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Isotope Signatures (isotope + signature)
Kinds of Isotope Signatures Selected AbstractsQuantifying root lateral distribution and turnover using pine trees with a distinct stable carbon isotope signatureFUNCTIONAL ECOLOGY, Issue 1 2005K. JOHNSEN Summary 1In order to help assess spatial competition for below-ground resources, we quantified the effects of fertilization on root biomass quantity and lateral root distribution of mid-rotation Pinus taeda trees. Open-top chambers exposed trees to ambient or ambient plus 200 µmol mol,1 atmospheric CO2 for 31 months. 2Tank CO2 was depleted in atmospheric 13C; foliage of elevated CO2 trees had ,13C of ,42·9, compared with ,29·1 for ambient CO2 trees. 3Roots 1 m from the base of elevated CO2 -grown trees had more negative ,13C relative to control trees, and this difference was detected, on average, up to 5·8, 3·7 and 3·7 m away from the trees for 0,2, 2,5 and >5 mm root-size classes, respectively. Non-fertilized tree roots extended as far as fertilized trees despite the fact that their above-ground biomass was less than half that of fertilized trees. 4These results are informative with respect to root sampling intensity and protocol, and the distances required between experimental manipulations to evaluate below-ground processes of independent treatments. 5Fine-root turnover has usually been estimated to range from weeks to 3 years, representing a major avenue of carbon flux. Using a mixing model we calculated that 0,2 mm roots had a mean residence time of 4·5 years indicating relatively slow fine-root turnover, a result that has major implications in modelling C cycling. [source] Stable carbon isotope signature of ancient maize agriculture in the soils of Motul de San José, GuatemalaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2007Elizabeth A. Webb Soil profiles collected from a 2.5-km transect radiating from the Maya center of Motul de San José were analyzed for the stable carbon-isotope composition of their soil organic matter. The residues of maize (Zea mays), the only C4 plant known to have been cultivated in this area by the ancient Maya, impart a carbon-isotope signature to the underlying soil organic matter reservoir that is distinct from that produced by the native C3 forest vegetation. The varying turnover rates of the humic acid and humin fractions of the soil organic matter allowed us to distinguish between the presence of modern and ancient maize residues in these soils, and to delineate the lateral extent of maize cultivation at this ancient Maya site. The strongest isotopic evidence of maize residues is preserved in the soils surrounding the peripheral settlement of Chäkokot and at one locality within the urban center of Motul de San José. © 2007 Wiley Periodicals, Inc. [source] Associations between carbon isotope ratios of ecosystem respiration, water availability and canopy conductanceGLOBAL CHANGE BIOLOGY, Issue 10 2004N. G. McDowell Abstract We tested the hypothesis that the stable carbon isotope signature of ecosystem respiration (,13CR) was regulated by canopy conductance (Gc) using weekly Keeling plots (n=51) from a semiarid old-growth ponderosa pine (Pinus ponderosa) forest in Oregon, USA. For a comparison of forests in two contrasting climates we also evaluated trends in ,13CR from a wet 20-year-old Douglas-fir (Pseudotsuga menziesii) plantation located near the Pacific Ocean. Intraannual variability in ,13CR was greater than 8.0, at both sites, was highest during autumn, winter, and spring when rainfall was abundant, and lowest during summer drought. The ,13CR of the dry pine forest was consistently more positive than the wetter Douglas-fir forest (mean annual ,13CR: ,25.41, vs. ,26.23,, respectively, P=0.07). At the Douglas-fir forest, ,13CR,climate relationships were consistent with predictions based on stomatal regulation of carbon isotope discrimination (,). Soil water content (SWC) and vapor pressure deficit (vpd) were the most important factors governing ,13CR in this forest throughout the year. In contrast, ,13CR at the pine forest was relatively insensitive to SWC or vpd, and exhibited a smaller drought-related enrichment (,2,) than the enrichment observed during drought at the Douglas-fir forest (,5,). Groundwater access at the pine forest may buffer canopy,gas exchange from drought. Despite this potential buffering, ,13CR at the pine forest was significantly but weakly related to canopy conductance (Gc), suggesting that ,13CR remains coupled to canopy,gas exchange despite groundwater access. During drought, ,13CR was strongly correlated with soil temperature at both forests. The hypothesis that canopy-level physiology is a critical regulator of ,13CR was supported; however, belowground respiration may become more important during rain-free periods. [source] Variability in the carbon isotope signature of Prochilodus lineatus (Prochilodontidae, Characiformes) a bottom-feeding fish of the Neotropical regionJOURNAL OF FISH BIOLOGY, Issue 6 2007C. A. Lopes The spatial and seasonal variability of stable carbon isotopes in detritivorous Prochilodus lineatus, primary producers and particulate organic carbon (POC) were examined to promote a better understanding of the trophic dynamics of food webs in Neotropical ecosystems. Spatial variability in carbon isotope composition in the species showed a decreasing gradient in the Upper Paraná River system, from the Paraná River and Itaipu Reservoir subsystems to the Baía and Ivinheima subsystems. Fish ,13C followed the isotopic trend of POC along the Paraná River and Baía subsystem. Seasonal differences were not observed in fish. The analysis of percentile contribution of C3 and C4 sources in the species diet revealed the predominance of C3 plants (phytoplanktonic and periphytic algae and riparian vegetation) in most of the analysed subsystems and seasons. Nevertheless, the considerable participation of riparian vegetation was verified, especially in the Ivinheima subsystem in the dry season. C4 macrophytes presented a maximum contribution along the Upper Paraná River. These results demonstrate the existence of specific variability for the consumer and their food sources in different environments of the same ecosystem. [source] Digestion and Assimilation of the Free-living Nematode Panagrellus redivivus Fed to First Feeding Coregonid Larvae: Evidence from Histological and Isotopic StudiesJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2005Christian Schlechtriem The free-living nematode Panagrellus redivivus is a potential source of live food for first feeding fish. The digestion and assimilation of nematodes by larval fish were investigated with the aid of a histological and stable isotope approach. Larvae of whitefish Coregonus lavaretus were reared for 8 d with nematodes and compared with an unfed control. Nematodes were readily ingested by 3-d-old larvae. Different stages of nematode digestion could be observed in transverse sections of fish larvae sampled on Day 6 at regular intervals after feeding. Nematodes were produced on corn medium. In this way nematodes with a stable carbon isotope signature clearly different from the isotopic pattern of the fish larvae could be obtained. Stable carbon isotope signatures for lipids and lipid-free matter of fish larvae sampled on Days 2 and 8 after first feeding were clearly influenced by the stable isotopic pattern of the nematodes. The high acceptance of the nematodes by Coregonus lavaretus larvae and the early onset of digestion and nutrient retention positively confirm the potential of PanagreUus redivivus as a live food for first feeding fish larvae. [source] Sea cucumber habitat differentiation and site retention as determined by intraspecific stable isotope variationAQUACULTURE RESEARCH, Issue 10 2010Matthew J Slater Abstract Stable carbon and nitrogen isotope ratios (,13C/,15N) were assessed as a means to ascertain the recent in situ feeding history of the common New Zealand sea cucumber Australostichopus mollis in relation to nutrient enrichment from a longline green-lipped mussel (Perna canaliculus) farm in Northern New Zealand. ,13C and ,15N isotopic signatures and the ratios of sea cucumbers sampled from within the impact footprint of the mussel farm were compared with those of sea cucumbers residing on adjacent natural reefs. Sea cucumbers from beneath mussel farming longlines had significantly different ,13C stable isotope signatures in comparison with sea cucumbers collected from neighbouring natural reef habitats. This difference supports the hypothesis that sea cucumbers in the same bay maintain distinctly different feeding histories, with those residing beneath mussel farming longlines deriving tissue carbon from sediment impacted by farming activities. This hypothesis is further supported by the finding that the isotope signature of sediment collected from beneath the mussel farm is consistent with the expectation that sea cucumbers were feeding on and consuming sediment enriched with bivalve waste (faeces and pseudo-faeces). In contrast, the nitrogen stable isotope signature (,15N) was found to be similar between sites for both sea cucumbers and assumed food sources. Both findings lend support to the viability of future sea cucumber/green-lipped mussel farm polyculture systems. Sea cucumbers in different locations (mussel farm, natural reef) possessed distinctly different isotope signatures, suggesting that mixing of sea ranched sea cucumbers with natural reef populations would be negligible or non-existent. Similarities between the isotope signatures in low metabolic tissue of sea cucumbers residing at the mussel farm site to that of mussel farm-impacted sediment suggest that cucumbers beneath mussel farms appear to have high rates of retention at the farm site. [source] Burying beetle Nicrophorus investigator reproduction on Pacific salmon carcassesECOLOGICAL ENTOMOLOGY, Issue 1 2006M. D. Hocking Abstract., 1.,In many undisturbed watersheds along the Pacific Rim, anadromous salmon (Oncorhynchus spp.) provide a predictable source of carrion to the riparian zone, largely due to horizontal transfer of salmon carcasses by bears (Ursus spp.) and other vertebrates. 2.,Burying beetles are important members of the north-temperate carrion fauna, and may utilise salmon carcasses and remnants for breeding. In this study, isotopic and observational data are reported that demonstrate previously unrecognised Nicrophorus investigator (Zetterstedt) reproduction on large salmon carcasses from five watersheds in coastal British Columbia. 3.,Stable isotope signatures (,15N and ,13C) of adult beetles collected in autumn indicate a diet of salmon origin in all but one individual from all watersheds, suggesting that this beetle,salmon association is widespread. Comparison of autumn isotope signatures to individuals collected randomly in summer suggests that isotope signatures represent the larval carrion source from the previous autumn rather than immediate adult diet. 4.,In a survey of N. investigator use of salmon carcasses from two watersheds, 35 broods were observed on chum and pink salmon carcasses, including 16 natural brood complexes containing over 100 larvae, and five ranging from 250 to 750 larvae. 5.,Overall, north-coastal populations of N. investigator breed on the rich and reliable salmon resource and may exhibit a system of communal breeding on these carcasses. This is most relevant when the dramatic reduction in salmon spawning biomass over the last century is considered. [source] Alternative use of food resources causes intra-cohort variation in the size distribution of young-of-the-year perch (Perca fluviatilis)ECOLOGY OF FRESHWATER FISH, Issue 3 2008R. Urbatzka Abstract,,, Body sizes of young-of-the-year (YOY) perch (Perca fluviatilis) at the end of their first summer are extremely variable and range in different studies between 4 and 15 cm. To analyse whether size divergences in YOY perch may be attributed to alternative use of food resources, adult perch were stocked into two previously fishless ponds and growth, size distribution and food intake of the YOY perch were recorded. In addition to perch, adult bream (Abramis brama) were introduced to produce juvenile bream that could serve as a food resource for YOY perch. The body sizes of YOY perch at the end of the experiment ranged from 32 to 168 mm with a bimodal size distribution. The combination of stomach content analyses and stable isotope signatures revealed that the small size cohort were planctivorous/benthivorous while the large size cohort was piscivorous/cannibalistic. Results implicated that different feeding behaviour contributed to the size divergences in YOY perch and that the extreme growth of the large size cohort was induced by piscivory. [source] Chemical amplification in an invaded food web: Seasonality and ontogeny in a high-biomass, low-diversity ecosystem,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Carla A. Ng Abstract The global spread of invasive species is changing the structure of aquatic food webs worldwide. The North American Great Lakes have proved particularly vulnerable to this threat. In nearshore areas, invasive benthic species such as dreissenid mussels and round gobies (Neogobius melanostomus) have gained dominance in recent years. Such species are driving the flow of energy and material from the water column to the benthic zone, with dramatic effect on nutrient and contaminant cycling. Here, we develop a stage-structured model of a benthified food web in Lake Michigan with seasonal resolution and show how its bioaccumulation patterns differ from expected ones. Our model suggests that contaminant recycling through the consumption of lipid-rich fish eggs and mussel detritus is responsible for these differences. In southern Lake Michigan's Calumet Harbor (Chicago, IL, USA), round gobies have nitrogen isotope signatures with considerable spread, with some values higher than their predators and others lower than their prey. Contrary to patterns observed in linear pelagic systems, we predict that polychlorinated biphenyl (PCB) concentrations in these fish decrease with increasing size due to the lipid- and benthos-enriched diets of smaller fish. We also present here round goby PCB concentrations measured in 2005 after an invasional succession in Calumet Harbor and demonstrate how the change from one invasive mussel species to another may have led to a decrease in round goby PCB accumulation. Our results suggest that benthic-dominated systems differ from pelagic ones chiefly due to the influence of detritus and that these effects are exacerbated in systems with low species diversity and high biomass. [source] Effects of stream restoration and wastewater treatment plant effluent on fish communities in urban streamsFRESHWATER BIOLOGY, Issue 10 2006ROBERT M. NORTHINGTON Summary 1. Fish community characteristics, resource availability and resource use were assessed in three headwater urban streams in Piedmont North Carolina, U.S.A. Three site types were examined on each stream; two urban (restored and unrestored) and a forested site downstream of urbanisation, which was impacted by effluent from a wastewater treatment plant (WWTP). Stream basal resources, aquatic macroinvertebrates, terrestrial macroinvertebrates and fish were collected at each site. 2. The WWTPs affected isotope signatures in the biota. Basal resource, aquatic macroinvertebrate and fish ,15N showed significant enrichments in the downstream sites, although ,13C signatures were not greatly influenced by the WWTP. Fish were clearly deriving a significant part of their nutrition from sewage effluent-derived sources. There was a trend towards lower richness and abundance of fish at sewage-influenced sites compared with urban restored sites, although the difference was not significant. 3. Restored stream sites had significantly higher fish richness and a trend towards greater abundance compared with unrestored sites. Although significant differences did not exist between urban restored and unrestored areas for aquatic and terrestrial macroinvertebrate abundances and biotic indices of stream health, there appeared to be a trend towards improvements in restored sites for these parameters. Additional surveys of these sites on a regular basis, along with maintenance of restored features are vital to understanding and maximising restoration effectiveness. 4. A pattern of enriched ,13C in fish in restored and unrestored streams in conjunction with enriched ,13C of terrestrial invertebrates at these sites suggests that these terrestrial subsidies are important to the fish, a conclusion also supported by isotope cross plots. Furthermore, enriched ,13C observed for terrestrial invertebrates is consistent with some utilisation of the invasive C4 plants that occur in the urban riparian areas. [source] Taxon-specific variation in the stable isotopic signatures (,13C and ,15N) of lake phytoplanktonFRESHWATER BIOLOGY, Issue 5 2006KRISTIINA VUORIO Summary 1. The variability in the stable isotope signatures of carbon and nitrogen (,13C and ,15N) in different phytoplankton taxa was studied in one mesotrophic and three eutrophic lakes in south-west Finland. The lakes were sampled on nine to 16 occasions over 2,4 years and most of the time were dominated by cyanobacteria and diatoms. A total of 151 taxon-specific subsamples covering 18 different phytoplankton taxa could be isolated by filtration through a series of sieves and by flotation/sedimentation, followed by microscopical identification and screening for purity. 2. Substantial and systematic differences between phytoplankton taxa, seasons and lakes were observed for both ,13C and ,15N. The values of ,13C ranged from ,34.4, to ,5.9, and were lowest in chrysophytes (,34.4, to ,31.3,) and diatoms (,30.6, to ,26.6,). Cyanobacteria were most variable (,32.4, to ,5.9,), including particularly high values in the nostocalean cyanobacterium Gloeotrichia echinulata (,14.4, to ,5.9,). For ,13C, the taxon-specific amplitude of temporal changes within a lake was usually <1,8, (<1,4, for microalgae alone and <1,8, for cyanobacteria alone), whereas the amplitude among taxa within a water sample was up to 31,. 3. The values of ,15N ranged from ,2.1, to 12.8, and were high in chrysophytes, dinophytes and diatoms, but low in the nitrogen-fixing cyanobacteria Anabaena spp., Aphanizomenon spp. and G. echinulata (,2.1, to 1.6,). Chroococcalean cyanobacteria ranged from ,1.4, to 8.9,. For ,15N, the taxon-specific amplitude of temporal changes within a lake was 2,6,, (2,6, for microalgae alone and 2,4, for cyanobacteria alone) and the amplitude among taxa within a water sample was up to 11,. 4. The isotopic signatures of phytoplankton changed systematically with their physical and chemical environment, most notably with the concentrations of nutrients, but correlations were non-systematic and site-specific. 5. The substantial variability in the isotopic signatures of phytoplankton among taxa, seasons and lakes complicates the interpretation of isotopic signatures in lacustrine food webs. However, taxon-specific values and seasonal patterns showed some consistency among years and may eventually be predictable. [source] Selectivity and competitive interactions between two benthic invertebrate grazers (Asellus aquaticus and Potamopyrgus antipodarum): an experimental study using 13C- and 15N-labelled diatomsFRESHWATER BIOLOGY, Issue 2 2005N. ABERLE Summary 1. Tracer experiments with two diatoms labelled with 13C (Nitzschia palea) and 15N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different grazer treatments. 2. The results revealed a significant decline in algal biovolume in all grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two grazers. 3. The selectivity index Q, which provides information on the uptake ratio of 13C to 15N, showed a significant time effect for both grazer species and a significant difference between single- and mixed-grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by grazers and, therefore, served as an ideal tool for the detection of passive selectivity. 4. Our results indicate a shift in feeding preferences related to between-species competition and a potential divergence of trophic niches when species coexist. [source] Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivityFRESHWATER BIOLOGY, Issue 2 2003Thomas Hein SUMMARY 1.,The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13-month period. 2.,Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water. 3.,The mean C : N ratio and ,13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; ,33,) to the main channel (8.4; ,25,). At the dynamic floodplain site, the C : N ratio and the ,13C signature of the POM increased with hydrological connectivity (expressed as water age). 4.,Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (>80% of the total POM pool) and a ,13C signature of POM of more than ,25, in the dynamic floodplain. 5.,Plankton derived carbon, indicated by C : N ratios less than eight and ,13C values lower than ,25,, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages. 6.,At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non-refractory POM compared with prerestoration conditions. [source] Explaining isotope trophic-step fractionation: why herbivorous fish are differentFUNCTIONAL ECOLOGY, Issue 6 2007A. C. MILL Summary 1An assumed constant trophic fractionation of 15N/14N between consumer and diet (usually 3·4 for diet,muscle tissue differences) allows inferences to be made about feeding interactions and trophic level in food web studies. However, considerable variability surrounds this constant, which may conceal subtle differences about the trophodynamics of consumers. 2The feeding ecologies of herbivores and carnivores differ in terms of diet quality (in C : N terms) and food processing mechanisms, which may affect fractionation. 3We present a new model that explores how consumer feeding rates, excretion rates and diet quality determine the 15N/14N ratios in the consumer's tissues and hence influence the magnitude of trophic fractionation. 4Three herbivorous reef fish Acanthurus sohal, Zebrasoma xanthurum and Pomacentrus arabicus were chosen as study organisms. Empirical estimates of diet,tissue stable isotope fractionation were made in the field, and model parameters were derived from feeding observations and literature data. 5The trophic fractionation values of A. sohal, Z. xanthurum and P. arabicus were 4·69, 4·47 and 5·25, respectively, by empirical measurement, and 4·41, 4·30 and 5·68, respectively, by model, indicating that herbivores have a higher trophic fractionation than the currently accepted value of 3·4. 6The model was most sensitive to the excretion rate, which may differ between herbivores and carnivorous animals. This model is the first to determine stable isotope signatures of a consumer's diet mixture without applying a constant fractionation value. [source] Determination of isotope fractionation factors and quantification of carbon flow by stable carbon isotope signatures in a methanogenic rice root model systemGEOBIOLOGY, Issue 2 2006H. PENNING ABSTRACT Methanogenic processes can be quantified by stable carbon isotopes, if necessary modeling parameters, especially fractionation factors, are known. Anoxically incubated rice roots are a model system with a dynamic microbial community and thus suitable to investigate principal geochemical processes in anoxic natural systems. Here we applied an inhibitor of acetoclastic methanogenesis (methyl fluoride), calculated the thermodynamics of the involved processes, and analyzed the carbon stable isotope signatures of CO2, CH4, propionate, acetate and the methyl carbon of acetate to characterize the carbon flow during anaerobic degradation of rice roots to the final products CO2 and CH4. Methyl fluoride inhibited acetoclastic methanogenesis and thus allowed to quantify the fractionation factor of CH4 production from H2/CO2. Since our model system was not affected by H2 gradients, the fractionation factor could alternatively be determined from the Gibbs free energies of hydrogenotrophic methanogenesis. The fractionation factor of acetoclastic methanogenesis was also experimentally determined. The data were used for successfully modeling the carbon flow. The model results were in agreement with the measured process data, but were sensitive to even small changes in the fractionation factor of hydrogenotrophic methanogenesis. Our study demonstrates that stable carbon isotope signatures are a proper tool to quantify carbon flow, if fractionation factors are determined precisely. [source] Chemical and isotopic signatures of Na/HCO3/CO2 -rich geofluids, North PortugalGEOFLUIDS (ELECTRONIC), Issue 4 2006J. M. MARQUES Abstract Geochemical and isotopic studies have been undertaken to assess the origin of CO2 -rich waters issuing in the northern part of Portugal. These solutions are hot (76°C) to cold (17°C) Na,HCO3 mineral waters. The ,2H and ,18O signatures of the mineral waters reflect the influence of altitude on meteoric recharge. The lack of an 18O-shift indicates there has been no high temperature water,rock interaction at depth, corroborating the results of several chemical geothermometers (reservoir temperature of about 120°C). The low 14C activity (up to 9.9 pmC) measured in some of the cold CO2 -rich mineral waters (total dissolved inorganic carbon) is incompatible with the presence of 3H (from 1.7 to 4.1 TU) in those waters, which indicates relatively short subsurface circulation times. The ,13C values of CO2 gas and dissolved inorganic carbon range between ,6, and ,1, versus Vienna-Peedee Belemnite, indicating that the total carbon in the recharge waters is being diluted by larger quantities of CO2 (14C-free) introduced from deep-seated (upper mantle) sources, masking the 14C-dating values. The differences in the 87Sr/86Sr ratios of the studied thermal and mineral waters seem to be caused by water,rock interaction with different granitic rocks. Chlorine isotope signatures (,0.4, < ,37Cl < +0.4, versus standard mean ocean chloride) indicate that Cl in these waters could be derived from mixing of a small amount of igneous Cl from leaching of granitic rocks. [source] Strontium Isotopic Identification of Water-Rock Interaction and Ground Water MixingGROUND WATER, Issue 3 2004Carol D. Frost 87Sr/86Sr ratios of ground waters in the Bighorn and Laramie basins' carbonate and carbonate-cemented aquifer systems, Wyoming, United States, reflect the distinctive strontium isotope signatures of the minerals in their respective aquifers. Well water samples from the Madison Aquifer (Bighorn Basin) have strontium isotopic ratios that match their carbonate host rocks. Casper Aquifer ground waters (Laramie Basin) have strontium isotopic ratios that differ from the bulk host rock; however, stepwise leaching of Casper Sandstone indicates that most of the strontium in Casper Aquifer ground waters is acquired from preferential dissolution of carbonate cement. Strontium isotope data from both Bighorn and Laramie basins, along with dye tracing experiments in the Bighorn Basin and tritium data from the Laramie Basin, suggest that waters in carbonate or carbonate-cemented aquifers acquire their strontium isotope composition very quickly,on the order of decades. Strontium isotopes were also used successfully to verify previously identified mixed Redbeds-Casper ground waters in the Laramie Basin. The strontium isotopic compositions of ground waters near Precambrian outcrops also suggest previously unrecognized mixing between Casper and Precambrian aquifers. These results demonstrate the utility of strontium isotopic ratio data in identifying ground water sources and aquifer interactions. [source] Intra-lake stable isotope ratio variation in selected fish species and their possible carbon sources in Lake Kyoga (Uganda): implications for aquatic food web studiesAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Dismas Mbabazi Abstract The stable isotopes of nitrogen (,15N) and carbon (,13C) provide powerful tools for quantifying trophic relationships and carbon flow to consumers in food webs; however, the isotopic signatures of organisms vary within a lake. Assessment of carbon and nitrogen isotopic signatures in a suite of plants, invertebrates, and fishes in Lake Kyoga, indicated significant variation between two sites for ,13C (paired t = 6.305; df = 14, P < 0.001 and ,15N paired t = 1.292; df = 14; P < 0.05). The fish fauna in Bukungu was generally more 13C enriched (mean ,13C = ,16.37 ± 1.64,) than in Iyingo (mean ,13C = ,20.80 ± 2.41,) but more ,15N depleted (mean ,15N = 5.57 ± 0.71,) than in Iyingo (mean ,15N = 6.92 ± 0.83,). The simultaneous shifts in phytoplankton and consumer signatures confirmed phytoplankton as the major source of carbon for the food chain leading to fish. Limited sampling coverage within lakes may affect lake wide stable isotope signatures, and the same error is transferred into trophic position estimation. Consideration of potential intra-lake spatial variability in isotope ratios and size is essential in evaluating the spatial and trophic structure of fish assemblages. Résumé Les isotopes stables d'azote (,15N) et de carbone (,13C) sont des outils intéressants pour quantifier les relations trophiques et le flux de carbone vers les consommateurs de chaînes alimentaires; cependant, la signature isotopique des organismes varie au sein d'un même lac. L'évaluation des signatures isotopiques du carbone et de l'azote dans une suite de plantes, d'invertébrés et de poissons du lac Kyoga indiquait une variation significative entre deux sites pour ,13C (test t apparié = 6.305; df = 14; P < 0.05). La faune piscicole de Bukungu était généralement plus enrichie en ,13C (moyenne de ,13C = ,16.37 ± 1.64,) qu'à Iyingo (moyenne de ,13C = ,20.80 ± 2.41,) mais plus dépourvue de ,15N (moyenne de ,15N = 5.57 ± 0.71,) qu'Inyingo (moyenne de ,15N = 6.92 ± 0.83,). Les glissements simultanés des signatures du phytoplancton et des consommateurs confirmaient que le phytoplancton est la source principale de carbone de la chaîne alimentaire qui aboutit aux poissons. Une couverture limitée de l'échantillonnage dans les lacs peut affecter la signature des isotopes stables de tout le lac, et cette même erreur est reportée dans l'estimation de la situation trophique. Il est essentiel de tenir compte de la variabilité spatiale possible des taux et de la taille des isotopes dans les lacs lorsque l'on évalue la structure spatiale et trophique des assemblages de poissons. [source] The effects of preservation on fish tissue stable isotope signaturesJOURNAL OF FISH BIOLOGY, Issue 6 2006B. Kelly The effects of formalin and ethanol preservation on the ,13C and ,15N isotope signatures of Arctic charr Salvelinus alpinus muscle tissue were examined. The lipid content of the tissue samples studied ranged from 3·6 to 6·1% and was not correlated with the magnitude of observed isotopic shifts in preserved samples. Ethanol and formalin significantly depleted and enriched, respectively, the ,13C isotope signatures of preserved tissues when compared to control samples. Ethanol did not significantly enrich ,15N signatures in comparison to controls, whereas formalin did. A meta-analysis of multiple species effects further demonstrated significant preservation effects in fish tissue. Statistical analysis of data obtained by correcting preserved tissue isotope signatures with literature, bootstrapped or meta-analysis derived correction factors demonstrated significant differences between corrected and control sample isotope signatures or failure to produce a unity slope when the data sets were regressed against one another. Species-specific, bootstrapped linear correction models resulted in no such errors. Results suggest that species-specific correction methods should be used for fishes because of the known wide variation in fish tissue lipid content and composition. Accordingly, the use of pilot studies will be required to develop correction factors that properly adjust for preservation effects when interpreting temporal patterns in historic analyses of food webs. [source] Digestion and Assimilation of the Free-living Nematode Panagrellus redivivus Fed to First Feeding Coregonid Larvae: Evidence from Histological and Isotopic StudiesJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2005Christian Schlechtriem The free-living nematode Panagrellus redivivus is a potential source of live food for first feeding fish. The digestion and assimilation of nematodes by larval fish were investigated with the aid of a histological and stable isotope approach. Larvae of whitefish Coregonus lavaretus were reared for 8 d with nematodes and compared with an unfed control. Nematodes were readily ingested by 3-d-old larvae. Different stages of nematode digestion could be observed in transverse sections of fish larvae sampled on Day 6 at regular intervals after feeding. Nematodes were produced on corn medium. In this way nematodes with a stable carbon isotope signature clearly different from the isotopic pattern of the fish larvae could be obtained. Stable carbon isotope signatures for lipids and lipid-free matter of fish larvae sampled on Days 2 and 8 after first feeding were clearly influenced by the stable isotopic pattern of the nematodes. The high acceptance of the nematodes by Coregonus lavaretus larvae and the early onset of digestion and nutrient retention positively confirm the potential of PanagreUus redivivus as a live food for first feeding fish larvae. [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] Sulfur isotope analysis of cinnabar from Roman wall paintings by elemental analysis/isotope ratio mass spectrometry , tracking the origin of archaeological red pigments and their authenticityRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010Jorge E. Spangenberg The most valuable pigment of the Roman wall paintings was the red color obtained from powdered cinnabar (Minium Cinnabaris pigment), the red mercury sulfide (HgS), which was brought from mercury (Hg) deposits in the Roman Empire. To address the question of whether sulfur isotope signatures can serve as a rapid method to establish the provenance of the red pigment in Roman frescoes, we have measured the sulfur isotope composition (,34S value in , VCDT) in samples of wall painting from the Roman city Aventicum (Avenches, Vaud, Switzerland) and compared them with values from cinnabar from European mercury deposits (Almadén in Spain, Idria in Slovenia, Monte Amiata in Italy, Moschellandsberg in Germany, and Genepy in France). Our study shows that the ,34S values of cinnabar from the studied Roman wall paintings fall within or near to the composition of Almadén cinnabar; thus, the provenance of the raw material may be deduced. This approach may provide information on provenance and authenticity in archaeological, restoration and forensic studies of Roman and Greek frescoes. Copyright © 2010 John Wiley & Sons, Ltd. [source] Differences in the stable isotope signatures of seabird egg membrane and albumen , implications for non-invasive studiesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2009Petra Quillfeldt In many bird species, egg membranes can be obtained non-invasively after the chicks have hatched, and stable isotope analysis of egg membranes can be used to study the diet and foraging distribution of these birds during egg formation. It has been suggested that the enrichment factors of albumen and egg membranes differ for 13C, but are similar for 15N. In this study, we compared carbon and nitrogen stable isotopes of the membranes and albumen of individual eggs of three wild seabird species, the Southern Rockhopper penguin Eudypteschrysocome, the Imperial shag Phalacrocoraxatricepsalbiventer, and the Thin-billed prion Pachyptilabelcheri. We also included chicken eggs for comparison. Egg membranes were generally enriched in 13C, compared with albumen. The difference varied between species, with 2.1, in Rockhopper penguins, 1.6, in Imperial shags, but only 0.5, in Thin-billed prions and 0.4, in chicken eggs. Egg membranes were slightly enriched in 15N in Imperial shags (0.9,) and chickens (0.5,), compared with albumen, while there was no difference for Thin-billed prions and Rockhopper penguins. The isotopic values of carbon and nitrogen were correlated between albumen and egg membranes of individual eggs, suggesting that egg membranes can be used reliably to investigate trophic differences between individuals, seasons or colonies. Species-specific mathematical corrections could be used to compare results across studies that use different egg components. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation of starch and soluble sugars of plant material for the analysis of carbon isotope composition: a comparison of methods,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009Andreas Richter Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO2 fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO2 flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements. We here report on the comparison and evaluation of existing methods (acid and enzymatic hydrolysis for starch; ion-exchange purification and compound-specific analysis for sugars). The selectivity and reproducibility of the methods were tested using three approaches: (i) an artificial leaf composed of a mixture of isotopically defined compounds, (ii) a C4 leaf spiked with C3 starch, and (iii) two natural plant samples (root, leaf). Starch preparation methods based on enzymatic or acid hydrolysis did not yield similar results and exhibited contaminations by non-starch compounds. The specificity of the acidic hydrolysis method was especially low, and we therefore suggest terming these preparations as HCl-hydrolysable carbon, rather than starch. Despite being more specific, enzyme-based methods to isolate starch also need to be further optimized to increase specificity. The analysis of sugars by ion-exchange methods (bulk preparations) was fast but produced more variable isotope compositions than compound-specific methods. Compound-specific approaches did not in all cases correctly reproduce the target values, mainly due to unsatisfactory separation of sugars and background contamination. Our study demonstrates that, despite their wide application, methods for the preparation of starch and soluble sugars for the analysis of carbon isotope composition are not (yet) reliable enough to be routinely applied and further research is urgently needed to resolve the identified problems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Stable carbon isotopes as an indicator for soil degradation in an alpine environment (Urseren Valley, Switzerland)RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2009Monika Schaub Analyses of soil organic carbon (SOC) content and stable carbon isotope signatures (,13C) of soils were assessed for their suitability to detect early stage soil erosion. We investigated the soils in the alpine Urseren Valley (southern central Switzerland) which are highly impacted by soil erosion. Hill slope transects from uplands (cambisols) to adjacent wetlands (histosols and histic to mollic gleysols) differing in their intensity of visible soil erosion, and reference wetlands without erosion influence were sampled. Carbon isotopic signature and SOC content of soil depth profiles were determined. A close correlation of ,13C and carbon content (r,>,0.80) is found for upland soils not affected by soil erosion, indicating that depth profiles of ,13C of these upland soils mainly reflect decomposition of SOC. Long-term disturbance of an upland soil is indicated by decreasing correlation of ,13C and SOC (r,,,0.80) which goes in parallel with increasing (visible) damage at the site. Early stage soil erosion in hill slope transects from uplands to adjacent wetlands is documented as an intermediate ,13C value (,27.5,) for affected wetland soil horizons (0,12,cm) between upland (aerobic metabolism, relatively heavier ,13C of ,26.6,) and wetland isotopic signatures (anaerobic metabolism, relatively lighter ,13C of ,28.6,). Carbon isotopic signature and SOC content are found to be sensitive indicators of short- and long-term soil erosion processes. Copyright © 2009 John Wiley & Sons, Ltd. [source] A comparison of muscle- and scale-derived ,13C and ,15N across three life-history stages of Atlantic salmon, Salmo salarRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008R. Niloshini Sinnatamby Stable isotope signatures were obtained from paired scale and muscle tissue samples from smolt, post-smolt and one-sea-winter adult Atlantic salmon (Salmo salar). Post-smolt and adult scales were separated into central and outer (marine) portions with analyses carried out on the marine growth section of both life-history stages and the central portion for the adult scales. Muscle and scale ,13C and ,15N signatures were assessed (1) to determine whether a linear relationship exists between tissue types, (2) to determine if a constant offset exists between tissue signatures across all life-history stages, and (3) to evaluate whether underplating imparts a significant bias to life-history scale segments that would preclude their use in retrospective analyses of any ontogenetic dietary changes between life-history stages. Significant correlations were found to exist between muscle and scale stable isotope signatures obtained from smolts (,13C and ,15N) and adults (,15N). Both the muscle and the scale signatures captured the dietary shift associated with the transition from freshwater to the marine environment. Post-smolt and adult scales were depleted relative to muscle tissue, which may be attributed to isotopic differences in amino acid composition between muscle and scale tissues. The results suggest that scales may better represent dietary carbon sources because they are not influenced by lipid dynamics. The scale, however, appears less responsive to short-term shifts in diet relative to muscle and, therefore, must be used only to infer seasonally integrated dietary patterns for slow-growing life-history stages. Copyright © 2008 John Wiley & Sons, Ltd. [source] Stable isotopes may provide evidence for starvation in reptilesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2008Marshall D. McCue Previous studies have attempted to correlate stable isotope signatures of tissues with the nutritional condition of birds, mammals, fishes, and invertebrates. Unfortunately, very little is known about the relationship between food limitation and the isotopic composition of reptiles. We examined the effects that starvation has on ,13C and ,15N signatures in the tissues (excreta, carcass, scales, and claws) of six, distantly related squamate reptiles (gaboon vipers, Bitisgabonica; ball pythons, Pythonregius; ratsnakes, Elapheobsoleta; boa constrictors, Boaconstrictor; western diamondback rattlesnakes, Crotalusatrox, and savannah monitor lizards, Varanusexanthematicus). Analyses revealed that the isotopic composition of reptile carcasses did not change significantly in response to bouts of starvation lasting up to 168 days. In contrast, the isotopic signatures of reptile excreta became significantly enriched in 15N and depleted in 13C during starvation. The isotopic signatures of reptile scales and lizard claws were less indicative of starvation time than those of excreta. We discuss the physiological mechanisms that might be responsible for the starvation-induced changes in 13C and 15N signatures in the excreta, and present a mixing model to describe the shift in excreted nitrogen source pools (i.e. from a labile source pool to a nonlabile source pool) that apparently occurs during starvation in these animals. The results of this study suggest that naturally occurring stable isotopes might ultimately have some utility for characterizing nitrogen and carbon stress among free-living reptiles. Copyright © 2008 John Wiley & Sons, Ltd. [source] Sea cucumber habitat differentiation and site retention as determined by intraspecific stable isotope variationAQUACULTURE RESEARCH, Issue 10 2010Matthew J Slater Abstract Stable carbon and nitrogen isotope ratios (,13C/,15N) were assessed as a means to ascertain the recent in situ feeding history of the common New Zealand sea cucumber Australostichopus mollis in relation to nutrient enrichment from a longline green-lipped mussel (Perna canaliculus) farm in Northern New Zealand. ,13C and ,15N isotopic signatures and the ratios of sea cucumbers sampled from within the impact footprint of the mussel farm were compared with those of sea cucumbers residing on adjacent natural reefs. Sea cucumbers from beneath mussel farming longlines had significantly different ,13C stable isotope signatures in comparison with sea cucumbers collected from neighbouring natural reef habitats. This difference supports the hypothesis that sea cucumbers in the same bay maintain distinctly different feeding histories, with those residing beneath mussel farming longlines deriving tissue carbon from sediment impacted by farming activities. This hypothesis is further supported by the finding that the isotope signature of sediment collected from beneath the mussel farm is consistent with the expectation that sea cucumbers were feeding on and consuming sediment enriched with bivalve waste (faeces and pseudo-faeces). In contrast, the nitrogen stable isotope signature (,15N) was found to be similar between sites for both sea cucumbers and assumed food sources. Both findings lend support to the viability of future sea cucumber/green-lipped mussel farm polyculture systems. Sea cucumbers in different locations (mussel farm, natural reef) possessed distinctly different isotope signatures, suggesting that mixing of sea ranched sea cucumbers with natural reef populations would be negligible or non-existent. Similarities between the isotope signatures in low metabolic tissue of sea cucumbers residing at the mussel farm site to that of mussel farm-impacted sediment suggest that cucumbers beneath mussel farms appear to have high rates of retention at the farm site. [source] TIN ISOTOPY,A NEW METHOD FOR SOLVING OLD QUESTIONSARCHAEOMETRY, Issue 5 2010M. HAUSTEIN Tin was a vital commodity in times past. In central Europe, the earliest finds of tin-bronze date to about 2200 bc, while in Greece they are c. 400,500 years earlier. While there is evidence for prehistoric copper mining,for example, in the Alps or mainland Greece, among other places,the provenance of the contemporary tin is still an unsolved problem. This work deals with a new approach for tracing the ancient tin via tin isotope signatures. The tin isotope ratios of 50 tin ores from the Erzgebirge region (D) and 30 tin ores from Cornwall (GB) were measured by MC,ICP,MS. Most ore deposits were found to be quite homogeneous regarding their tin isotope composition, but significant differences were observed between several deposits. This fact may be used to distinguish different tin deposits and thus form the basis for the investigation of the provenance of ancient tin that has been sought for more than a century. Furthermore, the tin-isotope ratio of the ,Himmelsscheibe von Nebra' will be presented: the value fits well with the bulk of investigated tin ores from Cornwall. [source] THE POTENTIAL OF CARBONIZED GRAIN TO PRESERVE BIOGENIC 87SR/86SR SIGNATURES WITHIN THE BURIAL ENVIRONMENT*ARCHAEOMETRY, Issue 2 2009A. HEIER Carbonized grains survive for millennia in many archaeological contexts. Their stable structure raises the possibility that they preserve biogenic strontium isotope signatures. This hypothesis was investigated using short-term, laboratory experiments with modern grain immersed in Chalk solution. HCl leaching removed > 95% of secondary alteration from charred grain, and isotope ratios close to the starting value were recovered. This could not be achieved with uncharred grains. HCl leaching of archaeological carbonized grains produced comparable levels of decontamination. Although preliminary, these results suggest that strontium isotope analysis of archaeological carbonized grains from calcareous burial contexts could be used to investigate ancient trade and agriculture. [source] | |||||||||||||