Primary production of the northern Barents Sea

The majority of the arctic waters are only seasonally ice covered; the nort hern Parents Sea, where freezing starts at 80 to 81 degrees N in September, is one such area. In March, the ice cover reaches its greatest extension ( 74-75 degrees N). Melting is particularly rapid in June and July, and by Au gust the Barents Sea may be ice free. The pelagic productive season is rath er short, 3 to 3.5 months in the northern part of the Parents Sea (north of the Polar Front, 75 degrees N), and is able to sustain an open water produ ction during only half of this time when a substantial part of the area is free of ice. Ice algal production starts in March and terminates during the rapid melting season in June and July, thus equalling the pelagic producti on season in duration. This paper presents the first in Situ measurements o f both pelagic and ice-related production in the northern Parents Sea: pela gic production in summer after melting has started and more open water has become accessible, and ice production in spring before the ice cover melts. Judged by the developmental stage of the plankton populations, the norther n Parents Sea consists of several sub-areas with different phytoplankton si tuations. Estimates of both daily and annual carbon production have been ba sed on in situ measurements. Although there are few sampling stations (6 ph ytoplankton stations and 8 ice-algae stations), the measurements represent both pelagic bloom and non-bloom conditions and ice algal day and night pro duction. The annual production in ice was estimated to 5.3 g Cm-2, compared to the pelagic production of 25 to 30 g Cm-2 south of Kvitoya and 12 to 15 g Cm-2 further north. According to these estimates ice production thus con stitutes 16% to 22% of the total primary production of the northern Parents Sea, depending on the extent of ice-free areas.