HR: 14:15h
AN: OS52H-02    [PDF]
TI: High-Resolution TCO2 Measurements at the New England Shelfbreak Front: Implications for Biogenic Alkalinity Uptake
AU: * Bandstra, L
EM: lbandstr@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Administration Building, Corvallis, OR 97331 United States
AU: Hales, B
EM: bhales@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Administration Building, Corvallis, OR 97331 United States
AU: Takahashi, T
EM: taka@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Route 9W, Palisades, NY 10964 United States
AB: We have developed a system to accurately measure total inorganic carbon (TCO2) in a continuously flowing seawater stream at high resolution and high precision. The system is based on a gas-permeable membrane contactor, which allows us to quantitatively strip the CO2 evolved from an acidified seawater stream with a continuously flowing gas stream. The CO2 content of this strip gas stream, which is proportional to the TCO2 of the seawater stream via a simple mass balance, is then analyzed using an infra-red gas analyzer. Laboratory results have shown that the system has a response time of 6 seconds and is able to resolve changes in signal with +/- 0.07\% precision, or better than 1.5 umol/kg. Independent coulometric analyses of check samples collected in the field have shown the accuracy to be reliable to +/- 0.1\%. Coupled with the Lamont Pumping SeaSoar system, the TCO2 system has yielded high spatial resolution distributions of TCO2 across the New England Shelfbreak Front as part of the New England Shelfbreak Productivity Experiment (NESPEX). These TCO2 data, in conjunction with collocated PCO2 measurements of similar resolution, allowed us to calculate high spatial resolution distributions of alkalinity. Differences in distributions of alkalinity relative to TCO2 shoreward and seaward of the front in the context of in situ measurements of optical backscatter and fluorescence indicated a shift in the phytoplankton assemblages as the front was crossed. We are able to distinguish between coccolithophorid production on the seaward side of the front, as indicated by a near equivalence of biogenic TCO2 and alkalinity depletion, and non-coccolithophorid production shoreward of the front, as indicated by the absence of biogenic alkalinity depletion.
DE: 4806 Carbon cycling
DE: 4835 Inorganic marine chemistry
DE: 4894 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting