δ13C and δ15N in ancient and recent fish bones from the Mediterranean Sea

Abstract

The naturally occurring stable isotopes of nitrogen (¹⁵N/¹⁴N) and carbon (¹³C/¹²C) in animal tissues have been used successfully to establish trophic relationships and sources of nutrients in several marine food webs. Nitrogen isotopes show a stepwise enrichment between prey and consumer tissues through assimilation processes, while carbon isotopes remain practically unchanged, reflecting the isotopic signatures of primary productivity sources. This technique has been applied to the reconstruction of past human diets, with particular emphasis on the relative importance of marine resources in prehistoric economies. In the present study, δ¹³C and δ¹⁵N values were determined for fish remains from the Early Bronze Age site of Cova des Riuets on the east coast of the Balearic island of Formentera and bone samples from corresponding species of modern fish were also analysed to provide a stable carbon and nitrogen
baseline for palaeodietary studies in the western Mediterranean. The results show a great variability within marine ecosystems in terms of the stable isotope compositions of fish. This may be partly due to the natural complexity of marine ecosystems, but also to human influence on the environment, which can lead to a wide range of local responses to changing conditions. All this means
that much caution is required when using data from modern ecosystems to infer past human diets.