nitrate to ammonium in autumn. Plain Language Summary: Exploring the year‐round utilization of nitrate and ammonium by phytoplankton is essential for understanding marine productivity. The nitrogen isotope ratio of sinking particles has long been used for reconstructing the availability of nitrogenous nutrients in the overlying surface water. However, the nitrogen isotope signal of sinking particles represents the combined effects of nitrogen sources for phytoplankton and subsequent trophic transfers, such as zooplankton grazing on phytoplankton and bacterial deamination of organic matter. This study shows the seasonal transition of the dominant nitrogen source for phytoplankton in the northwestern North Pacific by using compound‐specific nitrogen isotope analysis of amino acids in sinking particles that can deconvolute the effect of trophic alterations on bulk nitrogen isotope signals. The compound‐specific nitrogen isotope analysis of amino acids revealed that most of the seasonal variation in the bulk nitrogen isotope signal of sinking particles arises from changes in the availability of nitrogenous nutrients. The seasonal patterns of the bulk nitrogen isotope ratio demonstrated that the dominant nitrogen source for phytoplankton switches from nitrate to ammonium in autumn. Our findings highlight the importance of ammonium as a major nitrogen source for phytoplankton in the high‐productivity subarctic ocean. Key Points: Nitrogen isotope analysis of amino acids in sinking particles can deconvolute the effect of trophic alterations on bulk nitrogen isotope signalsSeasonal variation in bulk nitrogen isotope ratios of sinking particles mainly arises from changes in the availability of nitrogenous nutrientsDominant nitrogen source for phytoplankton switches from nitrate to ammonium in autumn in the northwestern North Pacific [ABSTRACT FROM AUTHOR]

Understanding the contribution of fish to the human diet is an important debate in past population studies as it implies specific organization (e.g., adapted techniques and gender‐based activities) and relationship with the local or sublocal environments (e.g., mobility and seasonal‐based exploitation). In the Paris Basin, the role of fish has been discussed mainly from rare but obvious archaeological remains such as fish bones or hooks. Previous isotopic data from Neolithic human bone bulk collagen highlighted the potential of freshwater resources in protein diet but were not able to quantify it or even confirm its role. In this study, we conducted, for the first time on early farmers from France, compound‐specific isotope analysis on bone collagen amino acids (CSIA‐AA). Results indicate a particularly high trophic level of some humans with protein intake mainly based on terrestrial animal resources (domestic cattle and pig), whereas others rather have a plant‐based diet. Freshwater resources appeared to be not significant, and several possible food combinations are discussed. Pig particularly appears more herbivorous than previously assumed and has possibly consumed manured cereals from human food waste. [ABSTRACT FROM AUTHOR]

Nitrogen isotopic composition of amino acids has been widely applied to biochemical, ecological, archeological, and biogeochemical studies in an attempt to trace nitrogen source and transformation processes. For accurate isotope analysis of individual amino acids, we validated a preparative method involving the isolation of underivatized amino acids by ion-pair chromatographic separation and confirmed the consistency of nitrogen isotope composition. Ion-pair reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS) and gas chromatography/combustion coupled with isotope ratio mass spectrometry (GC/C/IRMS) were conducted for the purpose of separation of underivatized amino acids and nitrogen isotopic analysis, respectively. Firstly, we confirmed the resolution of proteinogenic and non-proteinogenic amino acids by the preparative ion-pair LC separation. Diagnostic product ions determined by mass spectrometry can support the rapid identification of individual amino acids in screening analyses. Secondly, we observed no dependency on nitrogen isotopic composition for the injection amount of underivatized amino acids and even for different chemical formula including neutral, acidic, sulfur-containing, heterocyclic, and aromatic species. The recovery during the LC was 91.7 ± 4.3% ( n = 3). The present method and strategy of LC coupled with GC/C/IRMS (i.e., comprehensive LC × GC/C/IRMS) are useful for the high precision determination of the nitrogen isotopic composition of amino acids, in conjunction with an appropriate pre-treatment of cation-exchange chromatographic procedures. [ABSTRACT FROM AUTHOR]

Zinc stable isotopes (δ66Zn) serve as a widely fingerprinting tool for detecting anthropogenic Zn contamination. However, there is a limited understanding of δ66Zn behavior during the sorption of Zn to minerals and organic matter. In this study, we have determined the δ66Zn values in specific fractions to investigate their effectiveness in tracing anthropogenic Zn. The revised Community Bureau of Reference (BCR) extraction procedure was applied to a coastal marine core from Osaka Bay and from a lacustrine core from Lake Biwa, both with a history of anthropogenic metal pollution. The δ66Zn values varied from −0.14 ‰ to +1.00 ‰ across the four to five chemical fractions with up to 0.9 ‰ variation within a single horizon. The highest δ66Zn values in the acid-soluble fraction (up to +1.00 ‰) could be explained by the preferential sorption of 66Zn to carbonates and/or the preferential incorporation of 66Zn into calcite. The complex isotopic fractionation during the sorption of Zn to and co-precipitation with Fe–Mn oxyhydroxides likely resulted in an unclear pattern of the δ66Zn values of the reducible fraction. Low δ66Zn values in the oxidizable fraction (Osaka Bay) agree with the 64Zn enrichment in phytoplankton. Higher δ66Zn values of the reducible and oxidizable fractions of the Lake Biwa core indicate that environmental conditions (e.g. ionic strength) and for instance different phytoplankton species or dissolved and suspended particulate matter input drive the Zn isotope fractionation depending on the system (marine vs. lacustrine). The δ66Zn values of the acid-soluble fraction (Osaka Bay and Lake Biwa), of the reducible fraction (only Lake Biwa) and of oxidizable fraction (only Osaka Bay) better reflected the temporal changes in the Zn concentration than the bulk sediment, indicating that these fractions could be a sensitive fingerprinting tool for anthropogenic Zn contamination. • δ66Zn values were analyzed in fractions extracted sequentially from two polluted sediment cores. • Carbonates can explain the highest (up to +1.00 ‰) values in the acid-soluble fraction. • Unclear δ66Zn pattern of the reducible fraction due to different fractionation mechanisms. • Incorporation of 64Zn into phytoplankton can explain the lowest δ66Zn values (down to −0.14 ‰). • δ66Zn values of the acid-soluble fraction best reflected the temporal change in Zn concentration. [ABSTRACT FROM AUTHOR]

Aquatic resource exploitations in human evolution have raised many questions related to cognitive abilities and subsistence developments. It has been pointed out that the evaluation of freshwater resource consumption based on conventional stable CN isotopic composition of bulk bone collagen faces some difficulties, primarily because isotopic distinction between terrestrial and freshwater animals can be ambiguous and, even worse, can show similar values. In this study we tested the potential of nitrogen isotope analysis of individual amino acids in this evaluation. Our preliminary results for archaeological human and faunal remains from Mesolithic and Epipalaeolithic sites in France (Noyen-sur-Seine and Pont d'Ambon) show that estimated trophic positions for terrestrial animals based on δ15N of glutamic acid and phenylalanine are more precise than the bulk collagen isotopic method, allowing human aquatic resource consumptions to be identified. However, since the ability to quantify is still limited, a combination of several approaches is recommended. [ABSTRACT FROM AUTHOR]

Abstract: Archaeological studies including stable carbon and nitrogen isotope analyses of bone collagen from human remains have suggested their heavy dependence on terrestrial foods during the Jomon period in the inland central region in Japan. However, it is not easy to quantitatively evaluate the extent of carnivory for archaeological human remains based on the bulk collagen chemistry, because of variable 15N-enrichment factor along the trophic step and background isotopic variations in ecosystems. In order to overcome these problems and more precisely evaluate diets of prehistoric humans who strongly adapted to terrestrial environment, in this study we applied nitrogen isotope analysis of individual amino acids in bone collagen to two inland human populations in the Jomon period. Our results suggest that the two populations were predominantly dependent on the C3-plant-based terrestrial ecosystem and consumed little aquatic resources. Furthermore, their mean trophic positions (2.7 for both cases) are closer to that of the fox (2.8–3.0) rather than those of pure herbivores (2.0–2.2), and show little change over time. These results are the first evidence that inland Jomon populations may have had more carnivorous diets than is traditionally considered. [Copyright &y& Elsevier]

Polycyclic aromatic hydrocarbons (PAHs) are produced by incomplete combustion of biomass and fossil fuel, yet PAHs have been rarely analyzed in coastal sediment cores as a tracer for human activities before industrialization. The aim of this study was to assess if the historical trend of PAHs can be related to past human activities. To this end, we have determined the concentrations of PAHs in a 9 m-long sediment core from Osaka Bay, which records history of the last 2400 years. The concentration of PAHs before the beginning of the 17th century CE, the beginning of the peaceful Edo period, was consistently low (<100 ng g−1) and mainly comprised of smoke-derived PAHs reflecting the natural background. A relative higher abundance of 4−6 ring PAHs from the early 17th century CE and a higher PAH concentration from the early 18th century CE until approximately 1800 CE agreed with a population increase, Cu smelting activities and increasing combustion of charcoal. The constant PAH concentration until the late 19th century CE overlapped with a decline in the population in the Osaka area. An increasing PAH concentration from the late 19th century CE marked the beginning of industrialization in the Modern age. The peak in PAH concentration in 1945 CE was likely caused by burning of wooden structures due to air raids on Osaka City. A second peak around 1980 CE indicated the introduction of cleaner energies. We conclude that PAHs in coastal sediment cores can be used to reconstruct past human activities. [ABSTRACT FROM AUTHOR]

Abyssal plains cover more than half of Earth's surface, and the main food source in these ecosystems is phytodetritus, mainly originating from primary producers in the euphotic zone of the ocean. Global climate change is influencing phytoplankton abundance, productivity, and distribution. Increasing importance of picoplankton over diatom as primary producers in surface oceans (especially projected for higher latitudes) is projected and hence altering the quantity of organic carbon supplied to the abyssal seafloor as phytodetritus, consequences of which remain largely unknown. Here, we investigated the in situ responses of abyssal biota from viruses to megafauna to different types of phytoplankton input (diatoms or cyanobacteria which were labeled with stable isotopes) at equatorial (oligotrophic) and temperate (eutrophic) benthic sites in the Pacific Ocean (1°N at 4277 m water depth and 39°N at 5260 m water depth, respectively). Our results show that meiofauna and macrofauna generally preferred diatoms as a food source and played a relatively larger role in the consumption of phytodetritus at higher latitudes (39°N). Contrarily, prokaryotes and viruses showed similar or even stronger responses to cyanobacterial than to diatom supply. Moreover, the response of prokaryotes and viruses was very rapid (within 1–2 days) at both 1°N and 39°N, with quickest responses reported in the case of cyanobacterial supply at higher latitudes. Overall, our results suggest that benthic deep‐sea eukaryotes will be negatively affected by the predicted decrease in diatoms in surface oceans, especially at higher latitudes, where benthic prokaryotes and viruses will otherwise likely increase their quantitative role and organic carbon cycling rates. In turn, such changes can contribute to decrease carbon transfer from phytodetritus to higher trophic levels, with strong potential to affect oceanic food webs, their biodiversity and consequently carbon sequestration capacity at the global scale. [ABSTRACT FROM AUTHOR]

Abstract: We report the molecular and stable isotopic (δD and δ13C) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21–33; maximum C23–C29) are found to be abundant in the insects (31–781μg/dry g), with a carbon preference index (CPI) of 5.1–31.5 and an average chain length (ACL) of 24.9–29.3. The isotopic compositions (mean±1σ, n =33) of the n-alkanes are −195±16‰ for hydrogen and −30.6±2.4‰ for carbon. The insect n-alkanes are depleted in D by approximately 30–40‰ compared with wax n-alkanes from C3 (−155±25‰) and C4 vascular plants (−167±13‰), whereas their δ13C values fall between those of C3 (−36.2±2.4‰) and C4 plants (−20.3±2.4‰). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift δD records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the δ13C records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (δD n -alkene −δD n -alkane =−17±16‰), but the δ13C values are almost identical to those of the n-alkanes (δ13C n -alkene −δ13C n -alkane =0.1±0.2‰). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes. [Copyright &y& Elsevier]

Abstract: We report the molecular and stable isotopic (δD and δ13C) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21–33; maximum C23–C29) are found to be abundant in the insects (31–781μg/dry g), with a carbon preference index (CPI) of 5.1–31.5 and an average chain length (ACL) of 24.9–29.3. The isotopic compositions (mean±1σ, n =33) of the n-alkanes are −195±16‰ for hydrogen and −30.6±2.4‰ for carbon. The insect n-alkanes are depleted in D by approximately 30–40‰ compared with wax n-alkanes from C3 (−155±25‰) and C4 vascular plants (−167±13‰), whereas their δ13C values fall between those of C3 (−36.2±2.4‰) and C4 plants (−20.3±2.4‰). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift δD records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the δ13C records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (δD n -alkene −δD n -alkane =−17±16‰), but the δ13C values are almost identical to those of the n-alkanes (δ13C n -alkene −δ13C n -alkane =0.1±0.2‰). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes. [Copyright &y& Elsevier]

This article presents an experimental analysis of the organic content of two serpentinized peridotite rocks of the terrestrial upper mantle. The samples have been dredged on the floor of the Ashadze and Logatchev hydrothermal sites on the Mid-Atlantic Ridge. In this preliminary analysis, amino acids and long chain n-alkanes are identified. They are most probably of biological/microbial origin. Some peaks remain unidentified. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers (GDGTs) in marine sediments helps inform their use in paleoceanography. Compound-specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect paleotemperature reconstructions. Similar analyses are warranted to investigate how analogous processes affecting GDGTs impact TEX86 paleotemperatures. Here we present radiocarbon measurements on individual GDGTs from Bermuda Rise and Santa Monica Basin sediments and discuss the results in the context of previous studies of co-depositional alkenones and foraminifera. The 14C contents of GDGTs and planktonic foraminifera in Bermuda Rise are very similar, suggesting a local source; and TEX86-derived temperatures agree more closely with foraminiferal temperatures than do temperatures. In contrast, GDGTs in Santa Monica Basin are depleted in 14C relative to both alkenones and foraminifera, and TEX86 temperatures agree poorly with known surface water values. We propose three possible factors that could explain these results: (i) GDGTs may be labile relative to alkenones during advective transport through oxic waters; (ii) archaeal production deep in the water column may contribute 14C-depleted GDGTs to sediments; and (iii) some GDGTs also may derive from sedimentary archaeal communities. Each of these three processes is likely to occur with varying relative importance depending on geographic location. The latter two may help to explain why TEX86 temperature reconstructions from Santa Monica Basin do not appear to reflect actual sea surface temperatures. Terrigenous GDGTs are unlikely to be major contributors to Bermuda Rise or Santa Monica Basin sediments, based on values of the BIT index. The results also indicate that the crenarchaeol regioisomer is governed by processes different from other GDGTs. Individual measurements of the crenarchaeol regioisomer are significantly depleted in 14C relative to co-occurring GDGTs, indicating an alternative origin for this compound that presently remains unknown. Re-examination of the contribution of crenarchaeol regioisomer to the TEX86 index shows that it is a significant influence on the sensitivity of temperature reconstructions. [Copyright &y& Elsevier]

Abstract: We describe an improved method for purification of sedimentary vanadyl and nickel porphyrins (i.e., naturally occurring metalloalkylporphyrins). For the purpose of compound-specific isotopic analyses, various sedimentary porphyrins were purified from the complex natural mixtures by the dual-step high-performance liquid chromatography (HPLC) method. The high-sample-capacity reversed-phase HPLCs by adding N,N-dimethylformamide to the mobile phase allow an efficient collection of fractions containing the target compounds even using analytical-scale columns. Furthermore, this method achieved improved chromatographic resolutions but significantly reduced the overall retention time down to 60% compared with the previous work. The target compounds were then isolated with the normal-phase HPLC with the baseline-resolution, which is necessary to avoid chromatographic isotopic fractionation. One of the advantages of this method is that it requires neither derivatization nor demetallation. The purity of these isolated compounds was demonstrated by various HPLC online detection methods utilizing a photodiode-array detector, a mass selective detector. The overall recoveries of Ni porphyrin, VO porphyrin, and porphyrin-free base, respectively, were estimated to be approximately 50–60%, 65%, and 85%. [Copyright &y& Elsevier]

Recent astronomical observations and planetary missions have found that complex organics are prevalent throughout the universe, from the solar system to distant galaxies. However, the detailed chemical composition and the synthesis pathway of these organics are still unclear. Circumstellar envelopes represent excellent laboratories to study the abiological synthesis of extraterrestrial organics. Novae, having very short dynamical lifetimes, can put severe constraints on the chemical pathway of organic synthesis. Here, we report a laboratory simulation of carbonaceous dust with inclusion of Nitrogen in the form of Quenched Nitrogen-included Carbonaceous Composite (QNCC). QNCC is produced by the quenched condensation of plasma gas generated from the nitrogen gas, and aromatic and/or aliphatic hydrocarbon solids by applying microwave discharge (2.45 GHz, 300 W). We have shown that the spectra of QNCC have a close resemblance to the observed infrared spectra of novae. The results of the infrared and X-ray analyses suggest that the nitrogen inclusion in the form of amine plays an important role in the origin of the broad 8 μm feature of dusty novae. We conclude that QNCC is at present the best laboratory analog of organic dust formed in the circumstellar medium of dusty classical novae, which carries the unidentified infrared bands in novae via thermal emission process. [ABSTRACT FROM AUTHOR]

The Almahata Sitta (AhS) meteorite is a unique polymict ureilite. Recently, carbonaceous chondritic lithologies were identified in AhS. Organic matter (OM) is ubiquitously found in primitive carbonaceous chondrites. The molecular and isotopic characteristics of this OM reflect its origin and parent body processes, and are particularly sensitive to heating. The C1 lithologies AhS 671 and AhS 91A were investigated, focusing mainly on the OM. We found that the OM in these lithologies is unique and contains primitive isotopic signatures, but experienced slight heating possibly by short‐term heating event(s). These characteristics support the idea that one or more carbonaceous chondritic bodies were incorporated into the ureilitic parent body. The uniqueness of the OM in the AhS samples implies that there were large variations in primitive carbonaceous chondritic materials in the solar system other than known primitive carbonaceous chondrite groups such as CI, CM, and CR chondrites. [ABSTRACT FROM AUTHOR]

A novel species of the family Alepocephalidae (slickheads), Narcetes shonanmaruae, is described based on four specimens collected at depths greater than 2171 m in Suruga Bay, Japan. Compared to other alepocephalids, this species is colossal (reaching ca. 140 cm in total length and 25 kg in body weight) and possesses a unique combination of morphological characters comprising anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Mitogenomic analyses also support the novelty of this large deep-sea slickhead. Although most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, behavioural observations and dietary analyses indicate that the new species is piscivorous. In addition, a stable nitrogen isotope analysis of specific amino acids showed that N. shonanmaruae occupies one of the highest trophic positions reported from marine environments to date. Video footage recorded using a baited camera deployed at a depth of 2572 m in Suruga Bay revealed the active swimming behaviour of this slickhead. The scavenging ability and broad gape of N. shonanmaruae might be correlated with its colossal body size and relatively high trophic position. [ABSTRACT FROM AUTHOR]

Radiocarbon natural abundance (Δ14C) has emerged as a useful dietary tracer in freshwater ecology for the past decade, yet its applicability for separating aquatic and terrestrial resources has not been examined quantitatively. Here, we report Δ14C values of stream invertebrates in different functional feeding groups collected from the upper South Fork Eel River watershed, northern California. We found that algae‐grazing insect larvae show low Δ14C values (−43.1 ± 21.8‰, mean ± standard deviation, N = 6), reflecting the signal of dissolved inorganic carbon weathered from ancient inorganic carbon or respiration of old organic carbon. In contrast, the Δ14C values of leaf‐shredding insect larvae (21.7 ± 31.9‰, N = 5) were close to those of contemporary atmospheric CO2 except at the SF Eel River where algal production was highest. The Δ14C values of predators (−6.1 ± 35.7‰, N = 14) were intermediate between those of grazers and shredders. In a Bayesian mixing model, Δ14C provided a more ecologically realistic estimate for terrestrial vs. aquatic source contributions to invertebrates with lower uncertainty (i.e., narrower credible interval) than did the stable carbon isotopes (δ13C). These results demonstrate that Δ14C can be used, in combination with δ13C, to more precisely estimate organic matter sources to stream animals. [ABSTRACT FROM AUTHOR]

Rationale: To achieve better precision and accuracy for δ13C analysis of individual amino acids (AAs), we have developed a new analytical method based on multi‐dimensional high‐performance liquid chromatography (HPLC) and elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). Unlike conventional methods using gas chromatography, this approach omits pre‐column chemical derivatization, thus reducing systematic errors associated with the isotopic measurement. Methods: The separation and isolation of individual AAs in a standard mixture containing 15 AAs and a biological sample, spear squid (Heterololigo bleekeri) were performed. AAs were isolated using an HPLC system equipped with a reversed‐phase column and a mixed‐mode column and collected using a fraction collector. After the chromatographic separation and further post‐HPLC purification, the δ13C values of AAs were measured by EA/IRMS. Results: The complete isolation of all 15 AAs in the standard mixture was achieved. The δ13C values of these AAs before and after the experiment were in good agreement. Also, 15 AAs in the biological sample, H. bleekeri, were successfully measured. The δ13C values of AAs in H. bleekeri varied by as much as 30‰ with glycine being most enriched in13C. Conclusions: The consistency between the δ13C values of reference and processed AAs demonstrates that the experimental procedure generates accurate δ13C values unaffected by fractionation effects and contamination. This method is therefore suitable for δ13C analysis of biological samples with higher precision than conventional approaches. We propose this new method as a tool to measure δ13C values of AAs in biological, ecological and biogeochemical studies. [ABSTRACT FROM AUTHOR]

The Aptian–Albian boundary is marked by one of the major oceanic perturbations during the Cretaceous, called Oceanic Anoxic Event (OAE) 1b. Extensive volcanic episodes at the Southern Kerguelen Plateau has been suggested as the trigger of OAE1b, but compelling evidence remains lacking. Here, we reconstructed the temporal variations of marine Os isotopic ratios across the Aptian–Albian boundary in the Tethyan and Pacific pelagic sedimentary records to elucidate the causal links between OAE1b, the biotic turnover, and volcanic episodes. Our new Os isotopic records show two negative spikes that correlate with a period of planktonic foraminiferal turnover across the Aptian–Albian boundary during OAE1b and suggest multiple submarine volcanic events. By comparing our Os isotopic profile with carbon isotopic compositions of carbonate, CaCO3 content, and the relative abundances of agglutinated foraminifera, we conclude that ocean acidification caused by the massive release of CO2 through extensive volcanic episodes could have promoted the major planktonic foraminiferal turnover during OAE1b. [ABSTRACT FROM AUTHOR]

• We discovered LCAs in the brackish Lake Takahoko, in northern Japan. • Two distinct Group II haptophytes are responsible for LCAs production. • Lake Takahoko may be suitable for alkenone paleotemperature reconstruction. Identifying the lacustrine haptophyte species that produce long-chain alkenones (LCAs) is essential for using alkenone unsaturation ratios to create lake water temperature reconstructions. We discovered LCAs in the brackish Lake Takahoko in northern Japan. The identity of LCA-producing species was investigated using 18S ribosomal DNA (rDNA) and organic geochemical analysis. Two distinct genetic groups, termed Tak-A and Tak-B, were identified within the Group II haptophyte phylotype. Tak-A was closely related to Hap-A, which was obtained from Lake George, USA; and Tak-B was identified as Isochrysis galbana. Because Hap-A and Isochrysis galbana have similar temperature calibrations, Tak-A and Tak-B were also expected to share similar calibrations. Therefore, the changes of their relative abundances in the lake should not significantly disturb paleotemperature reconstructions. The alkenone temperature recorded in the surface sediment corresponded to the lake temperature in early to late summer. This is likely related to the haptophyte bloom season in Lake Takahoko suggesting that this lake may be a viable location for creating a lacustrine alkenone paleotemperature record. [ABSTRACT FROM AUTHOR]

The long‐distance migrations by marine fishes are difficult to track by field observation. Here, we propose a new method to track such migrations using stable nitrogen isotopic composition at the base of the food web (δ15NBase), which can be estimated by using compound‐specific isotope analysis. δ15NBase exclusively reflects the δ15N of nitrate in the ocean at a regional scale and is not affected by the trophic position of sampled organisms. In other words, δ15NBase allows for direct comparison of isotope ratios between proxy organisms of the isoscape and the target migratory animal. We initially constructed a δ15NBase isoscape in the northern North Pacific by bulk and compound‐specific isotope analyses of copepods (n = 360 and 24, respectively), and then we determined retrospective δ15NBase values of spawning chum salmon (Oncorhynchus keta) from their vertebral centra (10 sections from each of two salmon). We then estimated the migration routes of chum salmon during their skeletal growth by using a state‐space model. Our isotope tracking method successfully reproduced a known chum salmon migration route between the Okhotsk and Bering seas, and our findings suggest the presence of a new migration route to the Bering Sea Shelf during a later growth stage. [ABSTRACT FROM AUTHOR]

Some xenolithic clasts in meteorites may have originated from unique primitive Solar System bodies. These clasts would provide novel insights into the early evolution of the Solar System. We conducted multiple analyses of organic matter (OM) in a CI-like xenolithic clast in the Zag (H5) meteorite including bulk elemental and isotopic analysis, FTIR, STXM/XANES, and NanoSIMS. The bulk C and N abundances in the Zag clast were +5.1 ± 0.4 wt.% and +0.26 ± 0.01 wt.%, respectively, which were the highest observed among various chondrite groups. The bulk δ13C value of the Zag clast was +23.0 ± 4.1‰ which was close to the value of the Tagish Lake meteorite; the δ15N value was +300 ± 3‰ which was close to the values of CR chondrites and Bells (a unique CM). The δD values of C-rich regions obtained by NanoSIMS were approximately +600 to +2000‰ which were close to the values of IOM from CI, CM and Tagish Lake. Some isotopic "hot spots" were observed with δD values up to ≈ +4000‰ and δ15N values up to ≈ +5500‰. The infrared transmission spectrum of the Zag clast was consistent with the abundant phyllosilicates and carbonates observed in the clast. The STXM showed abundant OM in various forms. C-XANES spectra from the OM were generally similar to CI/CM/CR chondrites. However, some variations existed in the molecular structures. OM in the Zag clast was partially associated with carbonates. The functional group, elemental and isotopic signatures of the OM in the Zag clast support the idea that the Zag clast is unique among known carbonaceous chondrite groups and originated from the outer Solar System such as aqueously-altered D/P type asteroids. [ABSTRACT FROM AUTHOR]

• We examined preparation and measurement methods for ultra-small-scale 14C at AORI, Univ Tokyo. • Applying a suitable pretreatment and fine-tuning of AMS allow ultra-small-scale 14C measurements. • The MCC and DCC are estimated to be 0.37 ± 0.13 μgC and <1.62 μgC, respectively. Small- to ultra-small-scale radiocarbon (14C) measurements are an essential technique for compound-specific radiocarbon measurements of fatty acids and amino acids. The Atmosphere and Ocean Research Institute at the University of Tokyo installed an NEC 250 kV single-stage accelerator mass spectrometer (AMS) in March 2013. We improved the pretreatment method to reduce modern and 14C-dead carbon contaminations. The modern and 14C-dead carbon contaminations from combustion and graphitization were estimated to be 0.37 ± 0.13 μgC and lower than 1.62 μgC, respectively. Furthermore, we examined an AMS measurement method that can be used to obtain a stable beam current intensity. As a result, we succeeded in conducting small- to ultra-small-scale 14C measurements. Typically, a sample of 100 µg of carbon (μgC) can be measured with a current of 25 μA in a low-energy Faraday cup for 30 min or more, whereas a sample of 10 μgC can be measured with a current of 1 μA in a low-energy Faraday cup for 15 min or more. [ABSTRACT FROM AUTHOR]

Tailoring the surface of biodegradable microparticles is important for various applications in the fields of cosmetics, biotechnology, and drug delivery. Chitin nanofibers (ChNFs) are one of the promising materials for surface tailoring owing to its functionality, such as biocompatibility and antibiotic properties. Here, we show biodegradable polymer microparticles densely coated with ChNFs. Cellulose acetate (CA) was used as the core material in this study, and ChNF coating was successfully carried out via a one-pot aqueous process. The average particle size of the ChNF-coated CA microparticles was approximately 6 μm, and the coating procedure had little effect on the size or shape of the original CA microparticles. The ChNF-coated CA microparticles comprised 0.2–0.4 wt% of the thin surface ChNF layers. Owing to the surface cationic ChNFs, the ζ-potential value of the ChNF-coated microparticles was +27.4 mV. The surface ChNF layer efficiently adsorbed anionic dye molecules, and repeatable adsorption/desorption behavior was exhibited owing to the coating stability of the surface ChNFs. The ChNF coating in this study was a facile aqueous process and was applicable to CA-based materials of various sizes and shapes. This versatility will open new possibilities for future biodegradable polymer materials that satisfy the increasing demand for sustainable development. [Display omitted] [ABSTRACT FROM AUTHOR]

Objective: The inhabitants of several sites in the Upper Tigris Valley, such as Hakemi Use, domesticated animals and cereals during the Pottery Neolithic period, while the inhabitants in this valley were hunter–gatherers in the Pre‐Pottery Neolithic period, consuming freshwater and terrestrial food resources. However, there is considerable uncertainty surrounding whether or not changes in dietary food composition accompanied the shift in food production away from foraging. In order to reveal the impact of the development of agriculture on the human diet over the Pre‐Pottery and Pottery Neolithic periods in this region, we analyzed the isotopic compositions of amino acids from the farmers at the Hakemi Use Pottery Neolithic site, and compared them with those from the Pre‐Pottery hunter–gatherers in the close region. Materials and Methods: Herein, we report the nitrogen isotopic compositions of amino acids, as well as both carbon and nitrogen isotopic compositions of bulk collagen, from human and faunal remains collected from Hakemi Use. Results: Whereas freshwater resources were consumed by hunter–gatherers in this region during the Pre‐Pottery period, the δ15N values of glutamic acid (δ15NGlu) and phenylalanine (δ15NPhe) suggest that freshwater food resources were rarely consumed by inhabitants following the development of agriculture. Discussion: Despite living in similar settings by the Tigris as its inhabitants during the Pre‐Pottery period, the farmers of the Pottery Neolithic period depended less on freshwater resources for their diets relative to the hunter–gatherers of the Pre‐Pottery Neolithic period. [ABSTRACT FROM AUTHOR]

Abstract In the estuary region of the Yangtze River (China), the oldest Neolithic civilization based on paddy rice cultivation flourished in the mid-Holocene (7.5–4.2 cal. kyr BP). However, although it is known that this Neolithic civilization collapsed at around 4.2 cal. kyr BP, the reason behind the collapse remains controversial. A sedimentary core (MD06-3040) collected from the inner shelf of the East China Sea, off the southeast coast of China, provides an excellent insight into estimate the Holocene regional paleoenvironment, including the alkenone based sea surface temperature (SST), atmospheric temperature (AT), and paleoproductivity. Extraordinarily severe abrupt cold episodes (i.e., 3–4 °C drop in SST) occurred frequently in the Yangtze delta region during 4.4–3.8 cal. kyr BP. These episodes could have been related to the global climatic transition called the "4.2 ka event", when the East Asian monsoon hydrological regime might have been altered. The cold episodes could be sufficiently severe to damage rice cultivation and their occurrence constitutes a plausible explanation for the demise of the Yangtze Neolithic civilization. Highlights • A marine sedimentary core provided paleotemperature records around the Yangtze delta. • Alkenone paleothermometer records suggested cold episodes occurred around 4.2 ka. • The cold climate could be related to the collapse of the Yangtze Neolithic civilization. [ABSTRACT FROM AUTHOR]

Abstract Padul is one of the few wetland sites in southern Europe and the Mediterranean region that exhibits an unusually large temporal span (>100 kyr) and continuous Quaternary sedimentary record. Previous core-based studies from Padul yielded paleoecological datasets (i.e., pollen and organic geochemistry), but with a poor age control that resulted in rather arbitrary climate inferences. Therefore, precise age control and a multidisciplinary approach is necessary to understand long-term regional environmental and climate change and the associated local response of the Padul wetland environment. Here we present a new long sediment record (Padul-15-05) from this wetland in the southern Iberian Peninsula with the aim of improving the age control of the sedimentary sequence and carrying out up-to-date high-resolution multiproxy analyses. In this study the age control is based on 61 AMS radiocarbon dates for the last ca. 50 kyr BP and on the extent of amino acid racemization (AAR) in mollusc shells extending back ∼118 kyr BP. No numerical ages are available for the bottom part of the core but the sediment accumulation rates (SAR) and the cyclostratigraphic analysis of the multiproxy data suggest that the core preserves a continuous record of the last ∼197 kyr (from late MIS 7 to present) with millennial-scale time resolution. Sedimentological (lithology, magnetic susceptibility, XRD, color), geochemical (XRF, TOC, C/N, % carbonate content) and paleontological (pollen, charophytes, gastropods) data show co-varying cyclical paleoenvironmental changes linked to orbital-scale climatic variability. Silicon, magnetic susceptibility (MS) and total organic carbon (TOC) data show periodicities between ∼26.2–19.6 kyr linked to insolation, which is strongly dominated by precession cycles at this latitude. High values of Si and MS data have been related to high siliciclastic/detrital input from Sierra Nevada range during minima in insolation due to enhanced soil weathering/erosion during regional aridity and lower forest cover recorded by the arboreal pollen, which could also be favored by a minor biogenic productivity. In addition, warm climate conditions during maxima in insolation mostly resulted in negative precipitation/evapotranspiration balance and low lake levels, while cold glacial and stadial periods were mainly characterized by positive precipitation/evapotranspiration balance, and therefore, high lake levels. The improved chronology of the Padul sedimentary sequence along with a multiproxy study permitted us to better relate environmental and vegetation changes to climatic events and to demonstrate how both local (i.e., lake level, sedimentation) and regional (i.e., vegetation) environments responded to orbital-scale climate changes. Highlights • A new long sedimentary record from the Padul wetland (Padul-15-05) with an improved age control of the last ∼ 200,000 years. • The multiproxy analysis of the Padul record show paleoenvironmental changes related with orbital-scale climate oscillations. • The multiproxy analysis reflects regional and local environmental changes linked to precession, which influenced insolation. [ABSTRACT FROM AUTHOR]

The separation and quantification of underivatized naturally occurring amino acids (AAs) by high-performance liquid chromatography (HPLC) is advantageous for reducing preparation time, running costs, and analytical errors, and is compatible with the isolation of intact AAs. This study establishes and validates an analytical method for the separation and quantification of underivatized AAs and taurine (Tau) in the sub- to several-nanomolar range (ca. 0.1–1.6 nmol) by optimizing ion-pair HPLC coupled to a corona charged aerosol detector (corona CAD). Chromatographic separation of 19 AAs and Tau was achieved using a porous graphite carbon (PGC) column and nonafluoropentanoic acid (NFPA) as a volatile ion-pair reagent. The response of the corona CAD to the AAs was highly dependent on the eluate composition, whereas these response factors were similar for AAs in eluate with similar compositions. Regression curves and coefficients (r 2 ) >0.998 were obtained for plots of injection amount versus peak area, except for Arg which co-eluted with a background peak. On the other hand, all plots of injection amount versus peak height regressed to curves with r 2  > 0.997. Repeat quantification based on peak area showed lower relative standard deviations (RSDs) (typically better than 5%) than those based on peak height. The present method is useful for quantifying AAs from proteins and Tau in the sub- to several-nanomolar range without derivatization, and constant repeatability can be maintained by quantification using peak areas. [ABSTRACT FROM AUTHOR]

Abstract: The abundance and biomass of benthic foraminifera are high in intertidal rocky‐shore habitats. However, the availability of food to support their high biomass has been poorly studied in these habitats compared to those at seafloor covered by sediments. Previous field and laboratory observations have suggested that there is diversity in the food preferences and modes of life among rocky‐shore benthic foraminifera. In this study, we used the stable nitrogen isotopic composition of amino acids to estimate the trophic position, trophic niche, and feeding strategy of individual foraminifera species. We also characterized the configuration and structure of the endobiotic microalgae in foraminifera using transmission electron microscopy, and we identified the origin of endobionts based on nucleotide sequences. Our results demonstrated a large variation in the trophic positions of different foraminifera from the same habitat, a reflection of endobiotic features and the different modes of life and food preferences of the foraminifera. Foraminifera did not rely solely on exogenous food sources. Some species effectively used organic matter derived from endobionts in the cell cytoplasm. The high biomass and species density of benthic foraminifera found in intertidal rocky‐shore habitats are thus probably maintained by the use of multiple nitrogen resources and by microhabitat segregation among species as a consequence. [ABSTRACT FROM AUTHOR]

Abstract: The present study systematically investigates shock‐induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen‐related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock‐induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock‐induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote‐sensing signature of the 3.3–3.6 μm absorption due to hydrogen‐related bonds on the surface of small bodies would be a promising indicator for the presence of less‐thermally‐altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample‐return spacecraft missions, such as Hayabusa2 and OSIRIS‐REx. [ABSTRACT FROM AUTHOR]

By presenting benthic foraminifera isotope profiles and bulk geochemical composition of core sediments, we offer a mutiproxy reconstruction of the central Okhotsk Sea oceanography between ∼130 to and ∼115 kyr, related to the marine isotopic stage 5e (MIS 5e). Sediments from the site MR0604-PC7A have been compared with paleo- sea surface temperatures and other records. This multiparameter approach allowed to recognize three periods for MIS 5e evolution, characterized by variations in marine productivity and bottom oxygenation. These variations have been ultimately associated with the production of Okhotsk Sea Intermediate Water and the presence or absence of nutrient contribution from the Pacific Deep Water into central Okhotsk Sea. Aeolian input reconstructed by Th/Sc ratio indicates higher values during the MIS 6 and MIS 5d compared with the MIS 5e. Eu ∗ values indicate an input of detrital material from Kurile Islands and East-Kamchatka during the late MIS 5e, absent during the early MIS 5e and glacial periods. [ABSTRACT FROM AUTHOR]

We describe the mass descrimination and validation of an offline method for purification of Li, Mg and S with an ion chromatograph coupled to an automated fraction collector for use prior to stable isotope measurements. Significant sub-fraction mass fractionation was observed for both the Li and the Mg stable isotope ratios. The lighter Li and heavier Mg isotopes were preferentially retained by the column, resulting in 7 Li/ 6 Li and 26 Mg/ 24 Mg biases up to 85.8‰ and 0.95‰, respectively. The isotopic compositions of Li, Mg, and S separated from seawater were δ 7 Li L-SVEC  = +30.9‰, δ 26 Mg DSM3  = −0.83 ± 0.10‰, and δ 34 S VCDT  = +19.4 ± 0.6‰; each chromatographic peak was completely recovered, and the results were in good agreement with the published values regardless of whether or not chemical suppressor was used. The purification method enables multi-isotope analysis of a sample using various mass spectrometry techniques, such as multiple-collector inductively coupled plasma and thermal ionization mass spectrometry. [ABSTRACT FROM AUTHOR]

The nitrogen isotopic composition of amino acids (δ 15 N AA ) is a promising tool for estimating the trophic position and nitrogen sources of organisms in grazing food webs. The utility of δ 15 N AA analysis of microbial processes in the biogeochemistry remains uncertain, because information about the δ 15 N AA values of chemotrophic microbes are still limited. In this study, we report the δ 15 N AA values in five cultured heterotrophic or chemolithoautotrophic microbes (one fungus, one bacterium, and three archaea) with controlled nitrogen sources in synthetic media. When the microbes were grown on ammonium, the apparent nitrogen isotopic fractionation of amino acids relative to glutamic acid in the microbes (e.g., −3.0 ± 1.0‰ for phenylalanine) was similar to those in algae. When the microbes were grown on a free amino acid mixture, the δ 15 N offsets of amino acids in the microbial cells relative to the amino acids in the culture media (e.g., +8.2 ± 0.8‰ for glutamic acid and +0.1 ± 0.2‰ for phenylalanine) were close to the standard isotopic fractionation between animals and their diets. These results suggest that the δ 15 N AA pattern can be used to distinguish two end-member metabolic modes in microbes (i.e., de novo synthesis of amino acids from inorganic nitrogen vs. assimilation of amino acids from environments). We also discussed the effects of metabolic pathways on the δ 15 N AA values and their fractionation with respect to the diversity of amino acid metabolism in microbes. These findings will form an important baseline for interpreting the δ 15 N AA values of organisms and detritus in natural environments. [ABSTRACT FROM AUTHOR]