CONTENTS 



Page 



TABLE OF CONTENTS i 



LIST OF TABLES iv 



LIST OF FIGURES i* 



PART I: INTRODUCTION 1 



PART II: MATERIALS AND METHODS 5 



Aquatic Communities and Water Quality 



Sedimentation 7 



Terrestrial Communities 



Wetland Plants 7 



Population Data 7 



PART III: RESULTS AND DISCUSSION 9 



Aquatic Communities 9 



Plankton — Mississippi River 9 



Phytoplankton — Illinois River 11 



Zooplankton — Illinois River 18 



Benthos — Illinois River 20 

 Possible Effects of Barge Traffic on Benthos 



in the Illinois River 25 



Benthos — Mississippi River 28 



Historical Perspective 28 



Pre-Dam and Post-Dam Surveys 28 



Species Composition Changes 29 



Effects of the Navigation System on Benthos 29 

 Importance of Benthos as Food for Fish 



and Wildlife 31 



Recent Changes in the Benthos 32 



Commercial Mussel Fishery — Illinois River _ 33 



Historical Perspective 33 



Pre- and Post-Dam Mussel Harvests 34 



Species Composition Changes 36 

 Economic Factors Affecting the Commercial 



Mussel Fishery 39 

 Effects of the Navigation System on the 



Mussel Fauna 40 



