GASES IN WATERS OF WISCONSIN LAKES. 



1287 



and 10 meters in Stone Lake, and the consequent using up of the supply of free 

 carbon dioxide. 



MANUFACTURED OXYGEN. 







2 



4 



6 



8 



10 



12 



14 



lb 



Id 



20 



22 



24 



26 



28 



30 



32 



34 



36 



38 



40 



42 



C 

 6 4 



2 2 







4 6 



Cb 



T 30 32 34 36 38' 

 10 12 14 lb. IS 



In other lakes this process goes on much more vigorously than it did in 

 Stone Lake. An illustration may be given from Beasley Lake, a little body 

 of water in the Waupaca chain (fig. 1 7) , where the oxygen at the thermocline 

 rises to the maximum of about 15 cubic centimeters, and where its presence 

 is accompanied by a marked increase of the alkalinity of the water. 



It must be remembered that 

 both the amount of oxygen and 

 of alkalinity represent the al- 

 gebraic sum of numerous com- 

 plicated processes. The amount 

 of oxygen is determined not 

 only by the quantity manu- 

 factured, but also by that con- 

 sumed, and the quantity or 

 deficiency of carbon dioxide 

 depends on the relation of the 

 rate of the manufacture of 

 starch to the rate of the de- 

 composition of the plankton. 

 The two processes are not nec- 

 essarily parallel, and we not in- 

 frequently find, as is shown in 

 figure 18, a great excess of 

 oxygen, while the carbon di- 

 oxide curve shows no traces of 

 the process which has manufac- 

 tured it. In the soft-water lakes 

 whose reaction is usually acid, 

 the manufacture of oxygen in 

 the cooler water may cause a change in the reaction of the water. This is 

 illustrated by Silver Lake (fig. 19), a small pond in northeastern Wisconsin, 

 where the oxygen maximum occurs at 7 meters, and at the same depth the 

 reaction changes from a positive acid to an equally positive alkaline one. It 

 returns to a slight acidity at 9 meters, and from this point the amount of free 

 carbon dioxide rapidly increases. 



In the smaller and shallower lakes the presence of this manufactured oxygen 

 at the thermocline region is often of great importance in extending the inhab- 

 itable region. Beasley Lake is perhaps the best illustration of this fact. The 



C T 



Fig. 13. — Lake Geneva, September 26. 1907. 



Cb 



