550 LAND ANIMALS 



manders, turtles, snakes, and mammals are all eliminated, to say noth- 

 ing of such swamp-dwelling invertebrates as snails, crustaceans, and 

 hydrocolous insects. 



An even more deleterious effect has been produced by man by the 

 dumping of industrial waste and city sewage into rivers or lakes. A 

 dramatic instance of this is given by the opening of the Chicago drain- 

 age canal in January, 1900, whereby the city wastes, formerly, in part 

 at least, emptied into Lake Michigan, were carried down to the Des 

 Plaines and finally to the Illinois rivers. Fortunately the ecology of 

 the latter stream had been well studied, particularly in the decade 

 before the opening of the drainage canal, and fortunately also these 

 studies were continued on an intensive scale for the two decades fol- 

 lowing, so that we have a fairly complete record of the results of this 

 experiment in waste disposal which was conducted on a geographic 

 scale. 



The so-called Sanitary Canal increased the average flow of the 

 Illinois River by 86% ; the mean rate was over 8000 cu. ft. per second 

 before the canal opened. The mean water level was raised about 3 ft. 

 The rooted vegetation along the margin of the old river and of the 

 old river lakes was flooded and killed and replaced in part by aquatic 

 plants. The greater depth caused a decrease in temperatures, especially 

 in summer temperatures. Although the Illinois River was not a clean 

 stream before the Sanitary Canal opened, nevertheless the amount of 

 contamination passing Peoria, 170 miles from Chicago, was increased 

 two and one-fourth times by the material brought in by the canal. 

 One of the first of the biological effects of the Chicago sewage was 

 to convert the lower Des Plaines and the upper Illinois rivers into a 

 vast open sewer with water grayish in color, offensive in odor, and 

 containing in summer only septic organisms such as the sewage fungus, 

 Sphaerotilus, and the Protozoa* characteristic of foul water. Sludge 

 collected along the bottom in slack waters which became 8 ft. or more 

 deep, and in late summer contained millions of tubificid worms. 

 Fishes were absent in summer, although they appeared in winter, as 

 did certain hardy invertebrates such as the pond snails Planorbis and 

 Limnaea, and Entomostraca. 



Before the Sanitary Canal opened in 1900, the first green plants 

 which are characteristic of clean water appeared in summer between 

 35 and 46 miles from Lake Michigan; in 1911 they were found only 

 from 80 to 110 miles downstream, and optimum conditions for such 



* Carchesium, Vorticella, Epistylis, Oikomonas, Bodo, and Paramecium 

 putrinum. 



