Compound-specific stable hydrogen (δ2 H) isotope analyses of fatty acids: a new method and perspectives for trophic and movement ecology.

RATIONALE Compound-specific stable isotope analysis (CSIA) is a powerful tool for a better understanding of trophic transfer of dietary molecules in and across ecosystems. Hydrogen isotope values (δ2 H) in consumer tissues have potential to more clearly distinguish dietary sources than 13 C or 15 N values within and among habitats, but have not been used at the fatty acid level for ecological purposes. METHODS Here we demonstrate a new online high-capacity gas chromatography-isotope ratio mass spectrometry technique (2 H-CSIA) that offers accurate and reproducible determination of δ2 H values for a range of fatty acids from organisms of aquatic food webs. RESULTS We show that lipid extracts obtained from aquatic sources, such as biofilms, leaves, invertebrates, or fish muscle tissue, have distinctive δ2 H values that can be used to assess sources and trophic interactions, as well as dietary allocation and origin of fatty acids within consumer tissue. CONCLUSIONS The new 2 H-CSIA method can be applied to evaluate sources and trophic dynamics of fatty acids in organisms ranging from food web ecology to migratory connectivity.