PHYTOPLANKTON OF THE BELLINGSHAUSEN SEA 143 



THE SEASON 1930-1 



During this season forty-seven stations, at which phytoplankton material was col- 

 lected, were worked by the ' Discovery II ' in the Bellingshausen Sea, mostly during the 

 first three weeks of January. Considerable difficulty has been experienced in grouping 

 the stations for tabulation. The analyses of the phytoplankton hauls are given in 

 Tables XLVII-LII. Of these the first two consist of two definite lines worked north 

 of Adelaide Island, the third treats of all the stations worked between the Palmer 

 Archipelago and 70° W long., excluding those dealt with in the first two tables, and the 

 remaining three deal with the stations worked farther to the westward grouped between 

 necessarily arbitrary limits. The positions of all the stations at which phytoplankton 

 material was collected are shown in Fig. 74. To the westward it became apparent that 

 the time difference between the outward and homeward bound passages was not suf- 

 ficiently great to be reflected in marked changes in the nature of the phytoplankton, 

 but at a few of the more easterly stations the conditions had changed considerably, the 

 interval being nearly three weeks. 



The long line worked on an approximately north-westerly course from Adelaide 

 Island may be described first, as it affords the best grounds of comparison with that 

 worked by the ' William Scoresby ' during the previous season. On this occasion ten 

 stations were worked at somewhat greater intervals, the line being carried up to 

 64° 17' S, 75" 3s' W (Table XLVII). At the innermost station (St. 584), it will be seen 

 that although small in volume, the catch contained millions of the minute species 

 Chaetoceros neglectus and Ch. tortissimiis, the former strongly dominant and the 

 association generally bearing a close resemblance to that found in the Palmer Archi- 

 pelago. Farther ofl!"shore, at St. 583, Corethron valdiviae predominated in a small haul in 

 which the only other form of much importance was Chaetoceros neglectus. At all three 

 of the succeeding stations to seaward (Sts. 585-587), very poor catches were obtained, 

 with Corethron valdiviae the most numerous form of a phytoplankton poor in both 

 species and individuals. A possible explanation of this extreme poverty lies in the fact 

 that the area was known to have been completely covered by pack-ice just prior to the 

 working of the stations. The conditions at the earliest stations worked in this area indicate 

 that a considerable interval is necessary, after the ice begins to break up, before extensive 

 phytoplankton development can take place. It was round the position of these inshore 

 stations in the following month of the preceding year that such a rich development of the 

 Corethron — Rhizosolenia gracillima association had been found. On this occasion the line 

 was spread over double the distance to the northward, and this association was not en- 

 countered until St. 588 was reached. It persisted in varying degrees at the three succeeding 

 stations to the northward, Sts. 589-59 1 , but with an increasing proportion of Chaetoceros 

 neglectus and with Nitzschia seriata, actually the most numerous organism at St. 591, 

 whereas in the preceding year the dominance of Corethron valdiviae and Rhizosolenia 

 gracillima had been most marked. It is evident that the development of this association 

 had not proceeded so far on this occasion, and it seems probable that open water is an 



