NITRATE DISTRIBUTION IN SUBARCTIC NORTHEAST PACIFIC OCEAN

Data are presented on the distribution of nitrate in the subarctic Northeast Pacific Ocean. Over most of the area nitrate is present at the surface throughout the year at a concentration above that limiting phytoplankton growth. However, within coastal regions and south of about 45°N, nitrate may become depleted during the spring and summer. It is suggested that the maintenance of high nitrate concentrations over much of the area is due to relatively intensive entrainment of deep water into the upper zone coupled with a slow rate of removal of nitrate by the primary producers. Nitrate depletion in the southern area may be explained by less intensive entrainment of deep water and the utilization of nutrients by a subsurface phytoplankton maximum beneath the seasonal thermocline. © 1969.