Wilkerson, F. P. Romberg Tiburon Centers, fwilkers@sfsu.edu
Dugdale, R. P. Romberg Tiburon Centers, rdugdale@sfsu.edu
Schaefer, M. Romberg Tiburon Centers, mschaefr@sfsu.edu
Marchi, A. Romberg Tiburon Centers, amarchi@sfsu.edu
Hogue, V. Romberg Tiburon Centers, vhohue@sfsu.edu

Our previous work in Monterey Bay has shown the important contribution by the larger cell sized (> 5 um) phytoplankton in taking up upwelled nitrate. During 1998 we carried out N uptake and assimilation studies every two months, occupying a station downstream from the upwelling center at Davenport. Nitrogen uptake was measured using 15N labelled nitrate or ammonium and samples were collected for in vitro nitrate reductase and glutamine synthetase assays. Our hypothesis is that during upwelling favorable conditions when nitrate concentrations in the bay are high, nitrate uptake and nitrate reductase activity by the larger cell sized autotrophs will dominate, in contrast to low nitrate conditions when ammonium uptake and glutamine synthetase by the smaller cells will dominate. Our ultimate goal is to determine which phylogenetic groups are responsible for nitrate and ammonium uptake and assimilation by using functional gene probes for the nitrogen transformation enzymes.
Day: Thursday, Feb. 4
Time: 08:45 - 09:00am
Location: Sweeney Center
Code: SS39TH0845S