Collaborative Research: Extending the potential for hydrogen isotope tracers in ecology: experiments, biochemistry and field studies

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The hydrogen isotopic composition of animal tissues has become as a valuable tool in the investigation of animal movements and the study of habitat use. However, the biochemical foundation needed for animal ecologists to confidently apply isotopic analyses to ecological problems has yet to be adequately revealed. This project will address that knowledge gap by advancing our understanding of fundamental processes controlling isotopic composition in tissues of vertebrates. New methodologies will be applied to analyze compound-specific isotopes of individual amino acids in animal tissues and to determine whether hydrogen can be directly routed from dietary amino acids into tissues. Biosynthetic mechanisms responsible for determining hydrogen isotope patterns observed in bulk tissues will be explored in a series of laboratory experiments. Results from this research will address the magnitude and degree of variation in isotope discrimination for animal tissues, and the biochemical mechanism of hydrogen incorporation into an animal's tissue from its food and water. To accomplish this work, the fish species tilapia will be reared in tanks with water and food components having unique and controlled isotopic compositions. The isotopic composition of individual amino acids, particularly those that are indispensible for growth, will be measured to trace incorporation from dietary protein, carbohydrate, lipid, and water into fish tissues. The research will be extended to a population-based study of black-throated blue warblers, for which the hydrogen isotopic composition of individual amino acids from feather, bone, and liver tissues will be measured from three locations that span the continental range for this bird species in North America. Results from this project will advance a new methodology and provide foundational knowledge for isotopic approaches to the study of animal ecology and behavior. The project will develop and teach a graduate level course on isotopic ecology, involve undergraduate students in the laboratory research, and conduct outreach to high school biology classes to foster understanding of biochemical ecology. It will also support workshops designed to raise awareness of the potential uses of stable isotopes in the biological sciences and set the stage for future collaboration with researchers in several Latin American countries.