SECT. 1] THE INFLUENCE OP ORGANISMS ON THE COMPOSITION OP SEA-WATER 



73 



atoms/m 3 . At depths greater than 4000 m a layer of relatively high phosphate 

 concentration extends northward under the North Atlantic Deep Water owing 

 to the intrusion of deep water from the Antarctic circumpolar region. 



The estimated preformed phosphorus content of the North Atlantic Deep 

 Water remains unchanged wherever its characteristic temperatures and 

 salinities are preserved (see Table IV). The fraction of phosphorus of oxidative 

 origin increases gradually from north to south, providing evidence that some 

 regeneration of phosphorus due to biological activity takes place in the deep 

 water as it drifts southward (see Fig. 17c). 



From the foregoing discussion it is clear that the vertical distribution of non- 

 conservative properties below any position on the ocean's surface is due primarily 

 to the pattern of horizontal flow of the underlying water masses, and to charac- 

 teristics which these water masses acquired at the time they were formed near 

 the sea surface. Biological processes modify the concentrations greatly only 

 near the sea surface, and their effects diminish rapidly with depth, as the 

 estimates shown in Table XI indicate. 



b. The horizontal distribution of nonconservative elements 



The deeper water of the Pacific and Indian Oceans is known to contain 

 substantially more phosphate and less oxygen than that of the Atlantic and 

 Arctic Oceans (Graham and Moberg, 1944). This fact is illustrated in Fig. 18, 



90 120 150 I8C) 150 120 90 



E 30 



90 120 



90 120 150 180 150 120 90 60 30 w E 30 60 90 '20 



Fig. 18. Distribution of phosphorus at depth of 2000 meters in the oceans of the world. 

 Contour interval, 0.25 mg atom/m 3 . (From Redfield, 1958. By courtesy of American 

 Scientist,) 



