Compound‐specific stable isotope analysis (
It is imperative to understand how chemical preservation alters tissue isotopic compositions before using historical samples in ecological studies. Specifically, although compound‐specific isotope analysis of amino acids (CSIA‐AA) is becoming a widely used tool, there is little information on how preservation techniques affect amino acid
We evaluated the effects of chemical preservatives on bulk tissue
Tissues in formaldehyde‐ethanol had higher bulk
The effects of preservation on bulk
- Award ID(s):
- 1637632
- NSF-PAR ID:
- 10460918
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Rapid Communications in Mass Spectrometry
- Volume:
- 33
- Issue:
- 10
- ISSN:
- 0951-4198
- Page Range / eLocation ID:
- p. 935-945
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract CSIA ) of amino acids (AA ) has rapidly become a powerful tool in studies of food web architecture, resource use, and biogeochemical cycling. However, applications to avian ecology have been limited because no controlled studies have examined the patterns inAA isotope fractionation in birds. We conducted a controlledCSIA feeding experiment on an avian species, the gentoo penguin (Pygoscelis papua ), to examine patterns in individualAA carbon and nitrogen stable isotope fractionation between diet (D) and consumer (C) (Δ13CC‐Dand Δ15NC‐D, respectively). We found that essentialAA δ 13C values and sourceAA δ 15N values in feathers showed minimal trophic fractionation between diet and consumer, providing independent but complimentary archival proxies for primary producers and nitrogen sources respectively, at the base of food webs supporting penguins. Variations in nonessentialAA Δ13CC‐Dvalues reflected differences in macromolecule sources used for biosynthesis (e.g., protein vs. lipids) and provided a metric to assess resource utilization. The avian‐specific nitrogen trophic discrimination factor (TDF Glu‐Phe= 3.5 ± 0.4‰) that we calculated from the difference in trophic fractionation (Δ15NC ‐D) of glutamic acid and phenylalanine was significantly lower than the conventional literature value of 7.6‰. Trophic positions of five species of wild penguins calculated using a multi‐TDFG lu‐Pheequation with the avian‐specificTDFG lu‐Phevalue from our experiment provided estimates that were more ecologically realistic than estimates using a singleTDFG lu‐Pheof 7.6‰ from the previous literature. Our results provide a quantitative, mechanistic framework for the use ofCSIA in nonlethal, archival feathers to study the movement and foraging ecology of avian consumers. -
Rationale Plant lipid biomarkers, such as plant waxes and terpenoids, and the stable isotopic composition of bulk leaves are widely used in both modern and paleoclimate studies for tracking vegetation and climate. However, the effects of different drying methods on the preservation of plant lipid biomarkers and the stable isotopic compositions of leaves are less explored. Here, we investigated various drying methods for the measurement of plant lipid concentrations and bulk leaf isotopic compositions.
Methods Leaves from four tree species (
,Acer rubrum ,Pinus sylvestris , andPlatanus occidentalis ) were collected and dried using air, an oven, a freeze‐dryer, and a microwave. We compared concentrations of leaf waxes and terpenoids and carbon (δ13C) and nitrogen (δ15N) isotopic compositions of leaves by different drying methods.Taxodium distichum Results The air, oven, freeze‐dryer, and microwave drying methods did not affect lipid concentrations significantly, and only a few homologues differed (38.1% or 41.8 μg/g on average) possibly due to biological variations or enhanced extraction efficiencies. The δ13C values were not affected by drying methods, whereas the δ15N values in oven‐dried leaves in some species were higher by 0.2–0.7‰ than those obtained by other methods. Though small, we attribute these patterns to loss of leaf compounds with lower isotope ratios during oven‐drying.
Conclusions Based on our results, each drying technique yielded equivalent results for all plant wax and terpenoid concentrations and bulk leaf δ13C values; however, oven‐drying modified the δ15N values.
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Rationale Nitrogen stable isotope ratio (δ15N) processes are not well described in reptiles, which limits reliable inference of trophic and nutrient dynamics. In this study we detailed δ15N turnover and discrimination (Δ15N) in diverse tissues of two lizard species, and compared these results with previously published carbon data (δ13C) to inform estimates of reptilian foraging ecology and nutrient physiology.
Methods We quantified15N incorporation and discrimination dynamics over 360 days in blood fractions, skin, muscle, and liver of
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Rationale The grey seal,
(GS), and the northern elephant seal,Halichoerus grypus (NES), come ashore for reproduction. This period involves intense physiological processes such as lactation in females and a developmental post‐weaning fast in juveniles. Previous studies have shown thatMirounga angustirostris δ 13C andδ 15N values are affected by starvation, but the precise effects of fasting associated with lactation and post‐weaning fast in seals remain poorly understood.Methods To examine the effect of lactation and post‐weaning fast on stable isotope ratios in GS and NES, blood and hair were sampled from 21 GS mother‐pup pairs on the Isle of May and on 22 weaned NES pups at Año Nuevo State Reserve during their respective breeding seasons. Milk samples were also collected from GS mothers. Stable isotope measurements were performed with an isotope ratio mass spectrometer coupled to an N‐C elemental analyser.
Results Changes in stable isotope ratios in blood components during fasting were similar and weak between GS and NES mothers especially in blood cells (GS:
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