521 



the plankton of the river, but even diminish the productivity 

 of the river water by lowering the relative amount of its nutri- 

 ent constituents. 



SPOON RIVER. 



In Spoon River we have a typical tributary of the larger 

 type, from prairie country, with no unusual contamination by 

 sewage or industrial wastes, draining 1,870 square miles, a little 

 more than one tenth of the basin above its mouth, and dicharg- 

 ing directly into the main channel. 



A detailed discussion of the environmental conditions in 

 this stream and of its plankton production will be found on 

 pages 340-350. It will suffice in this connection to recall the 

 facts that the recent origin of the tributary waters, its greater 

 turbidity, and burden of silt, all militate against plankton pro- 

 duction in this tributary. 



A consideration of the chemical conditions in Spoon River 

 and in the Illinois throws much light on the nutrition availa- 

 ble for the support of the plankton in tributary and channel 

 waters, a very important factor in the matter of plankton pro- 

 duction. In the following table the averages of all analyses 

 in these two streams and in Quiver Lake are given. 



CHEMICAL EXAMINATION OF WATER FROM THE ILLINOIS RIVER AT HAVANA, FROM 

 SPOON RIVER NEAR ITS MOUTH, AND FROM QUIVER LAKE— PARTS PER MILLION.* 





Spoon 

 River 



Illinois 



River 



Quiver 

 Lake 



Residue on 



Total 



522.3 

 167. 1 



367-5 

 304.1 



268.9 



248.2 



evaporation 



Loss on 

 ignition 



Total 



Dissolved 



41.9 

 24.4 



32.8 

 25.1 



27.5 

 25.6 





3-8 



21.6 



4.8 





14. 1 



10.4 



5-9 



fFree amm 



| Albuminok 



Nitrogen as<j Total or?ar 



onia 



.24 



.60 



1.29 



•039 

 1. 01 



.86 



.48 



1.03 



•H7 

 1.58 



.165 



•25 

 .61 



1 ammonia .... 

 tic 



u 



Nitrites . . . 





.023 

 .66 



titrates 







*Data from Tables X., XI., and XIII. 



