algae. The algae were less than one half as abundant at Station 2^2 as at 

 Station 250. To be perfectly in accord, nitrite and nitrate should be higher 

 at Station 252, but nitrite was lower and nitrate was the same. At Station 2514 

 free and albuminoid ammonia were reduced further, and the algae were about one 

 third as abundant as at Station 250. Nitrate was more concentrated at Station 

 25U than at Station 250, althout^h the potential supply, as indicated by the free 

 ammonia, was smaller. It appears that the great reduction in ammonia made it 

 impossible to support a population of plankton algae sufficiently large to re- 

 move nitrate as completely as at Station 250. It is not clear why nitrite 

 failed to increase along with nitrate, but in view of the complexity of the 

 bio-chemical processes, the failure need not be considered as a major ob- 

 jection to the general explanation offered. 



The proposed explanation for low nitrite and nitrate in this section 

 may be used to account for a similar situation in the Portage River Section 

 (page 93 ) . In the section last named, conditions differed from those at 

 Station 250 principally in the lower concentration of free and albuminoid 

 ammonia, and this difference was reflected in the smaller number of plankton 

 algae. In both places low nitrite and nitrate in the presence of much de- 

 composing organic matter can be explained best by the abundance of phytoplanktcn 



Rice (1917) studied the relation between nitrogen and plant grcv-th in 

 Winona Lake, Indiana, and reported condibions somewhat similar to those re- 

 ported here. He found that large aquatic plants were most abundant along the 

 shore nearest to sources of pollution, but that, at the height of the growing 

 season, there was very little nitrite and nitrate in the water. He concluded 

 that "in regions of very dense or even of fairly dense vegetation where great 

 contamination exists, a chemical determination of nitrates or nitrites as an 

 indicator of pollution in making a sanitary water analysis is absolutely 

 worthless in itself". He believed, however, that ammonia was not used by 

 the plants, but acted merely as reservoir from which nitrite and nitrate 

 were derived. 



Conclusions Regarding Pollution 



The data on oxygen and nitrogen show that the water of Maumee River near 

 its mouth was heavily polluted. The water of Maumee Bay also was polluted 

 but there was marktd improvement as the water moved out into the bay. At a 

 distance of 8.5 miles from the mouth of the river, nitrogen deterird nations 

 indicated light pollution, but the recovery ^^dth respect to oxygen content 

 was more abrupt. At the mouth of the river, the oxygen content was sometimes 

 high and sometimes low, as a result of reversing currents in the river. There 

 were no marked oxygen withdrawals at a distance of 2.25 miles or more from the 

 mouth of the river. A probable exception to this statement should be noted 

 for the water immediately in contact with the bottom. Since the so-called 

 bottom samples were taken some distance above the bottom, the maximum effect 

 of deposited organic matter on the oxygen content would not be detected. In 

 Maumee Bay, at the depths studied, the harmful effect of the pollution 



110 



