BIOMASS AND PRODUCTIVITY DISTRIBUTIONS AND THEIR VARIABILITY IN THE BARENTS SEA

On the basis of results that largely have been derived from the Norweg ian research programme Pro Mare (1984-1989), an overview of the distri bution of biomass and productivity at different trophic levels of the pelagic Barents Sea ecosystem is presented, with comments on year-to-y ear and horizontal variations. Average biomasses for the whole Parents Sea and several years range from 2000 kg of carbon km(-2) for each of Calanus spp. and phytoplankton stocks, down to 0.1 kg carbon km(-2) f or the polar bear population. Phytoplankton blooms that deplete the wi nter nutrients give rise locally to a ''new'' productivity of 40-50 g C m(-2). Areal differences, however, are pronounced in terms of annual productivity: the ''new'' fraction is more than twice as high in the southern (Atlantic) part of the Barents Sea as in the areas north of t he oceanic Polar Front (90 vs. <40 g C m(-2) yr(-1)). Wind-generated v ertical mixing (in association with passing atmospheric depressions) a nd turbulence generated on and around banks in the southern part are c rucial in accounting for this difference. In the northern half of the Parents Sea a pronounced upper layer stability caused by the supply of meltwater from seasonal ice retards mixing so that ''new'' production is small following the depletion of winter nutrients - high productiv ity is restricted to the 20-50 km wide ice edge bloom. Year-to-year va riations in fish stocks are pronounced and have always been so there e xists no ''ecological balance'' in any meaningful sense. These variati ons are clearly related to the influx of Atlantic water to the Parents Sea (i.e. ''warm'' years are high-productive years) and, thus, ultima tely to the same forcing factors that determine climate variations in coastal Europe. Thus, sound management may diminish the annual fluctua tions in fish stock sizes but certainly cannot eradicate them. (C) 199 7 International Council for the Exploration of the Sea.