C-2 



QUALITATIVE ECOSYSTEM DESCRIPTION 



A conceotual model diagram of the Antarctic marine 

 ecosystem is presented in Ficrure 1. Boxes indicate eco- 

 system components . Any organism found south of the Con- 

 vergence can be placed into one cf the ccrxartrr.er.ts . 

 Dissolved organic and inorganic nurrients and organic 

 detritus are also included. These nonliving components 

 are nuTrier." '::Is r.ecessary to comolete the nutrient 

 cycles . 



In Figure I, bcx size is net related tc -ctal standing 

 stocks of the compartments. Quantitative estimates cf 

 standing stocks are given in Figure 3 . 



Arrows show material exchange ar-d rrophic (feeding) 

 flows among ecosystem com.iDonents . The dark arrows repre- 

 sent pathways with the largest annual total flows. They 

 also indicate the most imDcrrant Dredator-prey relaticn- 

 ships . 



Nurrienrs enter the sysrem through ur-.rellir.g . They 

 are lost through A.ntarctic Bottom. Water f zr-.^zLzr. . through 

 sinking to the sediments , and through harvest cr em.igra- 

 tion of anim.al3 . Broken arrov/s represent the conrribution 

 of dead organisms to organic detritus. 



't::p lank ten prcvice SO to 90% of the primary pro- 

 or carbon fixation, in Antarctic waters (El-Saved, 

 sen, 1375). Phytoplankton are single celled 

 planes. Dominant Antarctic species are diatoms (Holm- 

 Hanser. , ee al. , 1977). Other plants in rhe ecosystem are 

 algae growing in the bottom layer of one-year sea ice 

 which may provide 10 to 15% of annual prim.ary production 

 '?-r.t, 1953, 1968, 1971) and some seaweeds (BIOKiASS, 1977). 



-r^f^e 



Kr: 



Krill are euphausiid cruseaceans which are eaeen by 

 baleen whales. They are classified as zooplankton or 

 m.icronekton. The main species are Euphausi a superba , E. 

 crustalloropkias , and Thysanoessa macrura (Nemotc , 1959). 

 Frc.- ehe Antarctic Convergence south, the predominant krill 

 species is Euphausia superba (Marr, 1952). Euphausia 

 superba is the only krill species of commercial interest. 



Krill play a very important role in the dynamics of 

 the Ajntarctic marine ecosystem. They are the main herbi- 

 vore. '.-Jith zooplankton, rhe-" facilitate nuerier.e 



