MICROPLANKTON 



225 



Distribution of the main groups of microplankton 



First survey 

 The estimated numbers of the main groups of microplankton present in the hauls from each station 

 are given in Table 14, with the approximate distances of the stations from the nearest point on the 

 coast. The fractions examined, number of species or other categories recognized in each count, and 

 the settlement volumes of the catches are also given, together with percentages of the main groups 

 relative to the totals, as shown by the column headings. These data, excepting the percentages, are 

 also shown graphically in Figs. 58-64, designed to aid general description of the results on each 

 separate line of stations. 



2o°- 



25 - 



WE POINT 



WALVIS BAY 



s 

 o 

 u 



T 

 H 



30. 



SYLVIA HILL 



ORAVCE 

 R. 



SURVEY I 



1 1 1 1 1 1 r 



0° 15° EAST 



Fig. 57. Distribution of the microplankton, estimated totals per net haul, survey I, March 1950. 



(Station numbers are shown in Fig. 1.) 



Fig. 57 shows the estimated microplankton totals in the first survey contoured logarithmically. 

 From this the concentration of the heaviest catches in the coastal waters, more particularly in the 

 centre of the region, is quite clear. The zone of rich coastal microplankton was narrow in the south, 

 off the mouth of the Orange river, and reached its greatest extent seawards off Walvis Bay. The increase 

 in width of the zone with decreasing latitude up to this point was interrupted by one deep constriction 

 at the seaward end of the Sylvia Hill line. North of Walvis Bay the coastal microplankton was much 

 less abundant, though still richer, especially in phytoplankton, than that of the offshore waters. The 



