Equations for Lipid Normalization of Carbon Stable Isotope Ratios in Aquatic Bird Eggs

摘要: Stable isotope ratios are biogeochemical tracers that can be used to determine the source of nutrients and contaminants in avian eggs. However, interpretation stable carbon lipid-rich eggs is complicated because 13C depleted lipids. Variation abundance therefore obscured by variation percent Past attempts establish an algebraic equation correct for lipid content have been unsuccessful, possibly they relied partly on data from coastal or migratory species may obtain egg lipids different habitats than protein. We measured carbon, nitrogen sulphur 175 eight aquatic birds. Carbon, isotopes were enriched lipid-extracted samples compared with non extracted samples. A logarithmic using C∶N ratio tissue calculated 90% within ±0.5‰. Calculating separate equations laid (pelagic, offshore terrestrial-influenced) improved fit. equation, rather a linear as often muscle, was necessary accurately relatively high muscle meant relationship did not approximate between ratio. Because extraction alters (and cannot corrected algebraically), we suggest isotopic measurement bulk followed normalization good solution homogenated eggs, at least when it possible complete chemical analyses each isotope.