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. The 14C ages of five algal and nine mollusk samples were measured by accelerator mass spectrometry (AMS). Marine 14C 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 ± 34 14C yr) and ΔR value (–9 ± 34 14C yr) than mollusks (R 513 ± 53 14C yr; ΔR 154 ± 52 14C 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-depleted 14C. In examining new data together with previously published data, the marine reservoir effect (MRE) for the Adriatic area is estimated to be 424 ± 57 14C yr (ΔR is 77 ± 57 14C yr). Without mussel shells, the estimated MRE is 378 ± 44 14C yr (ΔR is 28 ± 45 14C yr). The presented values are comparable to the MREs and mean ΔRs obtained for the Mediterranean by other authors.

Variation of the 1.5 ka surface water marine radiocarbon reservoir age in the Adriatic based on the study of algal rims

“…Based on those records we provide several lines of evidence that the alga which lives in the intertidal zone has a lower marine radiocarbon reservoir age than the mean surface water MRE. On the other hand, shells (mytilid bivalves) from algal rims reveal higher Features, processes, evolution and problems reservoir ages than global means, similar to previously published data (FAIVRE et al, 2015). Furthermore, as living exclusively in the intertidal zone L. byssoides, could reflect longterm surface water MRE variations as surface ocean radiocarbon time series can provide a unique opportunity to study both air-sea 14 CO 2 exchanges and ocean circulation dynamics.…”

“…Mediterranean rocky coasts: Features, processes, evolution and problems reservoir ages than global means, similar to previously published data (FAIVRE et al, 2015). Furthermore, as living exclusively in the intertidal zone L. byssoides, could reflect longterm surface water MRE variations as surface ocean radiocarbon time series can provide a unique opportunity to study both air-sea 14 CO 2 exchanges and ocean circulation dynamics.…”

“…Till now continuous marine 14 C records have only been acquired from a limited number of biogenic calcifying archives. Currently, only sparse 14 C data are available for the Mediterranean Sea in order to constrain the MRE with limited age ranges (SIANI et al, 2000(SIANI et al, , 2001REIMER and MCCORMAC, 2002;MCCULLOCH et al, 2010;TISNÉRAT-LABORDE et al, 2013;FAIVRE et al, 2015). In this framework, several research lines on algal and shell MREs (shells inhabiting algal rims) have been initiated, which could together provide records on MRE variability throughout the 1.5 ka period.…”

The Usiminas shellmound on the Cabo Frio Island: Marine reservoir effect in an upwelling region on the coast of Brazil

“…Such influence is expected to increase the MRE local offset, leading to positive DR values. According to Goodfriend and Flessa (1997), areas of strong upwelling of old, cold and deep water such as the California coast and the Pacific coast of South America have reservoir effects higher than average.…”

An Online Application for ΔR Calculation

“…Regional differences from the global curve are handled in calibration by including an offset ΔR(t) although in practice this value is often assumed to be constant. Although ΔR(t), the time-dependent regional offset from the global marine curve, was clearly defined in Stuiver et al (1986), there have been recent publications where calculations for samples with precisely known calendar age were made overly complicated and the results less precise (Alves et al 2015;Faivre et al 2015) by inappropriately using phase models in OxCal (Bronk Ramsey 2009). ΔR values calculated from independently dated samples, such as U-Th dated corals, have not always included the calendar age uncertainty (e.g.…”