Using Laser Ablation-ICP-MS to generate culture-based foraminiferal calibration relationships for Neogloboquadrina dutertrei

Abstract:

Neogloboquadrina dutertrei is a deep-dwelling non-spinose planktic foraminifer that is abundant in tropical to mid-latitude regions. The Mg/Ca ratio and stable oxygen isotope geochemistry of this species are used to reconstruct thermocline hydrography (cf. Spero et al, 2003). Live culture experiments using this species are not common owing to the difficulty in collecting and maintaining these species in the laboratory. The existing calibration data for this species consists of two temperature points that were combined with data from live culture experiments on a related species, N. incompta (formerly N. pachyderma dextral) (Von Langen et al, 2004). We extended the temperature calibration for this species (from 16 – 19°C to 12 – 22°C) and developed a pH calibration (pH 7.85 – 8.4). Specimens were collected via plankton net from the Southern California Bight and cultured at the Wrigley Marine Science Center, Santa Catalina Island during the summer of 2013-2014. We use isotopically labeled seawater (43Ca, 87Sr, and 138Ba) to identify discrete portions of calcite that grew in culture. We use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for trace element analysis and obtain paired stable isotope analyses on chambers that grew entirely in culture. The calcite-labeling technique we employ here can be applied to other marine calcifiers grown in culture and/or future culture work with foraminifers.