C-16 



(Gulland, 1970) for krill, a wet weight biomass of 225 x 10 

 tons can be calculated. Working on a production to biomass 

 argument, with a production to biomass ratio of 1.8:1 (Allen, 

 1971) and a production estimate of 330 x 10^ tons as derived 

 from the chart in Figure 3, a biomass estimate of 183 x 10^ 

 tons is calculated. High range of krill biomass estimates 

 is represented by 930 to 1950 x 10^ tons (Makarov and Shev- 

 kov, 1972). 



Krill biomass estimates represent a summer or maxi- 

 mum standing stock. Annual average values are lower. For 

 the remainder of the paper, discussions and calculations 

 use the value of 25 x 10^ tons for an annual average and 

 600 X 10^ tons for a summer maximum biomass. 



Figure 2 lists estimates of population sizes for the 

 compartments of the Antarctic marine ecosystem as in Figure 

 1. 



Phytoplankton production values are reliable. Exten- 

 sive data collection over the whole southern ocean has 

 contributed to the estimates. Recent estimates center 

 around the range of 25 to 35 gC/m /year, similar to produc- 

 tion values in other oceanic waters. However, in the Ant- 

 arctic, production is concentrated in the summer season 

 rather than spread throughout the year. 



Krill estimates are not reliable. They are based on 

 speculations, not quantitative data. However, an estimated 

 standing stock range of 250 to 600 x 10" tons and an annual 

 production rate of 300 x 10" tons are compatible with 

 phytoplankton production estimates. A primary production 

 estimate of 25 gC/m^/year yields 9500 x 10° tons available 

 to herbivores each year. If half of that is consumed by 

 krill with only a 10% assimilation efficiency, an annual 

 krill production of 450 x 10^ tons can be supported. 



Other Zooplankton 



Because of the difficulties of sampling zooplankton 

 in patches and of taking net tows in pack ice , reliable 

 estimates of non-krill zooplankton are not available. It 

 is usually assumed as in Gulland (1970) that the biomass 

 of other zooplankton is the same as that of krill. This 

 estimate is a very soft number and not reliable. However, 

 the lack of reliability is not significant because of low 

 utilization of non-krill zooplankton in the food chain. 

 An indication of relative abundance of krill and other 

 zooplankton would be useful. A specific population esti- 

 mate, however, is much more important for krill than it 

 is for other zooplankton. 



