136 DISCOVERY REPORTS 



In years when the autumnal increase in old Bellingshausen Sea water is unusually 

 rich, as it seemed to be in April 1930, it is possible that there is a considerable invasion 

 of small Chaetocerids, Nitzschio seriata, etc., into the northern half of Bransfield Strait 

 quite late in the year. An association of this type was found at St. 376 (pp. 75, 76 and 

 Table XX). Apart from this there is little doubt that the maximum phytoplankton 

 development is in late spring, though the disparity between the quantities present at 

 the different seasons is by no means so marked as in the other areas investigated. 



THE PHYTOPLANKTON OF THE BELLINGSHAUSEN SEA 



The interpretation of our results from this area must necessarily be more speculative 

 than that placed upon the material collected in the Bransfield Strait, for observations in 

 spring and early summer are not available, and we have little direct evidence as to the 

 phytoplankton to the north of this rather ill-defined area. All our observations were 

 obtained south of the 64th parallel, and conditions in the older water between that 

 latitude and the Antarctic convergence remain unknown, apart from such conclusions 

 as can be drawn from the material collected in the southern half of Drake Passage in 

 surface water that undoubtedly originated in that area. 



In the Bellingshausen Sea proper, phytoplankton material was collected at twenty 

 stations, worked mostly in February, by the 'William Scoresby' during the 1929-30 

 season, and at forty-seven stations worked mostly in January by the ' Discovery II ' in 

 the following year. 



THE SEASON 1929-30 



On her voyages to the Bellingshausen Sea during this season the ' William Scoresby ' 

 was mainly engaged in other work, and apart from the valuable line worked off Adelaide 

 Island, material is available only from a small number of widely scattered stations. It 

 has been found impossible to group the latter into strictly logical sequence, though their 

 significance can be made out fairly well when the results obtained during the following 

 season are taken into consideration: a purely arbitrary grouping has perforce been 

 adopted in the tables. The positions of the stations are shown in Fig. 71. The dominant 

 species are indicated by symbols in Fig. 72, and the phytoplankton totals, to the nearest 

 hundred thousand, in Fig. 73. 



Table XLIII gives the full analyses of the phytoplankton hauls at St. WS 495 worked 

 to the west of Adelaide Island late in December, and at three other stations to the south- 

 west worked in February. Conditions at St. WS 495 were interesting, as this station 

 was worked earlier in the year than any of the others in this area. Here the littoral or 

 ice-form Nitsschia closteriiim was dominant in a haul of moderate size, in which a fair 

 number of species were recorded, the other more numerous forms being Corethron 

 valdiviae, Rhizosokfna gracillima and Chaetoceros neglectus, all of which have been found 

 to be of the first importance in this area somewhat later in the year. 



