Trophic-level interpretation based on d15N values: implications of tissue-specific fractionation and amino acid composition

4 from one trophic level to the next Thus, carbon isotope ratios can trace different sources of primary productivity, whereas nitrogen isotope ratios are used as trophic position indicators. Stable isotope approaches have improved our understanding of food-web relationships, resource partitioning, the importance of specific nutrient sources and habitat usage of migrating species (