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Aeolianites with a mixed clastic and carbonate detrital mineralogy are typical deposits of tropical coastal desert environments. These deposits are genetically related to transgressive–regressive cycles, with the shallow‐marine carbonate detrital component being deflated from the exposed seafloor during episodes of glacial sea‐level lowstands, transported and later accumulated onto more continental areas. A detailed investigation of the granulometric and petrographic properties of the Late Pleistocene to Holocene Ghayathi Formation in the United Arab Emirates provides a comprehensive numerical dataset that reveals the complex spatio‐temporal depositional and diagenetic evolution of a mixed siliciclastic–carbonate continental aeolianite. Fifty‐one thin sections and forty‐four rock samples of three sedimentary units (Madinat‐Zayed, Ghayathi and Fuwayrit formations) from the United Arab Emirates were analyzed for their grain‐size distribution, mineralogy and the bulk stable‐carbon and oxygen isotopic composition. Sorting, skewness and kurtosis of the grain‐size distributions provide evidence for a divergent aerodynamic behaviour between the carbonate and siliciclastic particles. The different grain‐size distributions between the inland and coastal sections of the Ghayathi Formation indicate that continental mixed clastic−carbonate aeolianites are affected by density‐driven selective transport and consequent traction sorting due to the nature of carbonate detritus. The transport decoupling of the different detrital components resulted in a 'continental sorting' effect, with the inland sections yielding layers characterized by a better sorted detritus than the coastal areas. All detritus originally composed of aragonite has been removed by dissolution during early meteoric diagenesis, with its shapes frequently preserved by micritic envelopes. The bulk stable‐isotope composition of the carbonate fraction reflects a decreasing degree of meteoric cementation from coastal to inland areas. The high complexity of the lateral and vertical distribution of the sedimentary, diagenetic and isotopic properties of continental mixed aeolianites, such as the Ghayathi Formation, highlights the problem of recognizing such deposits in the pre‐Quaternary sedimentary record. [ABSTRACT FROM AUTHOR]

Since the early 1990s, aerial insectivorous birds have shown serious population declines in North America, but it is not clear if factors common to all species within this guild account for these declines. Among sympatric swallows, population trends differ, and this may be due to differences in ecology operating throughout the annual cycle. Although these species all feed on aerial insects, prey taxa can differ tremendously in their “aeroecology” and use by swallows. We examined the potential for dietary differences among three species of swallows, Barn Swallow (Hirundo rustica), Cliff Swallow (Petrochelidon pyrrhonota), and Tree Swallow (Tachycineta bicolor), breeding sympatrically in southern Ontario, Canada. Potential interspecific differences in nestling diet were examined using two endogenous biomarkers, DNA barcoding of nestling feces and stable isotope analysis (δ 2H, δ 13C, δ 15N) of nestling feathers. We found evidence for differences in dietary sources of provisioned young where Barn Swallows provisioned more terrestrial-based prey, Cliff Swallows provisioned an intermediate diet, and Tree Swallows the most aquatic-emergent insect diet. We suggest this information may help to identify potential factors contributing to differential declines of aerial insectivores operating on the breeding grounds, including diet quality. [ABSTRACT FROM AUTHOR]

In plant science, 2,4-dinitrophenylether of iodonitrothymol (DNP-INT) is frequently used as an alternative to 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone (DBMIB) to examine the capacity of plastoquinol and semiquinone to reduce O2. DNP-INT is considered to be an effective inhibitor of the photosynthetic electron transfer chain (PETC) through its binding at the Q0 site of Cyt- b6f. The binding and action of DNP-INT has been previously characterized spectroscopically in purified Cyt- b6f complex reconstituted with Plastocyanin, PSII membranes and plastoquinone, as well as in isolated thylakoids based on its property to block MV-mediated O2 consumption. Contrary to the conclusions obtained from these experiments, we observed clear reduction of P700+ in samples incubated with DNP-INT during our recent investigation into the sites of oxygen consumption in isolated thylakoids. Therefore, we carried out an extensive investigation of DNP-INT's chemical efficacy in isolated thylakoids and intact leaves. This included examination of its capacity to block the PETC before PSI, and therefore its inhibition of CO2 fixation. P700 redox kinetics were measured using Dual-PAM whilst Membrane Inlet Mass Spectrometry (MIMS) was used for simultaneous determination of the rates of O2 evolution and O2 consumption in isolated thylakoids and CO2 fixation in intact leaves, using two stable isotopes of oxygen (16O2, 18O2) and CO2 (12C, 13C), respectively. Based on these investigations we confirmed that DNP-INT is unable to completely block the PETC and CO2 fixation, therefore its use may produce artifacts if applied to isolated thylakoids or intact cells, especially when determining the locations of reactive oxygen species formation in the photosynthetic apparatus. [ABSTRACT FROM AUTHOR]

Most anthropogenic nitrogen (N) reaches coastal waters via rivers carrying increasing loads of sewage, fertilizer, and sediments. To understand anthropogenic N impacts, we need to understand historical N-dynamics before human influence. Stable isotope ratios of N preserved in carbonates are one way to create temporal N records. However, records that span periods of human occupation are scarce, limiting our ability to contextualize modern N dynamics. Here, we produce a fossil-bound N-record using coral subfossils, spanning 6700 years in China's Greater Bay Area (GBA). We found that during the mid-to-late Holocene, the GBA's coastal N was dominated by fluvial sources. The weakening of the Asia monsoon throughout the late-Holocene decreased river outflow, leading to a relative increase of marine nitrate. This source shift from riverine-to-ocean dominance was overprinted by anthropogenic N. During the late 1980s to early 1990s, human development and associated effluent inundated the coastal system, contributing to the decline of coral communities. [Display omitted] • Carbonate-bound nitrogen from coral faithfully tracked marine nitrogen-source changes over the last 6,700 years. • Coral carbonate-bound δ 15N values decreased from the mid-Holocene to the late-Holocene by ~2 ‰. • Decline in δ 15N values is driven by a decrease in the East Asian monsoon intensity. • Elevated δ 15N values caused by anthropogenic N are unique over 6,700 years, and coincide with regional coral declines. [ABSTRACT FROM AUTHOR]

Abstract: The TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms) sea-surface temperature (SST) proxy is based on the distribution of isoprenoid glycerol dialkyl glycerol tetraether (GDGT) membrane lipids of pelagic Thaumarchaeota that are preserved in marine sediments. It is a valuable tool for reconstructing past SSTs from sedimentary archives; however there are still major uncertainties as to the effects of variables other than temperature on the proxy. Here we present the first study of GDGT variability across early Cretaceous interbedded pelagic and shelf-sourced turbiditic sediments from two Deep Sea Drilling Project (DSDP) sites in the western North Atlantic. The results indicate that a small, but consistent, offset in TEX86 ratios, equivalent to ~1–2°C of temperature difference, occurs between interbedded lithologies of a similar age. The offset can be attributed to spatial differences in sea-surface temperatures or thaumarchaeotal populations between the shelf and the open ocean, or to secondary diagenetic effects related to oxic degradation of the GDGTs. Of these, a difference in either thaumarchaeotal taxa or ecology between those living in the shelf and ocean areas seems most plausible. Regardless of the root cause of the offset, these findings highlight the necessity of careful sample selection prior to TEX86 analysis, to ensure robust interpretation of palaeotemperature trends. [Copyright &y& Elsevier]

Abstract: Intercropping biofuel feedstocks in managed forests of the southeastern United States is a potentially sustainable source of renewable energy. Ecological effects of energy crops in forests are poorly understood, and it is unknown whether the ecological role of native rodents is influenced by alternative food resources. Therefore, we used a stable isotope analysis to compare diet and trophic responses of white-footed mice (Peromyscus leucopus) in 1) plots where switchgrass (Panicum virgatum), a C4 plant, was intercropped with loblolly pine (Pinus taeda), a C3 plant, 2) plots of loblolly pine, and 3) plots of monocropped switchgrass. We collected fur from live-trapped rodents and potential dietary sources in 2010. We predicted δ13C and δ15N values of mice in switchgrass plots would reflect a C4-based, granivorous, diet if there was an effect of intercropping on the functional role of mice. Del13C values of mouse fur in monocropped switchgrass, but not intercropped switchgrass plots, shifted more toward a C4 signal. However, δ15N values indicated that mice remained functionally omnivorous across treatments. Our results were supported by isotope values from invertebrates across guilds. Diet and trophic position of white-footed mice was not influenced by intercropping switchgrass in pine plantations indicating they maintained their functional role in this biofuels management regime. Future research should focus on individual and population responses of rodents to altered vegetation structure where biofuels feedstocks are grown and indirect effects on inter- and intra-species interactions. [Copyright &y& Elsevier]

Abstract: Previous studies have demonstrated the potential of archaeologically-recovered insect remains to stand as evidence of past human activities such as trade and industry. The present investigation reports the recovery of stable-isotopes from modern and Neolithic insect fauna and explores their utility in addressing issues of palaeoeconomic significance. While in its infancy, the application of stable-isotope methods towards archaeological insects may provide insight into exchange patterns and land-usage in the past. In the present analysis, stable-isotopes from modern and archaeological insects showed potential as a means of assessing local versus non-local signatures. Further study is recommended. [Copyright &y& Elsevier]

Abstract: Asymmetric dimethylarginine (ADMA, N G,N G-dimethyl-l-arginine) is an endogenous inhibitor of nitric oxide (NO) synthesis, a potential risk factor for cardiovascular diseases and a powerful biochemical parameter in clinical studies. In our previous work we have reported on a GC-tandem MS method for the accurate and precise quantification of ADMA in biological fluids using de novo synthesized [2H3]-methyl ester ADMA (d3Me-ADMA) as internal standard (IS). This method provides basal ADMA concentrations in biological fluids that agree with those obtained by other groups using other validated methods for ADMA. Unanimously, de novo synthesized stable-isotope labeled analogues are considered not ideal IS, because they must be prepared in a matrix different from the biological sample. Recently, [2,3,3,4,4,5,5-2H7]-ADMA (d7-ADMA) has become commercially available and we took this opportunity to test the reliability of the de novo synthesized d3Me-ADMA as an IS for ADMA in GC-tandem MS. In this article, we report on the re-validation of the previously reported GC-tandem MS method for ADMA in human plasma and urine using d7-ADMA as IS, and on comparative quantitative analyses of ADMA by GC-tandem MS using d7-ADMA and d3Me-ADMA. After thorough standardization of d7-ADMA and methods validation, we obtained by GC-tandem MS very similar ADMA concentrations in plasma and urine using d7-ADMA and d3Me-ADMA. The present study gives a proof of evidence for the aptitude of 2H3-ADMA as IS in GC-tandem MS and suggests that de novo synthesis of stable-isotope labeled alkyl esters of amino acids and amino acid derivates may be a generally applicable method in mass spectrometry-based methods for amino acids. This approach is especially useful for amino acids for which no stable-isotope labeled analogues are commercially available. [Copyright &y& Elsevier]

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Abstract: In a sediment core from the leeward side of the Great Bahama Bank (Ocean Drilling Program ODP-Leg 166, 1006A-24H, early Pliocene) several paleoceanographic proxies were compared with carbonate mineralogy. The proxies measured on the planktonic foraminifera species Globigerinoides sacculifer are Mg/Ca and Sr/Ca elemental ratios, and δ 18O values. These proxies are widely used in pelagic sediments to derive parameters of water masses, such as paleo-temperature and -salinity. To produce quantitative estimates it is necessary to verify that the primary shell mineralogy of the foraminifera was not altered diagenetically. Diagenetic alteration can be rapid in periplatform settings relative to pelagic deep-sea sediments, since the meta-stable carbonate phases provide an additional driving force for recrystallisation. We show that the Sr/Ca ratio of foraminiferal calcite can be used to assess the degree of diagenetic alteration of their shell chemistry. Using this method, we demonstrate that the primary signal in the oxygen-isotope ratios is preserved in the studied core. In the Mg/Ca record, the relative change of foraminiferal Mg/Ca ratios seems to be preserved, but absolute values are influenced by diagenesis. The second set of proxies comprises δ 13C and C/N ratios of organic carbon. These are used in pelagic sediments in order to assess the origin of organic carbon (terrestrial or marine phytoplankton). It is demonstrated here that a simple two-end mixing model cannot explain the observed co-occurrence of relatively high δ 13Corg and C/N values. As the δ 13Corg values co-vary with the aragonite content, we attribute this signature to varying contribution of organic carbon from benthic algae, which are also the major aragonite producers on the platform top. [Copyright &y& Elsevier]

Food web interactions in animal communities can be investigated through the measurement of stable isotopes (e.g. δ15N, δ13C). We used this approach in a community of 14 species of seabirds breeding on the Argentinean Patagonian coast. Tissue samples were collected from nestling and adult seabirds, as well as prey, during three consecutive breeding seasons in 28 breeding colonies. Relative to those in other temperate and polar regions,this seabird community showed a high degree of overlap in trophic level (TL) among species (93% of species within a TL range of 0·7) and also a comparatively high mean trophic level (4·1). Relative positions of seabirds in relation to prey suggest that most species feed on pelagic fish and to a lesser extent on invertebrates. Stable isotope values of specialist feeders, Olrolg's (Larus atlanticus) and dolphin gulls (Leucophaeus scoresbii), which were previously assumed to feed mainly on crabs and sea lion excrement, respectively, suggested a broader diet than expected. Based on stable isotope values of individuals, groups of phylogenetically related species generally showed a high degree of overlap within each group. Given the degree of isotope overlap in this species-rich community, coexistence could be interpreted as a consequence of superabundance of food or species diversification in morphology and foraging strategies. The short range of trophic level makes these seabirds vulnerable to the reduction of fish stocks due either to commercial fishing or stochastic fluctuations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/Ni ratio of pyrite characterized submarine-magmatic hydrothermal ore process. • High-temperature VMS system > 300 °C formed from multiple sulfur sources. • Geochemical trends in sphalerite and pyrite by LA-ICP-MS suggest VMS-type deposits in the Betul belt. • PCA on pyrite and sphalerite helps in the reconstruction of the metallogeny and exploration prospectivity. • Chalcopyrite disease in sphalerite reflect high-temperature ore fluid and metamorphism. The Paleoproterozoic volcanogenic massive sulfide (VMS) deposits in the Betul belt (BB) (ca.1.7 Ga) in central India are well-known for their low-grade Zn-Cu-Pb sulfide mineralization. The physicochemical conditions of ore formation, size, grade, extent, and nature of mineralization are the ongoing debates and concerns to the exploration agencies for the last two decades. Field examination, drill core analysis, petrography, and scanning electron microscopic studies reveal the occurrence of chalcopyrite, sphalerite, pyrite, galena with minor pyrrhotite in the form of dissemination, stringers, and semi-massive sulfide veins. We present the minor-trace element contents in sphalerite and pyrite from drill core samples of four deposits (Banskhapa, Jangaldehri, Biskhan, and Bhuyari), analyzed by electron probe microanalyzer (EPMA) and in-situ laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) for determining ore-forming temperature, ore genesis and exploration prospectivity. The EPMA and LA-ICP-MS studies of sphalerite display a slightly high concentration of trace elements like Mn, In with a mean value of 3533 ppm and 33 ppm, respectively. On the other hand, Ga, Ge, and Ag content are low in abundance along with a low concentration of Bi, Pb, and Sb in all four deposits. Pyrites show low Ni and high Co/Ni (mostly > 1) ratios and variable Ti, Se, As, and Mn. Multivariate statistical analysis, especially the principal component analysis (PCA) of these trace elements, defines the geochemical variations among the Betul belt deposits. The ore-forming temperature is estimated using sphalerite thermometry (374 °C to 402 °C) and pyrite thermometry (225 °C to 484 °C). The geochemical discrepancies occur due to magmatic-hydrothermal activities caused by the sub-volcanic intrusions, followed by recrystallization and remobilization of the sub-microscopic inclusions during subsequent metamorphism. Additionally, sulfur isotope analysis provides insights into the sulfur source variations, metals, and mineralization. Carbon and Oxygen isotopes are used to understand the physicochemical conditions of the ore-forming environment. Sphalerite, pyrite, and chalcopyrite from Banskhapa deposit suggest a broad range of δ34S values (7.27–7.79‰, 8.37–8.61‰, and 6.58–6.72‰ respectively, n = 7), which advocate sulfur mostly derived by thermochemical reduction (TSR) of seawater sulfate with some input of magmatic sulfur leaching from the igneous basement. Carbon and oxygen isotope studies of carbonates from Jangaldehri and Bhuyari deposits (δ 13C: −6.0 to −13.45‰ with an average value of −9.51‰, n = 7; δ 18O: 7.32‰ to 20.58‰ with an average value of 15.65‰, n = 7) indicate that the carbonates formed from a hydrothermal fluid (seawater with an insignificant magmatic input), the mixing of hydrothermal fluid with ingressing seawater, or both in the mineralized zone. These processes collectively led to Zn-Cu and Zn-Cu-Pb mineralization in the Betul belt. High temperature, strong isotopic and trace element geochemical variations in sphalerites (Ag-Mn, In/Cd-Mn, In/Cd-Fe, Mn-In/Ge, Fe-In/Ge, Fe-In) and pyrite (Ni-Co, As-Cu, Ag-Au, and Se-Te) attest to the mineralization as being volcanogenic massive sulfide (VMS) deposits in Betul belt and differentiated from other genetic types like Mississippi Valley-type (MVT), sedimentary-exhalative (SEDEX), skarn, porphyry, and epithermal hydrothermal deposits. [ABSTRACT FROM AUTHOR]

A double-blind controlled Ca supplementation trial was conducted for 6 months in thirty-four 7-year-old Chinese children from Hongkong and Jiangmen, China. The children were randomly allocated to the study group (n 17) or control group (n 17), and a CaCO3 tablet (300 mg Ca) or a placebo tablet was taken daily. True fractional Ca absorption (TFCA) was evaluated before and after the trial using stable isotopes: 8 mg44Ca mixed in 100 g chocolate milk was given after an intravenous injection of 0·75 mg 42Ca. There was no significant difference in baseline TFCA between the study group (60·6 (SD 11·4)%) and the controls (58·2 (SD 9.0)% P = 0·55). Serum 25-hydroxycholecalciferol levels were comparable between the two groups (P = 0·71). After 6 months, TFCA of the study group (55·6 (SD 12·7)%) was significantly lower than that of the controls (64·3 (SD 10·7)% P = 0·015). By comparing the individual changes in TFCA after the trial between the two groups there was a non-significant reduction in TFCA (5·03 (SD 12·4)% P = 0·11, Wilcoxon signed-rank test) in the study group (60·6–55·6%), whereas a significant increase in TFCA (6·17(SD 7·7)% P = 0·004, Wilcoxon signed-rank test) was observed in the controls (58·2–64·3%). The differential in TFCA between the two groups after 6 months was significantly different (P = 0·001), and remained significant after adjustment for baseline dietary intakes, weight and height by multiple-regression analysis (P = 0·003). If the mechanism of TFCA from chocolate milk in response to the treatment effects is similar to that from the total diet, then our results suggest that children with adequate vitamin D status can adapt to a change in Ca intake by adjusting the efficiency of TFCA. In corollary, children on habitually-low Ca diets have a higher TFCA than the counterparts with higher Ca diets. [ABSTRACT FROM PUBLISHER]

The effect of cross-seasonal interactions on reproduction and fitness in migratory species is of increasing interest to ecologists, particularly because of the conservation implications of habitat change. Variation in contaminant levels that can affect reproduction in migratory species may reflect differing exposure across seasons. We examined the relationship between concentrations of liver selenium, a known teratogen, and winter trophic level in breeding White-winged Scoters (Melanitta fusca) using claw δ15N values as an index of winter trophic level. Claw δ15N was a significant predictor of variation in breeding ground selenium levels (r = 0.32), and liver selenium increased by approximately 12 ± 5 SE μgâg-1 with one trophic level increase in δ15N (Î"3). This relationship demonstrates that contaminant exposure from wintering or staging areas can result in higher levels in birds on breeding grounds, where some contaminants are more likely to have impacts.

Southern Siberia is currently undergoing rapid warming, inducing changes in vegetation, loss of permafrost, and impacts on the hydrodynamics of lakes and rivers. Lake sediments are key archives of environmental change and contain a record of ecosystem variability, as well as providing proxy indicators of wider environmental and climatic change. Investigating how hydrological systems have responded to past shifts in climate can provide essential context for better understanding future ecosystem changes in Siberia. Oxygen isotope ratios within lacustrine records provide fundamental information on past variability in hydrological systems. Here we present a new oxygen isotope record from diatom silica (ẟ18O diatom) at Lake Baunt (55°11′15″N, 113°01,45″E), in the southern part of eastern Siberia, and consider how the site has responded to climate changes between the Younger Dryas and Early to Mid Holocene (ca. 12.4 to 6.2 ka cal BP). Excursions in ẟ18O diatom are influenced by air temperature and the seasonality, quantity, and source of atmospheric precipitation. These variables are a function of the strength of the Siberian High, which controls temperature, the proportion and quantity of winter versus summer precipitation, and the relative dominance of Atlantic versus Pacific air masses. A regional comparison with other Siberian ẟ18O diatom records, from lakes Baikal and Kotokel, suggests that ẟ18O diatom variations in southern Siberia reflect increased continentality during the Younger Dryas, delayed Early Holocene warming in the region, and substantial climate instability between ~10.5 to ~8.2 ka cal BP. Unstable conditions during the Early Holocene thermal optimum most likely reflect localised changes from glacial melting. Taking the profiles from three very different lakes together, highlight the influence of site specific factors on the individual records, and how one site is not indicative of the region as a whole. Overall, the study documents how sensitive this important region is to both internal and external forcing. • A new diatom isotope based palaeohydrological record for southern Siberia. • Providing important evidence of regional responses to global climate forcing in the palaeohydrology of southern Siberia. • Complements existing studies of this region from Lake Baikal and Lake Kotokel. • Highlights the sensitivity of the region to wider climate forcing, alongside the impact of local factors. • Evidence for significant shifts in palaeohydrology linked to Early Holocene climatic instability and localised factors. [ABSTRACT FROM AUTHOR]

In this study, we used stable-isotope analysis to determine the importance of different food resources in the diet of an endemic gull species of the Atlantic coast of southern South America during the non-breeding period. We compared the isotopes 15N and 13C in the blood of Olrog's Gulls (Larus atlanticus) of different ages with those in potential prey of the Gulls. We also determined the abundance of Olrog's Gull in their wintering areas and attending coastal fisheries operations in a small region of Argentina. An isotope-mixing model showed differences in the isotopic signatures of adult, subadult and juvenile Gulls. Although the isotope-mixing model showed crabs as the main prey, it also showed that demersal and pelagic fish may be important in the diet. We speculate that the demersal and pelagic fish in the diet, shown by their isotopic signatures in the Gulls, may be taken in association with coastal fisheries, particularly bottom otter-paired trawling. At-sea observations showed that Olrog's Gulls were one of the most-common birds attending fishing operations of the Argentine coastal fishing fleet, taking advantage of fish mostly made available through hauling operations. [ABSTRACT FROM AUTHOR]