Effect of the fluorescent indicator calcein on Mg and Sr incorporation into foraminiferal calcite

The development of particular analytical methods like laser ablation-inductively coupled plasmamass spectrometry (LA-ICP-MS) renders it possible to determine the composition of a single chamber of foraminifers tests. This is crucial in the investigation of benthic foraminifers since the growth of new chambers under laboratory conditions does not face the difficulties associated with experiments involving reproduction. The addition of chambers can be recognized by the incorporation of the fluorescent dye calcein. When added to the culture medium, previously formed chambers are not affected, and calcein is only incorporated in calcite that is formed in its presence. However, it has never been verified whether calcein affects the element incorporation into foraminiferal calcite. In order to investigate and quantify possible effects, specimens of the benthic foraminifer Ammonia tepida were cultured in the presence and absence of calcein (15 degrees C, salinity 33), and Mg and Sr in newly formed chambers were analyzed with LA-ICP-MS. Magnesium concentrations of cross sections and longitudinal sections of foraminifera from the same experiment were also analyzed by electron microprobe measurements. Additionally, the impact of calcein on Mg and Sr incorporation in inorganically precipitated calcium carbonate crystals was quantified. Results show that presence of calcein does not impact the incorporation of Mg and Sr into biologically and inorganically precipitated calcium carbonate.