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



71 



about a t 27.3, and their values decrease northward. This trend is interrupted in 

 the equatorial region where a localized increase in concentration occurs. 



6000 m 



25 



(t, 26 



27 



2000 m 



S 50° 40° 30° 20° 10° 0° 10° 20° 30° 40° 50° N 



Fig. 17. Distribution of phosphorus fractions along western trough of Atlantic Ocean. 

 (a) Phosphate phosphorus, (b) Preformed phosphorus, (c) Phosphorus of oxidative 

 origin. Ordinates, sigma-Z surfaces and depths in meters. Abscissa, latitude. Contour 

 interval, 0.2 mg atom/m 3 . (Recalculated from data used by Redfield, 1942, and 

 additional stations. Phosphorus corrected for salt error. Phosphorus of oxidative 

 origin estimated using AO/AP= —276.) 



The origins of the distribution of inorganic phosphorus are illuminated by the 

 distributions of preformed phosphorus and phosphorus of oxidative origin. 

 Preformed phosphorus also has maximal concentrations in the intermediate 

 layer which diminish northward from the sub -surface of the subantarctic 

 region and disappear at about 15°N (see Fig. 17b). This fraction is a conserva- 

 tive property. Its pattern of distribution and attenuation is very similar to that 

 of salinity, which suggests that it is due to the intrusion of subarctic and 

 antarctic intermediate water at an intermediate depth of the ocean. Since pre- 

 formed phosphorus accounts for about one-half of the inorganic phosphorus in 



