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 eastem and westem provinces ofthe Nordic Seas. Ice-related physical and biological seasonality as well as pelagic settings jointly control fluxes in the westem Polar Province which receives southward flowing water of Polar origin. Sediment trap data from this realm highlight a predominantly physical flux control which leads to exports of siliceous particles within the biological marginal ice zone as a prominent contributor. In the northward flowing waters of the eastem Atlantic Province, feeding Strategie . life histories and the succession of dominant mesozooplankters (copepods and pteropods) are central in controlling fluxes. Furthermore, more calcareous matter is exported here with a shift in flux seasonality towards surnrner/autumn. Dominant pelagic processes modeled numerically as to their impact on annual organic carbon exports for both provinces confirrn that interannual flux variability is related to changes in the respective control mechanisms. Annual organic carbon exports are strikingly similar in the Polar and Atlantic Provinces (2.4 and 2.9 g m-2 y-1 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 ( l.4 and 0.6 g m-2 y-1) and carbonate (6.8 and 10.4 g m-2 y-1). lnterannual 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, l000 min 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 advected/re uspended particles) are often juxtaposed to primary (pelagic) fluxes, a pattem which is most prominent in the Atlantic Province. Spatial variability within theAtlantic 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 easonally 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 pattems may be differentiated and interannual variability can be analyzed in this manner to improve our ability to couple pelagic export pattems with benthic and geochemical sedimentary processes in seasonally ice-covered seas.

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.

Description: Results obtained from short-term (8 h to 24 h intervals) measurements of physical, chemical and biological properties of the 70 m water column from an anchor station in the Bornholm Sea over a 10-day period are presented and discussed. Phytoplankton biomass concentration and production rates indicated that the spring bloom was in progress in this period. The onset of the spring bloom occurred prior to the advent of thermal stratification. Peak growth rates, accompanied by nutrient depletion and biomass accumulation in surface layers, were concomitant with calm weather and a cloudless sky after which a part of the population was observed to sink out of the water column unimpeded by the permanent halocline. Maximum sinking rates of the dominant species, Skeletonema costatum, ranged between 30 to 50 m per day during this event. The development of the spring bloom apparently takes place in a series of events during which periods of low production alternate with periods of high production and rapid sedimentation of parts of the population.

Description: Im August 1966 wurden zwischen Cuxhaven und Edinburgh 39 Oberflachenproben in 10 sm Abstand und 17 Tiefenproben auf 5 Vertikalstationen entnommen. Es wurden die Verteilung von Temperatur, Salzgehalt, Trübung, Gelbstoff-, Chlorophyll a- und Eiweißgehalt und die Artenzusammensetzung des größeren Phytoplanktons untersucht. Folgende Wassermassen wurden beobachtet: 1. Das Wasser der Deutschen Bucht mit hohen Werten für die Trübung, den Gelbstoff-, Chlorophyll- und Eiweißgehalt. Das Phytoplankton ist durch den Reichtum an Diatomeen mit der vorherrschenden Art Rhizosolenia imbricata var. shrubsolei gekennzeichnet. 2. Das salzreiche Doggerbankwasser atlantischer Herkunft, das sehr niedrige Werte für die untersuchten biologischen Faktoren aufweist. Neben den Diatomeen werden Dinoflagellaten häufig. 3. Das Britannische Ostktüstenwasser mit einem leicht erhöhten Gelbstoffgehalt aber sonst ebenfalls sehr niedrigen Werten für Trübung, Chlorophyll a und Eiweiß. Die Kieselalgen sind von Peridineen abgelöst worden. Die Leitform ist Ceratium furca. Der Küsteneinfluß ist an der schottischen Küste sehr viel geringer als in der Deutschen Bucht. Die niedrigen Chlorophyll- und Eiweißwerte in der offenen Nordsee kennzeichnen das sommerliche Minimum in der Planktonentwicklung.