that the waters contained a residual phosphorus content of 0.32 to 0.55 /ng - at 1 ' 

 when the nitrogen was virtually exhausted. This excess phosphorus is reflected in low 

 N:P ratios of concentration. The ratio of inorganic compounds of nitrogen and 

 phosphorus (N:P) in water samples collected at 10 m (33 ft) at several locations and 

 various times of year ranged from 1.21 to 7.08 (by atoms). In contrast, the total N:P 

 ratio for the same samples ranged from 14.9 to 30.2. Thus the organic matter is 

 greatly enriched in nitrogen when compared with the inorganic source of nitrogen 

 and phosphorus in the water. In the decomposition of organic matter, phosphorus is 

 released more rapidly than is nitrogen, contributing to the low N:P ratio of concen- 

 tration in the water. 



Goldman (1976) has studied the growth and composition of a marine diatom. 

 Phaeodat'tylum tricornutum, in seawater enriched with sewage wastes or with added 

 nutrients. Some of his results are illustrated in Figure 1 . The typical N: P ratio in the 

 wastewater ranged from 5 to 10 (by atoms), whereas the ratio in the algae ranged 

 from 10 to 20. All of the cultures in Goldman's experiments were nitrogen-limited as 

 evidenced by the fact that the N:P ratio in the algae was consistently greater than the 

 N:P ratio in the medium in which they were grown. 



Typical IMP Ratios 

 in Wastewater 



30 



25 



0) 

 CD 



< 



c 



CD 



20 



15 



10 







IMP Ratios Wastewater-Seawater Mixture 



Figure 1 . Comparison of atomic NP ratios observed in wastewater-seawater mixtures 

 and in Phaeodacty/um tricornutum (from Goldman, 1976) 



71 



