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gaps in our specific understanding of interactions within 

 Antarctic communities tremendously complicates predicting 

 likely outcomes of hioman interference. Even so, ecological 

 generalities may lend insight into future possibilities for 

 the Antarctic marine ecosystem. Three topics which relate 

 to current discussions of the Southern Ocean are competition, 

 predation, and ecosystem stability. Review of the voluminous 

 ecological literature pertaining to these areas is clearly 

 beyond the scope of this paper. Therefore, selected examples 

 will be used to illustrate the sorts of relationships present 

 in similar systems. 



In his paper on the nature of a particular Antarctic 

 marine community, Dayton (1972) reviewed some ecological 

 principles regarding competition, predation, and community 

 resilience. He cited research on competition and predation 

 in marine and intertidal invertebrates (Connell, 1961a, 

 1961b, 1970; Glynn, 1965; Paine, 1966; Dayton, 1971). These 

 studies demonstrated the striking effects which the competitory 

 and predatory pressures contributed by all members of the 

 community have on each other in shaping the community. 

 Barnacles, snails, mussels, and sea-stars compete for resources 

 and form complex predator-prey relationships. Modifying the 

 environment or manipulating the population levels of any of 

 these components had a strong effect on the whole community. 



Similar to Paine' s (1969) reference to a "keystone 

 predator" (one which has dominant influence in structuring 

 the community) , Dayton (1972) defined "foundation species" 

 as those species at low levels in the food web which contribute 

 in a major way to community structure. In communities which 

 have been manipulated, one can identify foundation species 

 which are critical to the preservation of the community 

 structure itself. Altering the birth or death rates of such 

 species can have serious consequences in altering the organization 

 and relationships within the community. Species through 

 which a significant portion of the energy and nutrients of a 

 system flow represent a fundamental unit of the system 



(e.g., krill) . If they are removed or disturbed, the 

 effects on the ecosystem can be much more dramatic than 

 disturbing species which do not occur in such critical roles 



(e.g. , whales) . 



Of immediate concern is whether or not krill fisheries 

 will impact krill stocks to the point where they, as a 

 foundation species, might be involved in a shift in community 

 structure. Would a shift in trophic relationships from a 

 phytoplankton-krill-marine mammal food chain to a phytoplankton- 

 copepod-fish food chain be facilitated by manipulating krill? 



