i8 



DISCOVERY REPORTS 



Some idea of the later autumn phosphate values of the surface water in the southern 

 region near Enderby Land may be had from the results of section 6 in 45 ° E towards 

 the Crozets in the first half of May 1934 (Sts. 1361-1366, Plate X), and section 7 in 

 late April 1932 (Sts. 855-864, Plate XII). The observations in the Antarctic zone are 

 given in Table II. The two ice-edge stations were made in comparable positions about 

 18 days apart though in different years. The phytoplankton conditions were very 

 different; at St. 1361 a very small catch was recorded, whilst at St. 855 there was a rich 

 phytoplankton concentration for the time of the year and the latitude. From the above 



Table II 



* Ice-edge station. 



table it is seen that at St. 1361, a station where a poor diatom catch was found, the 

 surface phosphate was as high probably as it is at any time of the year, and the silicate 

 was reduced, whilst St. 855, with a rich phytoplankton, had a low phosphate content 

 in the surface and a silicate content equal probably to the maximum at any season at 

 this latitude. The observed nutrient salt values do not agree either with one another or 

 with the amount of phytoplankton found at each station ; it would have been expected 

 that St. 855 would show low values for both phosphate and silicate contents, and 

 St. 1 361 high values for each nutrient salt if there were an immediate connexion between 

 nutrient salt concentration and the density of the phytoplankton. However, we can 

 assume that the rich phytoplankton found at St. 855 was due primarily to a localized 

 concentration which was now, i.e. late April, a fraction of its former concentration. 

 This follows because in late April the concentration was large, and therefore it can be 

 argued that at the end of February it must have been greater still unless the April 

 concentration were due to an autumnal outburst ; this, however, is unlikely in view of 

 the nature and volume of the catch. The ice-edge phytoplankton is characterized by 

 a long steady growth period from November to the end of March, and, exceptionally, the 



