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Constraining environmental controls on the incorporation of Mg, Na and Sr in cultured Globigerina bulloides: implications for biomineralisation and high latitude palaeoceanography.

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Title: Constraining environmental controls on the incorporation of Mg, Na and Sr in cultured Globigerina bulloides: implications for biomineralisation and high latitude palaeoceanography.
Authors: Sykes, F.E.1 (AUTHOR) freya.e.sykes@uit.no, Ezat, M.M.1 (AUTHOR), Westgård, A.1 (AUTHOR), Foster, G.L.2 (AUTHOR), Meilland, J.3,4 (AUTHOR), Chalk, T.B.4 (AUTHOR), Milton, J.A.2 (AUTHOR), Chierici, M.5 (AUTHOR)
Source: Geochimica et Cosmochimica Acta. Jul2026, Vol. 424, p229-241. 13p.
Subjects: Biomineralization, Paleoceanography, Foraminifera, Carbonate minerals, Temperature effect, Antarctic climate
Abstract: The incorporation of elemental impurities into the shells of the spinose planktic foraminifera Globigerina bulloides , as a function of the physical environment they grew in, can provide insights into foraminiferal biomineralisation and be exploited for use in palaeoceanographic reconstructions. The full potential remains unrealised however due to the absence of culture-based proxy calibrations exploring cold temperatures (<14°C) and other environmental variables (e.g. salinity, pH etc.). To address these gaps, we have cultured G. bulloides at low temperatures (6–13°C) and across a range of salinities (30.4–37.8) and varied carbonate chemistry (pH 7.7–8.3, decoupled [CO 3 2–] 77–225 µmol/kg). This study presents elemental ratios (Mg/Ca, Na/Ca, and Sr/Ca) for these cultured G. bulloides, measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry, with the aim of improving the utility of this species for high-latitude climate reconstructions. We extend existing Mg/Ca culture-based calibrations to 6°C, and observe higher temperature sensitivity compared to pre-existing Mg/Ca calibrations derived from sub-tropical and Southern Ocean specimens, which we hypothesise results from latitudinal and/or ocean basin-based differences in genotype. We also report a strong inverse relationship between Na/Ca and temperature that may offer a new pH-independent palaeothermometer. Na/Ca and Sr/Ca are both sensitive to [CO 3 2–] at constant pH, but in opposite directions. For Sr/Ca, this may be related to changes in other DIC components, such as [HCO 3 –]. None of the presented elemental ratios display significant relationships with salinity. However, in the case of Na/Ca this may result from confounding carbonate chemistry effects, which once corrected for, do reveal an underlying positive (if not statistically significant) correlation. Our findings provide critical insights into element incorporation within biogenic carbonates and expand the applicability of G. bulloides in palaeoceanographic studies into (sub)polar regions. [ABSTRACT FROM AUTHOR]
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Abstract:The incorporation of elemental impurities into the shells of the spinose planktic foraminifera Globigerina bulloides , as a function of the physical environment they grew in, can provide insights into foraminiferal biomineralisation and be exploited for use in palaeoceanographic reconstructions. The full potential remains unrealised however due to the absence of culture-based proxy calibrations exploring cold temperatures (<14°C) and other environmental variables (e.g. salinity, pH etc.). To address these gaps, we have cultured G. bulloides at low temperatures (6–13°C) and across a range of salinities (30.4–37.8) and varied carbonate chemistry (pH 7.7–8.3, decoupled [CO 3 2–] 77–225 µmol/kg). This study presents elemental ratios (Mg/Ca, Na/Ca, and Sr/Ca) for these cultured G. bulloides, measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry, with the aim of improving the utility of this species for high-latitude climate reconstructions. We extend existing Mg/Ca culture-based calibrations to 6°C, and observe higher temperature sensitivity compared to pre-existing Mg/Ca calibrations derived from sub-tropical and Southern Ocean specimens, which we hypothesise results from latitudinal and/or ocean basin-based differences in genotype. We also report a strong inverse relationship between Na/Ca and temperature that may offer a new pH-independent palaeothermometer. Na/Ca and Sr/Ca are both sensitive to [CO 3 2–] at constant pH, but in opposite directions. For Sr/Ca, this may be related to changes in other DIC components, such as [HCO 3 –]. None of the presented elemental ratios display significant relationships with salinity. However, in the case of Na/Ca this may result from confounding carbonate chemistry effects, which once corrected for, do reveal an underlying positive (if not statistically significant) correlation. Our findings provide critical insights into element incorporation within biogenic carbonates and expand the applicability of G. bulloides in palaeoceanographic studies into (sub)polar regions. [ABSTRACT FROM AUTHOR]
ISSN:00167037
DOI:10.1016/j.gca.2026.05.022