Life in the dark and cold - invertebrates of the Antarctic deep sea.

The ANDEEP expeditions have led to a large increase in knowledge about species numbers in the deep Southern Ocean (almost 90% in the case of the Isopoda), extensions of bathymetric ranges, a rediscovery of enigmatic taxa known only from single records and different oceans: The first molecular data have been obtained for deep-sea Foraminifera, Ostracoda, Isopoda and Porifera. There are many fascinating discoveries, for example, the first deep-sea records of calcareous sponges or platycopid ostracods south of the polar front. The picture emerging from these new data is quite complex and diverse and communities on the Southern Ocean deep-sea floor show different zoogeographical patterns. Taxa such as the Foraminifera and Polychaeta document the existence of strong faunal links between the deep Weddell Sea and the North Atlantic, consistent with the general direction of thermohaline circulation, whereas 585 (86%) of the SO isopod crustacean species are yet undescribed; more than half of these new species are rare and occur only at one or few sites. These divergent patterns suggest that we are only beginning to explore and understand the Southern Ocean biodiversity and much more research will be necessary in this environment in future. Interesting follow-up questions include the evolutionary significance of these different biogeographic patterns (e.g. in terms of species longevity), the factors determining whether species are rare or abundant, and the functional role of the abundant species, as well as the many rare species, in Southern Ocean deep-sea ecosystems