PHYTOPLANKTON OF THE WEDDELL SEA AREA 91 



reaches its most northerly latitude in about that meridian. However, these stations are 

 too remote from the more intensively studied area to do more than indicate the con- 

 ditions obtaining along the ice-edge in early spring. The analyses of the hauls from these 

 stations are contained in Table XXVI. 



It will be seen that at St. 453, worked a short distance to the north-west of Bouvet 

 Island, which was free from pack-ice at this time, the phytoplankton was very scanty, 

 with Corethron valdiviae dominant, and Fragilaria antarctica the most numerous among 

 the other forms present. A similar poor phytoplankton was encountered at St. 460 which 

 was worked at a considerable distance west-south-west of Bouvet Island. In addition 

 to the above-named species Nitzschia seriata was of some importance here. The scanty 

 phytoplankton at these two stations in the old Antarctic surface water that had travelled 

 a long way from the Weddell Sea, shows how the minimal winter conditions persist into 

 early spring. This is probably rendered possible by the retardation of the north-easterly 

 flow of the water during winter. In conjunction with the observations round South 

 Georgia during the next few weeks of this season the conditions at these stations also 

 serve to show how sudden the spring increase must be when it does begin. 



In the series of observations made still farther to the west in a lane in the pack-ice 

 (St. 461), seven hauls with the Gran net were taken. The analyses of the material from 

 these hauls indicate that while the quality of the phytoplankton remained fairly constant, 

 its quantity varied very considerably (see p. 16). The hauls provide a good illustration 

 of the extent of this variability in nature, as the discrepancies observed were too large to 

 be due merely to errors in estimation. These hauls may probably be taken as giving a 

 good picture of the phytoplankton present along the ice-edge in the older eastern 

 Weddell Sea immediately before the great spring increase. Though poor in comparison 

 with catches obtained during the height of that phenomenon, it will be seen that they 

 were very much richer in species and individuals than the two previous hauls to the 

 north-east. The principal species met with were : Chaetoceros neglectus, Nitzschia seriata, 

 Fragilaria antarctica f. bouvet and normal form, Synedra spathulata, Corethron valdiviae 

 and Thalassiosira antarctica, in that order of importance. It is an interesting fact that 

 this association resembles that found far to the south later in the season, in surface water 

 of a different type, more closely than that found to be typical of the eastern Weddell Sea 

 water at the height of the season. It was evident that the ice here had scarcely begun to 

 melt, and the small proportion of Th. antarctica was alone sufficient to show that the 

 spring increase proper had yet to begin. Th. antarctica was found to show a very 

 strong spring maximum in all types of Antarctic surface water round South Georgia 

 less than a month later. The time of the spring increase in the older eastern Weddell Sea 

 water during the 1930-1 season may thus be laid down with some certainty as occurring 

 about the first week in November. 



The next piece of work in this area consisted of a line of stations worked from a point 

 to the south-east of South Georgia, westwards past the South Orkney Islands to the 

 vicinity of Elephant and Clarence Islands in December 1930. The positions of these 

 stations will be found in Fig. 32. Phytoplankton collections were made at only seven of 



