Sr partitioning in two benthic foraminifera 1

16 The shallow water benthic foraminifera Ammonia aomoriensis and Amphistegina 17 lessonii were grown at different seawater Sr/Ca and the test Sr/Ca ratio was determined by 18 Laser-Ablation-Inductively-Coupled-Plasma-Mass-Spectroscopy. When grown over a range 19 of varying seawater Sr concentrations, A. aomoriensis test Sr/Ca is positively correlated with 20 seawater Sr/Ca. The linear regression has a slope of 0.17, which represents the overall Sr 21 partitioning coefficient KDSr. The same holds, if seawater Ca concentration is changed in 22 order to change the seawater Sr/Ca. In the case of A. lessonii, the slopes of the linear 23 regressions representing KDSr differ from one another. If the Sr concentration of seawater is 24 changed, the slope, i.e. KDSr, is 0.16. If the Ca concentration of seawater is changed, the slope 25 is 0.32. This difference in KDSr can be explained by the relatively high Mg content of A. 26 lessonii, which distorts the calcite lattice and weakens the discrimination against Sr. The Mg 27 content of A. aomoriensis is too low to observe the influence on Sr partitioning. All data are 28 compatible with a recently developed model for minor element partitioning in foraminifera 29 (Nehrke et al. 2013, Mewes et al. 2015a). 30

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