PHYTOPLANKTON OF BRANSFIELD STRAIT 



117 



siderable numbers. Turning to the northernmost station on the line, St. WS 476, the 

 inshore character of the surface water was indicated by the presence of the small species 

 of Tintinnid previously referred to (p. no). The catch here was not so large, less than 

 five million phytoplankton organisms being estimated to be present ; Corethron valdiviae 

 was again dominant, but Thalassiosira antarctica accounted for nearly 25 per cent of the 

 catch. At the next station to the southward, Corethron again predominated in a much 

 richer haul, in which Fragilaria antarctica, Thalassiosira antarctica, Rhizosolenia gracil- 

 lima, Biddidphia striata and Coscinodiscus bouvet were all more abundant than has been 

 found usual in this area. 



56° 



Fig. 56. Reference chart showing the positions of the stations worked in Bransfield Strait 

 in November 1929, and in December 1930. 



Still farther to the southward, at St. WS 478, a much smaller catch was obtained, more 

 comparable to that from the inshore station, except that Corethron was more markedly 

 dominant. Local current systems have been encountered in this vicinity on other 

 occasions, and it is possible that this break in the continuity of rich hauls is to be 

 ascribed to some such cause, as the phytoplankton at the succeeding station, St. WS 479, 

 closely resembled that at St. WS 477 both in character and bulk, the only notable 

 difference being that Thalassiosira antarctica and Fragilaria antarctica were not so 

 numerous. As before, Corethron was strongly dominant, a statement which also applies 

 to the catch at the next station, St. WS 480, where the proportion of the smaller forms 

 decreased still further, despite the fact that the rise in salinity indicates that the region 

 of the Weddell Sea influence was being approached. 



