The primary aim of this expedition was to investigate the spatial and temporal distribution, the ecology and physiology, as well as competition of co-occurring gadoid species (Atlantic cod, Polar cod, haddock) in the communities of Arctic and Atlantic influence around Svalbard. We sampled the benthic and pelagic communities (including plankton) on the shallow shelf regions of Svalbard to estimate the effects of climate change on Arctic ecosystems to obtain a picture of the entire system structure and function for a long-term monitoring program of the ‘Atlantification’ of the Svalbard region. We assessed the potential impact of changes in trophic interaction (predator-prey relations) of Atlantic cod (Gadus morhua), Polar cod (Boreogadus saida), haddock (Melanogrammus aeglefinus) and decapod crabs on the productivity and stability of benthic and pelagic communities in Arctic ecosystems, into which their distribution ranges now extend due to ocean warming. In addition to a stock assessment and distribution analysis of gadoid fish and decapod crabs, we aimed to obtain specimens of these species in the Atlantic and polar waters around Svalbard, which were transported alive back to Germany. Laboratory experiments under scenarios of climate change at the Alfred Wegener Institute then provided (and still provide) further insight into capacities for adaptation, performance and interaction of selected species of the Arctic ecosystem around Svalbard. The results will on the one hand be used in an international Norwegian-German project and the pan-Arctic data management system (Piepenburg et al. 2011), on the other hand they will flow into fisheries modelling at the University of Hamburg, the Thuenen Institute and socio-economic modelling approaches that build on the German ocean acidification project BIOACID (www.bioacid.de).