Abstract
Carbon and nitrogen stable isotope ratios of bone collagen are an established method for dietary reconstruction, but this method is limited by the protein preservation. Zinc (Zn) is found in bioapatite and the isotopic compositions of this element constitute a very promising dietary indicator. The extent of fractionation of Zn isotopes in marine environments, however, remains unknown. We report here on the measurement of zinc, carbon and nitrogen isotopes in 47 marine mammals from the archaeological site of Arvik in the Canadian Arctic. We undertook this study to test and demonstrate the utility of Zn isotopes in recent mammal bone minerals as a dietary indicator by comparing them to other isotopic dietary tracers. We found a correlation between δ66Zn values and trophic level for most species, with the exception of walruses, which may be caused by their large seasonal movements. δ6Zn values can therefore be used as a dietary indicator in marine ecosystems for both modern and recent mammals.
Highlights
The main biochemical method of determining the diets of recent and fossil mammals is the measurements of the stable isotope ratios of carbon (C) and nitrogen (N) in bone protein
Knudson and collaborators [1] suggested that strontium (Sr) stable isotopes could be an indicator of trophic level (TL), and it appears possible that calcium (Ca) isotopes in bone and dental enamel could indicate dairy consumption and weaning [2,3,4] or other dietary information [5]
The cortical part of the bones seems to be preserved from these processes, with one exception: one bearded seal δ66Zn value (Individual 4806, Supporting Information) was an outlier and may fall on the regression line found for the cancellous bones (Fig 3A)
Summary
The main biochemical method of determining the diets of recent and fossil mammals is the measurements of the stable isotope ratios of carbon (C) and nitrogen (N) in bone protein (collagen). A number of researchers have explored the use of the isotope ratios of novel, ‘non-traditional’ elements in mammal tissues as additional dietary indicators, or as the primary dietary indicator where collagen preservation is poor. Martin and collaborators [6,7] demonstrated that magnesium (Mg) isotopes combined with other dietary indicators in dental enamel, such as trace elements and carbon stable isotope ratios, could be used to reconstruct ancient diets. Previous studies of zinc (Zn) isotopes in human blood highlighted strong differences
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