The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

A large fraction of globally produced methane is converted to CO2 by anaerobic oxidation in marine sediments. Strong geochemical evidence for net methane consumption in anoxic sediments is based on methane profiles, radiotracer experiments and stable carbon isotope data. But the elusive microorganisms mediating this reaction have not yet been isolated, and the pathway of anaerobic oxidation of methane is insufficiently understood. Recent data suggest that certain archaea reverse the process of methanogenesis by interaction with sulphate-reducing bacteria. Here we provide microscopic evidence for a structured consortium of archaea and sulphate-reducing bacteria, which we identified by fluorescence in situ hybridization using specific 16S rRNA-targeted oligonucleotide probes. In this example of a structured archaeal-bacterial symbiosis, the archaea grow in dense aggregates of about 100 cells and are surrounded by sulphate-reducing bacteria. These aggregates were abundant in gas-hydrate-rich sediments with extremely high rates of methane-based sulphate reduction, and apparently mediate anaerobic oxidation of methane.

A marine microbial consortium apparently mediating anaerobic oxidation of methane

Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane

The second edition of The Biomarker Guide is a fully updated and expanded version of this essential reference. Now in two volumes, it provides a comprehensive account of the role that biomarker technology plays both in petroleum exploration and in understanding Earth history and processes. Biomarkers and Isotopes in the Environment and Human History details the origins of biomarkers and introduces basic chemical principles relevant to their study. It discusses analytical techniques, and applications of biomarkers to environmental and archaeological problems. The Biomarker Guide is an invaluable resource for geologists, petroleum geochemists, biogeochemists, environmental scientists and archaeologists.

The Biomarker Guide

Contributors. Abbreviations. Introduction. 1. Stable isotope chemistry and measurement: a primer. Elizabeth W. Sulzman. Introduction. What isotopes are, what makes them distinct. Properties of ecologically useful stable isotopes. Technological advances and current trends in the ecological use of isotopes. Acknowledgments. References. 2. Sources of variation in the stable isotopic composition of plants. John D. Marshall, J. Renee Brooks, and Kate Lajtha. Introduction. Carbon isotopes. Nitrogen isotopes. Hydrogen and oxygen isotopes. Conclusions. References. 3. Natural 15N- and 13C-abundance as indicators of forest nitrogen status and soil carbon dynamics. Charles T. Garten, Jr, Paul J. Hanson, Donald E. Todd, Jr, Bonnie B. Lau, and Deanne J. Brice. Introduction. Significance of 15N-abundance to soil carbon sequestration. Vertical changes in soil 13C-abundance and soil carbon dynamics. Conclusions. Acknowledgments. References. 4. Soil nitrogen isotope composition. R. Dave Evans. Introduction. Sources of variation in soil 15N. Patterns of soil nitrogen isotope composition. Conclusions. References. 5. Isotopic study of the biology of modern and fossil vertebrates. Paul L. Koch. Introduction. Vertebrate tissues in the fossil record. Controls on the isotopic composition of vertebrate tissues. Preservation of biogenic isotope compositions by vertebrate fossils. Paleobiological applications. Conclusions. A post-script on workshops and literature resources. References. 6. Isotopic tracking of migrant wildlife. Keith A. Hobson. Introduction. Basic principles. Marine systems. Terrestrial systems (excluding deuterium). Using deuterium patterns in precipitation. Conclusions. References. 7. Natural abundance of 15N in marine planktonic ecosystems. Joseph P. Montoya. Introduction. Background. Isotopic variation in marine nitrogen. Source delineation and isotope budgets. Animal fractionation and food web processes. Isotopic transients in marine systems. Compound-specific nitrogen isotope analyses. Conclusions. Acknowledgment. References. 8. Stable isotope studies in marine chemoautotrophically based ecosystems: An update. Cindy Lee Van Dover. Introduction. Isotopic tracing of carbon at methane seeps. Whale falls. Hydrothermal vents. Conclusions. References. 9. Stable isotope ratios as tracers in marine food webs: An update. Robert H. Michener and Les Kaufman. Introduction. Methods of assessing food webs. Phytoplankton and particulate organic carbon. Phytoplankton and particulate organic nitrogen. Marine food webs. Stable isotopes in marine conservation biology. Conclusions. Acknowledgments. References. 10. Stable isotope tracing of temporal and spatial variability in organic matter sources to freshwater ecosystems. Jacques C. Finlay and Carol Kendall. Introduction. Overview of river food webs and stable isotope approaches. Stable isotope ratios of organic matter sources in stream ecosystems. C, N, and S isotopic variability and its applications in river ecology. Conclusions. Acknowledgments. References. 11. Stable isotope tracers in watershed hydrology. Kevin J. McGuire and Jeff McDonnell. Introduction. Basic concepts in watershed hydrology. Why are stable isotopes needed?. General concepts in isotope hydrology. Applications of isotope hydrology in watershed and ecosystem studies. Conclusions. Acknowledgments. References. 12. Tracing anthropogenic inputs of nitrogen to ecosystems. Carol Kendall, Emily M. Elliott, and Scott D. Wankel. Introduction. Isotopic compositions of major N sources to ecosystems. Processes affecting the isotopic composition of DIN. Separating mixing of sources from the effects of cycling. Applications to different environmental settings. What sources of agricultural and urban sources of nitrate can be distinguished using isotopes?. Other tools for tracing anthropogenic contaminants. Conclusions. References. 13. Modeling the dynamics of stable-isotope ratios for ecosystem biogeochemistry. William S. Currie. Introduction. Designing consistent model-data linkages and comparisons. Principles and techniques of stable isotope modeling. Conclusions. Acknowledgments. References. 14. Compound-specific stable isotope analysis in ecology and paleoecology. Richard P. Evershed, Ian D. Bull, Lorna T. Corr, Zoe M. Crossman, Bart E. van Dongen, Claire Evans, Susan Jim, Hazel Mottram, Anna J. Mukherjee, and Richard D. Pancost. Introduction. Why use compound-specific stable isotopes?. Analytical considerations in compound-specific stable isotope analysis. Applications of compound-specific stable isotope approaches in ecology and paleoecology. Conclusions. References. Index

Stable isotopes in ecology and environmental science

Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence

Methane oxidation in sediment and water column environments—Isotope evidence

Anaerobic methane oxidation associated with marine gas hydrates: superlight C-isotopes from saturated and unsaturated C20 and C25 irregular isoprenoids

http://directory.umm.ac.id/Data%20Elmu/jurnal/O/Organic%20Geochemistry/Vol31.Issue11.Nov2000/1056.pdf

Michael J. Whiticar

Papers

Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane

Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence

Methane oxidation in sediment and water column environments—Isotope evidence

Anaerobic methane oxidation associated with marine gas hydrates: superlight C-isotopes from saturated and unsaturated C20 and C25 irregular isoprenoids

Archaea mediating anaerobic methane oxidation in deep-sea sediments at cold seeps of the eastern Aleutian subduction zone