2. Shoreline erosion into Lake 



Superior: > 4,000,000 metric tons per year 



3. Resuspension of lacustrine >300,000 metric tons per year for 

 clay in Lake Superior: depths of 7 21 meters (< 70 feet). 



Chemical Effects 



The water quality of western Lake Superior is directly affected by ex- 

 tensive erosion of the glacial-lacustrine red clay deposits (Dikas et at . , 

 1973). In addition to loss of property value, increased turbidity in 

 drinking water, and a decrease in aesthetic value, Bahnick (1976) has 

 attributed the following aquatic chemical changes to red clay turbidity. 



In addition to human health effects, the problems of biotic effects of 

 red clay turbidity centers on the overall effect upon the fisheries 

 resource of Lake Superior. Recent studies have approached this problem 

 from the viewpoint of turbidity effects upon species composition, feeding, 

 predation, distribution, mortality and growth. Swenson (1975) has found 

 the following preliminary results: 



1. Changes in food habits of major species can be expected to 

 result indirectly from turbidity through its influence on 

 light penetration, fish distribution and distribution of 

 plankton suites. Increased predation by pelagic smelt on 

 larval herring as a result of turbidity may have resulted 

 in the decline of commercial lake herring population as 

 smelt can be expected to leave the bottom during turbid 

 periods and increase predation pressure on the herring 

 larval . 



2. Turbidity may have indirect effects on walleye feeding 

 success, rates and time. 



3. Tank experiments indicate lake trout have a preference for 

 low turbidity, while walleye showed a demonstrated pre- 

 ference for the highest turbidity levels. 



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