Independent impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera

Laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration ([CO32-]), and thereby calcite saturation state (Ω), on Mg and Sr incorporation into calcite of two species of shallow-water benthic foraminifera: Ammonia tepida and Heterostegina depressa. Impact on Mg and Sr incorporation by increased seawater [CO32-] and thereby higher Ω, is absent in either species. Comparison to results from a similar culturing experiment, in which Ω was varied as a function of [Ca2+], reveals that saturation state affects incorporation of Mg and Sr through calcium- rather than carbonate availability. The similarity in response by both species is surprising since the average Mg/Ca ratio is ~ 70 times higher in H. depressa than in A. tepida. Furthermore, these results suggest that the ions involved in biomineralization (i.e. Ca2+ and DIC) are processed by separate cellular transport mechanisms. The similar response of Mg and Sr incorporation in this study suggests that only differences in the Ca2+ transport mechanism affect divalent cation partitioning.

Dueñas-Bohórquez A., Raitzsch M., de Nooijer L. J., & Reichart G.-J., in press. Independent impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera. Marine Micropaleontology doi:10.1016/j.marmicro.2011.08.002. Article (subscription required).


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