New Data on Marine Radiocarbon Reservoir Effect in the Eastern Adriatic Based on Pre-Bomb Marine Organisms from the Intertidal Zone and Shallow Sea

Abstract

Radiocarbon analyses of 14 modern, pre-bomb marine organisms collected between AD 1836 and 1946 along the eastern Adriatic coast were performed. The14C ages of five algal and nine mollusk samples were measured by accelerator mass spectrometry (AMS). Marine14C reservoir ages (R) and regional offsets (ΔR) were calculated and compared. The marine reservoir ages of shells and algae significantly differ, even though both inhabit the hard substrate from the intertidal zone to shallow sea. Coralline algae had a considerably lower reservoir age (355 ± 3414C yr) and ΔR value (–9 ± 3414C yr) than mollusks (R 513 ± 5314C yr; ΔR 154 ± 5214C yr), though the variability of R was high in both groups. Although the microlocations of pre-bomb samples were not known and the studied mollusk species are able to inhabit marine or estuarine environments, it can be assumed that they were not significantly influenced by a freshwater admixture, due to their δ13C values being mostly in the marine range. However, as the entire eastern Adriatic is formed in carbonates, mollusk shells could be influenced by limestone-depleted14C. In examining new data together with previously published data, the marine reservoir effect (MRE) for the Adriatic area is estimated to be 424 ± 5714C yr (ΔR is 77 ± 5714C yr). Without mussel shells, the estimated MRE is 378 ± 4414C yr (ΔR is 28 ± 4514C yr). The presented values are comparable to the MREs and mean ΔRs obtained for the Mediterranean by other authors.