134 encrusted (C) and non-encrusted (NC) G. truncatulinoides specimens were picked based on availability from January 2010 through March 2014. Whole shell G. truncatulinoides were cleaned according to modified procedures for laser ablation (Vetter and others, 2013; Fehrenbacher and others, 2015). Samples were cleaned by ultrasonicating in methanol followed by triple-rinsing in Milli-Q water (18.2 megohmcentimeters [MΩ-cm]). Shells were then oxidatively cleaned at 60° Celsius (C) for 30 minutes in a buffered hydrogen peroxide solution (1:1 mix of 30% hydrogen peroxide and 0.1N sodium hydroxide [NaOH]) to remove remnant organic matter. Finally, the shells were again triple rinsed in Milli-Q water. Once dry, each individual's length was measured across the diameter of the umbilical side, from the tip of the final chamber to the opposite side and weighed on a microbalance. 1 error on length measurements (± 16 micrometers [µm]) and weight measurements (± 0.6 micrograms [µg]) are based on repeated measurements by separate analysts.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was conducted at The University of California, Davis Stable Isotope Laboratory, using Photon Machines 193 nm ArF ultraviolet (UV) excimer laser with an ANU HelEx dual-volume laser ablation cell coupled to an Agilent 7700x quadrupole-ICP-MS. G. truncatulinoides specimens were placed on double sided carbon tape, spiral side up, to ensure a horizontal sampling surface for each chamber. Laser spot size of 44x44 µm in diameter was used with a repetition rate of 6 hertz (Hz) (non-encrusted forms) and 8 Hz (encrusted forms). For the smallest foraminifera, the spot size was decreased to 30x30 µm to ensure ablation within a single chamber. Depth profiles were obtained on each chamber (F through up to F7). If chambers were large enough, up to 3 repeat spot analyses were obtained to assess reproducibility. Masses measured were 24Mg, 25Mg, 27Al, 44Ca, 55Mn, 88Sr, 89Y, and 138Ba. Standard Reference Materials under the National Institute of Standards and Technology (SRM NIST) 610, 612, and 614 glass standards were run before and after each batch of samples as an external standard. An Orbulina universa shell, which is demonstrated to have highly reproducible trace element profiles throughout, was analyzed before and after each run as an internal working standard (7.0 ± 0.7 mmol/mol Mg/Ca, 2σ, Fehrenbacher and others, 2015). Outliers in the Mg/Ca profiles that were greater than ± 6 standard deviations from a 3-point rolling mean were removed from raw LA-ICP-MS signals, then data were reduced using Iolite Software (Paton and others, 2011).
Stable isotopes, δ18O and δ13C of calcite (δ18Oc and δ13Cc), were analyzed on individual foraminifera, ranging in weight from 5 to 95 µg, after LA-ICP-MS analyses were completed. Foraminifera were roasted under vacuum at 75°C for 1 hour to eliminate remaining volatile organics from carbon tape. Isotopic analyses were performed at The University of California, Davis Stable Isotope Laboratory, on a Fisons Optima isotope ratio mass spectrometer (IRMS). The IRMS is calibrated using the NBS-19 standard and has a long-term one sigma precision for carbonates ± 0.04 ‰ and ± 0.05 ‰ for δ13Cc and δ18Oc, respectively. This is based on 110 standards analyzed during the summer 2016.