164 
BULLETIN OF THE BUREAU OF FISHERIES 
NOTES ON VEGETATION 
May 15: 
A few cattails along north side. 
Aphanizomenon approaching water bloom stage. 
May 26: Cattails northwest corner. Some Elodea. 
June 16: 
A few cattails along northwest corner. 
Some Elodea scattered. Ranunculus rare. 
June 30: 
Elodea cover about 5 per cent of area. 
Blanket algae cover about 25 per cent of area. 
Cattails present. 
June 23: 
Elodea cover about 2 per cent of area. 
Blanket algae cover about 2 per cent of area. 
Cattails present. 
August 16: Blanket algae cover about 25 per cent of area. 
LIMNOLOGICAL DATA 
The samples from D 9 were taken on the same days as those from D 4 and D 5 
and at 10-day intervals. The limnological data are given in Table 10. 
Table 10 shows that the temperature range in D 9 was practically the same as 
that in D 4 and D 5. The minimum temperature observed is that of 11.1° C. on 
September 29. The maximum of 27.2° C. occurred on June 30 and on July 28. 
The transparency of the water in D 9 was lower than that in D 4 and D 5 until 
July 20. From July 28 on, however, it was more transparent than the water in D 4 
and compared favorably with that in D 5. The minimum transparency of 6 inches 
on June 9 is due, at least, in part to the water bloom caused by the blue-green algae 
Aphanizomenon and Anabaena. Table 10 shows that the organic matter on this 
date amounted to 20.24 milligrams per liter of water. Phytoplankton counts for 
that date show that there were present per liter of water 4,635,000 filaments of 
Aphanizomenon and 6,345,000 filaments of Anabaena. 
The reaction of the water varied from a minimum pH of 7.7 to a maximum of 
9.1. The pH values of 9.0 on June 9 and August 29 correspond to the second greatest 
and the greatest alkalinity, respectively. The low pH values of 7.7 and 7.8 on July 
10 and 20, respectively, correspond to the disappearance of the blanket algae from the 
surface and to a decrease in the organic matter from 8.57 milligrams per liter to 1.30 
milligrams per liter. The variations in pH are shown in Figure 6. 
Table 10 shows that free C0 2 was present in varying amounts on seven different 
dates. At other times there existed a phenolphthalein alkalinity. The free C0 2 
reached a maximum of 12.64 p. p. m, on July 10. The maximum phenolphthalein 
alkalinity of 38.42 p. p. m. occurred on August 29. The maximum of 12.64 p. p. m. of 
free C0 2 corresponds to the minimum pH of 7.7. The latter, as has already been 
pointed out, corresponds to a decrease in the organic matter and the disappearance of 
the blanket algae. The alkalinity of 30.34 p. p. m. on June 9 corresponds to the water- 
bloom stage of Aphanizomenon and Anabaena. The alkalinities of 38.42 and 28.32 
on August 29 and September 29, respectively, correspond to an abundant growth of 
blanket algae. (No formal observations on the vegetation were made after August 
16, but blanket algae and some vegetation had to be removed before the pond was 
drained.) The variations in free C0 2 are shown in Figure 6. 
