Relationship between individual chamber and whole shell Mg/Ca ratios in Trilobatus sacculifer and implications for individual foraminifera palaeoceanographic reconstructions

• Published in: Scientific reports Vol. 11; no. 1; p. 463
• Main Authors: Rustic, Gerald T., Polissar, Pratigya J., Ravelo, Ana Christina, DeMenocal, Peter
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.01.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/2738; 704/106/413; Correlation coefficient; Emission measurements; Growth chambers; Humanities and Social Sciences; Life span; Mass spectrometry; Mass spectroscopy; multidisciplinary; Science; Science (multidisciplinary); Scientific imaging; Trace elements
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-80673-8

Precisely targeted measurements of trace elements using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) reveal inter-chamber heterogeneities in specimens of the planktic foraminifer Trilobatus (Globigerinoides) sacculifer . We find that Mg/Ca ratios in the final growth chamber are generally lower compared to previous growth chambers, but final chamber Mg/Ca is elevated in one of thirteen sample intervals. Differences in distributions of Mg/Ca values from separate growth chambers are observed, occurring most often at lower Mg/Ca values, suggesting that single-chamber measurements may not be reflective of the specimen’s integrated Mg/Ca. We compared LA-ICPMS Mg/Ca values to paired, same-individual Mg/Ca measured via inductively coupled plasma optical emission spectrometry (ICP-OES) to assess their correspondence. Paired LA-ICPMS and ICP-OES Mg/Ca show a maximum correlation coefficient of R = 0.92 (p < 0.05) achieved by applying a weighted average of the last and penultimate growth chambers. Population distributions of paired Mg/Ca values are identical under this weighting. These findings demonstrate that multi-chamber LA-ICPMS measurements can approximate entire specimen Mg/Ca, and is thus representative of the integrated conditions experienced during the specimen’s lifespan. This correspondence between LA-ICPMS and ICP-OES data links these methods and demonstrates that both generate Mg/Ca values suitable for individual foraminifera palaeoceanographic reconstructions.