The absence of strong acids or alkalies in appreciable quantities 

 is indicated by the close correlation between the amount of dissolved 

 oxygen and the excess or deficiency of free carbon dioxide in the water, 

 even near the mouths of the rivers. That is, the degree of acidity or 

 alkalinity to phenolphthalein was such as might be expected from the 

 oxygen content of the same saiuple, knowing that low oxygen is ordinarily 

 associated with an excess, and high oxygen with a deficiency, of free 

 carbon dioxide. Moreover pH values were never extremely high or 

 extremely low. 



However, data on acidity or alkalinity would give no clue to the 

 presence of neutral chemicals or those with weakly acid or basic properties, 

 which might be highly toxic to living organisms. Phenol and some of its 

 derivatives are common industrial wastes of this type. Fortunately 

 published data on the amount of phenols in parts of Western Lake Erie are 

 available (Donaldson and Furman, 1927). This paper r eports 210 tests made 

 at four stations, three near Toledo Harbor Light and one near the mouth of 

 Detroit River. Phenol was detected in 86 of the 210 samples. The max- 

 imum amount in any one sanple was 52 parts per billion; the mean at Toledo 

 Harbor Light was 3.6, and at the mouth of Detroit River 7.9 parts per 

 billion. Numerous analyses were made of wastes which enter Maumee River 

 and its tributary streams at Toledo. The waste showing the highest concen- 

 tration of phenol contained 37,800 parts per billion (0,0038 per cent), 

 Baskina (1926) reported that Cyclops insignis was unharmed by solutions 

 of phenol weaker than 1/200 Normal (0,0U7 per cent), which is more than 

 ten times as strong as the \;aste indicated above. If w e take into account 

 the great dilution which the wastes undergo in the river and in Maumee 

 Bay, it seems highly improbable that concentrations sufficient to be 

 harmful to the most delicate plankton organisms would ever occur in the 

 bay or lake. 



It is possible that chemicals other than phenols are present in 

 concentrations great enough to be harmful to organisms, but the possibility 

 seems remote. The best indirect evidence on this point is afforded by 

 the data on abundance of plankton in different sections of the lake. If 

 poisonous substances kill the plankton organisms, we should expect to 

 find little plankton where there is definite evidence of pollution, as 

 in the Haumee Bay Section. Contrary to such expectation, the water of 

 this section contained much more plankton, both plant and animal, than 

 the water of the Island Section, In fact, throughout the area studied, 

 the more heavily polluted stations yielded a greater abundance of plankton 

 than the stations polluted only lightly. Obviously, then, in the 

 polluted areas, the factors making for great production of plankton were 

 more effective than any possible factors tending toward destruction of 

 plankton. 



138 



