The water was rather low in oxygen at t he station near Pointe 

 Mouillee. The cause of this condition is not evident. It seems im- 

 probable that the vrater was derived from Detroit River, for the stations 

 above Pointe Mouillee contained much more oxygen. It minht be supposed 

 that the water came from Huron River, but the few data obtained by the 

 Michigan Stream Control Commission in 1931 (unpubliahed) do not indicate 

 an oxygen deficiency in the lower part of the river. However, not 

 enough samples were taken in the river to justify the conclusion that 

 it could not be responsible for the condition noted off Pointe Mouillee, 

 The presence of water higher in oxygen at the station nearer the mouth 

 of the river is not an insurmountable objection to this explanation, 

 for the river is subject to reversals of current near the mouth. A 

 change from outgoing to ingoing current may have taken place just before 

 the sample was taken near the mouth of the river, so that the water at 

 that point would be from Detroit River rather than from Huron River, 

 That such a situation actually existed is suggested by the fact that the 

 amount of oxygen at the point off the river was almost the sane as in 

 Detroit River three miles above. The amount of oxygen at a point be- 

 tween Grosse Isle and Bois Blanc Island was noticeably greater than at 

 the two preceding points, wliich are closer to the west shore of the 

 river, Howe\er, the evidence is too scanty to justify the conclusion 

 that the observed condition near the west shore is the usual one or that 

 the condition resulted from pollution. 



The water of Lake St. Clair enters Detroit River with a high 

 content of dissolved oxygen. This is well shown by results obtained at 

 the intake for the Detroit water supply (Detroit Department of Water 

 Supply, 1930), Over a period of a year from July, 1929 to June, 1930, 

 the lowcv'st observed value was 9«0 parts per million in June, 1930, and 

 the mean was 11.7 parts per million, which would be near the saturation 

 point. Additional data on chemical conditions in Detroit River are 

 given in Table U^, On September 23, 1930, a series of six samples was 

 taken along a line from the south end of Lake St. Clair to Station 126, 

 in Lake Erie near the mouth of Detroit River. The sampling points near 

 Belle Isle, Ambassador Bridge, and Fighting Island were in mid-stream. 

 Mo claim is made that samples from these points give an adequate idea 

 of conditions in cross-sections of the river. They were taken inciden- 

 tally during an excursion to Lake St, Clair for plankton samples, and 

 represent conditions onlj'- at the time and place indicated. 



There was an abundance of oxygen at all of the stations listed 

 in the table. The sky was overcast during the entire period of sampling 

 and it is reasonable to suppose that higher results would have been 



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