Transactions - American Fisheries Society . ) a degree or two above the temperature which gravityalone would give it. The distribuiion of oxygen is quite differ-ent from that showii in any of the preceding diagTams. \t thesurface the amount is about the same as in other lakes and thereis a marked decline in the oxygen at the upper part of tlie coolwater. Then the oxygen begins to increase, becomes greater thanthe amount found at the •surface, and at the de])th of -10 metersis nearly 7 cc. per liter. From the depth of 50 meters it declines,until at the bottom only a fraction of a cubic centimet
Transactions - American Fisheries Society . ) a degree or two above the temperature which gravityalone would give it. The distribuiion of oxygen is quite differ-ent from that showii in any of the preceding diagTams. \t thesurface the amount is about the same as in other lakes and thereis a marked decline in the oxygen at the upper part of tlie coolwater. Then the oxygen begins to increase, becomes greater thanthe amount found at the •surface, and at the de])th of -10 metersis nearly 7 cc. per liter. From the depth of 50 meters it declines,until at the bottom only a fraction of a cubic centimeter is alnindant sup])ly of oxygen in the lower water depends onthe gTcat volume of this water in comparison to the amount of 15G Thirfy-fiffh Annual Meeting decomposable matter discharged into it. The water absorl)edlarge quantities of oxygen during the fall and winter and onlya part of this stock has been exhausted, most rapidly at the hot-. Fig. 9—Green Lake. Sept. 6. 1905. torn and at the upper part of the cool water—tlie two ;-where the greatest amount of chemical activity seems to takeplace. The oxygen nowhere becomes so low as to make it im-possible for a considerable number of animals to live in the waterand in the mud beneath it. American Fisheries Society. 157 Green Lake is the only lake in Sonthern Wisconsin in wliichan oxygen curve of this character could be drawn. In most lakesthe bottom water is practically devoid of oxygen in September. In Lake ]\Iendota the whole of the cooler liottom water be-comes oxygen-free at a comparatively early period of the sum-mer and there is a long period there when the lower water can-not l)e utilized l)y animals. Jf this statement were true of alllakes, the smaller lakes would have only a very shallow surfacestratum which could he utilized. But in many smaller lakes anoperation goes on which materially increases the amount of oxy-gen anil tile thickness of the stra
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