tuhificid worms were noticeably more abimdant than they were at stations 

 in the Island Section, but still were below the number arbitrarily 

 chosen as being indicative of pollution. At Station ll6, the Tubificidae 

 were absent, but the number of Hexagenia was snail in spite of the pre- 

 dominance of mud on the bottom. More complete data were obtained in 1928, 

 when five samples were taken on four dates. The mean counts per square 

 meter were: Hexagenia, lU5j Tubificidae, 27; and Chironomidae, 26U. 

 Thus, the evidence of clean bottom on this side of the channel is fairly 

 conclusive in spite of the small number of samples, and the limit of the 

 zone of light pollution may be placed between Stations 25U and 112, 



It will be noted that Stations 110, 2$[i, and lllj had rather 

 large numbers of Sphaeriidae, mostly of the genus Musculium, Although 

 Musculium transversum is known to be highly tolerant to pollution, its 

 value as an index organism in the cases cited is largely discounted by 

 the facts that a large majority were juvenile indi.viduals, and that 

 Musculium commonly has a "spotty" distribution. Certain of the stations, 

 particularly Station ll6, had large numbers of chironomid larvae as 

 compared to stations in the Island Section. Since the species of 

 chironomids were not determined, it is impossible to state whether there 

 is any significance attached to their presence. 



Summary statement regarding pollution in the 

 Maumee Bay Section 



In the summers of 1929 and 1930, a study was made of the natvure 

 of the bottom materials and their included animals at three stations 

 situated on the steamship channel of Toledo Harbor. In 1930 the study 

 was extended to a number of special stations, most of v/hich were located 

 in the neighborhood of the outer or lakeward end of the channel. A few 

 samples were taken in 1928, 



The results of this study may be summarized, in terms of the 

 extent and degree of pollution, as follows. The bottom was heavily 

 polluted from the mouth of Maumee River to a distance of about 3 1/2 miles 

 along the steamship channel; it was moderately polluted for the next 1 l/2 

 miles, and lightly polluted for the remaining h miles to the outer end 

 of the channel. There was no evidence of pollution at a distance of one 

 mile in three directions from the outer end of the channel, or along the 

 south shore of the lake east of Little Cedar Point. The extent of the 

 three zones of pollution is shown in Figure 23. The question of the 

 shoreward extension of the lines between zones is a matter of conjecture, 

 since no data are available for that part of the harbor outside of the 

 channel. The lines were extended to the shores in what appeared to be 



281 



