Normally, the natural aging process proceeds at a 

 slow pace measured by the geological time scale. 

 However, man has so accelerated this time scale, 

 through his discharge of nutrients to the lakes, that 

 significant aging is observed within a generation. 



Accelerated eutrophication is emphasized in 

 this report because it is the most critical problem, 

 in terms of impairment of benefits, facing the 

 Great Lakes. Its remedy will require a number of 

 curative measures. Other problems such as buildup 

 of dissolved solids and oxygen depletion are closely 

 intertwined with eutrophication.^'' 



Accelerated eutrophication of Lake Erie is 

 manifest in the following ways: 



— Blue-green algal blooms and other algal groups 

 such as diatoms produce noxious odors and at 

 times appear as unsightly scum on the water 

 surface. 



— These same algae impart unpleasant tastes to 

 water supplies. 



— Dissolved oxygen levels are depressed in ther- 

 mally stratified areas. 



— Bottom-dwelling fauna change from clean water 

 forms to less desirable forms that are tolerant to 

 pollution and low oxygen concentration. 



— Fisheries resources have changed from highly 

 prized game fish, such as pike, trout, and whitefish 



J. F. Can, Dissolved Oxygen in Lake Erie, Past and 

 Present, University of Michigan Great Lakes Research 

 Division Publication No. 9, pp. 1-14. 





W^ ',f?^' 



Figure 11. Symptoms of accelerated eutroph- 

 ication in the Great Lakes include odorous and 

 unsightly algal blooms which foul beaches and 

 deteriorate water quality. (Department of the 

 Interior photo) 



to the coarse, less valuable fish such as carp, 

 catfish, and sheepshead. 



— Nuisance filamentous algae growing in shallow 

 waters near shore break loose and wash up onto 

 shores and beaches. 



— Unsightly, odorous conglomerates of algal and 

 other pollutants interfere with recreational use of 

 waters and beaches, clog municipal and industrial 

 water intakes, and depress property values. 



Water quality assessments indicated that nearly 

 all of Lake Erie is eutrophic. Lake Ontario is on 

 the verge of becoming eutrophic, and Lake 

 Michigan is exhibiting some of the symptoms of 

 eutrophy in certain areas, particularly in the 

 southwestern portion. Isolated examples of pollu- 

 tion have been observed in Lakes Huron and 

 Superior, although their water quality is generally 

 considered good.^" 



Oxygen can be depleted through the addition 

 of organic substances to the receiving bodies of 

 water and the proliferation of algae associated 

 with eutrophic conditions. Organic pollutants, 

 where controllable, can be dealt with by implement- 

 ing treatment methods required to meet water 

 quahty standards. 



The principal nutrients of concern in the 

 enrichment process of eutrophication are phos- 

 phorus and nitrogen compounds. Other nutrients 

 also have been implicated as contributors to 

 accelerated eutrophication, including vitamins, 

 growth hormones, and amino acids. In addition, 

 trace elements are known to play a major role in 

 the process, but their relative importance is ill- 

 defined." 



The most important contributors to eutrophica- 

 tion ranked in order are: 



— Municipal wastewater 



— Sedimentation 



— Agricultural runoff. 



Alfred M. Beeton, "Indices of Great Lakes Eutrophi- 

 cation," Proceedings, Ninth Conference on Great Lakes 

 Research, Great Lakes Research Division, University of 

 Michigan, PubUcation No. 15, 1966. 



^'e. J. Martin, and L. W. Weinberger, "Eutrophication 

 and Water Pollution," ibid. 



III-43 



