ANTARCTIC SURFACE WATER 21 



In the eastern part of the south Pacific in early November 1934 the average ice-edge 

 value for the surface phosphate was about 112 mg., whilst in an area between 66f° and 

 59!° S and between 8o° and 109J W an average surface value for fourteen stations was 

 105 mg. This was at a time when the phytoplankton outburst had begun and the phos- 

 phate results showed this by the reduction of the ice-edge value to 112 mg. 



In 8o° W we have ice-edge results from the months of March, September, October 

 and November 1934, but in considering these the effect of the differing latitude of the 

 ice-edge in the various months must be taken into account. Observations were also 

 made in December 1933, but there are good reasons for considering these unreliable 

 and they are not included in the following table which consists of the phosphate data 

 at the ice-edge stations together with the latitude of the stations. 



In March the ice-edge was farthest south and the surface value was still some 23 per 

 cent less than in the bottom of the surface layer. Regeneration has raised the content 

 from a probable minimal value of 85-90 mg. The effect of seasonal variation in the 

 latitude of the ice-edge is best seen in the September and late October figures that for 

 October being greater than the value in September. There was practically no phyto- 

 plankton activity in September and not much more in October. The September value 

 was less of course because the ice-edge was far north at this time, but even so the value 

 is considered to be low. The fall from late October to mid-November, during which 

 time the ice-edge retreated a short distance to the south, can be accounted for by the 

 increase of phytoplankton activity. 



In January 193 1 on a line of stations north and west of Adelaide Island, which is 

 situated in the south-east of the Bellingshausen Sea, the surface phosphate increased 

 from 73 mg. inshore to 104 at the outermost station. The low value near the coast was 

 accompanied by a heavy concentration of phytoplankton. 



In late December 1930 off the north-west coast of Graham Land between Anvers 

 Island and Adelaide Island the surface phosphate at three stations was 103, 102 and 

 93 mg., at a time when the phytoplankton had by no means come to a maximum. 



In general terms it may be stated that in the Antarctic zone, when allowance is made 

 for the differing time of the maximum concentration of the phytoplankton across the 

 zone, the phosphate and silicate values at the surface fall from south to north. In the 

 above remarks the surface phosphate content at the southern end of the Antarctic zone 

 has been described as far as our present knowledge allows, and the distribution at the 

 northern end of the zone will now be considered. 



In April 1930 (in section 1, Plate III) at St. 384, a position just south of the Antarctic 

 convergence in the Drake Passage, the surface water had a phosphate content of 1 15 mg., 



