Towards the use of radiocarbon as a dietary proxy: Establishing a first wide-ranging radiocarbon reservoir effects baseline for Germany

Radiocarbon reservoir effects (RREs) are observed when the 14C concentration of aquatic reservoirs is lower than the contemporary atmosphere. Within these reservoirs, aquatic species will also have a 14C depleted signal, and humans feeding on these species will show a dietary RRE. Human dietary RREs are often viewed as a problem for the establishment of reliable chronologies. However, they also represent an opportunity to introduce radiocarbon as a dietary proxy when investigating possible past human consumption of aquatic food groups. Here, a synthesis of previously published and new radiocarbon dates on edible aquatic species from central and northern Germany is presented. The samples were collected from modern and archaeological contexts. The goal was to provide an approximate RRE baseline within Germany. The results show that within the German context, local RREs in edible aquatic species are usually large and variable. The variability in local RREs implies that precise quantitative human dietary estimates will most likely not be possible. However, the large values of local RREs allow the use of 14C measured in human bone collagen as an extra dietary proxy that can aid in detecting the consumption of aquatic food groups when traditional isotopic proxies (δ13C and δ15N) do not provide unambiguous estimates.