Nitrogen- and carbon-isotope fractionation between mothers and offspring in red-backed voles (Clethrionomys gapperi)

2005 ◽  
Vol 83 (5) ◽  
pp. 712-716 ◽  
Author(s):  
David T.J Sare ◽  
John S Millar ◽  
Frederick J Longstaffe
Keyword(s):  
Carbon Isotope ◽  
Small Mammals ◽  
Isotope Fractionation ◽  
Stable Carbon Isotopes ◽  
Mammary Glands ◽  
Trophic Relationships ◽  
Clethrionomys Gapperi ◽  
Stable Carbon ◽  
Isotopic Enrichment ◽  
In The Wild

Small mammals are income breeders, but the degree to which females draw from maternal reserves and partition nutrients to the mammary glands in the wild is not known. This study examined stable-nitrogen and stable-carbon isotopes in red-backed vole, Clethrionomys gapperi (Vigors, 1830), hair to determine mother–offspring trophic relationships and to consider the extent to which voles rely on maternal reserves during lactation. Both dependent and independent young showed isotopic enrichment in 15N and depletion of 13C in their hair relative to mothers. We suggest that growing offspring, both dependent and independent, may catabolize body reserves to support both growth and moult. We propose that the nitrogen- and carbon-isotope compositions of hair may be more useful indicators of metabolic rate than mother–offspring trophic relationships in small mammals.

scholarly journals Anaerobic methane oxidation by nitrate: kinetic isotope effect

2018 ◽  
Vol 10 (1) ◽  
Author(s):  
Vasiliy A. Vavilin
Keyword(s):  
Dynamic Model ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Stable Carbon Isotopes ◽  
Stable Carbon ◽  
Fractionation Factor ◽  
Kinetic Isotope

The ratio of stable carbon isotopes (13C/12C) in different environments serves as a significant limitation in estimating the global balance of methane [Hornibrook et al., 2000]. In this case, the value of 13C/12C largely depends on the kinetic isotope effect associated with the metabolism of microorganisms that produce and consume CH4. The article suggests a dynamic model of the processes of methane formation and its anaerobic oxidation with nitrate by methanotrophic denitrifying microorganisms (DAOM), which allowed estimating the fractionation factor of stable carbon isotopes. In the experiment with peat from the minerotrophic bog [Smemo, Yavitt, 2007], the dynamics of the amount of methane and was measured. The dynamic model showed that the introduction of nitrate leads to a slow decrease in the partial pressure of methane. Since methane in the DAOM process is a substrate, methane is enriched with heavier carbon 13C in the system under study. This leads to an increase in the value . The carbon isotope fractionation factor during methane oxidation with nitrate was equal to 1.018 and comparable with the fraction of carbon isotope fractionation in the process of acetoclastic methanogenesis (1.01). Model calculations have shown that during incubation the apparent fractionation factor of carbon isotopes with the simultaneous formation of methane and DAOM slowly decreases. The ratio of 13C/12C isotopes in dissolved and gaseous methane practically does not differ. The model showed that an increase in the initial concentration of nitrate increases the rate of DAOM, which leads to a decrease in the concentration of dissolved methane. In this case, the value of 13C/12C increases. In field studies, Shi et al. (2017) showed that the presence of DAOM in peat bogs in which fertilizers penetrate can be controlled by the amount of nitrate used and the depth of penetration into the anoxic layer. Two MATLAB files describing DAOM are attached to the article.

scholarly journals Stable Carbon Isotope Fractionation by Methylotrophic Methanogenic Archaea

2012 ◽  
Vol 78 (21) ◽  
pp. 7596-7602 ◽  
Author(s):  
Jörn Penger ◽  
Ralf Conrad ◽  
Martin Blaser
Keyword(s):  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Stable Carbon Isotope ◽  
Methanogenic Archaea ◽  
Methanosarcina Barkeri ◽  
Stable Carbon ◽  
Methyl Fluoride ◽  
Content Type ◽  
Carbon Isotope Fractionation ◽  
Stable Carbon Isotope Fractionation

ABSTRACTIn natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C1compounds such as methanol as the substrate. To determine the contributions of individual substrates to methane production, the stable-isotope values of the substrates and the released methane are often used. Additional information can be obtained by using selective inhibitors (e.g., methyl fluoride, a selective inhibitor of acetoclastic methanogenesis). We studied stable carbon isotope fractionation during the conversion of methanol to methane inMethanosarcina acetivorans,Methanosarcina barkeri, andMethanolobus zinderiand generally found large fractionation factors (−83‰ to −72‰). We further tested whether methyl fluoride impairs methylotrophic methanogenesis. Our experiments showed that even though a slight inhibition occurred, the carbon isotope fractionation was not affected. Therefore, the production of isotopically light methane observed in the presence of methyl fluoride may be due to the strong fractionation by methylotrophic methanogens and not only by hydrogenotrophic methanogens as previously assumed.

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