ZOOPLANKTON IN THE SOUTHERN OCEAN 227 



the Discovery data in so far as the greatest catches were in the Antarctic zone. Furthermore, the 



Antarctic volumes were also greater than those of catches with similar nets in waters off New South 



Wales (Sheard, 1047, p. 17). 



SUMMARY 



1. This paper is based on material collected with the Discovery pattern 70 cm. vertical closing net. 

 The volumes of 2185 samples from 366 stations were measured by the displacement method, and the 

 results are given in the Appendix. 



2. The data from repeated lines of stations are treated diagrammatically. They show that through- 

 out the sub-Antarctic and Antarctic the vertical distribution of the standing crop of zooplankton is on 

 the whole similar in any one month. 



3. The average monthly volumes of samples in the sub- Antarctic and Antarctic show that during 

 the summer months the bulk of the zooplankton is concentrated in the surface waters day and night. 

 But in the winter there is a migration of plankton into deep water, and the largest concentrations 

 occur in the warm deep current. 



4. There appears to be little seasonal variation in the total standing crop of zooplankton in the 

 whole water column sampled (i.e. 1 000-0 m.). 



5. Regional differences are considered, and it is shown that there is a gradient in the quantity of 

 zooplankton from low to high latitudes reaching a maximum between 50 and 55 S. The largest 

 samples are not taken by the N70V in the highest latitudes or the coldest waters. But it is pointed 

 out that the very large concentrations of Euphausia superba (above 20 mm. in length) that occur in 

 certain regions of the Antarctic, are for all practical purposes not sampled by the N70V. 



6. A tentative estimate is made of the relative standing crops of zooplankton (or that limited part 

 of it sampled by the N70V) in the major geographical zones covered by the observations. 



7. Within the Antarctic zone as a whole, there appears to be little circumpolar variation in the 

 standing crop of zooplankton. 



8. The standing crops of zooplankton in the West Wind, Weddell and East Wind Drifts are com- 

 pared and, in so far as rather limited data allow, it is shown that in all sectors of the Southern Ocean 

 the richest area is that of the West Wind Drift. 



9. The results are compared in a very general way with those of other workers, and although the 

 data are not strictly comparable, it is shown that the standing crop of zooplankton in the Antarctic is 

 at least four times as great as that in the tropics. 



REFERENCES 



Apstein, C, 1909. Neue Apparate fur Meeresforschung. Mitt, dtsch. SeefischVer., xxv, pp. 354-58. 



Baker, A. de C, 1954. The Circumpolar Continuity of Antarctic Plankton Species. Discovery Rep., xxvn, pp. 201-18. 



Barnes, H., 1949. A Statistical Study of the Variation in Vertical Plankton Hauls with special reference to Loss of the Catch 



with Divided Hauls. J. Mar. Biol. Ass. U.K. xxvm, pp. 429-66. 

 Berardi, G., 1953. Apparechio per una precisa Valutazione Volumetrica di Campioni di Plancton. Mem. 1st. ital. Idrobiol. 



de Marchi., VII, pp. 221-27. 

 Bigelow, H. B. & Sears, M., 1939. Studies of the Waters of the Continental Shelf, Cape Cod to Chesapeake Bay. III. 



A volumetric study of the zooplankton. Mem. Mus. comp. Zool. Harv., liv, No. 4, pp. 183-378. 

 Clarke, G. L., 1940. Comparative Richness of Zooplankton in Coastal and Offshore Areas of the Atlantic. Biol. Bull, lxxviii 



(2), pp. 226-54. 

 Clowes, A. J., 1938. Phosphate and Silicate in the Southern Ocean. Discovery Rep., xix, pp. 1-120. 

 Dakin, W. J. & Colefax, A. N., 1940. The Plankton of the Australian coastal waters off New South Wales. Part I. Publ. 



Univ. Sydney, Dep. Zool., Monogr. No. 1. 

 Deacon, G. E. R., 1933. A General Account of the Hydrology of the South Atlantic Ocean. Discovery Rep., VII, pp. 171-238. 

 Deacon, G. E. R., 1937. The Hydrology of the Southern Ocean. Discovery Rep., xv, pp. 1-124. 

 Delsman, H. C, 1939. Preliminary Plankton Investigations in the Java Sea. Treubia, XVII, No. 2, pp. 139-81. 

 Ealey, E. H. M., 1953. Letter to the Editor. J. du Conseil, xix, No. 3, p. 368. 



