Popp, B. N.. University of Hawaii, popp@soest.hawaii.edu
Hanson, K. N.. University of Hawaii, khanson@soest.hawaii.edu
Bidigare, R. R.. University of Hawaii, bidigare@soest.hawaii.edu
Laws, E. A.. University of Hawaii, laws@soest.hawaii.edu
Wakeham, S. G.. Skidaway Institute of Oceanography, stuart@skio.peachnet.edu

Carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in Pacific Ocean environments varies systematically with the concentration of soluble reactive phosphate (SRP). This correlation is thought to be due to effects linking nutrient levels to growth rates and cellular carbon budgets for these microalgae, and most likely results from trace-metal limitations on algal growth. We review the relationships between growth rate, dissolved nutrient concentrations and fractionation and present new data on the carbon isotopic composition of alkenones in suspended organic matter from the equatorial Indian Ocean, the oligotrophic North Pacific and the Subantarctic Southern Ocean. We also present results from ship-board measurements of growth rates of the alkenone-producing algae in the Southern Ocean and compare these results with fractionation-growth relationships developed from laboratory-based chemostat experiments. Our results show that application of a global fractionation-SRP relationship adequately describes all data. The motivation for this work is to evaluate the proposed use of carbon isotopic compositions of alkenones as a proxy record of ancient [CO2(aq)]. Our results suggest that a global relationship may be useful but that field-derived local calibrations may provide more accurate estimates of paleo-[CO2(aq)].
Day: Monday, Feb. 1
Time: 02:00 - 02:15pm
Location: Eldorado Hotel
Code: SS32MO0200E