Lake Maxinkuckee, Physical and Biological Survey 113 



Microcystis, and, indeed, of most blue-green algae, are such as to 

 make it undesirable. Upon reaching the surface on hot days the 

 scum turns white and milky, emits a rank "green-corn" odor and 

 dies, giving all the water about it a milky tinge. Under such cir- 

 cumstances it is quite natural that bathers would avoid it. There 

 is, indeed, a prevalent notion that the plankton scum is irritating 

 to the skin, producing, in mild form, about the same symptoms as 

 those of ivy poisoning. Several people were met who claimed that 

 they had thus been poisoned. Two boys living in Culver claimed 

 to have so suffered, and another person reported that about 1904 

 or 1905, he had been badly poisoned by the water of Lake Maxin- 

 kuckee wherever it had touched him. A doctor diagnosed his case 

 as "old fashioned prairie itch." 



On another occasion, a young man, on being invited to go in 

 bathing during the period of plankton scum, remarked that he 

 was afraid of getting poisoned. We have never suffered nor 

 personally seen any one affected. In many parts of the country 

 there is a prejudice against going swimming during "dog days." 

 This probably has some reference to plankton-scum ; for along the 

 Maumee River at Defiance, Ohio, some boys were noted observing 

 some scum on the water and remarking: "It's coming dog-days 

 and we must quit going in swimming." 



A very heavy plankton-scum indicates an excess of vegetation 

 in the plankton. It is a decided nuisance both on account of the 

 prejudice against it and the uncleanly appearance it gives the 

 shore. It could, of course, be removed by the addition of sufficient 

 quantities of copper sulphate, but the use of this kills algse indis- 

 criminately and should not be attempted except as a last resort. 

 Minnows of various species (Notropis blennius, N. cayuga, Fundu- 

 lus diaphcmus, Labidesthes sicculus, etc.) and painted turtles eat 

 some of the plankton. Fresh water mussels, however, are the 

 heaviest feeders on it, subsisting almost entirely upon it and con- 

 suming considerable quantities. Their presence in the lake is de- 

 sirable, and they can easily be propagated in great numbers. Per- 

 haps the thick-shelled forms of Lampsilis luteola, such as those 

 found at Lake Pokegama, Minn., could be planted in sufficient 

 quantities to keep the excess of plankton down, and at the same 

 time, in due season, furnish a valuable amount of button material 

 for the markets. 



The study of the vertical distribution of the plankton carried 

 on by Juday in 1899 and by Young in 1900, and reported on by 

 them, was discontinued in the early autumn of 1900. After that 

 time efforts were made by whatever suitable means were at hand 



