Geochemistry and ecology of the Namibian upwelling system - Cruise No. MSM17/3 - January 30- March 07, 2011 - Walvis Bay (Namibia)-Dakar (Senegal). (English)

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Cruise MSM 17/3 onboard MARIA S. MERIAN was dedicated to the GENUS (Geochemistry and Ecology of the Namibian Upwelling System) project and represented the third field campaign within this program since 2009. The scientific work focused on the northern Benguela region between Lüderitz (26.6°S) and Kunene (17.25°S) under low to moderate upwelling conditions during austral summer and aimed to clarify relationships between climate change, biogeochemical cycles of nutrients, and ecosystem structure in one of the largest upwelling ecosystems. The cruise comprised empirical studies of processes and rates of ocean circulation, biogeochemical cycling of nutrients between the water column, biota and the sediments, trophic interactions and energy flows. Overall, the cruise was highly successful as we were able to conduct sampling at 97 stations without any technical or instrumental failure throughout the expedition. As a result it was possible to incorporate a number of additional stations into the initial cruise plan which allowed some of our research tasks to be supplemented. In addition to routine shipboard operations such as CTD casts and the deployment of various plankton nets and a multicorer we also recovered and redeployed a long-term mooring off Walvis Bay (23°S) and we were also able to deploy and recover a short-term oceanographic mooring and drifter system equipped with oceanographic sensors and a sediment trap. Unusual weather conditions prevailed, which led to a poleward shift of the Angola-Benguela Frontal Zone in the northern part of our study area, evidenced by the presence of subtropical water masses of Angola-Gyre origin at the northern stations off the Kunene River, accompanied by a shift in biota.