SUBMERSED AQUATIC VEGETATION DISTRIBUTION OF THE UPPER 
ILLINOIS RIVER 

Thad R. Cook and Mike A. McClelland
Illinois Natural History Survey, Illinois River Biological Station, Havana, Illinois 62644

The importance of aquatic vegetation to the ecological health of the Illinois River, and 
aquatic systems in general, is widely recognized.  Submersed aquatic vegetation (SAV) 
for example, serves as a main source of nutrition, nesting and rearing habitat for 
invertebrates, fish, waterfowl and other wetland organisms.  The importance of 
monitoring and documentation of these life forms is also widely recognized.  The 
relevance of historical and present-day SAV distribution, changes over time and factors 
influencing these changes are import when considering restoration.  Random sampling 
was conducted in three upper Illinois River reaches, Dresden, Marseilles, and Starved 
Rock in 2005 utilizing Long Term Resource Monitoring Program (LTRMP) vegetation 
monitoring protocols to document SAV distribution.  A total of 236 sites were sampled 
throughout the three reaches with no SAV documented in the Marseilles and Starved 
Rock.  However, 9 species of SAV were documented within the Dresden reach.  Water 
Stargrass Heteranthera dubia, Wild Celery Valisneria americana, and Eurasion 
watermilfoil Myriophyllum spicatum, had the highest frequency among vegetated sites 
with 41.0%, 31.8%, and 21.6% respectively.  Understanding factors influencing SAV 
distribution within these reaches is key to restoration planning and implementation efforts 
within large river systems. 

Keywords:  submersed aquatic vegetation, SAV, distribution, Illinois River, LTRMP