DISTRIBUTION OF THE MACROPLANKTON 

 IN THE ATLANTIC SECTOR OF THE 



ANTARCTIC 



By N. A. Mackintosh, d.Sc 

 (Text-figs. 1-48) 



INTRODUCTION 



IN the course of the oceanographical work which the Discovery Committee is con- 

 ducting in the south, tow-nets of four different kinds have been used systematically 

 for the study of the plankton. These are the 50 cm., 70 cm. and 1 m. nets, and the 

 young-fish trawl. Of the four the 1 m. net, towed obliquely (N 100 B), is the most 

 suitable for investigating the horizontal distribution of the larger plankton organisms. 

 The following report is concerned with the samples taken by this net in the Antarctic 

 surface waters, and its purpose is to find how the Antarctic environment of the whales 

 is reflected in the distribution and variations of the macroplankton. 



During the first commission of the R.R.S. ' Discovery ' in 1925-7 the 1 m. nets were 

 towed horizontally at routine stations, but it was found that a net towed obliquely from 

 about 100 m. to the surface gives a better representation of the plankton, and the latter 

 method was therefore adopted during the work of the 'William Scoresby' from 1927 

 to 193 1 and of the 'Discovery I Tin 1930 and 1931. The catches of the early horizontal 

 nets, many of which have already been examined by Hardy and Gunther (1934), are 

 not strictly comparable with those of the oblique nets ; we are thus concerned here 

 with the period 1927-31, and the stations taken into consideration are those in the true 

 Antarctic water, together with a few on the north side of the Antarctic convergence. 

 Of the species taken at these stations only one or two are confined to coastal regions, 

 and we are in fact dealing with the plankton population of the open ocean. 



During the period 1927-31 the majority of samples were collected in the neighbour- 

 hood of the Falkland Islands Dependencies, but lines of stations also extended from 

 Bouvet Island in the east to a point west of Peter 1st Island in the Bellingshausen Sea. 

 The positions of most of these stations are shown in Fig. 1 . 



The present report is based on the examination of about 600 samples from the 1 m. 

 nets. From such a large number it is possible to obtain a great deal of information about 

 the plankton, and the material is by no means exhausted by the results put forward in 

 the following pages. It is the purpose of this report, however, not so much to elucidate 

 the individual distribution of the various species as to examine the distribution of the 

 macroplankton as a whole, and to distinguish individual communities whose constitution 

 is dependent on the hydrological and geographical features of their environment. 



