stations in the Island Section, and the counts mit;ht well have been 

 included in the averages for thtat section, but in the interest of 

 consistency with other chapters in this report, the station has been 

 retained in the Detroit River Section. The differences in the 

 fauna here as compared with Station 126 are too obvious to reqioire. 

 mention. 



Pollution in the Detroit River Section 



As in the case of the Maianee Bay Section and the River Raisin 

 Section, an attempt was made to determine the degrep^and extent of 

 pollution in the Detroit River Section by taking, bottom samples at a number 

 of special stations in 1930. The problem of defining the limits of 

 pollution in this section is somewhat more difficult than in the other 

 sections because the wide mouth and voluminous discharge of the river 

 have permitted the diffusion of suspended organic debris over a large 

 area having different types of bottom. Since most of the stations near 

 the outer edge of the polluted area were sampled only once, and since 

 the organic debris was certainly distributed unevenly, the basis for 

 conclusions regarding the position of this outer edge must be regarded 

 as relatively insecure. Even though the data must be considered in- 

 adequate, it seems probable that any errors (in terms of area) arising 

 from their use would be small compared with the total area of Western 

 Lake Erie, 



Table 97 shows the results obtained at 10 stations located on 

 a course from Bois Blanc Light in Detroit River (Station 219) to a 

 point in the lake It miles distant (Station 13U), as shown in Figure 23, 

 The samples taken at the first four stations revealed considerable 

 variation in the type of bottom and in the abundance of the index 

 organisms. These marked variations probably resulted in part from the 

 dredging operations carried on from time to time by governmental 

 agencies. Such operations would tend to make the bottom markedly un- 

 even, and since the current is rather strong in th'is area, organic 

 debris would be swept from high points and irould settle in depressions. 

 Also the current would tend to keep debris in suspension for some 

 distance out into the lake, where its strength would be dissipated and 

 the debris deposited. That such a thing actually happened is sug- 

 gested by the fact that there were fewer tubificid worms at Station 219 

 than at four stations below it. It may be mentioned here that single 

 samples were taken at two stations not shown in the table. These were 

 221A and 221B, located one and one-half miles east and one mile west, 

 respectively, of Station 221, At Station 221A the bottom was composed 



293 



