SECTION 13 



SYNERGISTIC EFFECTS OF PHOSPHORUS AND HEAVY METAL LOADINGS ON 

 GREAT LAKES PHYTOPLANKTON 



E.F. Stoermer, L Sicko-Goad and D. Lazinskyl 



INTRODUCTION 



The Laurentian Great Lakes are one of the major physiographic features 

 of North America. They represent a tremendous resource to the people of 

 Canada and the United States. They provided European colonizers a route of 

 access to the interior of the continent and continue to provide an important 

 transportation artery, particularly for the raw materials of heavy industry. 

 In the early decades of the present century the Great Lakes supported an im- 

 portant fishing industry and their waters furnished a seemingly inexhaust- 

 ible supply of high quality potable water and industrial process and cool- 

 ing water. As a result of these favorable circumstances the shores of the 

 Great Lakes were a favored site for early settlement and have supported the 

 growth of several major population and industrial centers. 



Unfortunately, the byproducts of these populations and industrial con- 

 centrations have had effects on the Great Lakes ecosystem which damage the 

 yery resource potential which allowed their growth and development. During 

 the past several decades important fish stocks have been severely damaged 

 or, in some cases, entirely lost. Some of the stocks remaining have been 

 contaminated by heavy metals or organics to the point that there are serious 

 questions regarding their suitability for human consumption. Eutrophication 

 has also caused modifications in the composition and abundance of primary 

 producer communities which have had direct effects on the utility of Great 

 Lakes waters. Overproduction and changes in composition of the phytoplank- 

 ton assemblages of the Great Lakes have led to taste and odor problems in 

 municipal water supplies and additional treatment costs for removal of 

 biological materials from the water. Extreme overproductivity of benthic 

 communities has resulted in nuisance growths of attached algae such as 

 Cladophora . 



These problems have been recognized and considerable effort has been 

 directed towards defining the causes of water quality and associated re- 



^Great Lakes Research Division, University of Michigan, Ann Arbor, Michigan 

 48109. 



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