essential or nonessential amino acids) have offered a deeper view of trophic transfer, and trophic ecology in general, but these discrete molecular (or compound-specific) stable isotope assays require specialized preparation and complex gas or liquid chromatographic interfaces to combustion-based isotope ratio instruments, and, so far, are largely limited to 13C or 15N. 9- 11 In the past decade, technological advances in compound-specific isotope analysis (CSIA) of specific molecules extracted from tissues (e.g. 1- 5 Bulk tissue δ 2H or bulk lipid δ 2H analyses have been applied to track animal migration patterns and provenance of lipid synthesis 6- 8 and offer low-cost routine approaches, but suffer from several intrinsic challenges: (i) bulk tissue isotopic averaging of all molecular components, such as carbohydrates, proteins, and lipids, all of which undergoing anabolic and catabolic processes at different turnover times, thus distorting the bulk δ value depending on the current physiological state of the biological sample (ii) isotopic fractionation by biochemical processes (iii) bulk stable isotopic overlap of available food sources and (iv) specific to any H isotope exchange with environmental water. algae, leaves, feathers, muscle tissue, etc.) have been used since the 1980s to construct trophic models for terrestrial, freshwater, and marine ecosystems. δ 13C, δ 15N, δ 34S) of primary producers and consumer tissues (e.g.
Tracing trophic transfer of dietary energy sources and molecules in and among aquatic and terrestrial food webs is critical for understanding and quantifying trophic interactions of species. The new 2H-CSIA method can be applied to evaluate sources and trophic dynamics of fatty acids in organisms ranging from food web ecology to migratory connectivity. We show that lipid extracts obtained from aquatic sources, such as biofilms, leaves, invertebrates, or fish muscle tissue, have distinctive δ 2H values that can be used to assess sources and trophic interactions, as well as dietary allocation and origin of fatty acids within consumer tissue. Here we demonstrate a new online high-capacity gas chromatography–isotope ratio mass spectrometry technique ( 2H-CSIA) that offers accurate and reproducible determination of δ 2H values for a range of fatty acids from organisms of aquatic food webs. Hydrogen isotope values ( δ 2H) in consumer tissues have potential to more clearly distinguish dietary sources than 13C or 15N values within and among habitats, but have not been used at the fatty acid level for ecological purposes. Compound-specific stable isotope analysis (CSIA) is a powerful tool for a better understanding of trophic transfer of dietary molecules in and across ecosystems.
0 kommentar(er)
