C-15 



QUANTITATIVE ECOSYSTEM DESCRIPTION 



Stock Estimates 



Phytoplankton . Estimates of phytoplankton standing 

 stock and production are derived from annual average pro- 

 duction values for a small region extrapolated to the whole 

 southern ocean. Production values are given in gC/m^/year, 

 but most of the primary production occurs from November 

 through February. The average ocean area south of the 

 Convergence is 38 x lO^km^ (El-Sayed, in press). 



2 

 An average production value of about 16 eC/m /year 



(Holm-Hansen, et al., 1977) gives 6080 x 10° metric tons 

 wet weight produced. A conversion factor of 1 gram carbon 

 to 10 grams wet weight for phytoplankton is used (Everson, 

 in press). A production average of 25 gC/m^/year .Green, 

 1975) based on data for the Ross Sea produces a tctal pro- 

 duction estimate of 9500 x 10^ tons. An estimate of 40 

 gC/m^/year (Currie, 1964) yields a production estimate of 

 15200 X 10^ tons. An average production estimate of 100 

 gC/m^/year was used by Ryther (1963). That value was a 

 purely speculative estimate based on the concept that 

 Antarctic waters are significantly more productive than 

 those of other oceans. It has been shown by field data 

 collection to be unrealist ically high. 



All of the values given here measure net carbon fixa- 

 tion rates. Losses to respiration and- losses to leakage of 

 organic matter have already been accounted for. The num- 

 bers presented here are fixed carbon which becomes avail- 

 able to herbivores. 



Krill. In spite of the commercial and scientific 

 interest in krill, accurate estimates of krill abundance 

 are not available. The lack of information is partly due 

 to sampling techniques. Normal zooplankton collecting nets 

 do not caoture krill effectively since krill are stronger 

 swimmers than most zooplankton. High speed trawls, such 

 as those used in the fishing of krill, are more appropriate 

 for quantitative sampling. They have not been used over a 

 wide enough area to provide estimates. The swarming habit 

 of krill makes their distribution extremely patchy. It is 

 difficult to extrapolate a catch inside of one swarm to the 

 southern ocean as a whole. 



Participants at the SCAR Conference on Living 

 Resources of the Southern Ocean in Woods Hole. Massachusetts 

 in 1976 discussed total krill biomass in the 200-600 x 10^ 

 tons range. On the basis of 75 x 10^ tons dry weight 



