Ba incorporation in benthic foraminifera

Abstract

<p><strong>Abstract.</strong> Barium (Ba) incorporated in the calcite of many foraminiferal species is proportional to the concentration of Ba in seawater. Since the open ocean concentration of Ba closely follows seawater alkalinity, foraminiferal Ba/Ca can be used to reconstruct the latter. Alternatively, Ba/Ca from foraminiferal shells can also be used to reconstruct salinity in coastal settings where seawater Ba concentration corresponds to salinity as rivers contain much more Ba than seawater. Incorporation of a number of minor and trace elements is known to vary (greatly) between foraminiferal species and application of element/Ca ratios thus requires the use of species-specific calibrations. Here we show that calcite Ba/Ca correlates positively and linearly with seawater Ba/Ca in cultured specimens of two species of benthic foraminifera, <i>Heterostegina depressa</i> and <i>Amphistegina lessonii</i>. The slopes of the regression, however, vary 2–3 fold between these two species (0.33 and 0.78, respectively). This difference in Ba-partitioning resembles the difference in partitioning of other elements (Mg, Sr, B, Li and Na) in these foraminiferal taxa. A general trend across element partitioning for different species is described, which may help developing new applications of trace elements in foraminiferal calcite in reconstructing past seawater chemistry.</p>

Incorporation of Mg, Sr, Ba, U, and B in High‐Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

“…The strong correlation between Ba concentration in deep water and alkalinity allowed the estimation of past ocean alkalinity using Ba/Ca in benthic foraminifers (Hall & Chan, ). More recently, a relationship between Ba/Ca in calcite and seawater Ba/Ca have been observed (de Nooijer et al, ). U/Ca in foraminifers is thought to be negatively correlated to carbonate ion concentrations (Keul et al, ) and carbonate ion saturation state (Raitzsch et al, ).…”