UC Irvine

The annual cycle of the distribution of nitrate and ammonium concentrations in the PROBES area of the southeastern Bering Sea was highly interactive with the physical and biological processes. Nitrate concentrations were replenished over the shelf during the autumn and winter at a very uniform rate until the spring bloom commenced. In the middle shelf after nitrate concentrations were depleted in the upper mixed layer during the spring bloom, large quantities of ammonium were produced in the bottom layer. Cross-shelf diffusion, vertical diffusion, vertical mixing by storms, benthic release, and possibly nitrification interacted to supply nitrogen utilized by primary production. Nitrogen uptake by photosynthetic processes as estimated by nitrate depletion and nitrogen isotope measurements agreed with primary production estimates made by radiocarbon uptake rate measurements and ∑CO2 budgets. © 1985.