ANTARCTIC SURFACE WATER 



27 



chosen regions in the Antarctic. The two curves for these regions differ slightly ; that 

 for the southern region falls in general from September to the end of January and rises 

 from February to the end of May, whilst the northern curve falls steeply from 

 September to November, then falls very slowly to a minimum at the end of January 

 and rises steeply to the end of May. These rises and falls cannot always be attributed 

 to phytoplankton activity in situ, and it is suggested that the two curves are interrelated 

 and mirror the effect of phytoplankton activity in the past. 



SILICATE CONTENT AT THE SURFACE 

 The surface silicate contents at a series of stations made in February 1935 across the 

 Southern Ocean south of the South Atlantic Ocean and as far east as 44 E are given 

 in Table III. The phytoplankton conditions during the time these stations were made 

 have been discussed on p. 17 of this report. At the ice-edge in the region of io° W 

 the surface silicate value is 3200 mg., whilst towards the east the corresponding content 

 falls slightly until in 42^° E it is 2700 mg. Bearing in mind that during this cruise 

 phytoplankton production began earlier in the east than in the west it is reasonable to 

 postulate an ice-edge content of the order of 3000-3500 mg. for the surface, at least 



Table III 



* Denotes ice-edge station. 



between io° W and 42J E, before the main outburst of phytoplankton production. At 

 no station on the ice-edge anywhere around the Antarctic Continent has the surface 

 silicate content exceeded 3500 mg. at any time of the year. It is difficult to obtain an 

 accurate estimate of the amount of silicate withdrawn from the surface at the ice-edge 



4-2 



