Sambrotto, R. N. Lamont-Doherty Earth Obserevatory, 914-365-8150
, . N. ,
NEW (NITRATE) AND REGENERATED NITROGEN PRODUCTION IN THE ANTARCTIC POLAR FRONT REGION ALONG 170 DEGREES EAST
Incubation measurements of the rates of nitrate and urea uptake and ammonium uptake and regeneration were measured during two time periods of the 1997-98 growing season (Dec., 97- Jan. 98 and again during Feb., 98 - Mar. 98; early and late Austral summer) in the APF region along 170 degrees east. Rates of new production were greatest north of the APF. Temporally, rates of new production were greater throughout the region in the early summer, although the difference between the two sampling times was most dramatic south of the front, were new production fell to roughly a third of the rates measured earlier in the season. This decrease occurred despite consistently large concentrations (> 14 micromolar) of nitrate in surface waters throughout the region in both sampling periods. Rates of urea and ammonium uptake also decreased, but not as much as those for nitrate. The maintenance of elevated rates of ammonium regeneration, together with the accumulation of roughly 1 micromolar ammonium in surface waters south of the front, suggest the collapse of net growth and the dominance of heterotrophic conditions here in late summer.
Day: Thursday, Feb. 4
Time: 04:45 - 05:00pm
Location: Sweeney Center