430 
BULLETIN OF THE BUREAU OF FISHERIES 
The phytoplankton consisted chiefly of diatoms; an average of 7,386,000 diatoms 
per liter was obtained in the net catch taken on July 13, 1930. A maximum average 
of 94,700 green algse per liter of water was noted on the same date. The largest 
number of blue-green algge was found on September 7, 1929, namely, an average of 
71,900 per liter. 
o’malley lake 
Eight series of net catches were taken on O’Malley Lake, four in 1927, and two 
each in 1929 and 1930. (See Table 12.) In general, the Crustacea were not as 
abundant as in the Thumb Lake catches. The Cladocera were represented by a few 
Chydorus in one catch and by varying numbers of Bosmina in all of the catches. A 
maximum of 17 Bosmina per liter was taken in the 5-10 meter catch on July 10, 
1929. The Copepoda were represented by a maximum of 8 Diaptomus per liter in 
one catch and a maximum of 4 Cyclops per liter in another. Epischura appeared in 
three catches, with a maximum of 5 per liter in one. 
As in Karluk and Thumb Lakes, the Kotifera were the dominant group numerically 
in the zooplankton of O’Malley Lake. The catch taken on July 23, 1927, yielded the 
largest average number of rotifers, namely, 386 per liter. 
Protozoa and blue-green algae were found in relatively small numbers. The green 
algae reached a maximum average of almost 3,900 per liter on August 10, 1927. As 
in Thumb Lake, the phytoplankton of O’Malley Lake was dominated by the diatoms, 
but they were not as abundant in the latter as in the former lake; a maximum of 
562,600 diatoms per liter was obtained on August 10, 1927. 
Table 13 . — Average number of net 'plankton organisms per liter of water in seven American lakes 
COMPARISON OF KARLUK WITH OTHER LAKES 
Table 13 shows the average number of net plankton organisms per liter of water 
from surface to bottom in some lakes that are similar to Karluk Lake in depth and 
character. Four of the Finger Lakes of New York and one each from the States of 
California and Washington are included in this table. The series of catches repre- 
sented in these averages were taken with the same type and with the same size of 
plankton net, so that the general results obtained in the various lakes are comparable. 
The average number of Cladocera was larger in Cayuga and Seneca Lakes than in 
Karluk; they were about the same in Canandaigua and Karluk Lakes, but a smaller 
average was found in the other three lakes shown in the table. The average number 
of Copepoda and nauplii was larger in Karluk than in the other six lakes and the same 
was true of the Rotifera. The average number of protozoa in Cayuga Lake exceeded 
