C-111 



EXECUTIVE SUMMARY 



The -Antarctic marine ecosystem is considered to be all 

 waters south of the Antarctic Convergence with all the 

 plants and animals living there. The ecosystem is defined 

 biologically by the distribution of Euphausia superba 

 (krill), some phytoplankton, penguins, and fish, and seals 

 which are circumpolar but restricted south of the Conver- 

 gence. Other species, most importantly whales but also 

 some fish, birds, and perhaps cephalopods , migrate across 

 the Convergence providing a link with other ecosystems. 

 The Antarctic ecosystem is defined physically through the 

 boundary of the Convergence, circumpolar upwelling and 

 input of nutrients, transport by the Circumpolar Current, 

 a uniform low temperature, fluctuating pack ice area, and 

 the polar light regime. 



Most of the primary production is accomplished by 

 phytoplankton, one celled plants. Algae in sea ice and 

 some seaweeds also contribute. Krill are the dominant 

 herbivore. Krill have an unusual ecological role since 

 they are the main prey for fish, squid, Adelie penguins, 

 fur, crabeater, and leopard seals, and baleen whales 

 (fin, sei, blue, humpback, and minke whales). Other 

 carnivores in the system not feeding on krill are toothed 

 whales (sperm, killer, and some small whales) and elephant 

 seals. Ross seals, Weddell seals, and some fish eat 

 krill incidentally. 



Sei, minke, sperm and a few killer whales are now 

 harvested in Antarctic waters. Several fish species are 

 taken in commercial quantities. Squid, birds, and crabeater 

 seals are not now harvested, but are potential commercial 

 resources . 



The earliest estimates of production in Antarctic 

 waters were made in coastal areas or at the pack ice edge, 



the most productive regions. Extrapolating those values to 

 the whole southern ocean area produced unrealistlcally high 

 values, giving the false impression that Antarctic waters 

 were far more productive than other oceans. On the basis of 

 later measurements in open ocean waters which are more 

 representative of the area overall, estimates of total 

 annual productivity have been revised downward. 



Although total annual plant production is not signifi- 

 cantly greater in Antarctic waters than in other ocean 

 areas, concentration in a short intense growing season and 

 at the edge of moving pack ice makes production appear very 

 large. Unusually short food chains allow a greater propor- 

 tion of annual production to be transferred to carnivores, 

 thus supporting very high standing stocks of mammals and 

 birds . 



