Description: Pelagic processes and their relation to vertical flux have been studied in the Norwegian and Greenland Seas since 1986. Results of long-term sediment trap deployments and adjoining process studies are presented, and the underlying methodological and conceptional background is discussed. Recent extension of these investigations at the Barents Sea continental slope are also presented. With similar conditions of input irradiation and nutrient conditions, the Norwegian and Greenland Seas exhibit comparable mean annual rates of new and total production. Major differences can be found between these regions, however, in the hydrographic conditions constraining primary production and in the composition and seasonal development of the plankton. This is reflected in differences in the temporal patterns of vertical particle flux in relation to new production in the euphotic zone, the composition of particles exported and in different processes leading to their modification in the mid-water layers. In the Norwegian Sea heavy grazing pressure during early spring retards the accumulation of phytoplankton stocks and thus a mass sedimentation of diatoms that is often associated with spring blooms. This, in conjunction with the further seasonal development of zooplankton populations, serves to delay the annual peak in sedimentation to summer or autumn. Carbonate sedimentation in the Norwegian Sea, however, is significantly higher than in the Greenland Sea, where physical factors exert a greater control on phytoplankton development and the sedimentation of opal is of greater importance. In addition to these comparative long-term studies a case study has been carried out at the continental slope of the Barents Sea, where an emphasis was laid on the influence of resuspension and across-slope lateral transport with an analysis of suspended and sedimented material.

Description: Nutrient and oxygen levels and ratios, primary production and data on bacterial activity recorded during an enclosure experiment carried out in July/August 1974 in Kiel Bight are presented and discussed. Considerable amounts of nutrients were released from the sediments due to density displacement of interstitial water and this was found to have a direct effect on phytoplankton production. Ammonia levels outside the enclosure were low and, in contrast to other nutrients and oxygen which were highly correlated with each other, ammonia showed no correlation with any other parameter. Presumably, ammonia released from the sediments escaped detection due to rapid uptake by phytoplankton. Reactive nitrogen, specifically ammonia thus seemed to be the limiting factor for primary production during the experiment. Sediment flushing also led to increased bacterial numbers and activity in the water column, however, this effect could only be measured inside the enclosure. These aspects of sediment/water interaction and their effect on the dynamics of shallow coastal ecosystems are discussed.