SUMMARY AND CONCLUSIONS 363 



gaudichaudi and Salpa fusiformis , but also to a less extent in others (pp. 254-265). The 

 seasonal changes in the zooplankton are briefly discussed (p. 265). The plankton in the 

 surface layers is considered in relation to rough weather and evidence is given to show 

 that the state of the sea has little or no bearing on the number of organisms in the sur- 

 face layers (p. 268). The possibility of a lunar influence on the plankton is considered 

 (p. 268). The distribution of the zooplankton appears to be independent of the different 

 phytoplankton communities found (p. 230). 



Part V deals with the plankton in relation to the whale fisheries, the ecological 

 interrelationship of phytoplankton and zooplankton, and the mechanism of plankton 

 distribution. 



The distribution of both Blue and Fin whales during their sojourn in Antarctic waters 

 is shown to be closely correlated with that of their food Euphausia snperba (p. 273). The 

 factors determining the distribution of E. snperba within the area are considered ; tem- 

 perature and salinity do not offer a satisfactory explanation (p. 277). The Euphausians 

 appear to be distributed away from the areas of dense phytoplankton production 

 (p. 277). Former work on the influence of phytoplankton concentrations upon fish and 

 planktonic life is reviewed (pp. 277-279). The stations at which nets for the capture of 

 macroplankton organisms were used are arranged in order of ascending phytoplankton 

 values, and the numbers of macroplankton taken are shown to be greater at stations of 

 medium phytoplankton values than at those of low or high values (p. 281). 



Since (a) reduction in phosphate content of the top 50 m. of water has been shown to 

 correspond with phytoplankton production over a little time in the past (p. 285), and 

 (b) phytoplankton production appears to be inversely correlated with the distribution 

 of Euphausia snperba, and (c) the distribution of the Blue and Fin whales is closely 

 bound up with the distribution of E. snperba, it appeared to be possible, if the 

 correlation in " b" were true, to deduce in future surveys the distribution of the 

 whales direct from a knowledge of the phosphate values. Records of phosphate 

 values together with whale distribution charts are available from three later South 

 Georgia surveys and one South Shetlands survey. In each survey the whale distribution 

 was deduced from the phosphate values and the theoretical result compared with the 

 actual results from whale fishery returns; a good degree of correlation is obtained 

 for both Blue and Fin whales (pp. 285-296). pH values were also used in conjunction 

 with phosphate values. On another survey where phosphate observations were not 

 made but phytoplankton samples were taken, the distribution of the phytoplankton was 

 deduced from that of the whales and found to agree with the results of analysis (p. 297). 

 The correlations obtained in these different surveys provide evidence of a distribu- 

 tional relationship between phytoplankton and the Euphausians, and the governing of 

 the whale distribution by the latter. In the course of this discussion the influence of 

 ocean currents upon patches of plankton is briefly considered (p. 291). 



Relative reduction in phosphate content appears to be a better index in studying the 

 zoo-phytoplankton relationship than the phytoplankton itself (p. 300). It gives a 

 measurement of phytoplankton over a little time in the past. All zooplankton organisms 



