Takeda, S. Central Research Institute of Electric Power Industry, s-takeda@criepi.denken.or.jp
Nishioka, J. Central Research Institute of Electric Power Industry, nishioka@criepi.denken.or.jp
Wong, C. Institute of Ocean Sciences, wongcs@dfo-mpo.gc.ca
Johnson, W. K.. Institute of Ocean Sciences, johnsonk@dfo-mpo.gc.ca
Whitney, F. A.. Institute of Ocean Sciences, whitneyf@dfo-mpo.gc.ca

 
THE LIMITATION OF IRON, LIGHT AND TEMPERATURE TO PHYTOPLANKTON GROWTH IN THE NORTHEAST SUBARCTIC PACIFIC IN WINTER
 
Bottle incubation experiments were performed using ambient surface water in February 1998 at Station P in the northeast subarctic Pacific to test the iron-limitation hypothesis in winter. During the 7 days of incubation, controls exhibited little growth under low-light (42 uE/m2/s; 8:16h LD cycles), low-temperature (6C) and low ambient iron concentration (0.07 nM). Iron addition (1 nM) or high-temperature (13C) treatment alone did not show significant increases in Chl-a concentration compared to the controls, while Chl-a production was up 1.5 fold by high-light (170 uE/m2/s; 14:10h LD cycles) treatment. Combination of the high-light and high-temperature had a 2.3 fold increase in Chl-a level. In these high-light conditions, Chl-a concentration in <5 micron size fraction increased significantly over the first 4 days of incubation and then steadily declined, while increases of microzooplankton biomass were observed. The high-temperature and high-light treatment associated with the iron addition had the greatest effects (15.5 fold) on Chl-a biomass both in <5 micron and >5 micron size fractions. Overall, the results give strong evidence that light seems to be an important limiting factor in winter. Large phytoplankton is under the iron-limitation even in winter and microzooplankton appears to modulate the response of small phytoplankton to the increases in light and temperature.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: CS62TH0114S