PLANKTON PRODUCTION IN FISH PONDS 
149 
Ammonia nitrogen . — Table 4 shows that in C 1 the ammonia nitrogen varied 
from a m inimum of 0.012 p. p. m. to a maximum of 0.060 p. p. m. Except for the 
minimum value the variations are rather small; 0.044 p. p. m. to 0.060 p. p. m. In 
C 2 the ammonia nitrogen exhibits a far wider range of variations; namely, from 
0.052 p. p. m. to 0.60 p. p. m. Only once does the ammonia nitrogen in C 1 equal that 
in C 2. The maximum for ammonia nitrogen in C 2 occurs simultaneously with a 
decrease in the net loss on ignition and the dissolved oxygen and an increase in the 
free C0 2 . In C 3 the variation is from 0.060 p. p. m. (the maximum for C 1) to a maxi- 
mum of 0.252 p. p. m. The maximum occurs here somewhat later than in C 1 and C 2, 
but is associated with similar changes in the net loss on ignition, dissolved oxygen, 
and free C0 2 . In C 4 the maximum of 0.096 p. p. m. occurred on June 27 when the 
first observation was made. The minimum of 0.020 p. p. m. was present on Septem- 
ber 19 when the last observation was made. Since the maximum occurs at the begin- 
ning of the experiment, it can not be determined whether or not it is associated with 
a decrease in organic matter. 
The averages for nine determinations of ammonia nitrogen are as follows: C 1, 
0.047 p. p. m. ; C 2, 0.127 p. p. m. ; C 3, 0.094 p. p. m. ; and C 4, 0.044 p. p. m. 
Organic nitrogen . — The results of organic nitrogen determinations show that this 
form of nitrogen varied in C 1 from a minimum of 0.608 p. p. m. to a maximum of 2.0 
p. p. m. Figure 2 shows the variations in the organic nitrogen. In C 2 the organic 
nitrogen ranged from a minimum of 2.24 p. p. m. to a maximum of 6.43 p. p. m. For 
the variations in organic nitrogen see Figure 3. In C 3 the minimum was 2.56 
p. p. m. and the maximum 10.08 p. p. m. The variations in the organic nitrogen are 
shown in Figure 4. This last maximum is the largest amount of organic nitrogen 
that was ever encountered in this series of ponds. It coincides with the appearance 
of the maximum amount of organic matter of 58.8 milligrams per liter; 55.80 milli- 
grams of organic matter is not only the maximum for C 3 but the maximum for the 
series. In C 4 the organic nitrogen varied from a minimum of 0.240 p. p. m. to a 
maximum of 1.00 p. p. m. This pond has the smallest amount of organic nitrogen. 
It has also the smallest amount of organic matter. (Table 4.) 
The average for nine determinations of organic nitrogen are: C 1, 1.304 p. p. m.; 
C 2, 4.43 p. p. m. ; C 3, 4.403 p. p. m. ; and C 4, 0.704 p. p. m. These values for organic 
nitrogen would represent the following amounts of proteins: 8.150 p. p. m., 27.687 
p. p. m., 27.518 p. p. m., and 4.400 p. p. m. Nitrite nitrogen was never encountered in 
this series of ponds. 
Phosphorus . — The data on phosphorous determinations in Table 5 show that the 
determinations of soluble phosphorus were begun earlier than the other determina- 
tions except the net plankton. In C 1 the dissolved phosphorus was 1.28 p. p. m. on 
June 19. On the 22d it was up to 1 .50 p. p. m. and on June 27 it had increased to 1 .80 
p. p. m. This was the maximum for this pond. The rise in dissolved phosphorus 
from June 16 to 27 is undoubtedly due to a diffusion of the phosphorus of the super- 
phosphate which had been added on June 7 and 16. After June 27 the soluble phos- 
phorus decreased gradually until on August 6 only 0.045 p. p. m. was left. From 
August 6 there is an increase from 0.045 p. p. m. to 0.055 p. p. m. The big rise between 
August 9 and 20 is due in part to the addition of superphosphate (Table 1) and in part 
to the regeneration of dissolved phosphorus from the organic (fig. 2). On August 
30 the dissolved phosphorus was lower than on August 20 in spite of the fact that 
some more superphosphate was added on August 25 and that the increase in the net 
