ANTARCTIC SURFACE WATER 



5.1 



SEASONAL VARIATION OF PHOSPHATE IN THE 

 SURFACE LAYER IN 8o° W 



In 8o° W a series of observations for phosphate and silicate analysis were made in 

 five months in 1933-4, since the phosphate results of December 1933 were found to be 

 inaccurate only those taken in 1934 have been examined. The mean integral averages 

 of the 0-100 m. layer have been plotted and are shown in Fig. 16. Discussion of these 

 averages is handicapped by variation of the latitude of the ice-edge and of the Antarctic 

 convergence, and the narrowing of the Antarctic zone in 8o° W due to geographical 

 features. The ice-edge in March 1934 was some 280 miles farther south than in 

 September 1934, and the Antarctic convergence was over 60 miles farther south in March 

 than in September. In September and October the concentration of phytoplankton in 



LATITUDE 66 S 

 STATION n 



6.6° 



T 



1 rr 



A.C. 



SEPTJjOCT JNCN [MAR 



6,2° 60° 



(n't i^t 





5£?S 





o-x - 



O MARCH 1934 



X SEPTEMBER 1334 



A OCTOBER 1934 



■ NOVEMBER 1934 



O 

 0-~ 



Fig. 1 6. The average phosphate content of the o-ioo m. layer in 8o° W. 



the Antarctic surface water was very small, and even in November the main outburst 

 had hardly started ; the March observations were made after the peak concentration of 

 phytoplankton in the far south. 



At the Antarctic convergence in 8o° W very little variation of phosphate content 

 occurred in the o-ioo m. layer in the months of September, October and November, 

 whilst farther south, October averages were higher than in November. We have no 

 results for the critical period of early January to late February which would show the 

 effect of the peak concentrations near the convergence and at the ice-edge, and hence 

 only a very approximate estimate of the consumption of phosphate can be made. The 

 March observations were interesting because in the far south they show some effect of 

 the peak concentration of phytoplankton which must have been present some little 

 time previously. North of 64^° S, however, the March averages are seen to rise and 

 attain the highest values recorded for any month in corresponding latitude, as far as 

 about 59 S. This is at a time after peak conditions of phytoplankton concentration in 



