maintained 10 to 15 times as long as the oxygen demand created by the 

 same amount of organic material mixed with sand. The oxygen demand can 

 increase many-fold when sediment containing organic material and bacteria 

 is resuspended by waves or currents (Butts, 1974; Baumgartner and 

 Palotas, 1970). For example, Butts (1974) found that under quiescent 

 conditions the sediment oxygen demand in the Illinois River at mile 198.8 

 in Peoria Pool was 2.8 g/m 2 /day, while the demand was 20.7 g/m 2 /day 

 when the sediment was disturbed. At three sampling stations in Meredosia 

 Lake (mile 72-78) the sediment oxygen demand under quiescent conditions 

 ranged from 2.58 to 4.32 g/m 2 /day, and from 12.92 to 83.0 g/m 2 /day under 

 disturbed conditions (Personal Communication, 2 September 1975, 

 Mr. Thomas A. Butts, Associate Professional Scientist, Illinois State 

 Water Survey, Peoria, Illinois). The oxygen demand exerted by sediment 

 in some reaches of the river and in some bottomland lakes is great enough 

 to seriously diminish the oxygen supply in the water. 



In August 1974, dissolved oxygen levels in Meredosia Lake were 

 3 mg/1, while oxygen levels in the river on the same date were 6 mg/1. 

 The readings were taken in the middle of the afternoon on an overcast 

 day, and waves produced by a strong wind were resuspending bottom sedi- 

 ments in the lake. In the lake, a die-off of gizzard shad was occur- 

 ring, and almost all the fingernail clams maintained in plastic cages 

 on the bottom of the lake had died since they had last been checked in 

 mid-July. 

 Fingernail clam die-off (1955) 



Starrett (1972) documented the die-off of fingernail clams and 

 summarized the drastic effect on fish and waterfowl: 



"Fingernail clams (Sphaeriidae) virtually dis- 

 appeared from the river above Beardstown in the mid- 

 1950' s (Paloumpis and Starrett, 1960 and unpublished) 

 These organisms were an important food item in the 

 river and its bottomland lakes for carp and diving 

 ducks (Aythyinae) , particularly the lesser scaup 

 duck ( Ay thy a af finis ) . Following the disappearance 

 of the fingernail clams, a sharp decline occurred 

 in the numbers of lesser scaups using the middle 



53 



