The results obtained from seven other special stations in the 

 area east of Station 126 are shown in Table 99 • The location of 

 these stations is indicated in Figure 28. At Station 2.32, located two 

 miles approximately southeast of Station 126, the single sample showed 

 189 Tubificidae per square meter but no Hexagenia lai-vae, indicating 

 light pollution. The next three stations along the same course 

 (Stations 231, 230, and 229) yielded no evidence of pollution. At Sta- 

 tion 228, located two miles north and slightly west of Station 229, the 

 Tubificidae were present in small numbers, as were the mayfly larvae. 

 Two miles farther on the same course (Station 22?) there was definite 

 evidence of light pollution. At Station 226, located halfway between 

 Stations 22? and 225, there were few organisms of any kind, but the mud 

 had a distinct oily appearance and odor. On the basis of the small 

 amount of data from this region, the line of demarcation between the 

 zones of light pollution and clean bottom should be placed between 

 Stations 232 and 231 in the southeast series, and between Stations 22? 

 and 228 in the north series. When so placed, the zone of light pollution 

 includes three stations (Stations 223, 221;, and 225) at which no evidence 

 of pollution was found. The bottom was firm at each of these stations, 

 and it is probable that a considerable area about them had the same type 

 of bottom. The current of the river doubtless was responsible for the 

 failure of organic debris to lodge on the bottom, but it is not clear 

 why other stations, such as Station 222, were not affected in the same 

 way. 



Summary statement regarding pollution in 

 the Detroit River Section 



Samples were taken at two regular stations in both years and at 

 a number of special stations in 1930. Because of the large area affected 

 by pollution and the irregular distribution of the organic material, it 

 was not found possible to determine the limits of pollution as confidently 

 ss in the case of Maumee Bay Section and River Raisin Section. No evidence 

 of heavy pollution, as defined in this report, was found in the river 

 itself or in the lalre near its n:outh. The only station which showed 

 noderate pollution was located approximately three miles out from the 

 mouth of the river, but all of the area above this was assigned to the 

 zone of moderate Dollution. It was estinated that the outer edge of the 

 zone of light pollution extended a distance vprying from 3 1/2 to 7 1/2 

 miles from the mouth of the river. An unknov.. but comiiderable part of 



297 



