S. Kristiansen et al., NITROGEN CYCLING IN THE BARENTS SEA - SEASONAL DYNAMICS OF NEW AND REGENERATED PRODUCTION IN THE MARGINAL ICE-ZONE, Limnology and oceanography, 39(7), 1994, pp. 1630-1642
The uptake rates of nitrate, ammonium, and urea were measured with a N
-15 technique during seven cruises in the marginal ice zone (MIZ) in t
he Barents Sea in 1984-1988. The results from all the cruises were poo
led to obtain means for the prebloom, bloom, transition, and postbloom
periods. New production-nitrate uptake as percent of total uptake-was
high (92-96%) during the prebloom and bloom periods and decreased the
reafter. Regenerated production - summed ammonium + urea uptake as per
cent of total uptake-increased through the bloom cycle and was at its
maximum (75-93%) during the postbloom period. New production (as perce
nt of the total) was higher in the ice-filled parts than in the ice-fr
ee parts, especially during the postbloom period. Nitrate uptake rates
, however, were highest (9-25 nM h(-1)) in open and ice-free parts dur
ing the bloom and transition period. Mean growth rate of phytoplankton
-nitrogen was 0.5 doubling d(-1) during the bloom and ranged from 0.3
to 0.4 doubling d(-1) after the bloom. We hypothesize that primary pro
duction in the MIZ is not nutrient limited but is proportional to phyt
oplankton standing stocks.