Abstract
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.
