o detect and track the impact of large-scale environmental changes in a transition zone between the northern North Atlantic and the central Arctic Ocean, and to determine experimentally the factors controlling deep-sea biodiversity, the Alfred Wegener Institute for Polar and Marine Research (AWI) established the deep-sea long-term observatory HAUSGARTEN in 1999, which constitutes the first, and until now only open-ocean observatory in a polar region. HAUSGARTEN observatory in the eastern Fram Strait includes 17 permanent sampling sites along a depth transect (1000 - 5500 m water depth) and along a latitudinal transect following the 2500 m isobath crossing the central HAUSGARTEN station. Multidisciplinary research activities at HAUSGARTEN cover almost all compartments of the marine ecosystem from the pelagic zone to the benthic realm. Regular sampling as well as the deployment of moorings and different free-falling systems (bottom-lander) which act as local observation platforms, have taken place since the observatory was established in summer 1999. Frequent visual observations with towed photo/video systems allow assessing large-scale distribution patterns of mega/epifaunal organisms as well as their temporal development. To determine the factors controlling deep-sea biodiversity, various biological short- and long-term experiments are carried out at the deep seafloor using Remotely Operated Vehicles (ROV) at regular intervals over the past 12 years. Since the beginning of our investigations which includes the IPY period from 2007-2009 we monitored an abyssal warming, significant alterations in the species composition in the pelagic realm, a decrease in the quality of organic matter supply to the deep sea as well as considerable shifts in both, microbial and megafauna community composition at great water depths.