ANTARCTIC SURFACE WATER 



35 



Orkney Islands. North of the Ross Sea in 1934 the available data indicate that even 

 greater amounts of silicate were withdrawn and that the extent of the withdrawal may 

 have been limiting for the continued growth of phytoplankton. 



SILICATE CONTENT OF THE O-IOO M. LAYER 



The 0-100 m. averages of silicate content have been calculated for a large number 

 of stations in the Antarctic zone, and two seasonal curves have been drawn from two- 

 monthly means. One, the curve for the southern region, was constructed from the 



2000 



SEPT 



OCT 



NOV 



DEC 



JAN 



FEB 



MAR 



APR 



MAY 



Fig. 9. The average silicate contents of the 0-100 m. layer in the southern and northern regions in the 



Antarctic zone of the Southern Ocean. 



results at all stations within 200 miles of the ice-edge and the other, the curve for 

 the northern region, from observations at all stations within 300 miles south of the 

 Antarctic convergence. The two curves are shown in Fig. 9. We have no results for 

 June and July, so that the seasonal curves are not quite complete. 



The following features of the southern curve are worthy of notice. A steep fall 

 occurs from 1 September to 1 November, followed by a steep rise from 1 November 

 to 1 February, after which during February the rise is less pronounced ; in March a fall 

 occurs, but in April the rise begins again. 



5-2 



