OOS 21-1 - Applications and Frontiers of Amino Acid Stable Isotope Ratios in Ecological Research

Recent advances in isotope analysis of single compounds have made it possible to use the SIR of amino acids (AA) of carbon and nitrogen for a more detailed understanding of trophic level and resource use. AAs play a crucial role in nutrient exchange since all organisms synthesize proteins from the same set of 20 AAs. There are two groups of AAs: essential and nonessential. Consumers must obtain the former from the diet, while the latter can be either provided by the diet or synthesized in the body. Carbon stable isotope ratios (d13C) of EAAs are therefore commonly used as source tracers. Complementary to this, nitrogen stable isotope ratios (d15N) of AA amine groups can provide information about the trophic position of a consumer. The AAs that readily transaminate with other AAs during trophic transfer are termed ‘trophic’ AAs and the ones that do not are termed ‘source’ AAs. These dual features of carbon and nitrogen AAs can help to improve our understanding of physiological processes, food web functioning, and to reconstruct dominant basal dietary sources and trophic transfers at the specimen and community levels. However, there are still methodological challenges and uncertainties surrounding the interpretation of AA-SIR data. To address these points and explore new depths and possibilities in AA-SIR applications, this presentation will outline the state-of-the-art in the field and provide a guide to make AA-SIR more broadly accessible to ecologists of various backgrounds.