SEASONAL AND ANNUAL DYNAMICS OF PARTICULATE CARBON FLUX IN THE BARENTS SEA - A MODEL APPROACH

Mathematical modelling was used to explore the seasonal and annual var iability of primary, new and secondary production as well as sedimenta tion between 72-degrees and 80-degrees-N in the central Barents Sea du ring the years 1981 to 1983. 1981 and 1982 were years with extensive i ce coverage while 1983 experienced little sea-ice. The phytoplankton ' 'spring'' bloom started usually in April/May at about 75-degrees-N and was delayed from May/June in the south to August/September in the nor th as a function of thermal stratification and sea-ice dynamics. The m odel indicates that several, simultaneous spring bloom events, separat ed in space, can be found, especially during years with low ice covera ge. The annual estimates of primary production, secondary production a nd sedimentation decreased on average from 73, 7.3 and 48 to 18, 1.8 a nd 9 g C m - 2 year - 1 between the southern and the northern part of the Barents Sea respectively. The annual estimates of particulate carb on flux were much higher in 1983 compared to 1981-1982, especially in the north where up to 6 times higher rates were calculated for 1983. T he number of zooplankton species present in spring in the southern Bar ents Sea is governed by over-wintering success, but probably also infl uenced by advection of Atlantic water. The model was run for Atlantic water with 10,000, 3,000 or none copepods per m2 present in March, ind icating that sedimentation can vary between 38 and 61 g cm-2 year-1 du e to zooplankton grazing alone. This suggests that the supply of organ ic carbon to the aphotic zone of the Barents Sea is only partly determ ined by the strength and duration of phytoplankton blooms, but strongl y influenced by zooplankton dynamics.