The Role of Body Size in Complex Food Webs: A Cold Case - Advances in Ecological Research - page 191

Figure 2 Food web of the high Antarctic Weddell Sea. The vertical axis displays the
short-weighted trophic level ( Williams and Martinez, 2008 ). Nodes are scaled relative
to body size. Image created with FoodWeb3D ( Williams, 2010; Yoon et al., 2004 ).
Antarctic Weddell Sea collected since the 1983. The web had a relatively low
connectance of 0.067 in comparison with other marine webs ( Table 1 ), where
connectance varied between 0.22 for the Northeast US Shelf system ( Dunne
et al., 2004; Link, 2002 ) and 0.24 for the Benguela food web ( Yodzis, 1998 ;
food web analyzed in Dunne et al., 2004 ). Linkage density was the highest
reported so far with 33.19, in comparison with 7.0 for the Benguela web
and 17.8 for the Northeastern US Shelf. In the Weddell Sea food web, 6.7%
of the Weddell Sea species were top predators, (species with no consumers),
79.7 % were intermediate species (with predators and prey) and 13.6% species
were basal species (primary producers which are only prey). The percentages
of intermediate and top species were well in the range with the Benguela and
Northeastern US Shelf system, but in comparison, the higher percentage of
basal species (13.6% vs. 3-7%) reflected the better resolution at the basal
level (i.e. Dunne et al., 2004 ). The high degree of omnivory (67.8%)
was comparable with omnivory values reported for other marine webs
( Dunne et al., 2004 ).
These results reflected common features of the Weddell Sea system, differ-
ences in foraging behaviour and the extreme high degree of omnivory of
marine consumers, and explained the high linkage density observed. Most
fish and marine invertebrate species were opportunistic generalists with a
high trophic generality (Brenner et al., 2001; Dahm, 1996; Jacob et al., 2003,
2005 ) as indicated by the high number of documented feeding links.