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Stable Isotope Composition (stable + isotope_composition)
Selected AbstractsUse of a ,13C,,15N relationship to determine animal trophic positions in a tropical Australian estuarine wetlandAUSTRAL ECOLOGY, Issue 1 2010KÁTYA ABRANTES Abstract Stable isotope composition of organisms from different trophic groups collected from a semi-isolated wetland pool in the Ross River estuary, northern Australia, was analysed to determine if there was a consistent relationship between ,13C, ,15N and trophic level that could be used to assign trophic positions. A strong linear negative relationship between ,13C and ,15N was detected for the three trophic levels considered (primary producers, primary consumers and secondary consumers). This relationship was consistent among trophic levels, differing only in height, that is, on ,15N values, which indicate trophic positions. A difference of 3.6,3.8, between trophic levels was present, suggesting a ,15N fractionation of approximately 3.7,, a value slightly higher than the commonly assumed ,15N fractionation of approximately 3.4,. The relationship between ,13C and ,15N was similar for invertebrate and fish primary consumers, indicating similar ,15N trophic fractionation for both groups, meaning trophic positions and trophic length could be reliably calculated based on either invertebrates or fish. [source] Effect of irrigation and variety on oxygen (,18O) and carbon (,13C) stable isotope composition of grapes cultivated in a warm climateAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2010S. GÓMEZ-ALONSO Abstract Background and Aims:, ,13C values from Vitis vinifera leaves, whole grape, seed, pulp, skin and/or grape must sugars have been investigated as an integrated marker of vine water status or intrinsic water-use efficiency during berry growth and across region of origin, vintage and variety. The use of 18O/16O isotopic ratio as a marker of water addition, vintage and geographical origin has also been studied. This paper examines the effect of irrigation and grapevine variety on ,18O and ,13C of grape must from eight varieties, all cultivated in the same vineyard to reduce the effects from other variables. Methods and Results:, Stable isotope compositions of grape must water and sugar were determined by isotope ratio mass spectrometry. The result of the study showed statistically significant effects of irrigation and vine variety on both ,18O and ,13C. The effect of vintage on ,18O was only significant for non-irrigated vines. Conclusion:, This research highlights the effect of variety and irrigation on ,13C and ,18O of grape. Significance of the Study:, This is the first report to demonstrate that the varietal effect on ,13C and ,18O of grape is not due only to differences in the vegetative cycle of each variety. It further suggests that water exhibits a lower isotopic discrimination in the indigenous Spanish varieties studied than in non-indigenous varieties. [source] Do cyanobacteria dominate in eutrophic lakes because they fix atmospheric nitrogen?FRESHWATER BIOLOGY, Issue 6 2004L. R. Ferber Summary 1. The sources of nitrogen for phytoplankton were determined for a bloom-prone lake as a means of assessing the hypothesis that cyanobacteria dominate in eutrophic lakes because of their ability to fix nitrogen when the nitrogen : phosphorous (N : P) supply ratio is low and nitrogen a limiting resource. 2. Nitrogen fixation rates, estimated through acetylene reduction with 15N calibration, were compared with 15N-tracer estimates of ammonium and nitrate uptake monthly during the ice-free season of 1999. In addition, the natural N stable isotope composition of phytoplankton, nitrate and ammonium were measured biweekly and the contribution of N2 to the phytoplankton signature estimated with a mixing model. 3. Although cyanobacteria made up 81,98% of phytoplankton biomass during summer and autumn, both assays suggested minimal N acquisition through fixation (<9% for the in-situ incubations; <2% for stable isotope analysis). Phytoplankton acquired N primarily as ammonium (82,98%), and secondarily as nitrate (15,18% in spring and autumn, but <5% in summer). Heterocyst densities of <3 per 100 fixer cells confirmed low reliance on fixation. 4. The lake showed symptoms of both light and nitrogen limitation. Cyanobacteria may have dominated by monopolizing benthic sources of ammonium, or by forming surface scums that shaded other algae. [source] Modified passive capillary samplers for collecting samples of snowmelt infiltration for stable isotope analysis in remote, seasonally inaccessible watersheds 2: field evaluationHYDROLOGICAL PROCESSES, Issue 7 2010Marty D. Frisbee Abstract Twelve modified passive capillary samplers (M-PCAPS) were installed in remote locations within a large, alpine watershed located in the southern Rocky Mountains of Colorado to collect samples of infiltration during the snowmelt and summer rainfall seasons. These samples were collected in order to provide better constraints on the isotopic composition of soil-water endmembers in the watershed. The seasonally integrated stable isotope composition (,18O and ,2H) of soil-meltwater collected with M-PCAPS installed at shallow soil depths < 10 cm was similar to the seasonally integrated isotopic composition of bulk snow taken at the soil surface. However, meltwater which infiltrated to depths > 20 cm evolved along an isotopic enrichment line similar to the trendline described by the evolution of fresh snow to surface runoff from snowmelt in the watershed. Coincident changes in geochemistry were also observed at depth suggesting that the isotopic and geochemical composition of deep infiltration may be very different from that obtained by surface and/or shallow-subsurface measurements. The M-PCAPS design was also used to estimate downward fluxes of meltwater during the snowmelt season. Shallow and deep infiltration averaged 8·4 and 4·7 cm of event water or 54 and 33% of the measured snow water equivalent (SWE), respectively. Finally, dominant shallow-subsurface runoff processes occurring during snowmelt could be identified using geochemical data obtained with the M-PCAPS design. One soil regime was dominated by a combination of slow matrix flow in the shallow soil profile and fast preferential flow at depth through a layer of platy, volcanic rocks. The other soil regime lacked the rock layer and was dominated by slow matrix flow. Based on these results, the M-PCAPS design appears to be a useful, robust methodology to quantify soil-water fluxes during the snowmelt season and to sample the stable isotopic and geochemical composition of soil-meltwater endmembers in remote watersheds. Copyright © 2009 John Wiley & Sons, Ltd. [source] Isotopic evidence for endogenous protein contributions to greylag goose Anser anser flight feathersJOURNAL OF AVIAN BIOLOGY, Issue 2 2009Anthony D. Fox Feather stable isotope composition may not reflect local isoscapes in which they were grown if supplemented with protein of endogenous origin. Thus, feather isotope analysis, combined with knowledge of local isoscapes can be used to infer endogenous nutrient composition to feathers in cases where birds travel to moult. We investigated this possibility in a study of flightless moulting greylag geese Anser anser on the Danish island of Saltholm, which are known to mobilise endogenous protein stores (acquired at previous terrestrial staging locations in Sweden) to reconstitute muscle blocks and organs whilst feeding on a saltmarsh (i.e. marine-influenced) diet with contrasting stable isotope ratios. We used stable isotope (,13C, ,15N) measurements to test the prediction that new-grown flight feathers would have stable isotope values intermediate between those derived from a purely terrestrial C3 diet and one composed purely of saltmarsh plants. Feather ,13C and ,15N values were intermediate between those expected for feather material derived from local saltmarsh (i.e. exogenous) food items and Swedish terrestrial (endogenous muscle) sources, suggesting a mixing of endogenous and exogenous sources. These results confirm that moult migrant Anatidae exploit body stores to meet specific protein needs during the flightless period of remige regrowth and caution against the use of feather stable isotope ratios as direct indicators of the isotopic environment in which they were regrown, where endogenous contributions may occur. [source] Differences in stable isotope composition within and among zooplanktivorous Utaka cichlid populations from Lake MalawiAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Dieter Anseeuw Abstract Stable isotope analysis was used to determine whether five sympatric zooplanktivorous cichlids of the Utaka assemblage from Lake Malawi vary in isotopic signature as an indication of possible differences in food resource composition. The isotopic composition of the Utaka in combination with literature data about diet composition suggests that these species exploit a narrow range of zooplanktonic prey types. At five sampling locations, significant differences in ,13C and ,15N were detected among species but a consistent pattern across locations was absent. Significant intraspecific differences between locations were found. These differences were relatively low in view of the large geographic distances between the populations and there was no consistent spatial pattern among the species. The observed differences may be indicative of local variations in diet composition, which may help in reducing niche overlap among these zooplanktivores. Résumé Nous avons utilisé une analyse des isotopes stables pour déterminer si cinq cichlides sympatriques zooplanctivores appartenant ŕ l'assemblage Utaka du lac Malawi ont une signature isotopique différente, ce qui serait une indication de différences possibles dans la composition de leurs ressources alimentaires. La composition isotopique d'Utaka, combinée aux données publiées au sujet de la composition du régime alimentaire, suggčre que ces espčces exploitent une gamme réduite de types de proies zooplanctoniques. Ŕ cinq endroits échantillonnés, on a détecté des différences significatives de ,13C et ,15N parmi les espčces, mais il n'y avait pas de schéma cohérent parmi tous les sites. On a découvert des différences intraspécifiques significatives entre les sites. Ces différences étaient relativement faibles compte tenu des grandes distances entre les populations et il n'y avait pas de schéma spatial cohérent parmi les espčces. Les différences observées peuvent indiquer des variations locales de la composition du régime alimentaire, ce qui pourrait aider ŕ réduire le recouvrement des niches chez ces zooplanctivores. [source] Seasonal variation in terrestrial resource subsidies influences trophic niche width and overlap in two aquatic snake species: a stable isotope approachOIKOS, Issue 7 2010John D. Willson Quantifying diet is essential for understanding the functional role of species with regard to energy processing, transfer, and storage within ecosystems. Recently, variance structure in the stable isotope composition of consumer tissues has been touted as a robust tool for quantifying trophic niche width, a task that has previously proven difficult due to bias in direct dietary analyses and difficulties in integrating diet composition over time. We used carbon and nitrogen stable isotope analyses to examine trophic niche width of two sympatric aquatic snakes, banded watersnakes Nerodia fasciata and black swamp snakes Seminatrix pygaea inhabiting an isolated wetland where seasonal migrations of amphibian prey cause dramatic shifts in resource availability. Specifically, we characterized snake and prey isotope compositions through time, space, and ontogeny and examined isotope values in relation to prey availability and snake diets assessed by gut content analysis. We determined that prey cluster into functional groups based on similarity of isotopic composition and seasonal availability. Isotope variance structure indicated that the trophic niche width of the banded watersnake was broader (more generalist) than that of the black swamp snake. Banded watersnakes also exhibited seasonal variation in isotope composition, suggesting seasonal diet shifts that track amphibian prey availability. Conversely, black swamp snakes exhibited little seasonal variation but displayed strong ontogenetic shifts in carbon and nitrogen isotope composition that closely paralleled ontogenetic shifts in their primary prey, paedomorphic mole salamanders Ambystoma talpoideum. Although niche dimensions are often treated as static, our results demonstrate that seasonal shifts in niche dimensions can lead to changes in niche overlap between sympatric species. Such short-term fluctuations in niche overlap can influence competitive interactions and consequently the composition and dynamics of communities and ecosystems. [source] Assessing environmental and physiological controls over water relations in a Scots pine (Pinus sylvestris L.) stand through analyses of stable isotope composition of water and organic matterPLANT CELL & ENVIRONMENT, Issue 1 2007ELKE BRANDES ABSTRACT This study investigated the influence of meteorological, pedospheric and physiological factors on the water relations of Scots pine, as characterized by the origin of water taken up, by xylem transport as well as by carbon isotope discrimination (,13C) and oxygen isotope enrichment (,18O) of newly assimilated organic matter. For more than 1 year, we quantified ,2H and ,18O of potential water sources and xylem water as well as ,13C and ,18O in twig and trunk phloem organic matter biweekly, and related these values to continuously measured or modelled meteorological parameters, soil water content, stand transpiration (ST) and canopy stomatal conductance (Gs). During the growing season, ,18O and ,2H of xylem water were generally in a range comparable to soil water from a depth of 2,20 cm. Long residence time of water in the tracheids uncoupled the isotopic signals of xylem and soil water in winter. ,18O but not ,13C in phloem organic matter was directly indicative of recent environmental conditions during the whole year. ,18O could be described applying a model that included 18O fractionation associated with water exchange between leaf and atmosphere, and with the production of organic matter as well as the influence of transpiration. Phloem ,13C was assumed to be concertedly influenced by Gs and photosynthetically active radiation (PAR) (as a proxy for photosynthetic capacity). We conclude that isotope signatures can be used as effective tools (1) to characterize the seasonal dynamics in source and xylem water, and (2) to assess environmental effects on transpiration and Gs of Scots pine, thus helping to understand and predict potential impacts of climate change on trees and forest ecosystems. [source] Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositionsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2008Renbin Zhu Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using insitu field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean , values of the soil-emitted N2O were ,15N,=,,13.5,±,3.2, and ,18O,=,26.2,±,1.4, for the penguin colony, ,15N,=,,11.5,±,5.1, and ,18O,=,26.4,±,3.5, for the skua colony and ,15N,=,,18.9,±,0.7, and ,18O,=,28.8,±,1.3, for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93,µg,N2ON,kg,1). Under N2 conditions, much more N2O was formed (9.74,µg,N2ON,kg,1), and the mean ,15N and ,18O values of N2O were ,19.1,±,8.0, and 21.3,±,4.3,, respectively, from penguin colony soils, and ,17.0,±,4.2, and 20.6,±,3.5,, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Holocene boundary dynamics of a northern Australian monsoon rainforest patch inferred from isotopic analysis of carbon, (14C and ,13C) and nitrogen (,15N) in soil organic matterAUSTRAL ECOLOGY, Issue 6 2004D. M. J. S. BOWMAN Abstract Soil organic matter (SOM) was sampled from lateritic soil profiles across an abrupt eucalypt savanna,monsoon rainforest boundary on the north coast of Croker Island, northern Australia. Accelerator mass spectrometry dating revealed that SOM that had accumulated at the base of these 1.5 m profiles had a radiocarbon age of about 5000 years. The mean carbon and nitrogen stable isotope composition of SOM from 10 cm deep layers from the surface, middle and base of three monsoon rainforest soil profiles was significantly different from the means for these layers in three adjacent savanna soil profiles, suggesting the isotopic ,footprint' of the vegetation boundary has been stable since the mid Holocene. Although there were no obvious environmental discontinuities associated with the boundary, the monsoon rainforest was found to occur on significantly more clay rich soils than the surrounding savanna. Tiny fragments of monsoon rainforest and abandoned ,nests' (large earthen mounds) of the orange-footed scrubfowl, an obligate monsoon rainforest species, occurred in the savanna, signalling that the rainforest was once more extensive. Despite episodic disturbances, such as tropical storm damage and fires, the stability of the boundary is probably maintained because clay rich soils enable monsoon rainforest tree species to grow rapidly and achieve canopy closure, thereby excluding grass and reducing the risk of fire. Conversely, slower tree growth rates, grass competition and fire on the savanna soils would impede the expansion of the rainforest although high rainfall periods with shorter dry seasons may enable rainforest trees to grow sufficiently quickly to colonize the savanna successfully. [source] Effect of irrigation and variety on oxygen (,18O) and carbon (,13C) stable isotope composition of grapes cultivated in a warm climateAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2010S. GÓMEZ-ALONSO Abstract Background and Aims:, ,13C values from Vitis vinifera leaves, whole grape, seed, pulp, skin and/or grape must sugars have been investigated as an integrated marker of vine water status or intrinsic water-use efficiency during berry growth and across region of origin, vintage and variety. The use of 18O/16O isotopic ratio as a marker of water addition, vintage and geographical origin has also been studied. This paper examines the effect of irrigation and grapevine variety on ,18O and ,13C of grape must from eight varieties, all cultivated in the same vineyard to reduce the effects from other variables. Methods and Results:, Stable isotope compositions of grape must water and sugar were determined by isotope ratio mass spectrometry. The result of the study showed statistically significant effects of irrigation and vine variety on both ,18O and ,13C. The effect of vintage on ,18O was only significant for non-irrigated vines. Conclusion:, This research highlights the effect of variety and irrigation on ,13C and ,18O of grape. Significance of the Study:, This is the first report to demonstrate that the varietal effect on ,13C and ,18O of grape is not due only to differences in the vegetative cycle of each variety. It further suggests that water exhibits a lower isotopic discrimination in the indigenous Spanish varieties studied than in non-indigenous varieties. [source] Isotopic tracking of prehistoric pinniped foraging and distribution along the central California coast: preliminary resultsINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2002R. K. Burton Abstract Zooarchaeological data from Monterey Bay and the adjacent central California coast corroborate earlier observations from northern California and Oregon that Callorhinus ursinus (northern fur seal) was a much more common component in prehistoric marine mammal prey than its present pelagic distribution and foraging habits would predict. C. ursinus remains from mid-Holocene Monterey Bay occurrences are predominantly from female individuals, associated with an inshore piscifauna, and lack associated artifactual evidence for deep water exploitation. Taken together with evidence from Oregon, this suggests that mid-Holocene C. ursinus populations had different foraging, resting, and, arguably, reproductive behaviours than historically reported. Currently debated is whether the contrast between prehistoric and present patterns of pinniped species representation results from: 1) late Holocene prehistoric resource depression by aboriginal hunters, 2) depredations of the early historic fur trade, or 3) non-anthropogenic climatic or oceanographic change. The issue has thus far been addressed with presence or absence data on pinniped species and age/sex classes in dated contexts. While these are fundamental data, they cannot shed light on the nature of foraging behaviour of the species in question, a key dimension of the problem. This paper reports a pilot study utilizing stable isotope analysis aimed to elucidate prehistoric pinniped foraging patterns, specifically that of C. ursinus. Elements from six archaeological sites in Monterey and Santa Cruz counties were analysed for stable isotope compositions of carbon and nitrogen in bone collagen and compared to a latitudinally ordered modern dataset. Results for archaeological C. ursinus strongly suggest that prehistoric animals habitually foraged at lower latitudes than characterize the species today, supporting earlier claims of their year-round residency south of Alaska. Copyright © 2002 John Wiley & Sons, Ltd. [source] Isotopic evidence of dietary variations and weaning practices in the Gaya cemetery at Yeanri, Gimhae, South KoreaAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Kyungcheol Choy Abstract Stable carbon and nitrogen isotope analyses were conducted to investigate dietary variation in human skeletons (n = 109) from the Gaya cemetery at Yeanri located near Gimhae City, South Korea. The cemetery contained three distinct grave types dating to 4th,7th century AD. The main purposes of this research were to reconstruct palaeodiet in the Gaya population and to explore correlations between stable isotope compositions and burial types, inferred age, and sex of these individuals. The isotopic data indicate that the people at Yeanri consumed a predominantly C3 -based terrestrial diet supplemented with freshwater and/or marine resources. The comparison of isotopic results reveals significant differences in ,13C values among three adult burial types (wood-cist coffin: ,18.5 ± 0.5,, stone-cist coffin: ,18.1 ± 0.6,, mausoleum: ,17.8 ± 0.9,). Males in wood-cist and stone-cist coffins have relatively more elevated mean ,13C and ,15N values than females. The isotopic ratios from the two adult age groups (21,40 years and 40,60 years) indicate that there was no significant dietary change in individuals with age. The isotope data from the infants and children suggest the weaning was a gradual process that was completed between 3 and 4 years of age in the Gaya population. This evidence indicates that the dietary variations within the cemetery reflect social status, sex, and childhood consumption patterns. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Role of glaciohydraulic supercooling in the formation of stratified facies basal ice: Svínafellsjökull and Skaftafellsjökull, southeast IcelandBOREAS, Issue 1 2010SIMON J. COOK Cook, S. J., Robinson, Z. P., Fairchild, I. J., Knight, P. G., Waller, R. I. & Boomer, I. 2009: Role of glaciohydraulic supercooling in the formation of stratified facies basal ice: Svínafellsjökull and Skaftafellsjökull, southeast Iceland. Boreas, 10.1111/j.1502-3885.2009.00112.x. ISSN 0300-9483. There is need for a quantitative assessment of the importance of glaciohydraulic supercooling for basal ice formation and glacial sediment transfer. We assess the contribution of supercooling to stratified facies basal ice formation at Svínafellsjökull and Skaftafellsjökull, southeast Iceland, both of which experience supercooling. Five stratified basal ice subfacies have previously been identified at Svínafellsjökull, but their precise origins have not been determined. Analysis of stratified basal ice stable isotope compositions (,18O and ,D), spatial distribution and physical characteristics demonstrates that two subfacies present at both glaciers are consistent with supercooling. These ,supercool' subfacies account for 42% of stratified facies exposed at Svínafellsjökull, although estimates at Skaftafellsjökull are precluded by limited basal ice exposure. Owing to their high debris contents, supercooling-related facies contribute a debris flux of 4.8 to 9.6 m3 m,1 a,1 at Svínafellsjökull (83% of the stratified facies debris flux). Other stratified subfacies, formed by non-supercooling processes, account for 58% of the stratified basal ice at Svínafellsjökull, but only contribute a debris flux of 1.0 to 2.0 m3 m,1 a,1 (17% of the stratified facies debris flux). We conclude that supercooling has a significant role in glacial sediment transfer, although in stratified basal ice formation its role is less significant at these locations than has been reported elsewhere. [source] | ||||||||||||||||