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: A decade of particle flux measurements providse the basis for a comparison of the eastern and western province s of the Nordic Seas. Ice-related physical and biological seasonality as well as pelagic settings jointly control fluxes in the western Polar Province which receive s southward flowing water of Polar origin. Sediment trap data from this realm highlight a predominantly physical flux control which leads to exports of siliceous particle s within the biological marginal ice zone as a prominent contributor. In the northward flowing waters of the eastern Atlanti c Province, feeding strategies, life histories and the succession ofdominant mesozooplankters (copepods and pteropods) are central in controlling fluxes. Furthermore, more calcareous matter is exported here with a shift in flux seasonality towards summer I autumn. Dominant pelagic processes modeled numerically as to their impact on annual organic carbon exports for both provinces confirm that interannual flux variability is related to changes in the respecti ve control mechanisms. Annual organic carbon export s are strikingly similar in the Polar and Atlantic Province s (2.4 and 2.9 g/m**2/y at 500 m depth), despite major differences in flux control. The Polar and Atlantic Provinces, however, can be distinguished according to annual fluxes of opal (1.4 and 0.6 g/m**2/y) and carbonate (6.8 and 10.4 g/m**2/y). Interannual variability may blur this in single years. Thus, it is vital to use multi-annual data sets when including particle exports in general biogeochemical province descriptions. Vertical flux profiles (collections from 500 m, 1000 m in both provinces and 300-600 m above the seafloor deviate from the general vertical decline of fluxes due to particle degradation during sinking. At depths〉 1000 m secondary fluxes (laterally advectedlresuspended particles) are often juxtaposed to primary (pelagic) fluxes, a pattern which is most prominent in the Atlantic Province. Spatial variability within the Atlantic Province remains poorly understood, and the same holds true for interannual variability. No proxies are at hand for this province to quantitatively relate fluxes to physical or biological pelagic properties. For the seasonally ice-covered Polar Province a robust relationship exists between particle export and ambient ice-regime (Ramseier et al. this volume; Ramseier et al. 1999). Spatial flux patterns may be differentiated and interannual variability can be analyzed in this manner to impro ve our ability to couple pelagic export patterns with benthic and geochemical sedimentary processes in seasonally ice-covered seas.

Description: Concentrations of dissolved organic carbon (DOC) and nitrogen (DON) were measured during early austral Spring 1992 at a number of stations along the 6°W meridian between 47° and 60°S. This included the Polar Front in the north, the zone of melting sea-ice in the south, and waters of the Antarctic Circumpolar Current in between. Concentrations of DOC were low in deep water (34–38 ?M) with generally similar or slightly higher values in the surface mixed layer (38–55 ?M). DOC:DON ratios are wider in surface water than in deep water, i.e. surface accumulations contain relatively C-rich dissolved organic matter. The highly variable distribution of the surface DOC was not related to hydrographic or biotic features (fronts, plankton development) indicating the lability and transient occurrence of this material. Growth rates of bacteria were determined in subsamples from 51 0.8-?m-filtered batches of seawater incubated in the dark at in-situ temperature. Thymidine and leucine uptake and bacterial biomass change as well as changes in dissolved organic carbon in the batches, and oxygen consumption in parallel incubations correlated linearly over 2 weeks of incubation which allowed extrapolation to in-situ conditions. Bacterial growth in these experiments depended strongly on the amount of initial DOC. Growth in water from greater depth (1000 m) containing 38 ?M DOC was minimal, as were DOC-decrease and oxygen consumption. Higher rates were observed in surface water slightly enriched with DOC, and highest rates in surface water amended with DOC-rich melted sea ice. Bacterial growth efficiencies (biomass C-increase vs DOC consumed) were about 30%. The experiments showed that at least 40–60% of the DOC in excess of deep water concentrations was available to bacteria.