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

This book is written as a reference on organic substances in natural waters and as a supplementary text for graduate students in water chemistry. The chapters address five topics: amount, origin, nature, geochemistry, and characterization of organic carbon. Of these topics, the main themes are the amount and nature of dissolved organic carbon in natural waters (mainly fresh water, although seawater is briefly discussed). It is hoped that the reader is familiar with organic chemistry, but it is not necessary. The first part of the book is a general overview of the amount and general nature of dissolved organic carbon. Over the past 10 years there has been an exponential increase in knowledge on organic substances in water, which is the result of money directed toward the research of organic compounds, of new methods of analysis (such as gas chromatography and mass spectrometry), and most importantly, the result of more people working in this field. Because of this exponential increase in knowledge, there is a need to pull together and summarize the data that has accumulated from many disciplines over the last decade.

Organic geochemistry of natural waters

https://homepages.uc.edu/~algeot/Tribovillard-Algeo-etal-CG-2006.pdf

Trace metals as paleoredox and paleoproductivity proxies: An update

Preservation of elemental and isotopic source identification of sedimentary organic matter

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

Organic matter in sediments from Sites 515, 516, and 517 reflects a history of low marine productivity and of oxygenated bottom waters in the western South Atlantic since the Pliocene. Organic carbon contents are low, averaging 0.26% of sediment weight. Distributions of n-alkanes, /i-alkanols, and «-alkanoic acids show evidence of microbial reworking, and n-alkanes contain important terrigenous contributions, presumably of eolian origin. INTRODUCTION Organic matter contained within oceanic sediments is a reflection of the sources and depositional processes that participated in the sediment accumulation. In particular, the amounts and types of sedimentary organic components are products of biological production in surface waters, supplemented by materials transported by winds and currents and altered by microbial and chemical processes during passage through the water column and after burial. Evidence of these many factors is often preserved in the elemental, isotopic, and molecular composition of sediment organic matter. In order to identify the sources of organic matter in sediments and to characterize depositional paleoenvironments in the South Atlantic during the Neogene, sediment samples were obtained from three locations during DSDP Leg 72: in the Brazil Basin (Site 515, water depth 4250 m), on the Rio Grande Rise (Site 516, water depth 1313 m), and in the Vema Channel (Site 517, water depth 2963 m). Analyses of organic carbon concentrations, organic C/N ratios, and extractable lipid components were made. Both solvent-extractable (free) and alkaline hydrolyzeable (bound) lipid fractions were obtained, from which fatty acids, hydrocarbons, and fatty alcohols were separated. METHODS Five samples from the frozen organic geochemistry core sections from DSDP Sites 515, 516, and 517 (Fig. 1) were obtained. These muds were kept frozen until analysis. After the samples had been freeze-dried, their total carbon contents were measured with a Hewlett-Packard 185B CHN analyzer. Residual carbon was measured after HC1 dissolution of carbonates and was considered to represent the total organic carbon content. Percent calcium carbonate was calculated from the difference between initial and residual carbon contents. Organic matter C/N ratios were determined from residual carbon values. Percent organic carbon contents of the samples were calculated on a dry-weight basis for the original, carbonate-containing sediment. A two-stage extraction procedure was used. Soxhlet extraction with toluene/methanol yielded the easily extracted, unbound fraction of materials present in the samples. A second extraction with 0.5N KOH Barker, P. F., Carlson, R. L., Johnson, D. A., et al., Init. Repts. DSDP, 72: Washington (U.S. Govt. Printing Office). in methanol/toluene provided the hydrolyzeable, bound components. Both fractions were treated with methanolic boron trifluoride to convert fatty acids to their methyl esters, and then lipid subfractions were separated by column chromatography on alumina over silica gel. The classes so obtained contained alkanes and alkenes, aromatic hydrocarbons, fatty acid methyl esters, and hydroxy lipids, including sterols and alkanols. Hydroxy compounds were silylated with BSTFA before gas chromatography. Splitless injection gas-liquid chromatography was employed to determine the types and amounts of compounds making up the lipid subfractions. A Hewlett-Packard 5880 FID gas chromatograph equipped with a 20m SE54 fused silica capillary column was used with hydrogen as carrier gas. Quantification was attempted through the use of known amounts of internal standards added to each sample before column chromatography. Individual compounds were tentatively identified by retention times in this preliminary survey. Reported values have been corrected for laboratory contaminants and for mass discrimination over the wide molecular-weight ranges surveyed. RESULTS AND DISCUSSION Organic Carbon and C/N Values Concentrations of organic carbon in these Quaternary sediments are given in Table 1. Their mean value is 0.26%, which is in good agreement with means of 0.2% in modern deep-ocean sediments (Degens and Mopper, 1976) and of 0.3% in older samples from DSDP Legs 1 through 31 (Mclver, 1975). In view of the low organic carbon content of these Leg 72 samples, several paleoceanographic inferences can be made. First, the organic matter probably became incorporated into these sediments under oxygenated bottom water conditions, a situation not conducive to organic matter preservation (Hinga et al., 1979; Cobler and Dymond, 1980; Demaison and Moore, 1980). Second, the biological productivity of the surface waters of this part of the western South Atlantic was probably low throughout the Quaternary and the Pliocene. Both the low organic carbon values of all samples and the high carbonate concentrations at the shallower Sites 516 and 517 lead to this conclusion. Site 515 evidently is below the calcite compensation depth, and there has been a resulting loss of carbonate. Suess (1980) has noted that the flux of organic matter to the deep sea continually decreases with increasing depth, and Bishop and others (1978) have reported that the fraction of original organ-

/pdf/organic-geochemistry-of-quaternary-sediments-from-deep-sea-1c9sno3n5y.pdf

Organic Geochemistry of Quaternary Sediments from Deep Sea Drilling Project Leg 72, South Atlantic Ocean

Holocene climate change in northeastern China reconstructed from lipid biomarkers in a peat sequence from the Sanjiang Plain

Comparison of Michigan Basin crude oils (reply to comments by Illich and Grizzle and by Pruitt)

The amounts and compositions of interstitial gases found at the five sites cored on the Demerara Rise during Leg 207 are related to sediment lithology. Concentrations are low in the sedimentary units overlying Cenomanian–Santonian black shales, where they increase to maximum values. A microbial origin for most of the gases is inferred from the low thermal maturity of organic matter and the predominance of methane in their compositions. Active in situ gas generation is postulated to compensate for migration of methane out of the black shale units. Trace amounts of C4–C6 gases found in the black shale units likely migrated from deeper in the section.

http://www-odp.tamu.edu/publications/207_IR/VOLUME/CHAPTERS/IR207_09.PDF

9. microbial gases in black shale sequences on the demerara rise 1

We identified a suite of steroid biomarkers in sediments and surface soils around Lake Ximencuo, a typical glacial lake in the Nianbaoyeze region, eastern Qinghai-Tibet Plateau (QTP). Various sterols, stanols, sterones, and sterenes appear in the sediments and surface soil samples. Among these steroids, plant-derived β-sitosterol and the 5α-stigmastanol that is derived from it exhibit high relative abundances. Notably, we found that the relative abundance of 5α-stigmastanol and the 5α-stigmastanol/n-alkanol ratio in a core of Lake Ximencuo sediment increased significantly in the last 200–300 year. These biomarker changes are broadly consistent with the growth of human settlement and the rapid development of animal husbandry in this region, which resulted in the former nomadic pastoral lifestyles gradually being transformed into permanent settlements since the early eighteenth century. The environmental and cultural changes led to greater delivery to soils around the lake of β-sitosterol that was transformed into 5α-stigmastanol by microbial communities in soil horizons, which include aerobic and anaerobic bacteria, and eventually surface runoff transport of the increased abundance of 5α-stigmastanol into Lake Ximencuo. We further postulate that the progressively greater human impacts in the Nianbaoyeze region over the past 200–300 year have modified the kinds of microbes that participate in the biogeochemical cycles of local soils.

Philip A. Meyers

Papers

Organic Geochemistry of Quaternary Sediments from Deep Sea Drilling Project Leg 72, South Atlantic Ocean

Holocene climate change in northeastern China reconstructed from lipid biomarkers in a peat sequence from the Sanjiang Plain

Comparison of Michigan Basin crude oils (reply to comments by Illich and Grizzle and by Pruitt)

9. microbial gases in black shale sequences on the demerara rise 1

Paleoenvironmental significance of 5α-stigmastanol in surface soil and lake sediment from the Nianbaoyeze Mountains, eastern Qinghai-Tibet Plateau