Journal articles: 'Facteurs de discrimination (∆δ13C, ∆δ15N)'

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Therrien, J. F., G. Fitzgerald, G. Gauthier, and J. Bêty. "Diet–tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)." Canadian Journal of Zoology 89, no. 4 (April 2011): 343–47. http://dx.doi.org/10.1139/z11-008.

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Analysis of carbon (13C/12C) and nitrogen (15N/14N) stable isotope ratios (hereafter δ13C and δ15N, respectively) in animal tissues is a powerful tool in food-web studies. However, isotopic ratios of prey are not transmitted directly to a consumer, as a diet–tissue discrimination factor (denoted Δ) occurs between sources and consumer’s tissues. An accurate assessment of the diet of a consumer with stable isotopes thus requires that the Δ13C and Δ15N of the studied species are known. Our aim was to establish Δ13C and Δ15N values in the Snowy Owl ( Bubo scandiacus (L., 1758)). Moreover, we assessed the potential effect of ethanol preservation of blood samples on δ13C and δ15N values. We kept four captive adult Snowy Owls on a pure diet of mice for ≥6 weeks. We then collected mouse muscle and blood samples from the owls and analyzed their δ13C and δ15N values. Δ13C and Δ15N values (mean ± SE) for owl blood were +0.3‰ ± 0.2‰ and +1.9‰ ± 0.1‰, respectively. These values are the first discrimination factors ever reported in Strigiformes and are lower, for Δ15N, than those obtained in terrestrial carnivores and other bird species, including falcons. Preservation in ethanol did not significantly affect δ13C and δ15N values.

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Franssen, Nathan R., Eliza I. Gilbert, Angela P. James, and Jason E. Davis. "Isotopic tissue turnover and discrimination factors following a laboratory diet switch in Colorado pikeminnow (Ptychocheilus lucius)." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 2 (February 2017): 265–72. http://dx.doi.org/10.1139/cjfas-2015-0531.

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Stable isotope ecology has made great strides in quantifying energy transfer through food webs. However, trophic inferences gleaned from field-collected data can be limited when isotopic turnover and isotopic discrimination factors (Δ13C or Δ15N) are unknown. We quantified isotopic turnover and discrimination factors using an isotopic diet switch in the endangered Colorado pikeminnow (Ptychocheilus lucius). The estimated half-life for δ13C was 62 days or a 33% increase in mass and δ15N averaged 133 days or a 52% increase in mass. Growth and metabolic processes both contributed to rates of turnover, but metabolic processes had a stronger effect in δ13C than in δ15N. Lipid-corrected δ13C values resulted in discrimination factors of Δ13C between 0.67 and 0.82 and Δ15N between 2.31 and 2.93, values similar to other fishes. These results suggest sampling fin tissue may be a useful, nonlethal tool for isotopic studies. Fins also demonstrated enrichment in 13C that was not linked to the diet switch, highlighting the importance of controls in isotopic diet switch studies to verify species- and diet-specific estimates of isotopic turnover rates.

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Carolan, J. Veliscek, D. Mazumder, C. Dimovski, R. Diocares, and J. Twining. "Biokinetics and discrimination factors for δ13C and δ15N in the omnivorous freshwater crustacean, Cherax destructor." Marine and Freshwater Research 63, no. 10 (2012): 878. http://dx.doi.org/10.1071/mf11240.

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Knowledge and understanding of biokinetics and discrimination factors for carbon-13 (δ13C) and nitrogen-15 (δ15N) are important when using stable isotopes for food-web studies. Therefore, we performed a controlled laboratory diet-switch experiment to examine diet–tissue and diet–faeces discrimination factors as well as the biokinetics of stable-isotope assimilation in the omnivorous freshwater crustacean, Cherax destructor. The biokinetics of δ13C could not be established; however, the δ15N value of C. destructor tissue reached equilibrium after 80 ± 35 days, with an estimated biological half-time for 15N of 19 ± 5 days. Metabolic activity contributed to the turnover of 15N by nearly an order of magnitude more than growth. The diet–tissue discrimination factors at the end of the exposure were estimated as –1.1 ± 0.5‰ for δ13C and +1.5 ± 1.0‰ for δ15N, indicating that a δ15N diet–tissue discrimination factor different from the typically assumed +3.4‰ may be required for freshwater macroinvertebrates such as C. destructor. The diet–faeces discrimination factor for δ15N after 120 days was estimated as +0.9 ± 0.5‰. The present study provides an increased understanding of the biokinetics and discrimination factors for a keystone freshwater macroinvertebrate that will be valuable for future food-web studies in freshwater ecosystems.

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Hobbie, Erik A., Janet Chen, Paul J. Hanson, Colleen M. Iversen, Karis J. McFarlane, Nathan R. Thorp, and Kirsten S. Hofmockel. "Long-term carbon and nitrogen dynamics at SPRUCE revealed through stable isotopes in peat profiles." Biogeosciences 14, no. 9 (May 17, 2017): 2481–94. http://dx.doi.org/10.5194/bg-14-2481-2017.

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Abstract. Peatlands encode information about past vegetation dynamics, climate, and microbial processes. Here, we used δ15N and δ13C patterns from 16 peat profiles to deduce how the biogeochemistry of the Marcell S1 forested bog in northern Minnesota responded to environmental and vegetation change over the past ∼ 10 000 years. In multiple regression analyses, δ15N and δ13C correlated strongly with depth, plot location, C ∕ N, %N, and each other. Correlations with %N, %C, C ∕ N, and the other isotope accounted for 80 % of variance for δ15N and 38 % of variance for δ13C, reflecting N and C losses. In contrast, correlations with depth and topography (hummock or hollow) reflected peatland successional history and climate. Higher δ15N in plots closer to uplands may reflect upland-derived DON inputs and accompanying shifts in N dynamics in the lagg drainage area surrounding the bog. The Suess effect (declining δ13CO2 since the Industrial Revolution) lowered δ13C in recent surficial samples. High δ15N from −35 to −55 cm probably indicated the depth of ectomycorrhizal activity after tree colonization of the peatland over the last 400 years, as confirmed by the occasional presence of wood down to −35 cm depth. High δ13C at ∼ 4000 years BP (−65 to −105 cm) could reflect a transition at that time to slower rates of peat accumulation, when 13C discrimination during peat decomposition may increase in importance. Low δ13C and high δ15N at −213 and −225 cm ( ∼ 8500 years BP) corresponded to a warm period during a sedge-dominated rich fen stage. The above processes appear to be the primary drivers of the observed isotopic patterns, whereas there was no clear evidence for methane dynamics influencing δ13C patterns.

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Huneau, Jean-François, Olivier L. Mantha, Dominique Hermier, Véronique Mathé, Guillaume Galmiche, François Mariotti, and Hélène Fouillet. "Natural Isotope Abundances of Carbon and Nitrogen in Tissue Proteins and Amino Acids as Biomarkers of the Decreased Carbohydrate Oxidation and Increased Amino Acid Oxidation Induced by Caloric Restriction under a Maintained Protein Intake in Obese Rats." Nutrients 11, no. 5 (May 16, 2019): 1087. http://dx.doi.org/10.3390/nu11051087.

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A growing body of evidence supports a role for tissue-to-diet 15N and 13C discrimination factors (Δ15N and Δ13C), as biomarkers of metabolic adaptations to nutritional stress, but the underlying mechanisms remain poorly understood. In obese rats fed ad libitum or subjected to gradual caloric restriction (CR), under a maintained protein intake, we measured Δ15N and Δ13C levels in tissue proteins and their constitutive amino acids (AA) and the expression of enzymes involved in the AA metabolism. CR was found to lower protein mass in the intestine, liver, heart and, to a lesser extent, some skeletal muscles. This was accompanied by Δ15N increases in urine and the protein of the liver and plasma, but Δ15N decreases in the proteins of the heart and the skeletal muscles, alongside Δ13C decreases in all tissue proteins. In Lys, Δ15N levels rose in the plasma, intestine, and some muscles, but fell in the heart, while in Ala, and to a lesser extent Glx and Asx, Δ13C levels fell in all these tissues. In the liver, CR was associated with an increase in the expression of genes involved in AA oxidation. During CR, the parallel rises of Δ15N in urine, liver, and plasma proteins reflected an increased AA catabolism occurring at the level of the liver metabolic branch point, while Δ15N decreases in cardiac and skeletal muscle proteins indicated increased protein and AA catabolism in these tissues. Thus, an increased protein and AA catabolism results in opposite Δ15N effects in splanchnic and muscular tissues. In addition, the Δ13C decrease in all tissue proteins, reflects a reduction in carbohydrate (CHO) oxidation and routing towards non-indispensable AA, to achieve fuel economy.

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Villegas, Mariana, Catherine Soos, Gustavo Jiménez-Uzcátegui, Shukri Matan, and Keith A. Hobson. "Isotopic Niche Segregation among Darwin’s Finches on Santa Cruz Island, Galápagos." Diversity 13, no. 4 (March 30, 2021): 147. http://dx.doi.org/10.3390/d13040147.

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Darwin’s finches are a classic example of adaptive radiation involving differential use of dietary resources among sympatric species. Here, we apply stable isotope (δ13C, δ15N, and δ2H) analyses of feathers to examine ecological segregation among eight Darwin’s finch species in Santa Cruz Island, Galápagos collected from live birds and museum specimens (1962–2019). We found that δ13C values were higher for the granivorous and herbivorous foraging guilds, and lower for the insectivorous finches. Values of δ15N were similar among foraging guilds but values of δ2H were higher for insectivores, followed by granivores, and lowest for herbivores. The herbivorous guild generally occupied the largest isotopic standard ellipse areas for all isotopic combinations and the insectivorous guild the smallest. Values of δ2H provided better trophic discrimination than those of δ15N possibly due to confounding influences of agricultural inputs of nitrogen. Segregation among guilds was enhanced by portraying guilds in three-dimensional isotope (δ13C, δ15N, and δ2H) space. Values of δ13C and δ15N were higher for feathers of museum specimens than for live birds. We provide evidence that Darwin’s finches on Santa Cruz Island tend to be generalists with overlapping isotopic niches and suggest that dietary overlap may also be more considerable than previously thought.

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Robb, G. N., S. Woodborne, P. R. de Bruin, K. Medger, and N. C. Bennett. "The influence of food quantity on carbon and nitrogen stable isotope values in southern African spiny mice (Acomys spinosissimus)." Canadian Journal of Zoology 93, no. 5 (May 2015): 345–51. http://dx.doi.org/10.1139/cjz-2014-0134.

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Stable isotope analysis is frequently applied as a tool to examine dietary patterns in animals. However, some of the underlying assumptions associated with using this approach are increasingly being questioned. We carried out a controlled diet experiment on the southern African spiny mouse (Acomys spinosissimus Peters, 1852) to test a number of aspects relating to these assumptions and also examine the hypothesis that stable isotopes, especially δ15N, can be used to provide evidence of nutritional stress. We compared the δ13C and δ15N values of livers and blood from animals that were fed ad libitum with animals undergoing a 10% reduction in food supply. Food-restricted animals showed no significant difference in δ15N; however, δ13C values of both liver and blood were depleted. Restricted animals also had a significantly lower C:N ratio. We examined the role of lipids and found following lipid extraction that both livers and lipids still showed the same separation in carbon values. Tissue–diet discrimination values were also calculated and found to be higher for both Δ13C and Δ15N compared with other mice species. Empirical values for discrimination rates were then compared with values calculated using an alternative method based on employing generic values and were found to be dissimilar, suggesting the use of generic values are not always appropriate. Our results highlight the need for greater understanding of the assumptions associated with using stable isotope analysis to examine diet and we suggest that studying a single species under captive conditions presents an ideal method to begin to test these hypotheses.

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McAllister, LT, TE Van Leeuwen, JM Hanlon, CJ Morris, J. Potter, J. Wells, and M. Abrahams. "Sea cage aquaculture may provide an energetic subsidy to wild juvenile cod in coastal bays of southern Newfoundland, Canada." Marine Ecology Progress Series 674 (September 16, 2021): 241–55. http://dx.doi.org/10.3354/meps13832.

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Sea cage aquaculture can alter the spatial distribution of wild fish populations; however, little is known about the dietary habits of wild fish frequenting sea cages. We used wild juvenile cod Gadus morhua reared in the laboratory and fed either an aquafeed pellet or marine-based diet to determine trophic discrimination factors (TDFs) of stable carbon (δ13C) and nitrogen (δ15N) isotope values in white muscle tissue and baseline liver proportions of vegetable-oil based (VOB) fatty acids. We then used δ13C and δ15N and proportions of VOB fatty acids to investigate the dietary habits of wild cage-associated juvenile and adult Atlantic cod and adult Atlantic redfish Sebastes fasciatus. Cod and redfish were collected in the immediate area of sea cages and reference areas of no aquaculture production. Juvenile cod captured around sea cages had both elevated δ13C and δ15N values and proportions of VOB fatty acids, and isotopic fractionation comparable to laboratory cod fed an aquafeed diet. However, differences in δ13C and δ15N and proportions of VOB fatty acids between cage-associated and reference site adult cod and redfish were predominately absent. Results suggest that sea cages may provide an energetic subsidy to juvenile cod but perhaps not at the level to sustain adult cod or redfish. Therefore, the lack of differences suggests that both adult groups may be using cage sites opportunistically and only for short duration, as isotopic values and fatty acid proportions were not consistent with waste feed consumption despite individuals being collected in close proximity to sea cages.

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Beckett, Nicola M., Darren I. Grice, James F. Carter, and Sarah L. Cresswell. "Precursor discrimination of designer drug benzylpiperazine using δ13C and δ15N stable isotopes." Science & Justice 55, no. 1 (January 2015): 57–62. http://dx.doi.org/10.1016/j.scijus.2014.09.001.

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Lopes, Marta S., Salvador Nogués, and José L. Araus. "Nitrogen source and water regime effects on barley photosynthesis and isotope signature." Functional Plant Biology 31, no. 10 (2004): 995. http://dx.doi.org/10.1071/fp04031.

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Water stress and nitrogen (N) availability are the main constraints on barley (Hordeum vulgare L.) yield in Mediterranean conditions. Here we studied the combined effects of N source and water regime (WR) on plant growth, photosynthesis and carbon isotope discrimination (Δ13C) in barley grown under controlled conditions. The effects of these conditions on plant N isotope discrimination against the fertiliser (Δ15N) was also examined to assess whether the natural variation in plant N isotope composition is a reliable indicator of N nutrition. Six experimental treatments were established with three nutrient solutions containing ammonium (NH4+), nitrate (NO3–) or a mixture of the two (NH4+ : NO3–), each either well watered or moderately water stressed. The NH4+ : NO3– treatment resulted in the greatest biomass accumulation and photosynthetic capacity in both WRs. The NH4+ plants showed accelerated phenology and depressed growth. They also had the lowest photosynthetic rates in both WRs. This effect was mainly due to stomatal closure, while electron transport and carboxylation capacity of leaves were less affected. Consistent with lower stomatal conductance, leaf Δ13C was lower in plants that received NH4+, indicating higher water use efficiency (WUE) not only when irrigated, but also under water stress. In addition, leaf Δ13C and photosynthetic N use efficiency (PNUE) correlated positively with each other and with shoot biomass in both WRs. However, NO3– treatment produced the greatest Δ15N, which was higher in leaves than in roots. Leaf Δ15N was decreased by water stress only in plants in the NO3– treatment. We conclude that leaf Δ13C is an adequate trait to assess the differences in growth, photosynthetic activity and WUE caused by distinct N sources. However, the usefulness of natural abundance of 15N in plant tissue as a nitrogen source marker is restricted by the effect of WR and internal plant fractionation, at least for plants that received NO3–.

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Uriarte, Amaya, Alberto García, Aurelio Ortega, Fernando De la Gándara, José Quintanilla, and Raúl Laiz-Carrión. "Isotopic discrimination factors and nitrogen turnover rates in reared Atlantic bluefin tuna larvae (Thunnus thynnus): effects of maternal transmission." Scientia Marina 80, no. 4 (November 22, 2016): 447. http://dx.doi.org/10.3989/scimar.04435.25a.

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The use of stable isotope analysis to study animal diets requires estimates of isotopic turnover rates (half time, t50) and discrimination factors (Δ) for an accurate interpretation of trophic patterns. The stable isotopes of carbon and nitrogen were analysed for eggs and reared larvae of Thunnus thynnus, as well as for the different diets supplied during the experiment. The results showed high values of δ15N in eggs and larvae (n=646) until 4 DAH. After this time lapse, the stable isotope values declined progressively until 12 DAH, when notochord flexion began. The δ13C showed an inverse trend, suggesting that maternal inheritance of the stable isotopes is evident until pre-flexion stages. This study proposes a model for estimating maternal isotopic signatures of bluefin broodstock. After notochord flexion, larvae were fed with aquaculture-bred gilthead seabream, which resulted in a rapid increase of bluefin larvae δ15N values together with a rapid decrease in δ13C values. The estimated nitrogen half-time to reach the steady state from the diet was 2.5±0.3 days and the discrimination factor was 0.4±0.3(‰). These results represent the first data set that has allowed isotopic nitrogen turnover rates and discrimination factors of the larval stages of bluefin tuna to be estimated.

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Wells, R. J. David, Michael J. Kinney, Suzanne Kohin, Heidi Dewar, Jay R. Rooker, and Owyn E. Snodgrass. "Natural tracers reveal population structure of albacore (Thunnus alalunga) in the eastern North Pacific." ICES Journal of Marine Science 72, no. 7 (April 2, 2015): 2118–27. http://dx.doi.org/10.1093/icesjms/fsv051.

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Abstract Chemical signatures in otoliths and muscle tissue of albacore (Thunnus alalunga) from two regions of the North Pacific were characterized to examine population structure. Regions included northern (offshore northwest United States and Canada, >40°N) and southern (offshore southwest United States and Mexico, <40°N) areas where albacore have demonstrated region-specific differences in movement and size at age. Juvenile (ages 1–4 years) albacore were collected from each region through recreational and commercial fisheries over a 5-year period (2009–2013). Three different otolith chemistry assays were performed, including whole otoliths (proxy for lifetime signature), otolith edge (recent signature), and otolith core (nursery signature). Whole otolith δ13C and δ18O showed similar δ13C and enriched δ18O (∼0.5‰) values for juvenile albacore collected in the southern region; classification success to the two regions ranged from 78 to 91% during each year (similar age classes). Otolith edge δ13C and δ18O showed similar results as whole otoliths, but no regional differences were found for otolith core chemistry. Incorporation of trace element concentrations from whole otoliths improved discrimination between regions to 90–100% classification success during each year of the study, with significantly higher Ba:Ca, Mg:Ca, and Mn:Ca in albacore otoliths from the northern region. Albacore from the southern region also displayed enriched muscle δ13C (∼1.21‰) and δ15N (∼0.85‰) values relative to fish of the same size range from the northern region. Discrimination success between the two regions across all years using muscle δ13C and δ15N was 91%. Ultimately, results from this study suggest regional separation of albacore in the eastern North Pacific warranting region-specific vital rates in future modelling efforts.

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Schwartz-Narbonne, Rachel, Tessa Plint, Elizabeth Hall, Grant Zazula, and Fred J. Longstaffe. "Seasonal paleoecological records from antler collagen δ13C and δ15N." Paleobiology 47, no. 3 (March 5, 2021): 533–49. http://dx.doi.org/10.1017/pab.2021.1.

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AbstractCervids living in high latitudes have evolved to thrive in ecosystems that experience dramatic seasonal changes. Understanding these seasonal adaptations is important for reconstructing cervid life histories, ecosystem dynamics, and responses in the distant and not-so-distant past to changing seasonality caused by climate change. Cervid antlers provide a rare opportunity for insight into faunal seasonal ecology, as they are grown and shed each year. Stable isotopes of carbon and nitrogen measured directly from antlers have the potential to provide seasonal dietary data for individuals. If the isotopic signals in bone and antler are controlled by the same metabolic processes, then the stable carbon and nitrogen isotope compositions of collagen (δ13CColl and δ15NColl) from incrementally grown antler tissue provide time-constrained dietary signals from the spring and summer growth season. Bone, by comparison, provides an average signal over several years. The amino acid (glutamate and phenylalanine) δ15N in antlers from modern captive caribou showed similar trophic discrimination factors to earlier results for other collagenous tissues (bone, tooth dentin, and cementum). Hence, growth rate was not the primary control on the stable isotope composition of antler collagen. We applied this knowledge to assess seasonal shifts in Quaternary fossils of three Cervidae species: elk (Cervus elaphus), moose (Alces alces), and caribou (Rangifer tarandus). Paired antler–bone δ13CColl and δ15NColl from the same individual were used to identify differences between summer and annual diet and ecology. Intra-antler isotopic variability from serially sampled antlers was used to examine seasonal dietary shifts and specialization.

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Faberi, Angelo, Dario Compagnone, Fabio Fuselli, Alessandro La Mantia, Marcello Mascini, Camilla Montesano, Rachele Rocchi, and Manuel Sergi. "Italian Cheeses Discrimination by Means of δ13C and δ15N Isotopic Ratio Mass Spectrometry." Food Analytical Methods 11, no. 5 (December 19, 2017): 1467–75. http://dx.doi.org/10.1007/s12161-017-1110-0.

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Yousfi, Salima, Maria Dolores Serret, and José Luis Araus. "Shoot δ15N gives a better indication than ion concentration or Δ13C of genotypic differences in the response of durum wheat to salinity." Functional Plant Biology 36, no. 2 (2009): 144. http://dx.doi.org/10.1071/fp08135.

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We compared the performance of different physiological traits that reveal genotypic variations in tolerance to salinity in durum wheat. A set of 114 genotypes was grown in hydroponics for over 3 months. Three conditions: control, moderate (12 dS m−1) and severe (17 dS m−1) salinity, were maintained for nearly 8 weeks before harvest. The genotype biomass in control conditions correlated with the biomass at the two salinity levels. Subsequently, two subsets of 10 genotypes each were selected on the basis of extreme differences in biomass at the two salinity levels while showing relatively similar biomass in control conditions. Carbon isotope discrimination (Δ13C), nitrogen isotope composition (δ15N), and the concentration of nitrogen, phosphorus and several ions (K+, Na+, Ca2+, Mg2+) were analysed in the two subsets for the three treatments. At 12 dS m−1, K+ concentration, K+/Na+ ratio, Δ13C and δ15N correlated positively and Na+ correlated negatively with shoot biomass. Under control conditions and at 17 dS m−1 no correlation was observed. However, the trait that correlated best with genotypic differences in biomass was δ15N at 12 dS m−1. This trait was the first variable chosen at each of the two salinity levels in a stepwise analysis. We consider the possible mechanisms relating δ15N to biomass and the use of this isotopic signature as a selection trait.

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Hong, Wiley, Powers, Michener, Kaufman, and Hatch. "Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs." Diversity 11, no. 9 (September 12, 2019): 163. http://dx.doi.org/10.3390/d11090163.

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The great shearwater (Ardenna gravis) is a common pelagic bird with a distribution that spans almost the entire Atlantic basin, which in conjunction with its relatively high abundance, makes great shearwaters an effective bio indicator. We compared δ13C and δ15N values from the feathers, red blood cells (RBCs), and plasma of great shearwaters collected in 2014 and 2015 from the waters off Massachusetts and Cape Cod. The δ13C and δ15N values of RBCs were quite constant between sampling periods and years, suggesting a generally stable food web over that time period. However, the δ13C of plasma indicates a small seasonal change in diet between July and September for both years, with plasma δ15N values suggesting a slight increase in trophic level late in summer. Comparison of the δ15N of RBCs and plasma indicates that great shearwaters experienced a diet shift during the first few weeks of summer 2014, but not in 2015. Comparisons with other studies suggest that these shearwaters feed at a lower trophic level than great shearwaters sampled in the Bay of Fundy and that there is a decrease in δ13C with increasing latitude, which could indicate a more pelagic diet in northern waters. Stable isotope analysis of the sixth primary feathers provided evidence that these feathers are molted in the Northern Hemisphere and that the diet of great shearwaters shortly after arrival was different in 2014 and 2015. This study demonstrates that within species comparisons of tissue isotopic signatures over time and comparisons of isotopic signatures of tissues with different turnover rates, can detect changes in diet and be used as a tool to monitor for changes in marine food webs over time and space. The relevant signals remain informative even in the absence of species-specific data on tissue-diet discrimination factors, tissue turnover rates, or knowledge of dietary components and their stable isotopic signatures, suggesting dietary changes indicative of a corresponding change in the food web.

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Haberle, Jan, Renata Duffková, Ivana Raimanová, Petr Fučík, Pavel Svoboda, Vojtěch Lukas, and Gabriela Kurešová. "The 13C Discrimination of Crops Identifies Soil Spatial Variability Related to Water Shortage Vulnerability." Agronomy 10, no. 11 (October 31, 2020): 1691. http://dx.doi.org/10.3390/agronomy10111691.

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Spatial variability of crop growth and yields is the result of many interacting factors. The contribution of the factors to variable yields is often difficult to separate. This work studied the relationships between the 13C discrimination (Δ13C) of plants and the spatial variability of field soil conditions related to impacts of water shortage on crop yield. The 13C discrimination, the indicator of water shortage in plants, 15N (δ15N) discrimination, and nitrogen (N) content were determined in grains of winter wheat, spring barley, and pea. The traits were observed at several dozens of grid spots in seven fields situated in two regions with different soil and climate conditions between the years 2017 and 2019. The principles of precision agriculture were implemented in some of the studied fields and years by variable rate nitrogen fertilization. The Δ13C significantly correlated with grain yields (correlation coefficient from 0.66 to 0.94), with the exception of data from the wetter year 2019 at the site with higher soil water capacity. The effect of drought was demonstrated by statistically significant relationships between Δ13C in dry years and soil water capacity (r from 0.46 to 0.97). The significant correlations between Δ13C and N content of seeds and soil water capacity agreed with the expected impact of water shortage on plants. The 13C discrimination of crop seeds was confirmed as a reliable indicator of soil spatial variability related to water shortage. Stronger relationships were found in variably fertilized areas.

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Brauns, Mario, Iola G. Boëchat, Ana Paula C. de Carvalho, Daniel Graeber, Björn Gücker, Thomas Mehner, and Daniel von Schiller. "Consumer-resource stoichiometry as a predictor of trophic discrimination (Δ13C, Δ15N) in aquatic invertebrates." Freshwater Biology 63, no. 10 (June 29, 2018): 1240–49. http://dx.doi.org/10.1111/fwb.13129.

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Caut, Stéphane, Elena Angulo, and Franck Courchamp. "Discrimination factors (Δ15N and Δ13C) in an omnivorous consumer: effect of diet isotopic ratio." Functional Ecology 22, no. 2 (April 2008): 255–63. http://dx.doi.org/10.1111/j.1365-2435.2007.01360.x.

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Crawley, Karen R., Glenn A. Hyndes, and Mathew A. Vanderklift. "Variation among diets in discrimination of δ13C and δ15N in the amphipod Allorchestes compressa." Journal of Experimental Marine Biology and Ecology 349, no. 2 (October 2007): 370–77. http://dx.doi.org/10.1016/j.jembe.2007.05.025.

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Hussey, Nigel E., Jaclyn Brush, Ian D. McCarthy, and Aaron T. Fisk. "δ15N and δ13C diet–tissue discrimination factors for large sharks under semi-controlled conditions." Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 155, no. 4 (April 2010): 445–53. http://dx.doi.org/10.1016/j.cbpa.2009.09.023.

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Hiler, Waylon, Stanley E. Trauth, Benjamin Wheeler, Aimee Jimenez, Milica Radanovic, Joseph R. Milanovich, and Alan D. Christian. "Stable Isotope Analysis of Ozark Hellbender (Cryptobranchus alleganiensis bishopi) Living and Preserved Museum Tissue Reveals a Shift in Their Generalist Diet Composition." Ecologies 2, no. 2 (April 6, 2021): 187–202. http://dx.doi.org/10.3390/ecologies2020011.

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Ozark hellbenders (Cryptobranchus alleganiensis bishopi) have undergone marked population declines across their entire distribution. A variety of ecological life history research has been conducted to determine the cause(s) of the declines. Historically, hellbender diet studies used stomach content examination methods; however, alternative approaches such as less intrusive stable isotope analyses are now options for researchers. The goals of our study were to conduct stable isotope analysis on live and formalin-preserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, Arkansas. Also, we used stable isotope analysis to investigate if Spring River hellbender diets have changed over time. We sampled fish, live hellbenders (non-destructively), and formalin-preserved hellbender tissues from museum collections for stable isotope analysis. We sampled crayfish for assemblage composition and stable isotope analysis. The results of our stable isotope study revealed three main findings: (1) there were no statistically significant differences between hellbender δ13C and δ15N values among sites and hellbender stable C and N isotopes were correlated with body length; (2) traditional δ13C versus δ15N bi-plots and trophic discrimination values did not provide complete discernment in hellbender diets; however, Bayesian MixSIAR models revealed hellbenders to be generalists, and (3) the use of δ13C and δ15N values adjusted historic formalin-fixed and ethanol preserved hellbenders matched well with current crayfish and fish stable isotope values based on Bayesian MixSIAR models. These findings provide important diet information and a possible tool to examine dietary patterns from preserved specimens that may be used for hellbender conservation and management.

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Hwang, Y. T., J. S. Millar, and F. J. Longstaffe. "Do δ15N and δ13C values of feces reflect the isotopic composition of diets in small mammals?" Canadian Journal of Zoology 85, no. 3 (February 2007): 388–96. http://dx.doi.org/10.1139/z07-019.

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The stable isotope composition of carbon and nitrogen in feces can be a useful tool for reconstructing diet. To examine whether the isotopic composition of feces reflect those of diet, we determined the fractionation of 15N and 13C along the digestive tracts of several species of small mammals. There were significant differences in the δ15N values of digesta in different compartments of the gastrointestinal (GI) tract, with consistent enrichment of 15N in the stomach, intestine, and cecum, and the depletion of 15N in the colon (i.e., feces). Although feces had lower δ15N values than digesta in the cecum, feces of small mammals were significantly more enriched in 15N (by ~2.5‰) than diet. The mechanisms causing this enrichment in the GI tract may arise from the operation of different biochemical pathways within the different GI compartments. The stable carbon isotope composition of digesta in small mammals were similar along the GI tract, but the δ13C values of digesta and feces were significantly lower than reported previously for large ungulates (–3.5‰ vs. –0.5‰). The δ15N and δ13C values of feces did not directly reflect the isotopic compositions of these mammals’ diet. Our data offer evidence for variations in isotopic discrimination effects. This variation can probably be ascribed to metabolism of different body sizes of mammals and the complexities linked with digestive physiology of herbivores.

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Gouveia, Carla S. S., Vincent Lebot, and Miguel Pinheiro de Carvalho. "NIRS Estimation of Drought Stress on Chemical Quality Constituents of Taro (Colocasia esculenta L.) and Sweet Potato (Ipomoea batatas L.) Flours." Applied Sciences 10, no. 23 (December 5, 2020): 8724. http://dx.doi.org/10.3390/app10238724.

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Taro (Colocasia esculenta (L.) Schott) and sweet potato (Ipomoea batatas (L.) Lam.) are important food crops worldwide, whose productivity is threatened by climatic constraints, namely drought. Data calibration, validation, and model development of high-precision near-infrared spectroscopy (NIRS) involving multivariate analyses are needed for the fast prediction of the quality of tubers and shoots impacted by drought stress. The main objective of this study was to generate accurate NIRS models for quality assessment of taro and sweet potato accessions (acc.) subjected to water scarcity conditions. Seven taro and eight sweet potato acc. from diverse geographical origins were evaluated for nitrogen (N), protein (Pt), starch (St), total mineral (M), calcium oxalate (CaOx), carbon isotope discrimination (Δ13C), and nitrogen isotopic composition (δ15N). Models were developed separately for both crops underground and aboveground organs. N, Pt, St, and M models could be used as quality control constituents, with a determination coefficient of prediction (r2pred) between 0.856 and 0.995. δ13C, δ15N, and CaOx, with r2pred between 0.178 and 0.788, could be used as an informative germplasm screening tool. The approach used in the present study demonstrates NIRS’s potential for further research on crop quality under drought.

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Behrmann-Godel, J., and E. Yohannes. "Multiple isotope analyses of the pike tapeworm Triaenophorus nodulosus reveal peculiarities in consumer–diet discrimination patterns." Journal of Helminthology 89, no. 2 (January 22, 2014): 238–43. http://dx.doi.org/10.1017/s0022149x13000849.

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AbstractPrevious studies of dietary isotope discrimination have led to the general expectation that a consumer will exhibit enriched stable isotope levels relative to its diet. Parasite–host systems are specific consumer–diet pairs in which the consumer (parasite) feeds exclusively on one dietary source: host tissue. However, the small numbers of studies previously carried out on isotopic discrimination in parasite–host (ΔXP-HT) systems have yielded controversial results, showing some parasites to be isotopically depleted relative to their food source, while others are enriched or in equilibrium with their hosts. Although the mechanism for these deviations from expectations remains to be understood, possible influences of specific feeding niche or selection for only a few nutritional components by the parasite are discussed. ΔXP-HT for multiple isotopes (δ13C, δ15N, δ34S) were measured in the pike tapeworm Triaenophorus nodulosus and two of its life-cycle fish hosts, perch Perca fluviatilis and pike Esox lucius, within which T. nodulosus occupies different feeding locations. Variability in the value of ΔXP-HT calculated for the parasite and its different hosts indicates an influence of feeding location on isotopic discrimination. In perch liver ΔXP-HT was relatively more negative for all three stable isotopes. In pike gut ΔXP-HT was more positive for δ13C, as expected in conventional consumer–diet systems. For parasites feeding on pike gut, however, the δ15N and δ34S isotope values were comparable with those of the host. We discuss potential causes of these deviations from expectations, including the effect of specific parasite feeding niches, and conclude that ΔXP-HT should be critically evaluated for trophic interactions between parasite and host before general patterns are assumed.

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Marques, Thiago S., Luis A. B. Bassetti, Neliton R. F. Lara, Márcio S. Araújo, Carlos I. Piña, Plínio B. Camargo, and Luciano M. Verdade. "Isotopic Discrimination Factors (Δ13C and Δ15N) between Tissues and Diet of the Broad-Snouted Caiman (Caiman latirostris)." Journal of Herpetology 48, no. 3 (September 2014): 332–37. http://dx.doi.org/10.1670/12-274.

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Navarro, J., M. Albo-Puigserver, M. Coll, R. Saez, M. G. Forero, and R. Kutcha. "Isotopic discrimination of stable isotopes of nitrogen (δ15N) and carbon (δ13C) in a host-specific holocephalan tapeworm." Journal of Helminthology 88, no. 3 (March 4, 2013): 371–75. http://dx.doi.org/10.1017/s0022149x13000126.

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AbstractDuring the past decade, parasites have been considered important components of their ecosystems since they can modify food-web structures and functioning. One constraint to the inclusion of parasites in food-web models is the scarcity of available information on their feeding habits and host–parasite relationships. The stable isotope approach is suggested as a useful methodology to determine the trophic position and feeding habits of parasites. However, the isotopic approach is limited by the lack of information on the isotopic discrimination (ID) values of parasites, which is pivotal to avoiding the biased interpretation of isotopic results. In the present study we aimed to provide the first ID values of δ15N and δ13C between the gyrocotylidean tapeworm Gyrocotyle urna and its definitive host, the holocephalan Chimaera monstrosa. We also test the effect of host body size (body length and body mass) and sex of the host on the ID values. Finally, we illustrate how the trophic relationships of the fish host C. monstrosa and the tapeworm G. urna could vary relative to ID values. Similar to other studies with parasites, the ID values of the parasite–host system were negative for both isotopic values of N (Δδ15N = − 3.33 ± 0.63‰) and C (Δδ13C = − 1.32 ± 0.65‰), independent of the sex and size of the host. By comparing the specific ID obtained here with ID from other studies, we illustrate the importance of using specific ID in parasite–host systems to avoid potential errors in the interpretation of the results when surrogate values from similar systems or organisms are used.

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Jenkins, Edward, Julia Gulka, David J. Yurkowski, Nathalie R. Le François, Emiko Wong, and Gail K. Davoren. "Isotopic Discrimination (δ15N, δ13C) in Captive and Wild Common Murres (Uria aalge) and Atlantic Puffins (Fratercula arctica)." Physiological and Biochemical Zoology 93, no. 4 (July 2020): 296–309. http://dx.doi.org/10.1086/709460.

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Hobson, Keith A., and Travis W. Quirk. "Effect of age and ration on diet-tissue isotopic (Δ13C, Δ15N ) discrimination in striped skunks (Mephitis mephitis)." Isotopes in Environmental and Health Studies 50, no. 3 (February 7, 2014): 300–306. http://dx.doi.org/10.1080/10256016.2014.867852.

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Symes, Craig, Felix Skhosana, Mike Butler, Brett Gardner, and Stephan Woodborne. "Isotope (δ13C, δ15N, δ2H) diet–tissue discrimination in African grey parrot Psittacus erithacus: implications for forensic studies." Isotopes in Environmental and Health Studies 53, no. 6 (May 8, 2017): 580–96. http://dx.doi.org/10.1080/10256016.2017.1319832.

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Schumann, David A., Christopher S. Uphoff, Casey W. Schoenebeck, and Katie N. B. Graeb. "Incorporation of carbon and nitrogen isotopes in age-0 walleye (Sander vitreus) tissues following a laboratory diet switch experiment." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 4 (April 2018): 497–505. http://dx.doi.org/10.1139/cjfas-2017-0301.

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Trophic dynamics are often described by following the exchange of naturally occurring isotopes through aquatic communities. However, without experimentally derived isotopic turnover rates and discrimination factors for each species, tissue, and life stage, these trophic models can be misleading. We conducted a laboratory diet shift experiment to describe isotopic turnover and discrimination in age-0 walleye (Sander vitreus) dorsal muscle and gutted carcass samples. Although turnover of dietary δ13C (half-life: 10–12 days) and δ15N (half-life: ∼13 days) signatures was relatively rapid, the diet change was undetected in both tissues during a short transitional period (up to 1.2 times shorter in muscle). Our discrimination estimates generally conform to those of other fishes (ΔCarbon= 0.91, ΔNitrogen= 1.6), but were 30%–50% higher in muscle tissues than in gutted carcass samples. The assumption that young walleye tissues are in equilibrium with their diet is untrue for weeks following a diet shift, and when incorporated, discrimination factors differ between tissues. We provide tissue-specific parameters that remove uncertainty associated with the analysis of field collected isotopic age-0 walleye data.

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Montoro, Marta, Per M. Jensen, and Lene Sigsgaard. "Stable Isotope Enrichment (Δ15N) in the Predatory Flower Bug (Orius majusculus) Predicts Fitness-Related Differences between Diets." Insects 11, no. 4 (April 20, 2020): 255. http://dx.doi.org/10.3390/insects11040255.

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Mass rearing of insects, used both as biological control agents and for food and feed, is receiving increasing attention. Efforts are being made to improve diets that are currently in use, and to identify alternative diets, as is the case with the predatory flower bug (Orius majusculus) and other heteropteran predators, due to the high costs of their current diet, the eggs of the Mediterranean flour moth (E. kuehniella). The assessment of alternative diets may include measurements of the predator’s fitness-related traits (development time, weight, etc.), and biochemical analyses such as lipid and protein content in the diet and the insects. However, assessing diet quality via the predator’s fitness-related traits is laborious, and biochemical composition is often difficult to relate to the measured traits. Isotope analysis, previously used for diet reconstruction studies, can also serve as a tool for the assessment of diet quality. Here, the variation in discrimination factors or isotope enrichment (Δ15N and Δ13C) indicates the difference in isotopic ratio between the insect and its diet. In this study, we investigated the link between Δ15N and diet quality in the predatory bug Orius majusculus. Three groups of bugs were fed different diets: Ephestia kuehniella eggs, protein-rich Drosophila melanogaster and lipid-rich D. melanogaster. The isotopic enrichment and fitness-related measurements were assessed for each group. Results show a relation between Δ15N and fitness-related measurements, which conform to the idea that lower Δ15N indicates a higher diet quality.

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Hussain, M., Manuel Reigosa, and Adele Muscolo. "Carbon (δ13C) and Nitrogen (δ15N) Stable Isotope Composition Provide New Insights into Phenotypic Plasticity in Broad Leaf Weed Rumex acetosa under Allelochemical Stress." Molecules 23, no. 10 (September 25, 2018): 2449. http://dx.doi.org/10.3390/molecules23102449.

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Phenolic compounds, hydroquinone and cinnamic acid derivatives have been identified as major allelochemicals with known phytotoxicity from allelopathic plant Acacia melanoxylon R. Br. Several phenolic compounds such as ferulic acid (FA), p-hydroxybenzoic acid (pHBA) and flavonoid (rutin, quercetin) constituents occur in the phyllodes and flowers of A. melanoxylon and have demonstrated inhibitory effects on germination and physiological characteristics of lettuce and perennial grasses. However, to date, little is known about the mechanisms of action of these secondary metabolites in broad-leaved weeds at ecophysiological level. The objective of this study was to determine the response of Rumex acetosa carbon isotope composition and other physiological parameters to the interaction of plant secondary metabolites (PSM) (FA and pHBA) stress and the usefulness of carbon isotope discrimination (Δ13C) as indicative of the functional performance of intrinsic water use efficiency (iWUE) at level of plant leaf. R. acetosa plant were grown under greenhouse condition and subjected to PSM stress (0, 0.1, 0.5, 1.0, and 1.5 mM) for six days. Here, we show that FA and pHBA are potent inhibitors of Δ13C that varied from 21.0‰ to 22.9‰. Higher pHBA and FA supply enhanced/retard the Nleaf and increased the Cleaf while ratio of intercellular CO2 concentration from leaf to air (Ci/Ca) was significantly decreased as compared to control. Leaf water content and leaf osmotic potential were decreased following treatment with both PSM. The Ci/Ca decreased rapidly with higher concentration of FA and pHBA. However, iWUE increased at all allelochemical concentrations. At the whole plant level, both PSM showed pronounced growth-inhibitory effects on PBM and C and N concentration, root fresh/dry weight, leaf fresh/dry weight, and root, shoot length of C3 broad leaf weed R. acetosa. Carbon isotope discrimination (Δ) was correlated with the dry matter to transpiration ratio (transpiration efficiency) in this C3 species, but its heritability and relationship to R. acetosa growth are less clear. Our FA and pHBA compounds are the potent and selective carbon isotope composition (δ13C) inhibitors known to date. These results confirm the phytotoxicity of FA and pHBA on R. acetosa seedlings, the reduction of relative water content and the induction of carbon isotope discrimination (Δ) with lower plant biomass.

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Arneson, Lynne S., and Stephen E. MacAvoy. "Carbon, nitrogen, and sulfur diet–tissue discrimination in mouse tissues." Canadian Journal of Zoology 83, no. 7 (July 1, 2005): 989–95. http://dx.doi.org/10.1139/z05-083.

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Stable-isotope ratios are increasingly being used to examine ecological questions pertaining to dietary choices, physiological status, and animal migration. It has been shown that animal tissues reflect the isotopic signature present in food, altered by a small reproducible fractionation value. The average diet–tissue discrimination for δ13C and δ15N is approximately 1‰ and 3‰, respectively, although the degree of diet–tissue discrimination may be affected by a range of factors and vary between organisms and tissue types. Although the average δ34S is approximately zero, the sulfur diet–tissue discrimination values have only been determined for a few organisms. It is necessary to determine accurate diet–tissue discrimination values between tissue and dietary components to have confidence in any food-web study or determination of diet quality. In this paper, we determine carbon, nitrogen, and sulfur diet–tissue discrimination values for whole blood, liver, skeletal muscle, heart, brain, and fat (carbon only) from adult mice (Mus musculus L., 1758) equilibrated on three diets with unique isotopic signatures for carbohydrate carbon and for protein carbon, nitrogen, and sulfur. These data will aid researchers in choosing tissues to be used to examine food-web changes over time.

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Burgess, K. B., M. Guerrero, A. J. Richardson, M. B. Bennett, and A. D. Marshall. "Use of epidermal mucus in elasmobranch stable isotope studies: a pilot study using the giant manta ray (Manta birostris)." Marine and Freshwater Research 69, no. 2 (2018): 336. http://dx.doi.org/10.1071/mf16355.

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Stable isotope analysis of tissues with different turnover rates allows for a broader temporal view of a species’ feeding habits. Epidermal mucus is a rapid to medium turnover ‘tissue’ in teleost fish, but its use in elasmobranch dietary studies is unknown. In the present study, we conducted stable isotope analysis on mucus and muscle from the giant manta ray Manta birostris. Mucus δ13C values were depleted and closer to surface zooplankton δ13C values compared with muscle, whereas there was no significant difference in δ15N values between these two tissue types. Using diet tissue discrimination factors from the literature, there was no significant difference in the expected prey profile between muscle and epidermal mucus. However, a broader range in δ13C values of expected prey was shown for mucus compared with muscle. The results suggest that if M. birostris mucus is indicative of recent dietary intake, resource use during aggregative behaviour off Ecuador is broader, but with no obvious resource switching. The present study is the first example of using bulk stable isotope analysis to evaluate mucus to investigate feeding ecology in elasmobranchs. However, the time course for the change in mucus isotope signature still needs to be determined through controlled feeding studies in an aquarium setting.

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Newsome, Seth D., Gena B. Bentall, M. Tim Tinker, Olav T. Oftedal, Katherine Ralls, James A. Estes, and Marilyn L. Fogel. "Variation in δ13C and δ15N diet–vibrissae trophic discrimination factors in a wild population of California sea otters." Ecological Applications 20, no. 6 (September 2010): 1744–52. http://dx.doi.org/10.1890/09-1502.1.

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Paolini, Mauro, Luca Ziller, Kristian Holst Laursen, Søren Husted, and Federica Camin. "Compound-Specific δ15N and δ13C Analyses of Amino Acids for Potential Discrimination between Organically and Conventionally Grown Wheat." Journal of Agricultural and Food Chemistry 63, no. 25 (May 20, 2015): 5841–50. http://dx.doi.org/10.1021/acs.jafc.5b00662.

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Dennis, Caroline A., M. Aaron MacNeil, Jennifer Y. Rosati, Trevor E. Pitcher, and Aaron T. Fisk. "Diet discrimination factors are inversely related to δ15N and δ13C values of food for fish under controlled conditions." Rapid Communications in Mass Spectrometry 24, no. 24 (November 15, 2010): 3515–20. http://dx.doi.org/10.1002/rcm.4807.

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Caut, Stéphane, Elena Angulo, and Franck Courchamp. "Variation in discrimination factors (Δ15N and Δ13C): the effect of diet isotopic values and applications for diet reconstruction." Journal of Applied Ecology 46, no. 2 (April 2009): 443–53. http://dx.doi.org/10.1111/j.1365-2664.2009.01620.x.

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Malpica-Cruz, Luis, Sharon Z. Herzka, Oscar Sosa-Nishizaki, and Juan Pablo Lazo. "Tissue-specific isotope trophic discrimination factors and turnover rates in a marine elasmobranch: empirical and modeling results." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 3 (March 2012): 551–64. http://dx.doi.org/10.1139/f2011-172.

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There are very few studies reporting isotopic trophic discrimination factors and turnover rates for marine elasmobranchs. A controlled laboratory experiment was conducted to estimate carbon and nitrogen isotope trophic discrimination factors and isotope turnover rates for blood, liver, muscle, cartilage tissue, and fin samples of neonate to young-of-the-year leopard sharks ( Triakis semifasciata ). Trophic discrimination factors varied (0.13‰–1.98‰ for δ13C and 1.08‰–1.76‰ for δ15N). Tissues reached or were close to isotopic equilibrium to the new diet after about a threefold biomass gain and 192 days. Liver and blood exhibited faster isotope turnover than muscle, cartilage tissue, and fin samples, and carbon isotopes turned over faster than those of nitrogen. Metabolic turnover contributed substantially to isotopic turnover, which differs from most reports for young marine teleosts. We modeled the relationship between muscle turnover rates and shark size by coupling laboratory results with growth rate estimates for natural populations. Model predictions for small, medium, and large wild leopard sharks indicate the time to isotopic equilibrium is from one to several years.

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Seminoff, JA, TT Jones, T. Eguchi, DR Jones, and PH Dutton. "Stable isotope discrimination (δ13C and δ15N) between soft tissues of the green sea turtle Chelonia mydas and its diet." Marine Ecology Progress Series 308 (February 16, 2006): 271–78. http://dx.doi.org/10.3354/meps308271.

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Hobson, Keith A., and Franz Bairlein. "Isotopic fractionation and turnover in captive Garden Warblers (Sylvia borin): implications for delineating dietary and migratory associations in wild passerines." Canadian Journal of Zoology 81, no. 9 (September 1, 2003): 1630–35. http://dx.doi.org/10.1139/z03-140.

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There is currently a great deal of interest in using stable-isotope methods to investigate diet and migratory connections in wild passerines. To apply these methods successfully, it is important to understand how stable isotopes discriminate or change between diet and the tissue of interest and what the element-turnover rates are in metabolically active tissues. Of particular use are studies that sample birds non-destructively through the use of blood and feathers. We investigated patterns of isotopic discrimination between diet and blood and feathers of Garden Warblers (Sylvia borin) raised on an isotopically homogeneous diet (48% C, 5% N) and then switched to one of two experimental diets, mealworms (56.8% C, 8.3% N) and elderberries, Sambucus niger (47.4% C, 1.5% N). We established that the discrimination factors between diet and blood appropriate for stable carbon (δ13C) and nitrogen (δ15N) isotopes are +1.7‰ and +2.4‰, respectively. For feathers, these values were +2.7‰ and +4‰, respectively. Turnover of elemental nitrogen in whole blood was best approximated by an exponential-decay model with a half-life of 11.0 ± 0.8 days (mean ± SD). Corresponding turnover of carbon was estimated to range from 5.0 ± 0.7 to 5.7 ± 0.8 days. We conclude that this decoupling of nitrogen- and carbon-turnover rates can be explained by differences in metabolic routing of dietary macromolecules. Our results suggest that tracking frugivory in migratory passerines that switch diets between insects and fruits may be complicated if only a trophic-level estimate is made using δ15N measurements.

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Dubé, Monique G., Glenn A. Benoy, Sandra Blenkinsopp, Jenny-Marie Ferone, Robert B. Brua, and Leonard I. Wassenaar. "Application of Multi-stable Isotope (13C, 15N, 34S, 37Cl) Assays to Assess Spatial Separation of Fish (Longnose Sucker Catostomus catostomus) in an Area Receiving Complex Effluents." Water Quality Research Journal 40, no. 3 (August 1, 2005): 275–87. http://dx.doi.org/10.2166/wqrj.2005.033.

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Abstract Incorporation of stable isotope analysis (SIA) into routine environmental effects monitoring programs of receiving waters may enable determination of the spatial extent of biotic exposure and discrimination among sources of complex effluents. To evaluate this hypothesis, longnose sucker (Catostomus catostomus) were collected from four sites along the Athabasca River, Alberta (upstream reference site, two sites downstream of effluents from two pulp and paper mills, and a site downstream of effluent from a municipal sewage treatment plant). Stable isotopes of carbon, nitrogen, sulfur and chlorine were analyzed in bone, gonad, liver and white muscle tissues of the fish. In general, most sites and tissues differed according to δ13C, δ15N and δ34S values. Also, an interaction between site and tissue was observed for δ15N values. A better insight into the usefulness of stable isotopes was obtained through the use of multivariate discriminant function analysis. δ15N and δ34S signatures of gonad and liver tissues of males were most effective at classifying fish according to site (~70% for both tissues). For all tissues except bone, fish from the upstream reference site were most separable from all others, especially females. δ37Cl values for female gonads and male livers were related to sites downstream of the pulp and paper mills. Future research should routinely include SIA of fish tissues, but also of effluents, receiving waters and food web components to better resolve links between specific effluents and fish exposure.

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Kurle, Carolyn M., Paul L. Koch, Bernie R. Tershy, and Donald A. Croll. "The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (Δ13C and Δ15N) in mammalian omnivores." Isotopes in Environmental and Health Studies 50, no. 3 (April 30, 2014): 307–21. http://dx.doi.org/10.1080/10256016.2014.908872.

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Derbridge, Jonathan J., Jerod A. Merkle, Melanie E. Bucci, Peggy Callahan, John L. Koprowski, Jean L. Polfus, and Paul R. Krausman. "Experimentally Derived δ13C and δ15N Discrimination Factors for Gray Wolves and the Impact of Prior Information in Bayesian Mixing Models." PLOS ONE 10, no. 3 (March 24, 2015): e0119940. http://dx.doi.org/10.1371/journal.pone.0119940.

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DeMots, Rachel L., James M. Novak, Karen F. Gaines, Aaron J. Gregor, Christopher S. Romanek, and Daniel A. Soluk. "Tissue–diet discrimination factors and turnover of stable carbon and nitrogen isotopes in white-footed mice (Peromyscus leucopus)." Canadian Journal of Zoology 88, no. 10 (October 2010): 961–67. http://dx.doi.org/10.1139/z10-063.

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Stable isotope analysis has become an increasingly valuable tool in investigating animal ecology. Here we document the turnover rates for carbon in the liver, muscle, and whole blood tissue, as well as the tissue–diet discrimination values for carbon and nitrogen isotopes in the liver, whole blood, muscle, and hair, of the white-footed mouse ( Peromyscus leucopus (Rafinesque, 1818)). A 168-day diet-switching experiment was conducted with a laboratory population of white-footed mice. The δ13C values for all tissues deviated less than 1‰ from those of the diet except for whole blood, which had a slightly higher tissue–diet discrimination factor of 1.8‰. All tissues were enriched in 15N by approximately 3‰ relative to the diet except for liver tissue, which was 4.5‰ higher than the dietary δ15N value. Turnover rates for tissues of white-footed mice were ranked liver > whole blood > muscle. The half-lives calculated for liver tissue differed significantly between the two diet switches performed in this experiment. We demonstrate that there is potential for variation in tissue–diet discrimination values and tissue turnover rates between even closely related species. These findings highlight the importance of determining species-specific estimates of these parameters prior to the use of stable isotope analysis in field investigations of animal ecology.

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Mazumder, Debashish, Mathew P. Johansen, Brian Fry, and Emma Davis. "Muscle and carapace tissue–diet isotope discrimination factors for the freshwater crayfish Cherax destructor." Marine and Freshwater Research 69, no. 1 (2018): 56. http://dx.doi.org/10.1071/mf16360.

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This study examined a range of diets and two tissue types (muscle and carapace, representing protein and chitin biochemistry respectively) of Cherax destructor (Clark, 1936) to allow more accurate use of isotope data in trophic source estimates. The resulting Δ13Ctissue–diet and Δ15Ntissue–diet discrimination factors of muscle and carapace tissues showed significant differences among diets. For muscle, Δ13Ctissue–diet was higher (2.11–2.33‰) when C. destructor was fed with lamb, turkey and mixed animal and plant-based diets, 1.27–1.96‰ when C. destructor was fed with beef and kangaroo diets and negative (–1.36‰) when C. destructor was fed with an aquatic meat (tuna) diet. The Δ15Ntissue–diet discrimination factors were lower for muscle when C. destructor was fed aquatic meat (0.12‰) and mixed plant–animal diets (1.67‰), but higher for terrestrial meat diets (2.79–3.74‰). The Δ13Ctissue–diet for carapace followed similar patterns to that of muscle, but Δ15Ntissue–diet values were lower for carapace than muscle. Strong correlations were observed between muscle and carapace for δ13C (r=0.96, P<0.0001) and δ15N (r=0.82, P<0.0012) across the six diets evaluated, indicating that carapace can be used as a non-lethal alternative to muscle during field sampling.

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Gioacchini, Paola, Andrea Masia, Francesca Canaccini, Pietro Boldreghini, and Giustino Tonon. "Isotopic discrimination during litter decomposition and δ13C and δ15N soil profiles in a young artificial stand and in an old floodplain forest#." Isotopes in Environmental and Health Studies 42, no. 2 (June 2006): 135–49. http://dx.doi.org/10.1080/10256010600671357.

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Nilsen, Marianne, Torstein Pedersen, Einar Magnus Nilssen, and Stein Fredriksen. "Trophic studies in a high-latitude fjord ecosystem — a comparison of stable isotope analyses (δ13C and δ15N) and trophic-level estimates from a mass-balance model." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 12 (December 2008): 2791–806. http://dx.doi.org/10.1139/f08-180.

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Abstract:

Stable isotopes of δ13C and δ15N were used to examine food sources and trophic structure of 65 taxa, representing 19 ecological groups, in a high-latitude ecosystem. Discrimination was made between pelagic and benthic carbon sources, where feeding in most cases reflected the habitat. Trophic levels from these analyses, TLN, were compared with corresponding levels estimated by an Ecopath mass-balance model, TLE, constructed independently of the isotope data. The good correlation between the two methods (r2 = 0.72) supports the diet composition and the grouping of taxa into ecological groups in the model. However, when estimates diverged, this was often explained by the analyses of few taxa, taxa that were not the most representative for the group, or the analyses of specimens from a limited size range. Some assumed detrivores were assigned high TLN in favour of an abundant microbial community in the sediments. High TLN estimates for many invertebrate taxa, combined with relatively low TLN for fishes, suggest that parts of the benthic food web are decoupled from the classical food web.

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Blanchet-Aurigny, Aline, Monique Guillou, Fabrice Pernet, Jean-Dominique Gaffet, and Stanislas F. Dubois. "Tissue-diet discrimination factors of isotopic ratios (∆δ13C and ∆δ15N) in two brittle star species: Effect of reproductive state, diet and tissue composition." Journal of Experimental Marine Biology and Ecology 426-427 (September 2012): 68–77. http://dx.doi.org/10.1016/j.jembe.2012.05.013.

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Journal articles on the topic 'Facteurs de discrimination (∆δ13C, ∆δ15N)'

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