Dunes Park gave counts from 128 to 193 thousand units of blue-greens 

 and diatoms combined. At Dunes Park, filter paper collections showed 

 825 thousand units of blue-greens (Lyngbya), and 713 thousand units of 

 diatoms. Even in July, when a low diatom count would be expected, net 

 collections jaelded ii7U thousand diatoms per liter at Chicago. It is 

 extremely unlikely that these counts represent the normal amount of 

 phytoplankton in Lake Michigan, either for the lake as a whole or for 

 the region investigated. It is a well-known fact that the lake is polluted 

 along the heavily populated south shore, and it seems almost certain 

 that the algae have increased greatly as a result of the raw materials 

 for food manufacture addod to the water by the domestic sewage. For 

 that reason, it need not be concluded that Lake Michigan is more pro- 

 ductive than Lake Erie in the Island Section, 



Burkholder and Tressler (1932) made a study of the plankton 

 of some bays at the east end of Lake Ontario in June, July, and 

 August, 1931. Greens and blue-greens contributed very little to the 

 plankton as compared with diatoms. Only one station had a count of 

 more than 60 thousand units of greens per liter, and many had counts 

 between 10 and 30 thousand units. Blue-greens were more rare than 

 greens J the highest count was 30 thousand units, and the group was rare 

 or wanting at several stations. Diatoms were quite abundant at all 

 stations. The highest count was about 300 thousand units per liter, 

 and several were as high as 120 thousand. In general, these counts 

 are higher than those in Western Lake Erie at corresponding times of the 

 year. However it should be noted that the bays are shallow and somewhat 

 protected, so that they do not give us any idea of the amount of plankton 

 in the open lake. 



These few comparisons within the Great Lakes contribute little 

 toward an answer to the question of richness of plankton in Western Lake 

 Erie, About all that can be said with certainty is that Western Lake 

 Erie is more productive than the rest of the lake, and that it is more 

 productive than Lake St. Clair, From our knowledge of plankton produc- 

 tion in inland lakes, it seems probable that Lake Erie, because of its 

 shallowness, is the most productive of the five large lakes of the 

 system. 



Where possible, comparisons of the abundance of plankton by 

 weight are more satisfactory than by count. Several determinations of the 

 weight of plankton in the Island Section of Western Lake Erie were made 

 in autumn of 1929. The method was as follows: A one liter sample of 

 lake water was run through the electric centrifuge twice, and the plank- 

 ton transferred to a silica dish. The sample was dried at 60 degrees 



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