Compound-specific stable hydrogen isotope (δ² H) 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.