LIMNOLOGICAL STUDIES OF KARLUK LAKE 
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Cymbella Mexicana var. Kamtschatica, Cymbella ventricosa, Melosira crenulata, Navic- 
ula elliptica, Gomphonema subclavatum, Tabellaria flocculosa, etc. 
3. O’Malley Lake, 12 meters, July 28, 1927. — Diatoms fewer, 20 to 30 per cent 
of the mass. Much fine quartz sand and decayed plant tissue. Here Cyclotella 
Bodanica and Stephanodiscus Niagaras, although present, are few; Surirella elegans 
is frequent, but the bulk of the diatoms is made up of minute species — Tabellaria 
flocculosa, Melosira crenulata var. tenuis, Fragilaria construens, Ceratoneis arcus, 
Cymbella cistula, etc. 
4. O’Malley Lake, July 23, 1927. — The exact locality where this sample was taken 
was not recorded, but it was in comparatively shallow water, not over 2 meters, and 
probably near the head of the lake where the bottom consists largely of rather fine 
dark sand. Over half the mass is decayed plant tissue, mixed with sand. Cyclotella 
Bodanica, generally prolific in the other samples, seems to be wanting here, and 
Stephanodiscus Niagaras is scanty. Among the relatively few diatoms the following 
were prominent: Melosira crenulata var. tenuis, Navicula elliptica, Navicula viridis, 
Epithemia Zebra, Cymbella ventricosa, Fragilaria construens, Tabellaria flocculosa, etc. 
5. The Thumb, Karluk Lake ( station 2) Ifi meters, August 8, 1927. — Sixty per cent 
or more is diatoms, the rest decayed plant tissue and a mere trace of sand. Cyclotella 
Bodanica and Stephanodiscus Niagaras compose four-fifths of the diatom bulk. Also 
present were Cymbella Ehrenbergii, Cymbella gastroides, Cymbella cistula, Cymbella 
Helvetica, Navicula lata, Navicula major, Navicula viridis, etc. 
6. The Thumb, Karluk Lake, 88 meters, August 8, 1927. — Diatoms 30 to 40 per 
cent of the mass. Much sand and coarse plant tissue, moss and wood fiber. Cyclo- 
tella Bodanica and Stephanodiscus Niagarae dominant, about 3 to 1. Also Cymbella 
Mexicana var. Kamtschatica, Epithemia turgida, Surirella biseriata, Surirella elegans, 
Melosira arenaria, Melosira Italica, Fragilaria construens and desmids (Micrasterias). 
7. The Thumb, Karluk Lake, 17 meters, August 8, 1927.- — Not over 20 per cent 
diatoms, mostly decayed plant tissue and a little sand. Cyclotella Bodanica and 
Stephanodiscus Niagarae are here in abeyance; large chains of Melosira arenaria are 
frequent, also Amphora Lybica, Amphora ovalis, Navicula elliptica, Gomphonema 
geminatum, Cymbella Helvetica, Pleurosigma acuminatum. Some desmids ( Staura - 
strum g'racile ) and some pin-head sponge spicules. 
8. Karluk Lake, upper basin (station 1) 125 meters, August 13, 1927. — Seventy-five 
to eighty per cent of the mass is diatoms and of these four-fifths are Cyclotella 
Bodanica and Stephanodiscus Niagarae in their usual ratio of 3 to 1. The remainder 
is decayed plant tissue with practically no sand or spicules. Other diatoms are 
Cymbella gastroides, Cymbella cistula, Rhoicosphenia curvata, etc. 
It is noticeable that the greatest abundance of diatoms in the deposits is found 
in the main basins of Karluk Lake and in Thumb Lake. The bottom of O’Malley 
Lake, even in the center of its basin (sample 3) is much less rich than are the samples 
from the other two lakes. The three samples from The Thumb are interesting in that 
they show a distinct negative correlation between the proportion of diatoms in the 
deposits and the depth from which they came. The Thumb is really a large, well- 
marked bay containing one of the main basins of Karluk Lake. The largest stream 
tributary to Karluk Lake, Thumb Kiver, enters at the head of The Thumb and during 
and subsequent to the spawning season carries into the lake large quantities of organic 
matter derived from the decaying bodies of the spawned out salmon. In making 
the collections of bottom samples an attempt was made to get a series from about 
the center of the basin up toward the mouth of Thumb Kiver. The first sample of 
