Ba incorporation in benthic foraminifera
- 1Dept. of Ocean Sciences, Royal Netherlands Institute of Sea Research, Landsdiep 4, 1797 SZ 't Horntje, the Netherlands
- 2Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, the Netherlands
- 3Biogeosciences section, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
- 4The Laboratory, The Marine Biological Association of the United Kingdom, Citadel Hill, Plymouth, Devon, PL1 2PB, UK
- anow at: National Oceanography Centre, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK
Abstract. 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 in which 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: Heterostegina depressa and Amphistegina lessonii. The slopes of the regression, however, vary two- to threefold 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 develop new applications of trace elements in foraminiferal calcite in reconstructing past seawater chemistry.