WHAT PHYTOPLANKTON COMMUNITIES TELL US ABOUT MIXING OF WATER FROM THE NAVIGATION 
CHANNEL AND VEGETATION BED AT LOCK AND DAM 19, MISSISSIPPI RIVER.

Susan T. Meiers
Department of Biological Sciences, Western Illinois University, 1 University 
Circle, Macomb, IL  61455

Although several studies of large rivers such as the Mississippi have examined 
community composition throughout the year, few have examined how much mixing of 
water and species occurs among communities that exist within those rivers.  
Using observations of phytoplankton communities in the navigation channel and 
the vegetation bed above Lock and Dam 19, an approximate measure of the mixing 
of water from these regions was examined.  Sampling at the surface and 1 m below 
the surface occurred at 3 sites above the dam (mid-navigation channel, mid-
vegetation bed, and at the edge of the vegetation bed) and 5 sites below the dam 
(3 sites just below the dam at the Iowa side, Illinois side, and midway point 
below the dam; and 2 sites further down the river at mid-navigation channel and 
approximately 200 m north of Eagle Island near the Illinois shore).  Examination 
of above-dam phytoplankton communities indicates there is a small amount of 
water and community mixing between the navigation channel and the vegetation 
bed, and that the two sites do have different and community compositions.  

Keywords: phytoplankton, Mississippi River, algal community composition, aquatic 
vegetation, Lock and Dam 19