Petersen, Jassin, Schmiedl, Gerhard, Raddatz, Jacek, Bahr, André, Pross, Jörg and Mojtahid, Meryem (2025) Controls on barium incorporation into tests of benthic foraminifera from the Aegean Sea (Eastern Mediterranean Sea) – Towards a species-specific Ba/Ca calibration. Marine Micropaleontology, 194 . Art.Nr.: 102431. DOI 10.1016/j.marmicro.2024.102431.

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Abstract

Highlights:
• Barium incorporation into deep-sea benthic foraminiferal shells is species-specific.
• Ba/Ca develops a uniform signal between live and dead specimens.
• Melonis affinis is found with higher Ba/Ca ratios than Uvigerina mediterranea.
• Ba/Ca intra-test variability of both species is on average 16–24 % RSD per specimen.
• DBa in the Northern Aegean Sea ranges between 0.34 and 0.49.

Abstract:
We have analysed Ba/Ca ratios of live and dead benthic foraminifera (Uvigerina mediterranea and Melonis affinis) from core tops of seven sites located in the Aegean Sea by laser ablation ICP-MS. There are no significant Ba/Ca differences in live and dead specimens of U. mediterranea. For M. affinis we apply a threshold criterion for extremely high Ba/Ca in live specimens in order to highlight the overall uniform Ba/Ca signal. The Ba/Ca intra-test variability varies between 16 and 24 % relative standard deviation per specimen. It is attributed to biomineralisation processes i.e., vital effects. The Ba/Ca ratios of M. affinis are significantly higher than those of U. mediterranea throughout most of the sites and their respective samples from different sediment depths. The influence on Ba/Ca of both species by biomineralisation processes and/or microhabitat effects remains open. Linking the Ba/Ca ratios to measured Ba concentration of bottom waters from one of the studied sites, shows partition coefficients of DBa = 0.34, and DBa = 0.49 for U. mediterranea and M. affinis, respectively. We could not identify trends of Ba/Ca ratios to observed/ modelled gradients of relevant environmental factors between the seven analysed sites, such as primary productivity and associated Corg fluxes or TOC concentrations. Despite the demonstrated limited proxy potential in these parts of the Aegean Sea, we suggest that it is possible to employ Ba/Ca of infaunal benthic species in order to reconstruct export productivity in deep-sea areas with a less complex linkage between primary productivity and nutrient distribution in bottom waters.

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