A classic example of a permanent man-made 

 change is the conversion of the Zuider Zee in the 

 Netherlands from a salt water estuary to a fresh 

 water lake between 1932 and 1940. 



This modification added land area and fresh 

 water resources and decreased the vulnerability of 

 the area to winter storms. Valuable mussel and 

 oyster industries were destroyed but a limnetic 

 finfish industry has been established. 



Bold actions such as this should be included in 

 long range planning to cope with the increasing 

 demands of the Nation's development. However, 

 planning must always be accompanied by an 

 attempt to understand thoroughly the physical 

 and biological consequences. 



^ /I Waddenzee 



Figure 10. The old Zuider Zee, cut off by an 

 enclosure dike to convert an estuary to a lake 

 and dry land. 



VI. EUTROPHICATION^' 



Sophisticated instrumentation is hardly neces- 

 sary to alert the pubUc to the fact that something 

 has gone awry in Lake Erie. People cannot enjoy 

 its use in the same ways that they could 20 years 

 ago. It is also evident that the southern part of 

 Lake Michigan and parts of Lake Ontario exhibit 



some of the same symptoms as Lake Erie. Dr. 

 David C. Chandler, Director of the Great Lakes 

 Research Division, Institute of Science and Tech- 

 nology, University of Michigan, in testimony 

 before the panel stated that the common denomi- 

 nator limiting the multiple use of the Great Lake 

 resources is water pollution. Most authorities 

 agree. 



The Federal Water Pollution Control 

 Administration^ ° identifies the major physical 

 problems of the Great Lakes area as: 



— Over-enrichment of the lakes 



— Build-up of dissolved solids in the lakes 



— Bacterial contamination of the lakes and tribu- 

 taries 



— Chemical contamination from industrial waste 

 discharges 



— Oxygen depletion of the lakes and tributaries. 



Historically, young lakes are relatively barren 

 bodies of water in terms of the amount of 

 biological Ufe which they support. As aging prog- 

 resses, the material retained by a lake gradually 

 increases in the bottom sediments. Through bac- 

 terial and other decomposition of sediments, the 

 lake waters become richer in nutrient materials to 

 which phytoplankton, the population of zoo- 

 plankton, and higher animal forms respond as the 

 food supply increases. Finally, deposits from 

 biological activity, both organic and inorganic, and 

 materials from the tributary waters fill the basin to 

 the extent that rooted aquatic plants take com- 

 mand and gradually convert the area to marsh 

 land.^ ' 



The aging process is known as "eutrophica- 

 tion," which can be defined as the process of 

 enrichment with nutrients.'^ Accelerated eutro- 

 phication or over-enrichment of the lakes results 

 from the input of nutrient materials, mainly 

 nitrogen and phosphorus, from man's activities. 



Much of the material in this section was taken from a 

 contract report of the Commission, Pacific Northwest 

 Laboratories, Battelle Memorial Institute, Great Lakes 

 Restoration- Review of Potentials and Recommendations 

 for Implementation, June 17, 1968. 



Water Pollution Problems of the Great Lakes Areas, 

 1966. 



Clair N. Sawyer, "Basic Concepts of Eutrophica- 

 tion," Journal Water Pollution Control Federation, pp. 

 731-144, May 1966. 



^^K. M. Stewart and G. A. Rohhch, Eutrophication-A 

 Review, report to the State Water Quality Control Board, 

 State of California (1967). 



III-42 



