Can element chemical impurities in aragonitic shells of marine bivalves serve as proxies for environmental variability?

• DOI: 10.1016/j.chemgeo.2022.121215
• Publication Date: 2022-11-16T00:59:06Z
• Authors: Bernd R. Schöne; Soraya Marali; Anne Jantschke; Regina Mertz-Kraus; Paul G. Butler; Lukas Fröhlich
• Keywords: Trace element

In many biogenic and geogenic materials, ion impurities can provide serviceable proxies for environmental conditions. However, the element/Ca ratios of bivalve shells are notoriously challenging to interpret. Due strong vital effects, nonclassical nucleation growth mechanisms, and/or kinetic processes, concentration trace minor elements in marine typically remains below values observed inorganic CaCO3 precipitated from a solution resembling seawater chemistry but above those expected thermodynamic equilibrium. The interpretation is further complicated by non-lattice bound microstructure-specific element content. If conditions were still encoded shells, they should result statistically significantly reproducible chronologies between contemporaneous specimens same site. Here, we tested this hypothesis exemplarily studied seven twelve modern Arctica islandica collected four different localities North Atlantic (Faroe Islands, NE Iceland, Isle Man, Gulf Maine). Age-detrended weighted annual B, Mg, Sr Ba/Ca (Al, Zn Pb largely remained detection limit) measured most site, supporting that incorporation these was at least partly controlled forcings. Notably, agreement (explored with linear regression analyses sign tests) shell quantities weaker than respective suggesting available information on temperature, food water did not properly reflect in-situ which bivalves exposed or other extrinsic factors work. As aragonite – contrast expectations –, Sr/Ca, Mg/Ca B/Ca negatively correlated temperature (up 40% explained variability). link bulk phytoplankton often significance threshold, otherwise positive. Quantitative reconstructions based will remain impossible unless parent (= extrapallial fluid) actually formed known, including temporal changes thereof. This crucial compute representative partition coefficients required calibrate transfer functions.