Bidigare, R. R. University of Hawaii, bidigare@soest.hawaii.edu
Hanson, K. L. University of Hawaii, khanson@soest.hawaii.edu
Popp, B. N. University of Hawaii, popp@soest.hawaii.edu
Landry, M. R. University of Hawaii, landry@soest.hawaii.edu
Buesseler, K. O. Woods Hole Oceanographic Institution, kbuesseler@whoi.edu
Wakeham, S. G. Skidaway Institute of Oceanography, stuart@skio.peachnet.edu
Freeman, K. H. Pennsylvania State University, kate@pop2server.essc.psu.edu
Millero, F. J. University of Miami, fmillero@rsmas.miami.edu

 
IRON-STIMULATED CHANGES IN CARBON ISOTOPIC FRACTIONATION AND EXPORT BY EQUATORIAL PACIFIC PHYTOPLANKTON
 
Iron fertilization experiments in the equatorial Pacific show that the growth of "modern" phytoplankton is limited by iron availability. However, recent geological evidence from the equatorial Pacific and Southern Ocean suggests that iron did not stimulate productivity during glacial intervals, and calls into question this mechanism for controlling Pleistocene carbon dioxide levels. We present stable carbon isotopic data for phytol (an algal biomarker) which document up to 7 per mil isotopic enrichment during iron fertilization. We evaluate our data with a laboratory-derived model and show this variability is largely the result of elevated growth rates. Phytoplankton growth and isotopic enrichment were accompanied by a seven-fold increase in the export of particulate organic carbon as estimated from Th-234 activities. This is the first data set to provide direct evidence that enhanced productivity following iron stimulation can lead to both increased particulate export and an associated isotopic signal in an algal biomarker. Based on these results, we propose biomarker isotopic data be used in conjunction with paleo-carbon dioxide records to reconstruct paleo-growth rates. This approach provides a means to test for Pleistocene iron-stimulated changes in algal growth, in the geological record.
 
Day: Monday, Feb. 1
Time: 02:15 - 02:30pm
Location: Eldorado Hotel
 
Code: SS32MO0215E