unfavorable conditions imposed by the current, Presiunably the 

 plankton of the Island Section has increased as a result of pollu- 

 tion, both by the eastward drift of organisms produced near the river, 

 and by utilization of the excess nutritive material not used by orgsnisms 

 near the rivers. The relative positions of the sections with respect to 

 abundance of phytoplankton was the same as it was with respect to the 

 intensity of pollution as indicated by the content of albuminoid ammonia. 



Pollution has had another effect on the lake which is particularly 

 noticeable in the water of Maumee Bay, namely, the addition of a large 

 amount of particulate matter of organic origin. Although this material 

 is not living, much of it is so finely divided that rotifers and 

 Crustacea can utilize it readily as food. Thf? phytoplankton at the 

 two outer stations in the Maumee Bay Section was 26 times as abundant 

 as at Station 126, but this is not an accurate measure of the relative 

 abundance of food for the animals of the plankton. If the organic 

 detritus were added to the phytoplankton, the disparity between these 

 two sections would be still greater. But since there was no practic- 

 able method of determining the amount of detritus in the different 

 sections, the relative abundance of this source of food cannot be stated 

 numerically. However, it is reasonable to suppose that the abundance 

 of detritus, like the abundance of phytoplankton, varied directly with 

 the intensity of pollution as indicated by the content of albuminoid 

 ammonia. 



The zooplankton of Western Lake Erie 



Introduction 



Previous investigations in the Great Lakes 



Taxonomic and distributional studies of the plankton organ- 

 isms of the Great Lakes were made years before the earliest quantitative 



200 



