C-4 



regeneration in the euphotic zone during the growing season. 

 Plankton release organic and inorganic nutrients. Organics 

 are decomposed into inorganics which are necessary for plant 

 growth. Although upwelling brings massive amounts of 

 nutrients into the whole Antarctic ecosystem (Gordon, 1971), 

 regeneration in the euphotic zone during the spring is still 

 apparently necessary to account for the high observed levels 

 of plant growth (Green, 1975)- Krill provide the main food 

 resource for fish, cephalopods, penguins, crabeater seals, 

 leopard seals, and baleen whales (Permitin and Tarverdiyeva , 

 1972; Laws, 1977; Prevost, in press). Because krill are 

 concentrated in swarms, large animals can catch enough to 

 feed themselves adequately. The swarming habit also makes 

 harvesting feasible. The main consumers of krill are crab- 

 eater seals and cephalopods (Green, 1977). 



Other Zooplankton 



Copepods , amphipods, and chaetognaths dominate zoo- 

 plankton in the Pacific sector (Hopkins, 1971). In the 

 Antarctic ecosystem as a whole, other zooplankton may be 

 equal or greater in biomass to krill (Gulland, 1970). 

 Although other zooplankton may be as abundant as krill, 

 they are apparently not used as extensively by predators. 

 The disproportionate feeding on krill is indicated in 

 Figure 1, and is more striking from quantitative feeding 

 estimates in Figure 2. This apparent under-utilization of 

 non-krill zooplankton may be an artifact due to ignorance of 

 some aspects of Antarctic ecology. However, it is possible 

 that the dispersed distribution of other zooplankton, con- 

 trasted with krill swarms, makes them less accessible to 

 consumers . 



Ice Invertebrates 



Invertebrates associated with the sea ice algae 

 community are mainly amphipods (Andriashev, 1968) which are 

 eaten by fish fry (Knox, 1970). 



Birds 



Over 95% of the bird biomass in the Antarctic is 

 penguins. South of the Convergence, penguin populations 

 are dominated by Adelies, Pygoscelis adeliae, whose diet is 

 mainly krill (Prevost, in press). 



Fish and Cephalopods 



Cephalopods in the southern ocean are primarily squid. 

 They constitute significant portions of the diets 



