RESULTS 



Because of the large amount of data, only analyses of the 

 macrophytes from representative lakes are presented and 

 discussed in this section. Complete analytical data on 

 the samples from the additional lakes are presented in 

 the Appendix. 



Samples of 1970 



The analyses of Elodea from one of the most fertile 

 northern Wisconsin lakes sampled (Little John) and one of 

 the least fertile (Salsich) are presented in Tables 8 

 and 9. 



Concentrations of nitrogen and phosphorus in the lake 

 plants are of particular interest because these elements 

 most frequently have been considered limiting for aquatic 

 plant growth. In all Elodea samples from Little John 

 Lake, the nitrogen and phosphorus concentrations were well 

 above the critical concentrations of 1.60% and 0.14% in 

 the second one- inch segment. The lowest phosphorus 

 concentration was 0.40% on July 27 indicating very ade- 

 quate supplies of that element all during the growing 

 season. 



The lowest concentrations of elements in general were 

 observed in samples from July 27. This sampling apparently 

 was in the period of most rapid plant growth and greatest 

 pressure on nutrient supplies. However, even in the July 

 27 samples, the concentrations of all elements, except 

 nitrogen were at least double the critical concentrations 

 reported in Table 6. 



The nitrogen and phosphorus analyses of Elodea samples 

 from Salsich Lake contrast with the results from Little 

 John. The nitrogen concentrations were in general slightly 

 higher in the Salsich samples, but the phosphorus con- 

 centrations were considerably lower. For example, in the 

 second one-inch segment from July 28 the phosphorus con- 

 centration was only 0.18% and in the August 19 sample 

 0.15%. Comparable phosphorus values in the Little John 

 samples were 0.40 and 0.54%. The low values for Lake 

 Salsich plants, which were verified with a standard 

 colorimetric procedure, approach the critical concentration 

 of 0.14%, and indicate that in this lake phosphorus sup- 

 plies were close to limiting for Elodea growth. Further 

 additions of phosphorus could be expected to increase the 



27 



