of no pollution should be placed somewhere between Stations 25U and 

 2$6, and the small amount of evidence from Station 255 indicates that 

 it should be placed between this point and Station 25U. 



At the remaining five stations in the series the counts of 

 index organisms showed conditions tjipical of clean bottom. There was 

 considerable variation in the coimts, but the Tubificidae did not. 

 exceed hh per square meter, and HeXagenia larvae were never less than 

 182 per square meter. The results obtained in this series are shown 

 graphically in Figure 22. 



In connection with the question of the outward extension 

 of the area of polluted bottom, it is worthy of note that the outer end 

 of the steamship channel is located almost exactly halfway between 

 Stations 25U and 255, and thus marks the limit of the area of polluted 

 bottom. A study of the charts of this region shows that the depths 

 outside of the channel, near the outer end, are only slightly less than 

 those in the channel, and the question arises whether a channel of such 

 meager depth could operate as an important factor in determining the 

 distribution of organic debris derived from the river nine miles away. 

 In view of the slight depth of the channel near the outer end, one is 

 led to answer the question in the negative, but the biological evidence 

 presented in this section and in the section following indicates that 

 the question should be answered in the affirmative, Osbiirn (1926) 

 noted the importance of the channel in controlling the distribution 

 of organic debris in Maumee Bay, 



Pollution near the entrance to Toledo Harbor 



Having determined the lakeward extent of polluted bottom along 

 the line of the steamship channel, we may now consider the extent of 

 pollution on the sides of the channel. Because of the dangers of navi- 

 gation within the harbor outside of the channel, sampling was confined 

 to stations located along lines across the entrance, that is, at the 

 level of the outer end of the channel. Two series of stations were 

 established at this level, one of three stations on a line running in a 

 generally northwest direction from the end of the channel, the other of 

 four stations on a line running in a generally southeast direction from 

 the same point. The positions of these stations are shown in Figure 23. 

 The results obtained, along with those from Station 2Sk, are shown in 

 Table 89. In order to simplify matters, the distances and directions 

 are referred to Station 251i, as though it were located at the end of the 



275 



