Franck, V. M.. Marine Science Institute, franck@lifesci.ucsb.edu
Brzezinski, M. M.. Department of Ecology, Evolution and Marine Biology, brzezins@lifesci.ucsb.edu
Coale, K. H.. Moss Landing Marine Laboratory, coale@mlml.calstate.edu
Nelson, D. M.. College of Oceanic and Atmospheric Sciences, nelsonda@ucs.orst.edu

 
THE EFFECT OF IRON, ZINC AND SILICON AVAILABILITY ON SILICON UPTAKE ACROSS THE POLAR FRONTAL ZONE (PFZ), ANTARCTICA
 
One distinguishing feature of the PFZ in the Southern Ocean is the dramatic north to south gradient in dissolved silicon during austral spring and summer. As part of the US Southern Ocean JGOFS effort, we investigated the possibility that trace-metal limitation inhibits Si use south of the front while low dissolved silicon concentrations limit Si use north of the front. Using the radioisotope 32Si, we measured changes in Si uptake rates over time in two pairs of trace-metal enrichments, north and south of the PFZ, during austral spring (Oct-Nov, 1997) and summer (Jan-Feb, 1998). Additions of iron increased biomass-specific and total Si uptake rates 2-5 times over controls south of the front, but only 0.5-1.5 times over controls north of the front. Addition of dissolved silicon increased Si uptake rates 1-17 times in enrichments north of the front, where ambient Si was 5-15uM, but had no effect south of the front, where ambient Si was > 40uM. It appears that while ambient Fe north of the front is high enough to allow silicic acid to be depleted to rate-limiting levels, low Fe restricts Si depletion south of the front.
 
Day: Thursday, Feb. 4
Time: 02:30 - 02:45pm
Location: Sweeney Center
 
Code: SS31TH0230S