Abstract
In marine ecology, dietary interpretations of faunal assemblages often rely on nitrogen isotopes as the main or only applicable trophic level tracer. We investigate the geographic variability and trophic level isotopic discrimination factors of bone zinc 66Zn/64Zn ratios (δ66Zn value) and compared it to collagen nitrogen and carbon stable isotope (δ15N and δ13C) values. Focusing on ringed seals (Pusa hispida) and polar bears (Ursus maritimus) from multiple Arctic archaeological sites, we investigate trophic interactions between predator and prey over a broad geographic area. All proxies show variability among sites, influenced by the regional food web baselines. However, δ66Zn shows a significantly higher homogeneity among different sites. We observe a clear trophic spacing for δ15N and δ66Zn values in all locations, yet δ66Zn analysis allows a more direct dietary comparability between spatially and temporally distinct locations than what is possible by δ15N and δ13C analysis alone. When combining all three proxies, a more detailed and refined dietary analysis is possible.
Highlights
In marine ecology, dietary interpretations of faunal assemblages often rely on nitrogen isotopes as the main or only applicable trophic level tracer
Archaeology and palaeontology, accurately reconstructing trophic levels can be challenging. These reconstructions are required for effective management and conservation strategies[1], understanding changing predatorprey and foraging ecology related to climate change[2] and studying long-term environmental changes through the analyses of modern to fossil faunal assemblages[3,4]
The QjJx-1 site on Little Cornwallis Island is a notable exception with very high on-site P. hispida bone collagen δ15N variability (3.85‰)[15]
Summary
Dietary interpretations of faunal assemblages often rely on nitrogen isotopes as the main or only applicable trophic level tracer. Bone collagen and soft tissue bulk δ15N and δ13C values are the traditional geochemical proxies used for dietary and trophic level reconstructions[6,7,8]. These isotope analyses can be conducted on single collagen amino acids and provide more refined information on the trophic level of animals (e.g., corrected for baseline variability)[9,10], but these studies are still time consuming and expensive. For bone collagen, with its long turnover time[29], trophic level reconstructions can be compromised when animals frequently migrate between areas of differing food web baseline isotopic composition, or when comparing animals from spatially and temporally distinct locations
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