Mg/Ca anlaysis of foraminiferal calcite shells. Foraminifera obtained from sediments (benthic, Uvigerina spp.; sediment from ODP Site 1015, California Margin) and from plankton tows (planktonic, Orbulina universa, plankton tow specimens were collected near Green Island, Taiwan in May 2019 using a 1 m plankton net Sea-Gear, 150 µm mesh, 0-50 m depth), were analyzed. Mg/Ca were obtained applying Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and wavelength-dispersive X-Ray Spectroscopy by electron probe microanalyzer (EPMA). The goal is to assess the use of EPMA as an alternative technique for Mg/Ca analyses of foraminiferal calcite shells.