288 



DISCOVERY REPORTS 



P 2 s MGM PM 3 

 130 -. 



120- 



ogo 

 ° o 



0088 



o 

 o o 



whales to be widely spread, but avoiding the region in the south. The distribution of 



Fin and Blue whales is shown for December in Fig. 148; the whales are widely spread 



but are not found off the south end of 



the island. In January (Fig. 149) whilst 



a few are taken to the south the majority 



are still taken in the area of higher 



phosphate content. 



Fig. 151 shows the phosphate con- 

 tent, again as an average for the top 

 50 m., round South Georgia in the sur- 

 vey of January- February 1930. Condi- 

 tions here are quite different to those in 

 December-January 1928-9. Most of 

 the area is of low phosphate content, 

 but there is a limited region of higher 

 phosphate content off the north-east 

 coast, a very small patch off the north 

 end of the island, and another region of 



100- 



90- 



B0- 



814 16 18 820 22 24 26 28 830 32 34 836 pH 

 Fig. 150. Correlations of phosphate and pH values, each 

 averaged for the top 50 m., at stations in the December- 

 January 1928-9 survey. 



high phosphate content far to the west. These, having a phosphate content of over 90 mg. 

 per m. 3 , are shaded in the figure. Except for these regions, the area would appear to 

 have been flooded with a dense crop of phytoplankton, and we should expect the 

 Euphausians, and so the whales, to be concentrated in the areas of higher phosphate 

 content. In Fig. 153 we see the actual distribution of the whales during January. The 

 main concentration of Fin whales corresponds to that of the high phosphate content — 

 there is even a small concentration off the north end of the island. The Blue whales, 

 whilst in smaller numbers, have a distribution even more closely similar to that of the 

 high phosphate values. In February the numbers of Fin whales taken (also shown in 

 Fig. 153) were only just over a quarter of the number taken in January, and so few 

 Blue whales were taken that no chart has been given by Kemp and Bennett. This 

 would suggest that a supply of food originally concentrated in the small areas had either 

 become exhausted or scattered by the end of January. In February a small concentra- 

 tion of Fin whales was found in the region of higher phosphate content far over to the 

 west. The plankton and phosphate survey took place at the end of January and beginning 

 of February — the dates are shown in the phosphate chart. Mr Hart, who has just 

 published an account (1934) of the phytoplankton of this season, shows that actually 

 there was comparatively little phytoplankton at this time. Nevertheless, the phosphate 

 values, which are exceptionally low for this area when compared with other surveys, 

 point to there having been a heavy crop of phytoplankton earlier in the season, and it 

 appears likely that a former maximum efflorescence had died down by the time the 

 survey was taken at the end of January and early February. The pH values give some 

 support to this view. Fig. 154 shows a correlation between the pH values and the 

 phosphate content in the survey, expressed as averages for the top 50 m., in which the 



