HR: 0800h
AN: OS11A-0190    [Abstracts]
TI: Active pCO₂-Control of Seawater Culture Systems for Laboratory-Based Biogeochemical Experimentation Investigating Global Ocean Acidification
AU: * Hintz, C J
EM: chris.hintz@msci.sc.edu
AF: Dept. of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States
AU: Chandler, G T
EM: tchandler@sc.edu
AF: Dept. of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States
AU: Shaw, T J
EM: shaw@mail.chem.sc.edu
AF: Dept. of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States
AU: McCorkle, D C
EM: dmccorkle@whoi.edu
AF: Dept. of Marine Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AB: The large-scale effects of anthropogenic CO₂ rise and global ocean acidification on calcifying and photosynthetic organisms are not well understood. This ongoing uncertainty fundamentally limits our ability to fully understand global carbon cycling. Field-based studies are limited to the current environmental chemistries observed throughout the world's oceans – a prohibitively resource-intensive platform for manipulative experimentation. Moreover, complex carbonate system equilibria decoupled from the atmosphere are difficult to poise and maintain in laboratory seawater-based experiments lasting longer than a few hours or days. This severely limits the scope of biogeochemical experimentation for simulating past or future ocean chemistries. To address these experimental shortcomings we developed a novel system for the stringent control of pCO₂ in culture aeration and seawater. A custom CO₂ scrubbing system was designed which removes > 99.8% of atmospheric CO₂ at 3-4 L min^-1 aeration rate. High precision mass flow controllers integrated with a modular programmable process controller precisely mix high-purity (99.95%) compressed CO₂ with the preconditioned CO₂-free air stream for aeration into the culture system. Long-term maintenance of experimental CO₂ is within ± 2 μatm when operating between 150- 2000 μatm pCO₂. The system, in its current configuration, has the ability to simultaneously manipulate and maintain 3 separate carbonate chemistries using aeration pCO₂ and seawater alkalinity in independent 400-L seawater reservoirs. Future system expansion can easily maintain 5 or more separate chemistries. The goal of this research is to develop stringent control of seawater carbonate system chemistries for the deep- sea benthic foraminifera cultures housed at the University of South Carolina Arnold School of Public Health. Current experiments are investigating trace metal foraminiferal paleoproxy signatures that appear correlated with [CO₃^2-] very near calcite saturation. Our system's control of equilibrium pCO₂ allows precise maintenance of the culture's carbonate system chemistry very near, above and below calcite saturation, while maintaining realistic values for alkalinity and dissolved inorganic carbon. This research was funded by the University of South Carolina Arnold School of Public Health and the National Science Foundation - OCE 0647891.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 1694 Instruments and techniques
DE: 4806 Carbon cycling (0428)
DE: 4894 Instruments, sensors, and techniques
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting