Northern Benguela Upwelling Ecosystems Case Study - Cruise No. MSM18/5 - August 23 - September 19, 2011 - Walvis Bay (Namibia) - Walvis Bay (Namibia) (English)

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The overall aim of the MSM18/5 project was a case study of the average x-z-structure of the interplay between matter transfers and marine communities downstream an upwelling center in the Northern Benguela Current Region at 20°S. For this purpose, we repeated measurements on a transect perpendicular to the coast four times within three weeks. It covered a range from 10 to 500 km distance to shore and depths between 30 and >4000m at most. The program considered forcing functions, such as wind field, Ekman transport, curl driven upwelling, insolation, stratification, and proportions of inorganic nutrient inputs by upwelling and nitrogen fixation and their influence on ecosystems structure and function. We observed successive changes in plankton communities, including microbial communities, in processes like production, respiration and remineralization of nutrients by plankton, in changing importance of new and regenerated nutrient sources, in vertical flux of particulate matter by sedimentation. Finally, the role of meroplankton patterns and the reaction of benthic communities were considered. There was a positive relationship between the pseudo-age (determined by a combination of heat flux and changes in oxygen content) and the distance to shore in the upper 30m of the water column. This supports the idea of the practicability of the Eulerian approach. The scatter was highest between 100 and 200km. This is an indication for higher mesoscale variability by filaments, eddies etc., in this area.