Stable carbon isotope ratios animals

Fig. 6. Distribution of stable carbon isotope ratios in a seagrass meadow in the Torres Strait, compared with animals from offshore. Data from Fry et al., 1983.

The use of the stable isotope as a tracer in biological research has become increasingly common as evidenced by recent bibliographies (1,2), The effective use of this isotope has been established in the field of nutrition, where it has been applied in human clinical studies (3,4), in food science research and in ecological studies of animal food habits (6,7) Many nutrition studies are carried out at natural abundance levels of C Because these levels are low and because differences in the content of natural materials are small, stable carbon isotope ratios (13q/1 ) expressed in relative terms as 6 values A value represents the per mil (parts per thousand) deviation of the content of the sample from the international PDB limestone standard, the value of which has been set arbitrarily to 0 /oo Thus, a value of -27 0 %o would mean that the sample contained 27 parts per thousand less than the PDB standard Although the PDB standard no... 

Calcium carbonate is also the main constituent of the shells of sea animals, which make their shells from elements acquired from the surrounding waters. Now, the degree of fractionation of the oxygen isotopes as well as the formation of mineral carbonates and of animal shells in sea waters are determined on the basis of the temperature-dependent fractionation of the isotopes of oxygen the oxygen isotope composition of these materials reflects, therefore, the temperature at the time of their formation. Thus determining the isotope ratio between the stable isotopes of oxygen... 

Also the stable isotopes of nitrogen, like those of carbon, are fractionated when nitrogen is incorporated into the plants. Determining the isotopic ratios between nitrogen-15 and nitrogen-14 in animal remains also reveals information on the diets of ancient animals and humans (White 1999 de Niro 1987). 

Minor element contents and isotopic ratios are used for physiological purposes. Sr/Ca ratios in bone and teeth are said to reflect the diet of the animal (herbivores versus carnivores). Stable isotope analysis of teeth and bones provides direct information on the lifetime diets the nitrogen isotopes reflect the trophic level of the protein that has been consumed. Within an ecosystem, they can identify herbivores and carnivores, while the carbon isotopes tell mainly about the amount of protein in the diets from terrestrial versus marine ecosystems. 

Figure 1 Typical carbon and nitrogen stable isotope ratios of collagen extracted from various species. In this example the terrestrial animals consume only C3 plants (herbivores and omnivores) or animals that consume only C3 plants (carnivores and omnivores). The marine organisms are distinguished from the terrestrial organisms through the value, which is less depleted in The value indicates the trophic level of an organism in the food web.

Animals absorb carbon by ingesting plants or other animals. The ratio of —the most abundant stable isotope of carbon— to in a living system remains constant. Upon death, however, ingestion stops and the which is always undergoing radioactive decay, is no longer replaced in the cells. 

---