New methodologies to reduce measurement bias in high-throughput LA-ICP-MS and X-ray CT, and applications to planktonic foraminifera

Abstract

This commentary presents advancements in the study of foraminifera by integrating high-resolution imaging, innovative data processing methodologies, and geochemical analysis to investigate environmental, ecological, and evolutionary dynamics preserved in marine sediment cores. I present ten recommendations for X-ray microfocus computed tomography (μCT) imaging to enhance the volumetric analysis of individual foraminifera, enabling precise characterisation of internal structures such as chamber volumes, shapes, and pore distributions. These structures form the basis for linking morphology to environmental gradients and understanding species-specific adaptations to oxygen minimum zones.

Geochemical analysis using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) revealed ontogenetic trends in chamber wall thickness, demonstrating that earlier chambers are thicker due to secondary calcite overgrowth and more representative of environmental conditions compared to the penultimate and final chambers. Results suggest that Mg/Ca ratios in earlier chambers correlate strongly with δ18O, offering more reliable palaeoclimate reconstructions.

I present the LABLASTER package for the R statistical environment to automate data reduction workflows, improving accuracy, transparency, and reproducibility in geochemical analyses. By algorithmically detecting laser ablation endpoints in time-resolved LA-ICP-MS data, LABLASTER ensures consistent targeting of biologically relevant signals, facilitating more precise extraction of geochemical data from heterogenous bioarchives. These methodological advances establish a robust framework for studying morphological and geochemical signals in foraminifera and other carbonate-shelled organisms, providing new insights into past environments and evolutionary dynamics.

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ORCID for Thomas Ezard: orcid.org/0000-0001-8305-6605

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