Seasonal and diel changes in nutrient concentrations and nitrogen assimilation rates were used to assess the effects of NH4+ on NO3- assimilation. Surface-water NO3- concentrations ranged from 6 to 17 μM while NH4+ concentrations ranged from 0 to 0.4 μM. Total N assimilation ranged from 84 to 732 nM d–1...
Ammonium uptake and regeneration rates were measured in time course experiments with 15N as a tracer. Both ammonium uptake and regeneration rates measured over 12 to 18 h remained essentially constant. However, as the length of the incubations increased the amount of usable data decreased dramatically due to substrate depletion...
Insight into the dependence of benthic communities on biological and physical processes in nearshore pelagic environments, long considered a ``black box,'' has eluded ecologists. In rocky intertidal communities at Oregon coastal sites 80 km apart, differences in abundance of sessile invertebrates, herbivores, carnivores, and macrophytes in the low zone were...
The purpose of this study was to test the hypothesis that NH4+ uptake by heterotrophic bacteria in the subarctic Pacific is C limited. Addition of glucose (0.5–1.0 μM) stimulated NH4+ uptake in unfractionated water but had no effect on bacterial abundance. Glucose stimulation of NH4+ uptake was even greater in...
Chlorophyll a concentrations were measured as a function of depth from 28 to 48°N along 152°W in March 1991 with Whatman GF/F and 0.2‐µm Nuclepore filters. Surface Chl a concentrations measured with 0.2‐µm Nuclepore filters were up to fourfold higher than those measured with Whatman GF/F filters. The largest difference...
It has been suggested that production in offshore waters of the subarctic Pacific is limited by availability of dissolved Fe. Although that is not yet adequately established, the functional consequences of the limitation (if it exists) can be characterized from the results of the Subarctic Pacific Ecosystem Research (SUPER) program....
PN-specific, absolute, and Chl a-specific nitrate uptake rates were measured during two upwelling seasons and one winter off Oregon. Although PN-specific and absolute uptake rates showed no dependence on nitrate concentration, Michaelis-Menten kinetics applied when the uptake rates were normalized to Chl a. Chl a-specific nitrate uptake rates were saturated...
The uptake rates of nitrate, ammonium, and urea were measured with a ¹⁵N technique during seven cruises in the marginal ice zone (MIZ) in the Barents Sea in 1984–1988. The results from all the cruises were pooled to obtain means for the prebloom, bloom, transition, and postbloom periods. New production—nitrate...
PURPOSE: To determine physical, plankton and nutrient/chemical conditions over the continental
margin for climate change studies in NE Pacific. In particular, to make CTD and CTD/rosette and net
tow stations along 4 lines (off Newport, Coos Bay, Crescent City and Eureka), to make additional
stations along a fifth line (off...