ANTARCTIC SURFACE WATER 29 



a time previous to the season when the phytoplankton begins to increase in con- 

 centration, it is not possible to draw definite conclusions at present. 



An examination of the phytoplankton found in mid- April 1932 at St. 855 which 

 was situated on the ice-edge in 65 15' S, 48 437' E, gives some evidence of a 

 possible southerly movement of surface water in the eastern part of the area. Dr Hart 

 has examined the phytoplankton at this station, and he informs me that it is of a 

 type which was found in February 1935 in a position 63-64 S, 20-30 E, and its 

 concentration was about one-third of that found in February. A surface silicate value 

 of 3400 mg. at St. 855 indicates that considerable regeneration had taken place. Deacon 

 (1937, p. 28) suggests that the surface cyclonic movement comprising the west-going 

 surface current in the south of the Weddell Sea, the northward movement up the east 

 coast of Graham Land and the easterly current of Weddell water across the Atlantic- 

 Antarctic basin, may be completed by a southward surface movement in 20°-40° E, 

 although the temperature and salinity observations do not give much evidence for such 

 a movement. The question remains whether the appearance of the phytoplankton at 

 St. 855 is due to some such southerly surface movement, which, coming from 63°-64° S 

 in 20°-30° E in February, is found in 655° S, 485° E in mid-April. The value of 

 3400 mg. for the surface silicate at St. 855 indicates that regeneration has taken place, 

 and this might have occurred during such a possible southerly movement. In this 

 event it is possible that the southerly movement in the surface layer extends farther 

 to the east than 20°-40° E, and the phytoplankton found at St. 855 in mid-April 

 in 65!° S, 485° E would be a remnant of an earlier concentration which existed in 

 63°-64° S. It may have been carried to the east from 20°-40° E in the southerly part 

 of the West Wind Drift, before getting into a southerly movement in 40°-50° E. An 

 alternative explanation is that spores from the February diatoms in 63°-64° S sank below 

 the surface layer and travelled southwards on the top of the warm deep water, 

 eventually causing a late outburst on the ice-edge in mid-April in 48!° E. 



We have no silicate data for the southern region of the Antarctic zone between 48 E 

 and 130 E. At the ice-edge in late May 1932 in 63 41-4' S, 130 07' E (St. 887), the 

 surface silicate was 2680 mg. at a time when the phytoplankton was very poor. At this 

 station the warm deep water was as close to the surface as 80 m., but even so, the surface 

 layer was definitely poorer in silicate than at a corresponding position south of the 

 South Atlantic Ocean. The value of 2680 mg. may represent the maximum content of 

 the year in this position. 



There are no observations for silicate content south of the Tasman Sea, but in the 

 Southern Ocean south of the Pacific there are many data, including figures for the 

 months of January, February, March, September, October, November and December, 

 mostly in 1934. The observations range from 171!° W to 77°W, and thus the results 

 constitute a good picture of the ice-edge conditions in summer, early autumn and spring. 

 In September 1932, at the ice-edge north of the eastern entrance to the Ross Sea, the 

 surface silicate content was 2000-2500 mg. at about 61 \° S. Although the ice-edge is 

 far north for September in this position the main outburst of phytoplankton had not 



