The requirement for accurate diet-tissue discrimination factors for interpreting stable isotopes in sharks

Hydrobiologia ◽  
2010 ◽  
Vol 654 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Nigel E. Hussey ◽  
M. Aaron MacNeil ◽  
Aaron T. Fisk
Keyword(s):  
Stable Isotopes ◽  
Tissue Discrimination ◽  
Discrimination Factors

Diet–tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)

2011 ◽  
Vol 89 (4) ◽  
pp. 343-347 ◽  
Author(s):  
J.-F. Therrien ◽  
G. Fitzgerald ◽  
G. Gauthier ◽  
J. Bêty
Keyword(s):  
Stable Isotopes ◽  
Bird Species ◽  
Potential Effect ◽  
Mouse Muscle ◽  
Blood Samples ◽  
Web Studies ◽  
Tissue Discrimination ◽  
Discrimination Factors ◽  
Snowy Owl ◽  
Bubo Scandiacus

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.

Isotopic fractionation and turnover in captive Garden Warblers (Sylvia borin): implications for delineating dietary and migratory associations in wild passerines

2003 ◽  
Vol 81 (9) ◽  
pp. 1630-1635 ◽  
Author(s):  
Keith A Hobson ◽  
Franz Bairlein
Keyword(s):  
Stable Isotopes ◽  
Isotopic Fractionation ◽  
Carbon Turnover ◽  
Stable Carbon ◽  
Turnover Rates ◽  
Exponential Decay Model ◽  
N Isotopes ◽  
Discrimination Factors ◽  
Sylvia Borin ◽  
Element Turnover

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.

scholarly journals Variable δ15N Diet-Tissue Discrimination Factors among Sharks: Implications for Trophic Position, Diet and Food Web Models

PLoS ONE ◽  
2013 ◽  
Vol 8 (10) ◽  
pp. e77567 ◽  
Author(s):  
Jill A. Olin ◽  
Nigel E. Hussey ◽  
Alice Grgicak-Mannion ◽  
Mark W. Fritts ◽  
Sabine P. Wintner ◽  
...  
Keyword(s):  
Food Web ◽  
Trophic Position ◽  
Tissue Discrimination ◽  
Discrimination Factors
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