THE DISTRIBUTION OF THE STANDING CROP 

 OF ZOOPLANKTON IN THE SOUTHERN OCEAN 



By P. Foxton 



(Figs. 1-19) 



INTRODUCTION 



IN recent years much attention has been paid to the productivity and organic resources of the seas, 

 but there are formidable difficulties in the technique of quantitative sampling of the oceanic fauna 

 and flora, and little is known of the relative fertility of the oceans at different times and places. Investi- 

 gations on fertility are largely concerned with the primary production of phytoplankton (i.e. the amount 

 of organic matter synthesized in a given time), but take account not only of the rate of production and 

 consumption of both phytoplankton and zooplankton, but also of variations in the 'standing crop', 

 ' i.e. the amount or density of the plankton at a given place at the time of sampling. The standing crop 

 (which represents the amount of food available for consumers of the plankton) can be taken as an 

 indication of fertility only with certain reservations, of which the most important is that a fertile region 

 may yet have a small standing crop if a high rate of consumption keeps pace with a high rate of 

 production. 



The present paper, which is part of an investigation of the distribution and abundance of the 

 southern oceanic fauna, deals with the standing crop of zooplankton, and it depends on measurements 

 of the volume of plankton samples. These samples are all from one standard net, and in so far as no 

 single net can equally sample all planktonic animals from the most minute to the largest and most 

 active, it is an arbitrary part of the plankton fauna which is being measured. But it is a net which does 

 sample animals through a considerable range of sizes, the samples are comparable with one another, 

 and this paper is concerned with relative and not absolute quantities. 



Work on this aspect of oceanography was initiated by Hensen and his co-workers on the ' Plankton 

 Expedition '. They developed methods which have formed the basis of plankton research ever 

 since, but as with nearly all deep-sea expeditions the observations, though distributed over wide 

 oceanic areas, were not repeated at different times of year and therefore do not take account of 

 seasonal variations. (The main conclusions of this and other investigations in relation to plankton 

 production are briefly summarized in historical sequence by Dakin & Colefax, 1940.) 



Perhaps the most valuable body of data collected hitherto is that of the 'Meteor' Expedition 

 (Hentschel, 1936) which covered the central and southern Atlantic on fourteen latitudinal profiles, 

 during which 310 stations were worked. Even so, the observations were rather widely dispersed, 

 especially in the southern part of the area investigated, and (of necessity) they did not cover seasonal 

 variations. This applies also to the results of the 'Dana' Expeditions (Jespersen, 1923, 1935), which 

 cover a great geographical range mainly in sub-tropic and tropic latitudes, and to those of the ' Carnegie ' 

 (Graham, 1941 ; Wilson, 1942), which cruised in both Pacific and Atlantic waters. 



Inshore waters in most parts of the world have been well surveyed, and among the many works on 

 production and standing crop are those of Bigelow & Sears (1939), Clarke (1940), Redfield (1941) and 

 Riley (1941) in America; Gundersen (1951) in Norway; Sheard (1949) in Australia; Huntsman (1919) 

 in Canada; and Delsman (1939) in the Java Sea. Most of these studies, however, are not directly 



