LIMNOLOGICAL STUDIES OF KARLUK LAKE 
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nitrates which, in turn, serve as a source of nitrogen for the various plant forms that 
populate these lakes and streams; they are of special importance to the organisms 
that constitute the phytoplankton. 
No data are available for the phosphorus content of the red salmon, but Atwater 
(1892) states that P 2 0 5 constitutes 0.69 percent of the flesh of the California salmon and 
Taylor (1926) gives 0.57 per cent for the edible portion of the chinook salmon. From 
these results the P 2 0 6 content of the red salmon may be estimated as about 0.6 per 
cent, which is equivalent to 0.26 per cent when expressed in terms of the element 
phosphorus. This percentage represents about 5,000 kilograms of phosphorus in 
the estimated 2,000,000 kilograms of organic matter in the red salmon which migrate 
into these waters to spawn in an average year. In the process of decomposition this 
phosphorus is liberated and becomes available for the plants which thrive in these 
waters. 
Some of the salmon carcasses decompose in very shallow water or are washed up 
on the shores of the lakes and streams above the water line; in such cases a large part 
or all of the ammonia nitrogen is lost to the water, but the nitrates and phosphates 
of those decomposing on shore are washed back into the water by rain or melting 
snow and thus become available for the aquatic plants. The nitrates and phosphates 
derived from the decaying salmon are excellent fertilizers and serve to stimulate the 
growth of phytoplankton organisms. This is shown by the fact that enormous 
growths of certain algge are correlated with an abundance of decomposing salmon 
carcasses in Thumb Lake, and also by the fact that Karl uk Lake supports a larger 
crop of phytoplankton than several lakes belonging to the same class; the latter 
problem is discussed further in the section dealing with the plankton of Karluk Lake. 
The decomposition of the salmon carcasses in the lower courses of the streams 
accounts for the differences in the quantity of nitrogen and phosphorus found in the 
upper and lower courses of some of the streams. The samples taken at the upper 
stations were obtained from portions of the streams that were not occupied by the 
salmon, consequently the water in these localities contained only the nitrogen and 
phosphorus compounds leached from the earth through which the water had passed ; 
in the lower courses of the streams, on the other hand, these amounts were augmented 
by those derived from the decomposing salmon. Some of the streams were not as 
densely populated by the salmon as others, and this accounts for the differences noted 
between the different streams. 
CHEMISTRY OF BOTTOM DEPOSITS 
Five samples of bottom material were collected in Karluk Lake and one each 
from Thumb and O’Malley Lakes during July and August, 1927, for the purpose of 
making chemical analyses of them. One of the samples was taken in the deepest 
part of Karluk Lake, indicated as station 1 on the map, Figure 1. One was taken in 
the deeper part of The Thumb (station 2 on the map), and two others were secured 
in this basin of Karluk Lake. One sample was also obtained in the third or lower 
basin of Karluk Lake which is indicated as station 3 on the map. One sample was 
taken in the deepest part of Thumb Lake and another from that of O’Malley Lake. 
The samples were spread out and air dried as promptly as possible after they were 
secured. When dry they were placed in glass containers and kept until the analyses 
were made in the autumn of 1927. The air-dried samples were ground in a disk mill; 
the material was then spread out on watch glasses and dried in a vacuum desiccator 
