DISTRIBUTION OF ANTARCTIC MACROPLANKTON 



115 



The main plankton survey has usually been carried out near the middle of the season, 

 and in those years in which further hauls have been made later in the summer there has 

 been evidence of a reduction in the amount of plankton towards the autumn, at any 

 rate on the north side of the island. 



Fig. 30. Distribution of plankton quantities around South Georgia, 1930-1, Sts. WS 565-75. 



The following list includes all the N 100 B samples taken in the immediate vicinity 

 of South Georgia during the period 1927-31, and shows the average number of organ- 

 isms per haul for each group of stations. 



Average number 

 Number of organisms 



Date 

 1927-8 Feb .-March 



April 



1928-9 Aug.-Sept. 

 October 

 November 

 Dec-Jan. 



April 



1929-30 October 

 Jan -Feb. 



May 



1930- 



November 

 March 



Station 



WS 144-93 

 WS 196 



WS 257-96 

 WS311 

 WS313 

 WS 321-72 

 WS 417-26 



WS464 



3°°-5 8 

 393 



475-525 

 WS 565-75 



Position 



South Georgia survey 

 South-west side of South Georgia 



South Georgia survey 

 South-east of South Georgia 

 South-east of South Georgia 

 South Georgia survey 

 South side of South Georgia 



North side of South Georgia 

 South Georgia survey 

 North side of South Georgia 



South Georgia survey 

 North side of South Georgia 



of hauls per haul 



In Fig. 31 all four seasons are taken together and the average number of organisms 

 per haul for each group of stations is plotted according to the month or mean date at 

 which the stations were taken. As would be expected the plankton is much richer in the 

 summer than in the winter, but the regularity of the curve is broken by the low figure 

 for the 1928-9 survey (December-January). It is difficult to account for this, but the 

 patchiness of the plankton may be seen from Figs. 24, 26 and 27, and might well result 

 in irregularities in the curve. 



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