Life in a cold environment - Antarctica: Global Science from a Frozen Continent - page 185

Southern Ocean deep sea. Furthermore, in the Antarctic as has been seen
elsewhere, it is becoming clear through the application of molecular biological
techniques that some

' '

traditionally regarded as having circum-Antarctic
distributions are in reality composed of several cryptic species (species which are
morphologically alike and can only be discerned using molecular tools). The
existence of such

species

in the deep-sea biota may be a more general
feature than is currently appreciated. However, megafaunal diversity has been found
to be distinctly lower in the Southern Ocean deep sea, especially below around
2300m. The most important taxa here are the Porifera and Echinodermata, which
are also known to be important in other deep-sea areas.
Through their production of Antarctic Deep Water, the Weddell and Ross seas
may be important sources for taxa now living in the Atlantic or Paci

' species ocks '

c deep oceans,
as the isothermal water masses surrounding the Antarctic continent provide an
obvious conduit for the migration of shallow-water species into the deep sea and
then transport further north. In this respect the Antarctic shelf might serve as a
' biodiversity pump ' , seeding diversi cation in the deep-sea fauna worldwide. Recent

molecular data on the gene flow in bipolar species of single-celled Foraminifera

support this hypothesis, as do data on pressure tolerance of early larval stages of the
Antarctic sea urchin Sterechinus neumayeri which can persist to at least 2000m
depth.
Given the continuing lack of comprehensive survey and biogeographic data,
even now it remains impossible to assess properly levels of endemism in the
Southern Ocean deep sea. There do appear to be systematic differences between
biological groups related to their reproductive mode. For instance, brooding isopods,
which should have reduced possibility for gene flow, occur more locally with a high

number of species and many rare, apparently ' endemic ' , species in the deep sea

( 85%). Levels of species endemism for both shelled gastropods and bivalves are

approximately 75%, while other taxa with free-living larvae, such as polychaetes,
have apparently much wider zoogeographic distributions and even lower degrees
of endemism in the Southern Ocean deep sea than on the shelf.
While the ANDEEP project has revealed patterns of biodiversity within
different faunal groups and documented that these can vary signi cantly, we still

know very little about the ecology and role of deep-sea fauna in trophodynamic
coupling and nutrient cycling in oceanic ecosystems. To fill this knowledge gap, a

successor to the ANDEEP project, the ANDEEP-SYSTCO (SYSTem COupling) has
been started within the framework of the International Polar Year (IPY). SYSTCO
aims to investigate the functional biodiversity and the ecology of dominant abyssal
species and examine the trophic structure and functioning of abyssal communities
of the Atlantic sector of the Southern Ocean, focussing on the role and feeding of the
abundant key organisms. Investigations of the Southern Ocean deep-sea food web