during the presence of a pollutant in the water or sediment, mussels close their shells for 

 extended periods. The Mossel Monitor would be placed in an mussel bed, along with a 

 microcomputer, power supply, and recorder in a waterproof housing. The electronic 

 components can also be housed separately on shore. Data could be downloaded from The 

 Mossel Monitor hourly or daily, and analyzed for any changes in zebra mussel shell movement. 

 This equipment could also be set up to automatically alert a manager and to trigger a water 

 sampler to collect a sample of water when the alarm is given. Factors causing the stress response 

 could be identified by subsequent chemical analysis. 



In order for any monitoring program to be successful, it is necessary for the work to be 

 continuous. If biomonitoring is selected as a route of action for the protection of Illinois' native 

 mussels refuges, it should be supported by a long-term commitment of funds for personnel and 

 equipment. 



5. Conclusions 



1 . Toxic sediments did occur within Reach 15 of the Upper Mississippi River. These 

 sediments exhibited chronic, rather than acute toxic effects on deertoe mussels ( Truncilla 

 truncata) and waterfleas {Ceriodaphnia dubia). 



2. Organisms exposed to porewaters extracted from sediments of Sylvan Slough of Reach 15 

 displayed a toxic response indicating chronic toxicity. Sylvan Slough is an Illinois native 

 mussel refuge and home to the federally-endangered Higgin's-eye pearly mussel. Lampsilis 

 higginsi. 



3. The mussel filtering assav. with modification, is a eood method of detecting sediment 



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