In this paper the results from a workshop of the OSPAR Intersessional Correspondence Group on Eutrophication Modelling (ICG-EMO) held in Lowestoft in 2007 are presented. The aim of the workshop was to compare the results of a number of North Sea ecosystem models under different reduction scenarios. In order to achieve comparability of model results the participants were requested to use a minimum spin-up time, common boundary conditions which were derived from a widerdomain model, and a set of common forcing data, with special emphasis on a complete coverage of river nutrient loads. Based on the OSPAR requirements river loads were derived, taking into account the reductions already achieved between 1985 and 2002 for each country. First, for the year 2002, for which the Comprehensive Procedure was applied, the different horizontal distributions of net primary production are compared. Furthermore, the differences in the net primary production between the hindcast run and the 50% nutrient reduction runs are displayed. In order to compare local results, the hindcast and reduction runs are presented for selected target areas and scored against the Comprehensive Procedure assessment levels for the parameters DIN, DIP and chlorophyll. Finally, the temporal development of the assessment parameter bottom oxygen concentration from several models is compared with data from the Dutch monitoring station Terschelling 135. The conclusion from the workshop was that models are useful to support the application of the OSPAR Comprehensive Procedure. The comparative exercise formulated specifically for the

[1] The region off Cape Blanc along the northwest African coast is dominated by persistent upwelling and strong activity of small-scale eddies, filaments, and jets. Vertical particle camera profiles obtained during recent cruises in this region show that there exist two well-marked maxima of particle abundance in the water column, one at the surface and the other in subsurface layers between 200 m and 400 m depths. Using a highresolution (2.7 km) terrain-following coordinate ocean model with built-in ecosystem and sediment transport modules, we show that the surface particle maximum can be explained by local productivity, while the deeper, subsurface particle cloud most likely originates from particulate material eroded from the shallow shelf and transported offshore by vigorous filament activity and dynamic features of the flow. In the numerical experiments, particles are produced either by primary production in the surface layer or from prescribed sediment sources to mimic suspension and erosion along the shelf areas. Good agreement of modeled particle distributions with the data is achieved with a typical settling velocity of 5 m day À1. Time-averaged effective transport patterns of particles reveal distinct maxima between 20.5°N and 23.5°N off Cape Blanc. In the south of Cape Bojador and off Cape Timiris, on the other hand, the effective transport distance patterns suggest energetic offshore activity.Citation: Karakaş, G., N. Nowald, M. Blaas, P. Marchesiello, S. Frickenhaus, and R. Schlitzer (2006), High-resolution modeling of sediment erosion and particle transport across the northwest African shelf,

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The ocean off NW Africa is the second most important coastal upwelling system with a total annual primary production of 0.33 Gt of carbon per year (Carr in Deep Sea Res II 49:59-80, 2002). Deep ocean organic carbon fluxes measured by sediment traps are also fairly high despite low biogenic opal fluxes. Due to a low supply of dissolved silicate from subsurface waters, the ocean off NW Africa is characterized by predominantly carbonatesecreting primary producers, i.e. coccolithophorids. These algae which are key primary producers since millions of years are found in organic-and chlorophyll-rich zooplankton fecal pellets, which sink rapidly through the water column within a few days. Particle flux studies in the Mauretanian upwelling area (Cape Blanc) confirm the hypothesis of Armstrong et al. (Deep Sea Res II 49:219-236, 2002) who proposed that ballast availability, e.g. of carbonate particles, is essential to predict deep ocean organic carbon fluxes. The role of dust as ballast mineral for organic carbon, however, must be also taken into consideration in the coastal settings off NW Africa. There, high settling rates of larger particles approach 400 m day À1 , which may be due to a particular composition of mineral ballast. An assessment of particle settling rates from opal-production systems in the Southern Ocean of the Atlantic Sector, in contrast, provides lower values, consistent with the assumptions of Francois et al. (Global Biogeochem Cycles 16(4):1087. Satellite chlorophyll distributions, particle distributions and fluxes in the water column off NW Africa as well as modelling studies suggest a significant lateral flux component and export of particles from coastal shelf waters into the open ocean. These transport processes have implications for paleoreconstructions from sediment cores retrieved at continental margin settings.