114 



R. T. Prentki et al. 



10 



20 30 40 50 60 70 80 



fj.q P liter"' 



FIGURE 4-15. Nitrogen fixation rates in Pond B 

 subponds with various concentrations of 

 phosphorus (DRP and TDP). 



TABLE 4-15 The Primary Production, Chlorophyll Concentration, and 

 NH 3- N and PO^-P Amounts in Two Swimming Pools 

 in 1971* 



*Pond 8 was fertilized with PO4 on 17 July and with NH3 on August 7. 



