Refining C. wuellerstorfi and H. elegans Mg/Ca temperature calibrations

•New Mg/Ca temperature calibrations for H. elegans and C. wuellerstorfi.•Atlantic benthic Mg/Ca sensitivity to BWT is higher than the Indian and Pacific.•BWT controls C. wuellerstorfi Mg/Ca variability for the BWT range from 0 to 10 °C.•Where [DCO32 −]aragonite > 70 mmol kg− 1, Mg depletion in H. elegans was observed.

We present core top Mg/Ca, Sr/Ca and δ18O measurements for Cibicidoides wuellerstorfi and Hoeglundina elegans from the Timor Sea and the Makassar Strait, which span a bottom water temperature (BWT) range from 2 to 18 °C. In both species Mg/Ca ratios are positively and significantly correlated with BWT, while δ18O measurements are significantly anti-correlated with BWT. Comparison of calcification temperatures derived from Mg/Ca ratios and δ18O measurements yield comparable results and closely match CTD-measured temperatures. We integrate our results with previously published data sets from the Atlantic, Indian and Pacific Oceans and provide temperature calibration equations over the temperature range from 2 to 12 °C for H. elegans and from 0 to 10 °C for C. wuellerstorfi. We found geographical differences in the relation of benthic Mg/Ca ratios to BWT: C. wuellerstorfi shows Mg/Ca sensitivity to BWT of 19% increase in Mg/Ca per °C for the Atlantic Ocean and of 15% per °C for the Indian and Pacific Oceans. H. elegans shows Mg/Ca sensitivity to BWT of 16% increase in Mg/Ca per °C for the Atlantic Ocean and of 14% per °C for the Indian and Pacific Oceans. C. wuellerstorfi Sr/Ca variability appears to be mainly driven by carbonate ion saturation, whereas H. elegans Sr/Ca variability is closely linked to BWT in the compiled data sets from the Atlantic, Indian and Pacific Oceans.