60 



LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



TABLE II 

 Inorganic Nitrogen — Organism Relationships in Two Small Ohio Creeks 



and temperature were optimal for many species, and stream flows average. 

 Both creeks showed small amounts of nitrites and nitrates but admission 

 of a sewage effluent below Station 2 in Lytle Creek changed that condition. 

 Station 1 was above the town, some of whose street drainage was respon- 

 sible for the increase at Station 2. Within about four miles (Station 5) 

 nitrates had decreased to normal, nitrites had dropped nine-tenths, and 

 organisms had multiplied twenty-five times; there was a dense bloom of 

 Euglena, Chlamydomonas and Phacotus. 



Table III shows that temperature may keep populations low even if 

 sufficient nitrogen and phosphorus are present; but rising temperatures 

 result in a sharp increase of organisms, until the available nutrients are 

 lowered past a critical point, when organisms also decrease sharply. This 

 table does not indicate that most of the organisms in Lake Delevan in 

 January and February were quite small, whereas in April and May the 

 organisms were much larger and of different species. 



TABLE III 



Nitrogen-Phosphorus Organism Relations in Lake Delevan 



Detailed studies of these Wisconsin lakes gave the following average 

 inorganic nitrogen and phosphorus values over a year's cycle, shown in 

 columns one and two of Table IV and averaged from analyses of samples 

 collected during one year. 



