HR: 0800h
AN: PP31C-0533    [Abstracts]
TI: Diel Changes in U/Ca of Cultured Orbulina universa from Laser ICP-MS Profiles
AU: * Russell, A D
EM: adrussel@ucdavis.edu
AF: Department of Geology University of California, One Shields Ave, Davis, CA 95616, United States
AU: Eggins, S
EM: Stephen.Eggins@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra 0200, ACT, 0200, ACT, Australia
AU: Spero, H
EM: hspero@ucdavis.edu
AF: Department of Geology University of California, One Shields Ave, Davis, CA 95616, United States
AU: Sadekov, A
EM: Aleksey.Sadekov@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra 0200, ACT, 0200, ACT, Australia
AB: Bulk analyses of U/Ca in shells of cultured planktonic foraminifera (both symbiont-bearing Orbulina universa and symbiont-free Globigerina bulloides) showed a significant decrease with increasing pH (or carbonate ion). We explored the pH effect on U/Ca in calcite of cultured O. universa further by creating high-resolution compositional profiles of individual shells using laser ICP-MS. This approach takes advantage of the diel changes in the pH of the shell microenvironment that occur in symbiont-bearing species due to uptake and release of CO₂ during photosynthesis and respiration. Samples were grown in laboratory-cultures under a 12-hour high-light (day)-12-hour dark (night) cycle, which was synchronized with transfer of living foraminifers between seawater spiked with barium (to provide a geochemical time label) and natural seawater or seawater spiked only with U. Preliminary results show that U/Ca (along with Mg/Ca) increases at night and decreases during the day. These results are consistent with previous trends observed in bulk analyses and suggest that symbiont activity (or lack thereof) has an important influence over the metal composition of calcite shells.
DE: 0419 Biomineralization
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1065 Major and trace element geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting