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Marine mollusc shells to reconstruct the sea temperatures

06 Sep 2022
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A new multidisciplinary study involving ICTA-UAB researchers reveals that Calibration Free-LIBS can be a very valuable methodology for accurately measuring the molar concentration of trace elements in marine mollusc shells. The results have important implications for future climate and archaeological investigations.

Marine mollusc shells to reconstruct the sea temperatures

Marine molluscs have been exploited as a food resource by humans in the past. As a result, their shells are frequently preserved and found in archaeological sites all over the world. The chemical composition of these shells can act as a powerful recorder of seasonal sea temperature variations experienced by a mollusc in the past, enabling researchers to reconstruct past climate conditions, as well as to accurately establish the period of the year when it died/was collected by humans The elemental composition of marine mollusc shells can therefore offer valuable information about environmental conditions experienced by a mollusc during its lifespan. Previous studies have shown significant correlations between Mg/Ca concentration ratios measured on biogenic carbonate of mollusc shells and sea temperature.

In this context, Laser-Induced Breakdown Spectroscopy (LIBS) has proven to be particularly promising for accurate measurement of Mg/Ca ratios thanks to its high thru-put, versatility, no contact requirements, and limited sample preparation. Although, previous work had demonstrated that Mg/Ca ratios obtained along the growth axis of limpets using LIBS show very well-defined seasonal cycles that correctly reflect the annual variations in sea temperatures, more studies are required to improve this analytical technique.

In a new study published in the Talanta journal, Asier García-Escárzaga of the Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), in collaboration with scholars from German and Spanish research centres (Max Planck Institute, and Universities of Cantabria, Oviedo and Basque Country), applied a novel Calibration Free-LIBS for the calculation of Mg/Ca molar concentration ratios.

This CF-LIBS procedure is a quantitative algorithmic method that allows the elemental molar concentrations of materials to be obtained without the matrix effect, reducing thus the variability provoked by changes in experimental conditions between measurements. The authors of this new investigation validated their results by comparison with the actual values measured by from LA-ICP-MS technique.

The results obtained by these scientists allowed them to determine, for the first time, that Mg/Ca molar concentration measured in biogenic carbonates can be accurately inferred using the CF-LIBS technique. The validation of the CF-LIBS approach represents great potential for the rapid and large-scale paleoenvironmental and archaeological analysis of molluscs, and their implications for past human-marine interactions.