relationships between turbidity and aquatic plant production have 

 been reported by other researchers (Martin and Uhler, 1939: 120; Cham- 

 berlain, 1948: 352; Robel, 1961: 437). 



Other factors have been responsible for increasing turbidity in the 

 Illinois and Mississippi Rivers. Waves produced by wind can resuspend 

 bottom sediments and increase turbidity (Chamberlain, 1948: 342; Jackson 

 and Starrett, 1959: 163). Jackson and Starrett reported that as 

 wind velocity increased from 8 to 35 miles per hour at Lake Chautauqua 

 (LaGrange Pool, Illinois River) , the Jackson Turbidimeter Units in- 

 creased from 174 to 700. Rough fish, primarily carp, disturb the 

 false or soft mud bottom while feeding and cause sediment particles 

 to become resuspended, thereby increasing the turbidity of backwater 

 lakes and sloughs (Martin and Uhler, 1939: 120; Chamberlain, 1948: 

 353; Jackson and Starrett, 1959: 163). 



It can be seen that several factors are responsible for the in- 

 crease in turbidity of the Mississippi and Illinois Rivers. The end 

 result has been to restrict the amount of sunlight reaching the bottom — 

 sunlight needed by plants to germinate and manufacture food. 



Increased sedimentation has reduced the abundance of marsh and 

 submerged aquatic plants in both Pools 25 and 26. Sedimentation pro- 

 duces a soft, false bottom which covers the original firm substrate, 

 making it difficult for marsh and aquatic plants to gain or retain a 

 foothold. Wave action uproots insecurely anchored vegetation as well 

 as increases the water's turbidity. Sedimentation also affects aquatic 

 and marsh plants by smothering valuable plant beds and partially 

 filling backwater lakes and sloughs in the Illinois and Mississippi 

 River valleys. Yeager (1949: 55) indicated that extreme flood condi- 

 tions during the early growing seasons of 1943, 1944, and 1945 smothered 

 submerged and emergent plant beds with mud, decreasing the stands of 

 these plants in sloughs and lakes at Calhoun Point, Pool 26. As a 

 result of sedimentation filling the backwater lakes and sloughs, the 

 acreage of water is reduced and the bottom of the lakes becomes more 

 uniform in depth, thereby decreasing species diversity of the plant 

 community. 



