Geoscience Reference
In-Depth Information
A
B
Antarctica
Figure 1
Map of Antarctica. Grey star indicates the study area. Photographs
(
#
Julian Gutt, AWI) illustrate the three-dimensional structure of the benthic Wed-
dell Sea community (A) and the habitat provisioning nature of most of the species (B).
and retreat of sea ice, the geographically most extensive seasonal environ-
mental oscillation pattern in the world. Consequently, there are a number of
unusual ecological features, such as a high degree of endemism (
Arntz et al.,
1994, 1997
) and the occupation of the 'pelagic swarm fish niche' by euphau-
siid crustaceans (
Bergstrom and Chown, 1999; Ichii and Kato, 1991
).
The high Antarctic Weddell Sea shelf (
Figure 1
) is situated between 74 and
78
S with a length of approximately 450 km. Water depth varies from 200 to
500 m. Shallower areas are covered by continental ice, which forms the
coastline along the eastern and southern part of the Weddell Sea. Due to
the weight of the continental ice, the shelf edge lies 500-600 m below sea
level. The shelf area contains a complex three-dimensional habitat with large
biomass, intermediate to high diversity in comparison to boreal benthic
communities and a spatially patchy distribution of organisms (
Arntz et al.,
1994; Dayton, 1990; Teixido et al., 2002
).
The early trophic studies of the Southern Ocean ecosystem focused on a
seemingly simple pelagic food chain consisting of about three trophic levels
(primary production—krill—krill predators,
Tranter, 1982
), with little atten-
tion being paid to organisms below the size of krill or to members of the
benthic food web (
Clarke, 1985
). However, the rich epibenthic communities
in the Weddell Sea (
Arntz et al., 1994
) are dominated by large filter feeding
sponges which serve as habitats and food sources for numerous other benthic
