NORTHWESTERN" LAKES OF THE UNITED STATES. 
113 
Because of the shallowness of 
this lake, the phytoplankton flourishes 
and tends to decrease very materially 
the transparency of the water. The 
Secchi disk disappeared from view 
at a depth of less than 1 m. The lake 
was so shallow that the waves kept 
the water in circulation from top 
to bottom, and no thermocline had 
formed. 
The largest number of Crustacea 
per cubic meter of water was found 
in the bottom stratum of the lake. 
Fully 70 per cent of the Crustacea at 
this depth were Diaphanosoma leuch- 
tenbergianum. Diaptomus ashlandi 
was most abundant in the 0-2 m. stra- 
tum. (See fig. 22.) 
Nauplii were most abundant in 
the 4-6 m. stratum of the lake, about 
37 per cent of the total number being 
found there. 
The maximum number of Rotifera 
per cubic meter of water was found 
in the 0-2 m. stratum. Forty per 
cent of the Triarthra, 33.3 per cent of 
the Mastigocerca, and 46.4 per cent of 
the Anurxa cochlearis were in this 
layer. (See Table 12, p. 134.) The 
green and blue-green algae in Upper 
Klamath Lake consisted of Microcystis , 
Aphanocapsa,Staurastrum, Anabaena, 
and Pediastrum ; the maximum num- 
ber was found between 4 and 8 m. 
There were over 20,000,000 algae per 
cubic meter of water in this region 
of the lake. The maximum number 
of diatoms per cubic meter of water, 
consisting of Cyclotella, Melosira, and 
Navicula, was found in the 0-2 m. stra- 
tum, where there were over 19,000,000 
per cubic meter of water. 
31177°— 23 5 
Fig. 22.— Curves for Upper Klamath Lake, giving the temperature, dissolved gases, and plankton at all depths. C, free carbon dioxide; Cb, fixed carbon dioxide; 
oxygen; each given in cc. per liter. Plankton numbers are per cubic meter of water. 
